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Holzwarth N et al.

Tattoo tomography: Freehand 3D photoacoustic image reconstruction with an optical pattern

Other ApplicationsClinicalMSOT

Purpose : Photoacoustic tomography (PAT) is a novel imaging technique that can spatially resolve both morphological and functional tissue properties, such as vessel topology and tissue oxygenation. While this capacity makes PAT a promising modality for the diagnosis, treatment, and follow-up of various diseases, a current drawback is the limited field of view provided by the conventionally applied 2D probes. Methods : In this paper, we present a novel approach to 3D reconstruction of PAT data (Tattoo tomography) that does not require an external tracking system and can smoothly be integrated into clinical workflows. It is based on an optical pattern placed on the region of interest prior to image acquisition. This pattern is designed in a way that a single tomographic image of it enables the recovery of the probe pose relative to the coordinate system of the pattern, which serves as a global coordinate system for image compounding. Results : To investigate the feasibility of Tattoo tomography, we assessed the quality of 3D image reconstruction with experimental phantom data and in vivo forearm data. The results obtained with our prototype indicate that the Tattoo method enables the accurate and precise 3D reconstruction of PAT data and may be better suited for this task than the baseline method using optical tracking. Conclusions : In contrast to previous approaches to 3D ultrasound (US) or PAT reconstruction, the Tattoo approach neither requires complex external hardware nor training data acquired for a specific application. It could thus become a valuable tool for clinical freehand PAT.

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Dean-Ben XL et al.

Optoacoustic imaging of the skin

CancerInflammationClinicalMSOTRSOM

Optoacoustic (OA, photoacoustic) imaging capitalizes on the synergistic combination of light excitation and ultrasound detection to empower biological and clinical investigations with rich optical contrast while effectively bridging the gap between micro and macroscopic imaging realms. State-of-the-art OA embodiments consistently provide images at micron-scale resolution through superficial tissue layers by means of focused illumination that can be smoothly exchanged for acoustic-resolution images at diffuse light depths of several millimetres to centimetres via ultrasound beamforming or tomographic reconstruction. Taken together, this unique multi-scale imaging capacity opens unprecedented capabilities for high-resolution in vivo interrogations of the skin at scalable depths. Moreover, diverse anatomical and functional information is retrieved via dynamic mapping of endogenous chromophores such as haemoglobin, melanin, lipids, collagen, water and others. This, along with the use of non-ionizing radiation, facilitates a clinical translation of the OA modalities. We review recent progress in OA imaging of the skin in preclinical and clinical studies exploiting the rich contrast provided by endogenous substances in tissues. The imaging capabilities of existing approaches are discussed in the context of initial translational studies on skin cancer, inflammatory skin diseases, wounds and other conditions.

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Regensburger AP et al.

Optoacoustic Imaging in Inflammation

InflammationClinicalMSOT

Optoacoustic or photoacoustic imaging (OAI/PAI) is a technology which enables non-invasive visualization of laser-illuminated tissue by the detection of acoustic signals. The combination of “light in” and “sound out” offers unprecedented scalability with a high penetration depth and resolution. The wide range of biomedical applications makes this technology a versatile tool for preclinical and clinical research. Particularly when imaging inflammation, the technology offers advantages over current clinical methods to diagnose, stage, and monitor physiological and pathophysiological processes. This review discusses the clinical perspective of using OAI in the context of imaging inflammation as well as in current and emerging translational applications.

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Karlas A et al.

Optoacoustic imaging in endocrinology and metabolism

Other ApplicationsClinicalMSOT

Imaging is an essential tool in research, diagnostics and the management of endocrine disorders. Ultrasonography, nuclear medicine techniques, MRI, CT and optical methods are already used for applications in endocrinology. Optoacoustic imaging, also termed photoacoustic imaging, is emerging as a method for visualizing endocrine physiology and disease at different scales of detail: microscopic, mesoscopic and macroscopic. Optoacoustic contrast arises from endogenous light absorbers, such as oxygenated and deoxygenated haemoglobin, lipids and water, or exogenous contrast agents, and reveals tissue vasculature, perfusion, oxygenation, metabolic activity and inflammation. The development of high-performance optoacoustic scanners for use in humans has given rise to a variety of clinical investigations, which complement the use of the technology in preclinical research. Here, we review key progress with optoacoustic imaging technology as it relates to applications in endocrinology; for example, to visualize thyroid morphology and function, and the microvasculature in diabetes mellitus or adipose tissue metabolism, with particular focus on multispectral optoacoustic tomography and raster-scan optoacoustic mesoscopy. We explain the merits of optoacoustic microscopy and focus on mid-infrared optoacoustic microscopy, which enables label-free imaging of metabolites in cells and tissues. We showcase current optoacoustic applications within endocrinology and discuss the potential of these technologies to advance research and clinical practice.

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Hao K et al.

Cationic Flexible Organic Framework for Combination of Photodynamic Therapy and Genetic Immunotherapy Against Tumors

NanoCancerPreclinicalMSOT

Photodynamic therapy is a new type of anti-tumor therapy with excellent therapeutic effects and minor side effects. The key factor for photodynamic therapy is highly efficient loading and protection of photosensitizers. Covalent organic framework is a new type of organic porous material with rich sources and has huge development potential in the loading of photosensitizers. However, the π-π interaction between the rigid monomers inevitably causes aggregation and quenching between photosensitizers, which in turn affects the rate of reactive oxygen production. Here, newly designed cationic flexible organic framework nanoparticles (PEI-Por NPs) are synthesized via one-step method with PEI25K and meso-tetra(p-formylphenyl)porphyrin under microwave irradiation. The structure of the flexible organic framework can effectively inhibit the aggregation and quenching of porphyrin. In addition, PEI-Por NPs had excellent gene transfection ability both in vitro and in vivo. Excellent antitumor effect can be achieved by combining PEI-Por NPs’ photodynamic therapy capacity and PEI-Por NPs-mediated PD-L1 gene silencing with the guidance of fluorescence imaging and photoacoustic imaging. This cationic flexible organic framework material combines the advantages of flexible building units and rigid monomers, which provides a basis for the development of nano-photosensitizers and excellent gene carriers, and has great potential for clinical application.

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Groehl J et al.

Learned spectral decoloring enables photoacoustic oximetry

TechnologyPreclinicalClinicalMSOT

The ability of photoacoustic imaging to measure functional tissue properties, such as blood oxygenation sO[Formula: see text], enables a wide variety of possible applications. sO[Formula: see text] can be computed from the ratio of oxyhemoglobin HbO[Formula: see text] and deoxyhemoglobin Hb, which can be distuinguished by multispectral photoacoustic imaging due to their distinct wavelength-dependent absorption. However, current methods for estimating sO[Formula: see text] yield inaccurate results in realistic settings, due to the unknown and wavelength-dependent influence of the light fluence on the signal. In this work, we propose learned spectral decoloring to enable blood oxygenation measurements to be inferred from multispectral photoacoustic imaging. The method computes sO[Formula: see text] pixel-wise, directly from initial pressure spectra [Formula: see text], which represent initial pressure values at a fixed spatial location [Formula: see text] over all recorded wavelengths [Formula: see text]. The method is compared to linear unmixing approaches, as well as pO[Formula: see text] and blood gas analysis reference measurements. Experimental results suggest that the proposed method is able to obtain sO[Formula: see text] estimates from multispectral photoacoustic measurements in silico, in vitro, and in vivo.

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Liu X et al.

Dual-Stimulus Responsive Near-Infrared Reversible Ratiometric Fluorescent and Photoacoustic Probe for In Vivo Tumor Imaging

NanoCancerPreclinicalMSOT

Tumor-specific imaging is a major challenge in clinical tumor resection. To overcome this problem, several activatable probes have been developed for use in tumor imaging. However, most of these probes are activated based on a single-factor stimulation and are irreversible. Therefore, false signals that make tumor-specific imaging difficult are easily generated. We have developed a new dual-stimulus responsive near-infrared (NIR) reversible adenosine 5′-triphosphate (ATP)-pH probe for fluorescence and photoacoustic ratiometric imaging of tumors. Since the H+ and ATP content is significantly higher in the tumor microenvironment than that in normal tissues, the Förster resonance energy transfer-based probe ATP-pH was constructed with silicon rhodamine as the donor, CS dye as the acceptor, and ATP/H+ recognition units that could only be activated when both H+ and ATP were connected to the acceptor. The ATP-pH probe is reversibly activated by both the H+ and ATP, which effectively reduces the cumulative response of the probe in circulation after intravenous injection. Further, the NIR ratiometric property of the probe makes it suitable for in vivo imaging. Finally, our probe was successfully utilized in ratiometric photoacoustic and fluorescence tumor imaging and ratiometric fluorescence imaging-guided tumor resection.

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Wang S et al.

A tumor microenvironment–induced absorption red-shifted polymer nanoparticle for simultaneously activated photoacoustic imaging and photothermal therapy

NanoCancerPreclinicalMSOT

Tumor microenvironment-responsive therapy has enormous application potential in the diagnosis and treatment of cancer. The glutathione (GSH) level has been shown to be significantly increased in tumor tissues. Thus, GSH can be used as an effective endogenous molecule for diagnosis and tumor microenvironment-activated therapy. In this study, we prepared a tumor microenvironment-induced, absorption spectrum red-shifted, iron-copper co-doped polyaniline nanoparticle (Fe-Cu@PANI). The Cu(II) in this nanoparticle can undergo a redox reaction with GSH in tumors. The redox reaction induces a red shift in the absorption spectrum of the Fe-Cu@PANI nanoparticles from the visible to the near-infrared region accompanying with the etching of this nanoparticle, which simultaneously activates tumor photoacoustic imaging and photothermal therapy, thereby improving the accuracy of in vivo tumor imaging and the efficiency of photothermal therapy. The nanoparticle prepared in this study has broad application prospects in the diagnosis and treatment of cancer.

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Liu N et al.

Facile Synthesis of a Croconaine-Based Nanoformulation for Optoacoustic Imaging and Photothermal Therapy

NanoCancerPreclinicalMSOT

Near-infrared (NIR) light absorbing theranostic agents can integrate optoacoustic imaging and photothermal therapy for effective personalized precision medicine. However, most of these agents face the challenges of unstable optical properties, material-associated toxicity, and nonbiodegradability, all of which limit their biomedical application. Several croconaine-based organic agents able to overcome some of these limitations have been recently reported, but these suffer from complicated multistep synthesis protocols. Herein, the use of CR760, a croconaine dye with excellent optical properties, is reported for nanoparticle formulation and subsequent optoacoustic imaging and photothermal therapy. Importantly, CR760 can be conveniently prepared in a single step from commercially available materials. Furthermore, CR760 can be covalently attached, via a polyethylene glycol linker, to the αv β3 integrin ligand c(RGDyC), resulting in self-assembled nanoparticles (NPs) with cancer-targeting capability. Such CR760RGD-NPs exhibit strong NIR absorption, high photostability, high optoacoustic generation efficiency, and active tumor-targeting, making them ideal candidates for optoacoustic imaging. Due to favorable electron transfer, CR760RGD-NPs display a 45.37% photothermal conversion efficiency thereby rendering them additionally useful for photothermal therapy. Targeted tumor elimination, biosafety, and biocompatibility are demonstrated in a 4T1 murine breast tumor model. This work points to the use of CR760RGD-NPs as a promising nanoagent for NIR-based cancer phototheranostics.

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Zheng BD et al.

A pH-sensitive nanoagent self-assembled from a highly negatively-charged phthalocyanine with excellent biosafety for photothermal therapy

NanoCancerPreclinicalMSOT

Photothermal therapy (PTT) is a promising strategy for cancer treatment. However, the development of highly efficient photothermal agents with excellent biosafety, particularly with low liver retention, is very meaningful for clinical applications, but it is also challenging. We herein prepared a pH-sensitive nanoagent (NanoPc3) by the self-assembly of a zinc(ii) phthalocyanine substituted with hexadeca-sulphonates linked by hydrazone bonds for photoacoustic imaging and PTT. Due to the highly negative surface potential (-30.80 mV in water), NanoPc3 could effectively escape the phagocytosis of the reticuloendothelial system and be rapidly cleared from normal tissues, leading to little accumulation in the liver and excellent biosafety. The highly negatively-charged NanoPc3 changed into nearly neutral nanoparticles (NanoPc3H) under slightly acidic conditions, resulting in enhanced cellular uptake and retention time in tumor tissues. Moreover, the tumor of H22 tumor-bearing mice treated with NanoPc3 almost disappeared, suggesting an outstanding photothermal antitumor effect. NanoPc3 also hardly showed skin phototoxicity under irradiation. Its excellent antitumor effect and biosafety make NanoPc3 highly promising in clinical applications. This work will provide a new strategy for the design of tumor-targeted photothermal nanoagents with high biosafety.

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Zheng P et al.

A Multichannel Ca2+ Nanomodulator for Multilevel Mitochondrial Destruction-Mediated Cancer Therapy

NanoCancerPreclinicalMSOT

Subcellular organelle-targeted nanoformulations for cancer theranostics are receiving increasing attention owing to their benefits of precise drug delivery, maximized therapeutic index, and reduced off-target side effects. Herein, a multichannel calcium ion (Ca2+ ) nanomodulator (CaNMCUR+CDDP ), i.e., a cisplatin (CDDP) and curcumin (CUR) co-incorporating calcium carbonate (CaCO3 ) nanoparticle, is prepared by a facile one-pot strategy in a sealed container with in situ synthesized polydopamine (PDA) as a template to enhance Ca2+ -overload-induced mitochondrial dysfunction in cancer therapy. After systemic administration, the PEGylated CaNMCUR+CDDP (PEG CaNMCUR+CDDP ) selectively accumulates in tumor tissues, enters tumor cells, and induces multilevel destruction of mitochondria by the combined effects of burst Ca2+ release, Ca2+ efflux inhibition by CUR, and chemotherapeutic CDDP, thereby observably boosting mitochondria-targeted tumor inhibition. Fluorescence imaging of CUR combined with photoacoustic imaging of PDA facilitates the visualization of the nanomodulator. The facile and practical design of this multichannel Ca2+ nanomodulator will contribute to the development of multimodal bioimaging-guided organelle-targeted cancer therapy in the future.

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Tian Y et al.

NAD(P)H-triggered probe for dual-modal imaging during energy metabolism and novel strategy of enhanced photothermal therapy in tumor

NanoCancerPreclinicalMSOT

The reduced coenzymes (NADH and NADPH) are an important product in energy metabolism and closely related to the occurrence and development of cancer. So it is necessary to use a powerful detection tool to visualize NAD(P)H in energy metabolism of tumor cells and find a new strategy to improve cancer treatment based on NAD(P)H. Herein, a novel multifunctional probe (Cy-N) is synthesized with good near-infrared fluorescence (NIRF) response to NAD(P)H and the photoacoustic (PA) and photothermal properties are successfully activated by NAD(P)H. The probe is successfully applied in visualizing NAD(P)H in energy metabolism of tumor cells and imaging NAD(P)H in bacteria. Moreover, the probe can be used to image NAD(P)H in energy metabolism of tumor-bearing mice by dual-modal imaging (NIRF and PA). More importantly, in terms of the role of NAD(P)H in energy metabolism, the photothermal therapy (PTT) is activated by NAD(P)H and a novel strategy of enhanced PTT is proposed by injecting glucose. As far as we know, this is the first probe to detect NAD(P)H in energy metabolism through dual-modal imaging, and also the first probe to activate PTT based on NAD(P)H, which will provide important information of the diagnosis and treatment of cancer.

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Laramie MD et al.

Improved pentamethine cyanine nanosensors for optoacoustic imaging of pancreatic cancer

CancerPreclinicalMSOT

Optoacoustic imaging is a new biomedical imaging technology with clear benefits over traditional optical imaging and ultrasound. While the imaging technology has improved since its initial development, the creation of dedicated contrast agents for optoacoustic imaging has been stagnant. Current exploration of contrast agents has been limited to standard commercial dyes that have already been established in optical imaging applications. While some of these compounds have demonstrated utility in optoacoustic imaging, they are far from optimal and there is a need for contrast agents with tailored optoacoustic properties. The synthesis, encapsulation within tumor targeting silica nanoparticles and applications in in vivo tumor imaging of optoacoustic contrast agents are reported.

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Szucs Z et al.

Multi-modal imaging of high-risk ductal carcinoma in situ of the breast using C2Am: a targeted cell death imaging agent

CancerPreclinicalMSOT

Background : Ductal carcinoma in situ (DCIS) is a non-invasive form of early breast cancer, with a poorly understood natural history of invasive transformation. Necrosis is a well-recognized adverse prognostic feature of DCIS, and non-invasive detection of its presence and spatial extent could provide information not obtainable by biopsy. We describe here imaging of the distribution and extent of comedo-type necrosis in a model of human DCIS using C2Am, an imaging agent that binds to the phosphatidylserine exposed by necrotic cells. Methods : We used an established xenograft model of human DCIS that mimics the histopathological features of the disease. Planar near-infrared and optoacoustic imaging, using fluorescently labeled C2Am, were used to image non-invasively the presence and extent of lesion necrosis. Results : C2Am showed specific and sensitive binding to necrotic areas in DCIS tissue, detectable both in vivo and ex vivo. The imaging signal generated in vivo using near-infrared (NIR) fluorescence imaging was up to 6-fold higher in DCIS lesions than in surrounding fat pad or skin tissue. There was a correlation between the C2Am NIR fluorescence (Pearson R = 0.783, P = 0.0125) and optoacoustic signals (R > 0.875, P < 0.022) in the DCIS lesions in vivo and the corresponding levels of cell death detected histologically. Conclusions : C2Am is a targeted multi-modal imaging agent that could complement current anatomical imaging methods for detecting DCIS. Imaging the presence and spatial extent of necrosis may give better prognostic information than that obtained by biopsy alone.

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Zheng P et al.

Ultrasound-Augmented Mitochondrial Calcium Ion Overload by Calcium Nanomodulator to Induce Immunogenic Cell Death

InflammationPreclinicalMSOT

Immunogenic cell death (ICD), a manner of tumor cell death that can trigger antitumor immune responses, has received extensive attention as a potential synergistic modality for cancer immunotherapy. Although many calcium ion (Ca2+) nanomodulators have been developed for cancer therapy through mitochondrial Ca2+ overload, their ICD-inducing properties have not been explored. Herein, an acid-sensitive PEG-decorated calcium carbonate (CaCO3) nanoparticle incorporating curcumin (CUR; a Ca2+ enhancer) (PEGCaCUR) was prepared using a simple one-pot strategy. PEGCaCUR served as not only a Ca2+ nanomodulator inducing efficient mitochondrial Ca2+ overload but also an ICD inducer during improved synergistic cancer therapy. Combination of PEGCaCUR with ultrasound (US), PEGCaCUR+US, led to an enhanced ICD effect attributable to the enhanced mitochondrial Ca2+ overload, along with subsequent upregulation of reactive oxygen species levels. PEGCaCUR also facilitates photoacoustic/fluorescence dual-mode imaging, as well as effectively suppressing tumor growth and metastasis, indicating promising theranostic properties.

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Razansky D et al.

Multi-scale optoacoustic molecular imaging of brain diseases

NeuroPreclinicalMSOT

The ability to non-invasively visualize endogenous chromophores and exogenous probes and sensors across the entire rodent brain with the high spatial and temporal resolution has empowered optoacoustic imaging modalities with unprecedented capacities for interrogating the brain under physiological and diseased conditions. This has rapidly transformed optoacoustic microscopy (OAM) and multi-spectral optoacoustic tomography (MSOT) into emerging research tools to study animal models of brain diseases. In this review, we describe the principles of optoacoustic imaging and showcase recent technical advances that enable high-resolution real-time brain observations in preclinical models. In addition, advanced molecular probe designs allow for efficient visualization of pathophysiological processes playing a central role in a variety of neurodegenerative diseases, brain tumors, and stroke. We describe outstanding challenges in optoacoustic imaging methodologies and propose a future outlook.

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Guo X et al.

A full-spectrum responsive B-TiO2@SiO2-HA nanotheranostic system for NIR-II photoacoustic imaging-guided cancer phototherapy

NanoCancerPreclinicalMSOT

The second near-infrared (NIR-II) window (1000-1350 nm) usually offers further improved light penetration, a higher maximum permissible exposure (MPE), and a lower background signal. Development of NIR-II optical diagnosis and phototherapy technologies is of great significance for precise, efficient tumor therapy. In this work, a new type of Ti-based targeting agent (B-TiO2@SiO2-HA) nanotheranostic system with strong NIR-II absorption was designed and fabricated for the first time. Oxygen vacancies were formed in B-TiO2 and its band gap was narrowed, resulting in nanotheranostic systems with full-spectrum responses to stimulation with light. The experimental results showed that B-TiO2@SiO2-HA not only can enable high NIR-II photothermal conversion and provide excellent reactive oxygen species (ROS) production capacity, but also can enable high-resolution photoacoustic imaging (PAI) under NIR-II laser irradiation. Moreover, HA modification gives the nanotheranostic systems the useful ability to target high-CD44-expression tumor cells and tissues. In vitro and in vivo experiments demonstrated that B-TiO2@SiO2-HA exhibited a targeted photothermal/photodynamic (PTT/PDT) effect that produced tumor-cell ablation and apoptosis under the guidance of real-time NIR-II PA imaging. B-TiO2@SiO2-HA exhibits precise nanotheranostic potential for PAI-guided tumor-targeting phototherapy.

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Zhang Y et al.

Harnessing Radical-Mediated Photocaged Cyanine under Hypoxia for in vivo Precision Drug Release

NanoCancerPreclinicalMSOT

Photocaging holds promise for the precise manipulation of biological events in space and time. However, current near-infrared (NIR) photocages are oxygen-dependent for their photolysis and lack of timely feedback regulation, which has proven to be the major bottleneck for targeted therapy. Herein, we present a hypoxia-dependent photo-activation mechanism of dialkylamine-substituted cyanine (Cy-NH) accompanied by emissive fragments generation, which was validated with retrosynthesis and spectral analysis. For the first time, we have realized the orthogonal manipulation of this hypoxia-dependent photocaging and dual-modal optical signals in living cells and tumor-bearing mice, making a breakthrough in the direct spatiotemporal control and in vivo feedback regulation. This unique photoactivation mechanism overcomes the limitation of hypoxia, which allows site-specific remote control for targeted therapy, and expands the photo-trigger toolbox for on-demand drug release, especially in a physiological context with dual-mode optical imaging under hypoxia.

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Wang Y et al.

Nonlinear Iterative Perturbation Scheme with Simplified Spherical Harmonics (SP3 ) Light Propagation Model for Quantitative Photoacoustic Tomography

TechnologyPreclinicalMSOT

When using quantitative photoacoustic tomography (q-PAT) reconstruction to recover the optical absorption coefficients of tissue, the commonly used diffusion equation has several limitations in the case of the objects that have small geometries and high-absorption or low-scattering areas. Furthermore, the conventional perturbation reconstruction strategy is unsatisfactory when the target tissue containing large heterogeneous features. We herein present a modified q-PAT implementation that employs the higher-order photon migration model achieving the tradeoff between mathematical rigidity and computational efficiency. Besides, a nonlinear iterative method is proposed to obtain the perturbations of optical absorption considering the updating of the sensitivity matrix in calculating the fluence perturbations. Consequently, the distribution of tissue optical properties can be recovered in a robust way even if the targets with high absorption are included. The proposed approach has been validated by simulation, phantom and in vivo experiments, exhibiting promising performances in image fidelity and quantitative feasibility for practical applications.

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Barmin RA et al.

Air-Filled Bubbles Stabilized by Gold Nanoparticle/Photodynamic Dye Hybrid Structures for Theranostics

NanoPreclinicalRSOM

Microbubbles have already reached clinical practice as ultrasound contrast agents for angiography. However, modification of the bubbles’ shell is needed to produce probes for ultrasound and multimodal (fluorescence/photoacoustic) imaging methods in combination with theranostics (diagnostics and therapeutics). In the present work, hybrid structures based on microbubbles with an air core and a shell composed of bovine serum albumin, albumin-coated gold nanoparticles, and clinically available photodynamic dyes (zinc phthalocyanine, indocyanine green) were shown to achieve multimodal imaging for potential applications in photodynamic therapy. Microbubbles with an average size of 1.5 ± 0.3 μm and concentration up to 1.2 × 109 microbubbles/mL were obtained and characterized. The introduction of the dye into the system reduced the solution’s surface tension, leading to an increase in the concentration and stability of bubbles. The combination of gold nanoparticles and photodynamic dyes’ influence on the fluorescent signal and probes’ stability is described. The potential use of the obtained probes in biomedical applications was evaluated using fluorescence tomography, raster-scanning optoacoustic microscopy and ultrasound response measurements using a medical ultrasound device at the frequency of 33 MHz. The results demonstrate the impact of microbubbles’ stabilization using gold nanoparticle/photodynamic dye hybrid structures to achieve probe applications in theranostics.

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Fasoula NA et al.

Multicompartmental Non-invasive Sensing of Postprandial Lipemia in Humans with Multispectral Optoacoustic Tomography

Other ApplicationsClinicalMSOT

Objective : Postprandial lipid profiling (PLP), a risk indicator of cardiometabolic disease, is based on frequent blood sampling over several hours after a meal, an approach that is invasive and inconvenient. Non-invasive PLP may offer an alternative for disseminated human monitoring. Herein, we investigate the use of clinical multispectral optoacoustic tomography (MSOT) for non-invasive, label-free PLP via direct lipid-sensing in human vasculature and soft tissues. Methods : Four (n = 4) subjects (3 females and 1 male, age: 28 ± 7 years) were enrolled in the current pilot study. We longitudinally measured the lipid signals in arteries, veins, skeletal muscles, and adipose tissues of all participants at 30-min intervals for 6 h after the oral consumption of a high-fat meal. Results : Optoacoustic lipid-signal analysis showed on average a 63.4% intra-arterial increase at ~ 4 h postprandially, an 83.9% intra-venous increase at ~ 3 h, a 120.8% intra-muscular increase at ~ 3 h, and a 32.8% subcutaneous fat increase at ~ 4 h. Conclusion : MSOT provides the potential to study lipid metabolism that could lead to novel diagnostics and prevention strategies by label-free, non-invasive detection of tissue biomarkers implicated in cardiometabolic diseases.

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Pu Y et al.

A Gd-doped polydopamine (PDA)-based theranostic nanoplatform as a strong MR/PA dual-modal imaging agent for PTT/PDT synergistic therapy

CancerPreclinicalMSOT

Based on widely used photoacoustic imaging (PAI) and photothermal properties of polydopamine (PDA), a multifunctional Gd–PDA-Ce6@Gd-MOF (GPCG) nanosystem with a core–shell structure and strong imaging ability was constructed. Benefitting from the metal–organic framework (MOF) structure, GPCG nanoparticles (NPs) showed enhanced magnetic resonance imaging (MRI) ability with high relaxation rates (r1 = 3.72mM_x0002_1 s_x0002_1 and r2 = 216.14 mM_x0002_1 s_x0002_1). The MRI effect of Gd ions combined with the PAI effect of PDA, giving GPCG NPs a dual-modal imaging ability. The core, mainly composed of PDA and photodynamic hotosensitizer chlorin e6 (Ce6), achieved photothermal/photodynamic therapy (PTT/PDT) synergistic performance. Besides, to overcome the unexpected release of Ce6, the MOF shell realized pH-sensitive release and a high local concentration. Through in vivo studies, we concluded that GPCG NPs show a good inhibitory effect on tumor growth. In conclusion, we successfully obtained a GPCG theranostic nanoplatform and paved the way for subsequent design of imaging guided therapeutic nanostructures based on metal-doped PDA.

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Groehl J et al.

Deep learning for biomedical photoacoustic imaging: A review

TechnologyPreclinicalClinicalMSOT

Photoacoustic imaging (PAI) is a promising emerging imaging modality that enables spatially resolved imaging of optical tissue properties up to several centimeters deep in tissue, creating the potential for numerous exciting clinical applications. However, extraction of relevant tissue parameters from the raw data requires the solving of inverse image reconstruction problems, which have proven extremely difficult to solve. The application of deep learning methods has recently exploded in popularity, leading to impressive successes in the context of medical imaging and also finding first use in the field of PAI. Deep learning methods possess unique advantages that can facilitate the clinical translation of PAI, such as extremely fast computation times and the fact that they can be adapted to any given problem. In this review, we examine the current state of the art regarding deep learning in PAI and identify potential directions of research that will help to reach the goal of clinical applicability.

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Barmin RA et al.

Optoacoustic/Fluorescent/Acoustic Imaging Probe Based on Air-Filled Bubbles Functionalized with Gold Nanorods and Fluorescein Isothiocyanate

NanoCancerPreclinicalRSOM

Liquid/surfactant/gas interfaces are promising objects for nanoengineered multimodal contrasts, which can be used for biomedical imaging in preclinical and clinical applications. Microbubbles with the gaseous core and shell made of lipids/proteins have already acted as ultrasound (US) contrast agents for angiography. In the present work, microbubbles with a shell composed of Span 60 and Tween 80 surfactants functionalized with fluorescein isothiocyanate and gold nanorods to achieve a multimodal combination of US, fluorescence, and optoacoustic imaging are described. Optimal conditions for microbubble generation by studying the surface tension of the initial solutions and analyzing the size, stability, and charge of the resulting bubbles were found. By controlling and modifying bubbles’ surface properties, an increase in stability and storage time can be achieved. The functionalization of bubbles with gold nanoparticles and a dye by using an optimally selected sonication protocol was performed. The biomedical application’s potential in imaging modalities of functionalized microbubbles using a medical US device with a frequency of 50 MHz, fluorescence tomography, and raster-scanning optoacoustic mesoscopy measurements was evaluated. The obtained results are important for optimum stabilization and functionalization of gas/liquid interfaces and the following applications in the multimodal biomedical imaging.

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Zhong D et al.

Calcium phosphate engineered photosynthetic microalgae to combat hypoxic-tumor by in-situ modulating hypoxia and cascade radio-phototherapy

CancerPreclinicalMSOT

Rationale : Hypoxia is one of the crucial restrictions in cancer radiotherapy (RT), which leads to the hypoxia-associated radioresistance of tumor cells and may result in the sharp decline in therapeutic efficacy. Methods : Herein, living photosynthetic microalgae (Chlorella vulgaris, C. vulgaris), were used as oxygenators, for in situ oxygen generation to relieve tumor hypoxia. We engineered the surface of C. vulgaris (CV) cells with calcium phosphate (CaP) shell by biomineralization, to form a biomimetic system (CV@CaP) for efficient tumor delivery and in-situ active photosynthetic oxygenation reaction in tumor. Results : After intravenous injection into tumor-bearing mice, CV@CaP could remarkably alleviate tumor hypoxia by continuous oxygen generation, thereby achieving enhanced radiotherapeutic effect. Furthermore, a cascade phototherapy could be fulfilled by the chlorophyll released from photosynthetic microalgae combined thermal effects under 650 nm laser irradiation. The feasibility of CV@CaP-mediated combinational treatment was finally validated in an orthotropic breast cancer mouse model, revealing its prominent anti-tumor and anti-metastasis efficacy in hypoxic-tumor management. More importantly, the engineered photosynthetic microalgae exhibited excellent fluorescence and photoacoustic imaging properties, allowing the self-monitoring of tumor therapy and tumor microenvironment. Conclusions : Our studies of this photosynthetic microsystem open up a new dimension for solving the radioresistance issue of hypoxic tumors.

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Zhang S et al.

A simple strategy for simultaneously enhancing photostability and mitochondrial-targeting stability of near-infrared fluorophores for multimodal imaging-guided photothermal therapy

CancerPreclinicalMSOT

Near-infrared fluorophores are emerging as promising molecular tools for cancer theranostics because of their inherent biodegradability, low toxicity, and synthetic flexibility. However, they still suffer from several limitations, such as poor photostability and insufficient organelle-targeting stability during photothermal therapy. In this work, we introduce an “aldehyde functionalization” strategy for simultaneously enhancing photostability and mitochondria-immobilization of near-infrared fluorophores for the first time. Based on the proposed strategy, representative near-infrared organic molecules, namely AF-Cy, were rationally designed and synthesized. Upon aldehyde modification, the AF-Cy dyes displayed both remarkable photostability and mitochondrial-targeting stability. The strong absorption in the near-infrared region confers the AF-Cy dyes with outstanding fluorescent/photoacoustic imaging and photothermal therapy capabilities. Finally, in vitro and in vivo studies revealed the enhanced performance in inhibiting the growth of breast tumors under NIR laser radiation, and these results suggested the strong potential of AF-Cy dyes as efficient multimodal imaging-guided photothermal therapy agents, further highlighting the value of this simple strategy in the design high performance near-infrared fluorophores for tumor theranostics.

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Zhang S et al.

A simple strategy for simultaneously enhancing photostability and mitochondrial-targeting stability of near-infrared fluorophores for multimodal imaging-guided photothermal therapy

CancerPreclinicalMSOT

Near-infrared fluorophores are emerging as promising molecular tools for cancer theranostics because of their inherent biodegradability, low toxicity, and synthetic flexibility. However, they still suffer from several limitations, such as poor photostability and insufficient organelle-targeting stability during photothermal therapy. In this work, we introduce an “aldehyde functionalization” strategy for simultaneously enhancing photostability and mitochondria-immobilization of near-infrared fluorophores for the first time. Based on the proposed strategy, representative near-infrared organic molecules, namely AF-Cy, were rationally designed and synthesized. Upon aldehyde modification, the AF-Cy dyes displayed both remarkable photostability and mitochondrial-targeting stability. The strong absorption in the near-infrared region confers the AF-Cy dyes with outstanding fluorescent/photoacoustic imaging and photothermal therapy capabilities. Finally, in vitro and in vivo studies revealed the enhanced performance in inhibiting the growth of breast tumors under NIR laser radiation, and these results suggested the strong potential of AF-Cy dyes as efficient multimodal imaging-guided photothermal therapy agents, further highlighting the value of this simple strategy in the design high performance near-infrared fluorophores for tumor theranostics.

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Mohr H et al.

Mutation of the Cell Cycle Regulator p27kip1 Drives Pseudohypoxic Pheochromocytoma Development

CancerPreclinicalMSOT

Background : Pseudohypoxic tumors activate pro-oncogenic pathways typically associated with severe hypoxia even when sufficient oxygen is present, leading to highly aggressive tumors. Prime examples are pseudohypoxic pheochromocytomas and paragangliomas (p-PPGLs), neuroendendocrine tumors currently lacking effective therapy. Previous attempts to generate mouse models for p-PPGLs all failed. Here, we describe that the rat MENX line, carrying a Cdkn1b (p27) frameshift-mutation, spontaneously develops pseudohypoxic pheochromocytoma (p-PCC). Methods : We compared rat p-PCCs with their cognate human tumors at different levels: histology, immunohistochemistry, catecholamine profiling, electron microscopy, transcriptome and metabolome. The vessel architecture and angiogenic potential of pheochromocytomas (PCCs) was analyzed by light-sheet fluorescence microscopy ex vivo and multi-spectral optoacoustic tomography (MSOT) in vivo. Results : The analysis of tissues at various stages, from hyperplasia to advanced grades, allowed us to correlate tumor characteristics with progression. Pathological changes affecting the mitochrondrial ultrastructure where present already in hyperplasias. Rat PCCs secreted high levels of norepinephrine and dopamine. Transcriptomic and metabolomic analysis revealed changes in oxidative phosphorylation that aggravated over time, leading to an accumulation of the oncometabolite 2-hydroxyglutarate, and to hypermethylation, evident by the loss of the epigenetic mark 5-hmC. While rat PCC xenografts showed high oxygenation, induced by massive neoangiogenesis, rat primary PCC transcriptomes possessed a pseudohypoxic signature of high Hif2a, Vegfa, and low Pnmt expression, thereby clustering with human p-PPGL. Conclusion : Endogenous rat PCCs recapitulate key phenotypic features of human p-PPGLs. Thus, MENX rats emerge as the best available animal model of these aggressive tumors. Our study provides evidence of a link between cell cycle dysregulation and pseudohypoxia.

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Mohr H et al.

Mutation of the Cell Cycle Regulator p27kip1 Drives Pseudohypoxic Pheochromocytoma Development

CancerPreclinicalMSOT

Background : Pseudohypoxic tumors activate pro-oncogenic pathways typically associated with severe hypoxia even when sufficient oxygen is present, leading to highly aggressive tumors. Prime examples are pseudohypoxic pheochromocytomas and paragangliomas (p-PPGLs), neuroendendocrine tumors currently lacking effective therapy. Previous attempts to generate mouse models for p-PPGLs all failed. Here, we describe that the rat MENX line, carrying a Cdkn1b (p27) frameshift-mutation, spontaneously develops pseudohypoxic pheochromocytoma (p-PCC). Methods : We compared rat p-PCCs with their cognate human tumors at different levels: histology, immunohistochemistry, catecholamine profiling, electron microscopy, transcriptome and metabolome. The vessel architecture and angiogenic potential of pheochromocytomas (PCCs) was analyzed by light-sheet fluorescence microscopy ex vivo and multi-spectral optoacoustic tomography (MSOT) in vivo. Results : The analysis of tissues at various stages, from hyperplasia to advanced grades, allowed us to correlate tumor characteristics with progression. Pathological changes affecting the mitochrondrial ultrastructure where present already in hyperplasias. Rat PCCs secreted high levels of norepinephrine and dopamine. Transcriptomic and metabolomic analysis revealed changes in oxidative phosphorylation that aggravated over time, leading to an accumulation of the oncometabolite 2-hydroxyglutarate, and to hypermethylation, evident by the loss of the epigenetic mark 5-hmC. While rat PCC xenografts showed high oxygenation, induced by massive neoangiogenesis, rat primary PCC transcriptomes possessed a pseudohypoxic signature of high Hif2a, Vegfa, and low Pnmt expression, thereby clustering with human p-PPGL. Conclusion : Endogenous rat PCCs recapitulate key phenotypic features of human p-PPGLs. Thus, MENX rats emerge as the best available animal model of these aggressive tumors. Our study provides evidence of a link between cell cycle dysregulation and pseudohypoxia.

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Yang J et al.

Structurally symmetric near-infrared fluorophore IRDye78-protein complex enables multimodal cancer imaging

CancerPreclinicalMSOT

Rationale : Most contemporary cancer therapeutic paradigms involve initial imaging as a treatment roadmap, followed by the active engagement of surgical operations. Current approved intraoperative contrast agents exemplified by indocyanine green (ICG) have a few drawbacks including the inability of pre-surgical localization. Alternative near-infrared (NIR) dyes including IRDye800cw are being explored in advanced clinical trials but often encounter low chemical yields and complex purifications owing to the asymmetric synthesis. A single contrast agent with ease of synthesis that works in multiple cancer types and simultaneously allows presurgical imaging, intraoperative deep-tissue three-dimensional visualization, and high-speed microscopic visualization of tumor margins via spatiotemporally complementary modalities would be beneficial. Methods : Due to the lack of commercial availability and the absence of detailed synthesis and characterization, we proposed a facile and scalable synthesis pathway for the symmetric NIR water-soluble heptamethine sulfoindocyanine IRDye78. The synthesis can be accomplished in four steps from commercially-available building blocks. Its symmetric resonant structure avoided asymmetric synthesis problems while still preserving the benefits of analogous IRDye800cw with commensurable optical properties. Next, we introduced a low-molecular-weight protein alpha-lactalbumin (α-LA) as the carrier that effectively modulates the hepatic clearance of IRDye78 into the preferred renal excretion pathway. We further implemented 89Zr radiolabeling onto the protein scaffold for positron emission tomography (PET). The multimodal imaging capability of the fluorophore-protein complex was validated in breast cancer and glioblastoma. Results : The scalable synthesis resulted in high chemical yields, typically 95% yield in the final step of the chloro dye. Chemical structures of intermediates and the final fluorophore were confirmed. Asymmetric IRDye78 exhibited comparable optical features as symmetric IRDye800cw. Its well-balanced quantum yield affords concurrent dual fluorescence and optoacoustic contrast without self-quenching nor concentration-dependent absorption. The NHS ester functionality modulates efficient covalent coupling to reactive side-chain amines to the protein carrier, along with desferrioxamine (DFO) for stable radiolabeling of 89Zr. The fluorophore-protein complex advantageously shifted the biodistribution and can be effectively cleared through the urinary pathway. The agent accumulates in tumors and enables triple-modal visualization in mouse xenograft models of both breast and brain cancers. Conclusion : This study described in detail a generalized strategic modulation of clearance routes towards the favorable renal clearance, via the introduction of α-LA. IRDye78 as a feasible alternative of IRDye800cw currently in clinical phases was proposed with a facile synthesis and fully characterized for the first time. This fluorophore-protein complex with stable radiolabeling should have great potential for clinical translation where it could enable an elegant workflow from preoperative planning to intraoperative deep tissue and high-resolution image-guided resection.

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Yang J et al.

Structurally symmetric near-infrared fluorophore IRDye78-protein complex enables multimodal cancer imaging

CancerPreclinicalMSOT

Rationale : Most contemporary cancer therapeutic paradigms involve initial imaging as a treatment roadmap, followed by the active engagement of surgical operations. Current approved intraoperative contrast agents exemplified by indocyanine green (ICG) have a few drawbacks including the inability of pre-surgical localization. Alternative near-infrared (NIR) dyes including IRDye800cw are being explored in advanced clinical trials but often encounter low chemical yields and complex purifications owing to the asymmetric synthesis. A single contrast agent with ease of synthesis that works in multiple cancer types and simultaneously allows presurgical imaging, intraoperative deep-tissue three-dimensional visualization, and high-speed microscopic visualization of tumor margins via spatiotemporally complementary modalities would be beneficial. Methods : Due to the lack of commercial availability and the absence of detailed synthesis and characterization, we proposed a facile and scalable synthesis pathway for the symmetric NIR water-soluble heptamethine sulfoindocyanine IRDye78. The synthesis can be accomplished in four steps from commercially-available building blocks. Its symmetric resonant structure avoided asymmetric synthesis problems while still preserving the benefits of analogous IRDye800cw with commensurable optical properties. Next, we introduced a low-molecular-weight protein alpha-lactalbumin (α-LA) as the carrier that effectively modulates the hepatic clearance of IRDye78 into the preferred renal excretion pathway. We further implemented 89Zr radiolabeling onto the protein scaffold for positron emission tomography (PET). The multimodal imaging capability of the fluorophore-protein complex was validated in breast cancer and glioblastoma. Results : The scalable synthesis resulted in high chemical yields, typically 95% yield in the final step of the chloro dye. Chemical structures of intermediates and the final fluorophore were confirmed. Asymmetric IRDye78 exhibited comparable optical features as symmetric IRDye800cw. Its well-balanced quantum yield affords concurrent dual fluorescence and optoacoustic contrast without self-quenching nor concentration-dependent absorption. The NHS ester functionality modulates efficient covalent coupling to reactive side-chain amines to the protein carrier, along with desferrioxamine (DFO) for stable radiolabeling of 89Zr. The fluorophore-protein complex advantageously shifted the biodistribution and can be effectively cleared through the urinary pathway. The agent accumulates in tumors and enables triple-modal visualization in mouse xenograft models of both breast and brain cancers. Conclusion : This study described in detail a generalized strategic modulation of clearance routes towards the favorable renal clearance, via the introduction of α-LA. IRDye78 as a feasible alternative of IRDye800cw currently in clinical phases was proposed with a facile synthesis and fully characterized for the first time. This fluorophore-protein complex with stable radiolabeling should have great potential for clinical translation where it could enable an elegant workflow from preoperative planning to intraoperative deep tissue and high-resolution image-guided resection.

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Guo T et al.

Boron Quantum Dots for Photoacoustic Imaging-Guided Photothermal Therapy

NanoCancerPreclinicalMSOT

Photothermal therapy is a new type of tumor therapy with great potential. An ideal photothermal therapy agent should have high photothermal conversion effect, low biological toxicity, and degradability. The development of novel photothermal therapy agents with these properties is of great demand. In this study, we synthesized boron quantum dots (BQDs) with an ultrasmall hydrodynamic diameter. Both in vitro and in vivo studies show that the as-synthesized BQDs have good biological safety, high photoacoustic imaging performance, and photothermal conversion ability, which can be used for photoacoustic imaging-guided photothermal agents for tumor treatment. Our investigations confirm that the BQDs hold great promise in tumor theranostic applications.

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Guo T et al.

Boron Quantum Dots for Photoacoustic Imaging-Guided Photothermal Therapy

CancerPreclinicalMSOT

Photothermal therapy is a new type of tumor therapy with great potential. An ideal photothermal therapy agent should have high photothermal conversion effect, low biological toxicity, and degradability. The development of novel photothermal therapy agents with these properties is of great demand. In this study, we synthesized boron quantum dots (BQDs) with an ultrasmall hydrodynamic diameter. Both in vitro and in vivo studies show that the as-synthesized BQDs have good biological safety, high photoacoustic imaging performance, and photothermal conversion ability, which can be used for photoacoustic imaging-guided photothermal agents for tumor treatment. Our investigations confirm that the BQDs hold great promise in tumor theranostic applications.

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Zhang X et al.

Albumin-based fluorescence resonance energy transfer nanoprobes for multileveled tumor tissue imaging and dye release imaging

NanoCancerPreclinicalMSOT

Tumor tissue imaging and drug release imaging are both crucial for tumor imaging and image-guided drug delivery. It is urgent to develop a multileveled tumor imaging platform to realize the multiple imaging applications. In this work, we synthesized an albumin-based fluorescence resonance energy transfer (FRET) probe Cy5/7@HSA NPs containing two near-infrared cyanine dyes (CyBI5 and CyBI7) with high FRET efficiency (97 %). Excellent brightness and efficient FRET inside Cy5/7@HSA NPs enabled high-sensitive cell imaging and tumor imaging. This unique nanoprobe imaged 4T1 tumor-bearing mice with high sensitivity (TBR = 5.2) at 24 h post-injection and the dyes penetrated the tumor interior around 4 h post-injection. The release of dyes from nanoprobes was also tracked. This result shows the strong potential of this albumin-based FRET nanoprobe as multileveled tumor imaging platform for in vivo tumor imaging, drug delivery and image-guided surgery.

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Zhang X et al.

Albumin-based fluorescence resonance energy transfer nanoprobes for multileveled tumor tissue imaging and dye release imaging

CancerPreclinicalMSOT

Tumor tissue imaging and drug release imaging are both crucial for tumor imaging and image-guided drug delivery. It is urgent to develop a multileveled tumor imaging platform to realize the multiple imaging applications. In this work, we synthesized an albumin-based fluorescence resonance energy transfer (FRET) probe Cy5/7@HSA NPs containing two near-infrared cyanine dyes (CyBI5 and CyBI7) with high FRET efficiency (97 %). Excellent brightness and efficient FRET inside Cy5/7@HSA NPs enabled high-sensitive cell imaging and tumor imaging. This unique nanoprobe imaged 4T1 tumor-bearing mice with high sensitivity (TBR = 5.2) at 24 h post-injection and the dyes penetrated the tumor interior around 4 h post-injection. The release of dyes from nanoprobes was also tracked. This result shows the strong potential of this albumin-based FRET nanoprobe as multileveled tumor imaging platform for in vivo tumor imaging, drug delivery and image-guided surgery.

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Wen C et al.

Lysosome-Targeted Gold Nanotheranostics for In Situ SERS Monitoring pH and Multimodal Imaging-Guided Phototherapy

NanoCancerPreclinicalMSOT

The integration of surface-enhanced Raman spectrum (SERS) and fluorescence-photoacoustic multimodal imaging in near-infrared photothermal therapy is highly desirable for cancer theranostic. However, typically, gold nanotheranostics usually require an additional modification of fluorophores and complex design refinements. In this work, by integrating surface-modified cysteine-hydroxyl merocyanine (CyHMC) molecules onto AuNRs, a novel lysosome-targeted gold-based nanotheranostics AuNRs-CyHMC that combines the specificity of Raman spectrum, the speed of fluorescence imaging, and deep penetration of photoacoustic imaging was successfully fabricated. Interestingly, fluorescence and Raman signals in this AuNRs-CyHMC system do not interfere, but it has pH-sensitive Raman signals and self-fluorescence localization ability under different excitation wavelengths. Fluorescence co-localization experiments further confirmed the lysosome-targeting ability of AuNRs-CyHMC. Typically, the proposed nanotheranostics were capable of SERS monitoring pH changes in both phosphate-buffered saline and living cells. Meanwhile, in vitro and in vivo experiments revealed that AuNRs-CyHMC possessed excellent fluorescence-photoacoustic performance and could be used for multimodal imaging-guided photothermal therapy. Furthermore, our work implied that gold nanotheranostics can provide great potential for cancer diagnosis and treatment.

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Wen C et al.

Lysosome-Targeted Gold Nanotheranostics for In Situ SERS Monitoring pH and Multimodal Imaging-Guided Phototherapy

CancerPreclinicalMSOT

The integration of surface-enhanced Raman spectrum (SERS) and fluorescence-photoacoustic multimodal imaging in near-infrared photothermal therapy is highly desirable for cancer theranostic. However, typically, gold nanotheranostics usually require an additional modification of fluorophores and complex design refinements. In this work, by integrating surface-modified cysteine-hydroxyl merocyanine (CyHMC) molecules onto AuNRs, a novel lysosome-targeted gold-based nanotheranostics AuNRs-CyHMC that combines the specificity of Raman spectrum, the speed of fluorescence imaging, and deep penetration of photoacoustic imaging was successfully fabricated. Interestingly, fluorescence and Raman signals in this AuNRs-CyHMC system do not interfere, but it has pH-sensitive Raman signals and self-fluorescence localization ability under different excitation wavelengths. Fluorescence co-localization experiments further confirmed the lysosome-targeting ability of AuNRs-CyHMC. Typically, the proposed nanotheranostics were capable of SERS monitoring pH changes in both phosphate-buffered saline and living cells. Meanwhile, in vitro and in vivo experiments revealed that AuNRs-CyHMC possessed excellent fluorescence-photoacoustic performance and could be used for multimodal imaging-guided photothermal therapy. Furthermore, our work implied that gold nanotheranostics can provide great potential for cancer diagnosis and treatment.

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Wang Y et al.

Functionalized polymeric hybrid micelles as an efficient nanotheranostic agent for thrombus imaging and thrombolysis

VascularPreclinicalMSOT

Pathological thrombosis within a vessel hampers blood flow and is the mainspring of numerous fatal cardiovascular complications. In order to specifically image and dissolve a thrombus, we rationally designed a functionalized polymeric hybrid micelle (PHM) system self-assembled from amphiphilic polycaprolactone-polyethylenimine (PCL-PEI) and polycaprolactone-polyethylene glycol (PCL-PEG). Based on a biological component of thrombi, activated coagulation factor XIII (FXIIIa), which is responsible for fibrin crosslinking, we further developed FXIIIa-targeted near infrared imaging and thrombolytic nanoparticles, termed IR780/FPHM/LK NPs, through chemical conjugation of peptides to the system. In a ferric chloride (FeCl3)-induced mouse carotid thrombosis model, IR780/FPHM/LK NPs specifically targeted the thrombus and significantly enhanced the photoacoustic signal for an accurate diagnosis. When loaded with the fibrinolytic drug lumbrokinase (LK), FPHM remarkably dissociated the thrombus accompanied by an increase in the D-dimer level, a fibrin degradation product, and alleviation of fatal nonspecific hemorrhagic risk. Given its thrombus-specific imaging along with potent therapeutic activities, IR780/FPHM/LK NPs hold promise for developing nanotheranostic agents in preclinical thrombotic vascular disease models.

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Wang Y et al.

Functionalized polymeric hybrid micelles as an efficient nanotheranostic agent for thrombus imaging and thrombolysis

IschemiaPreclinicalMSOT

Pathological thrombosis within a vessel hampers blood flow and is the mainspring of numerous fatal cardiovascular complications. In order to specifically image and dissolve a thrombus, we rationally designed a functionalized polymeric hybrid micelle (PHM) system self-assembled from amphiphilic polycaprolactone-polyethylenimine (PCL-PEI) and polycaprolactone-polyethylene glycol (PCL-PEG). Based on a biological component of thrombi, activated coagulation factor XIII (FXIIIa), which is responsible for fibrin crosslinking, we further developed FXIIIa-targeted near infrared imaging and thrombolytic nanoparticles, termed IR780/FPHM/LK NPs, through chemical conjugation of peptides to the system. In a ferric chloride (FeCl3)-induced mouse carotid thrombosis model, IR780/FPHM/LK NPs specifically targeted the thrombus and significantly enhanced the photoacoustic signal for an accurate diagnosis. When loaded with the fibrinolytic drug lumbrokinase (LK), FPHM remarkably dissociated the thrombus accompanied by an increase in the D-dimer level, a fibrin degradation product, and alleviation of fatal nonspecific hemorrhagic risk. Given its thrombus-specific imaging along with potent therapeutic activities, IR780/FPHM/LK NPs hold promise for developing nanotheranostic agents in preclinical thrombotic vascular disease models.

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Jin Y et al.

Integration of TaOx with Bi2S3 for Targeted Multimodality Breast Cancer Theranostics

NanoCancerPreclinicalMSOT

Early identification and treatment of breast cancer is very important for breast conserving therapy and to improve the prognosis and survival rates of patients. Multifunctional nanotheranostic agents are of particular importance in the field of precise nanomedicine, since they can augment the visualization and treatment of cancer. We developed a novel Bi2S3 nanoparticle coated with a hyaluronic acid (HA)-modified tantalum oxide (TaOx) nanoshell (Bi2S3@TaOx-HA). The as-prepared core/shell nanoparticles exhibited a high Bi2S3 nanoparticle loading efficiency of (67 wt %). The TaOx nanoshell exhibited excellent biocompatibility and computed tomography imaging capacity, and the Bi2S3 nanoparticles exhibited an excellent photothermal transducing performance and computed tomography (CT) and photoacoustic imaging capacity. As a result of these merits, the Bi2S3@TaOx core-shell nanoparticles can act as a theranostic agent for CT/photoacoustically monitored enhanced photothermal therapy. These findings will evoke new interest in future cancer therapeutic strategies based on biocompatible functional nanomaterials.

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Jin Y et al.

Integration of TaOx with Bi2S3 for Targeted Multimodality Breast Cancer Theranostics

CancerPreclinicalMSOT

Early identification and treatment of breast cancer is very important for breast conserving therapy and to improve the prognosis and survival rates of patients. Multifunctional nanotheranostic agents are of particular importance in the field of precise nanomedicine, since they can augment the visualization and treatment of cancer. We developed a novel Bi2S3 nanoparticle coated with a hyaluronic acid (HA)-modified tantalum oxide (TaOx) nanoshell (Bi2S3@TaOx-HA). The as-prepared core/shell nanoparticles exhibited a high Bi2S3 nanoparticle loading efficiency of (67 wt %). The TaOx nanoshell exhibited excellent biocompatibility and computed tomography imaging capacity, and the Bi2S3 nanoparticles exhibited an excellent photothermal transducing performance and computed tomography (CT) and photoacoustic imaging capacity. As a result of these merits, the Bi2S3@TaOx core-shell nanoparticles can act as a theranostic agent for CT/photoacoustically monitored enhanced photothermal therapy. These findings will evoke new interest in future cancer therapeutic strategies based on biocompatible functional nanomaterials.

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Sun J et al.

Facile Synthesis of Melanin-Dye Nanoagent for NIR-II Fluorescence/Photoacoustic Imaging-Guided Photothermal Therapy

NanoCancerPreclinicalMSOT

Background : Laryngeal cancer is the second most common type of primary epithelial malignant tumor in the head and neck region, and the development of therapies that are more precise, efficient, and safe is necessary to preserve patient speech and swallowing functions as much as possible. Multi-modal imaging-guided photothermal therapy (PTT) can precisely delineate tumors, monitor the real-time accumulation of photothermal agents at the tumor site, accurately select the optimal region for irradiation, and predict the best time for laser treatment. Compared with exogeneous photothermal agents, endogenous melanin materials have better biosafety in vivo, in terms of native biocompatibility and biodegradability, as well as good near-infrared (NIR) absorbance. An NIR-II dye can be attached to melanin via a facile method, and applying a melanin-dye-based nanoprobe could be an excellent choice for the elimination of superficial laryngeal cancer while avoiding total laryngectomy. Methods : In this work, a promising nanoprobe was constructed using a facile EDC/NHS strategy involving an NIR-II dye and melanin nanoparticles. Results : The nanoprobe exhibited good water solubility, dispersibility, strong NIR-II fluorescence and photoacoustic (PA) signals, and higher photothermal performance. Cellular studies showed that the nanoprobe had low toxicity, excellent biocompatibility, and significantly enhanced imaging properties. After the nanoprobe was intravenously injected into Hep-2 laryngeal xenografts, superior dual-modal images were obtained at various time points, which revealed that the optimal photothermal treatment time was 8 h. Subsequently, PTT was carried out in vivo, and laryngeal tumors were completely eliminated after laser irradiation without any obvious side effects. Conclusion : These results indicate the immense potential of nanoprobes for the NIR-II fluorescence/PA imaging-guided photothermal therapy of laryngeal cancer.

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Sun J et al.

Facile Synthesis of Melanin-Dye Nanoagent for NIR-II Fluorescence/Photoacoustic Imaging-Guided Photothermal Therapy

CancerPreclinicalMSOT

Background : Laryngeal cancer is the second most common type of primary epithelial malignant tumor in the head and neck region, and the development of therapies that are more precise, efficient, and safe is necessary to preserve patient speech and swallowing functions as much as possible. Multi-modal imaging-guided photothermal therapy (PTT) can precisely delineate tumors, monitor the real-time accumulation of photothermal agents at the tumor site, accurately select the optimal region for irradiation, and predict the best time for laser treatment. Compared with exogeneous photothermal agents, endogenous melanin materials have better biosafety in vivo, in terms of native biocompatibility and biodegradability, as well as good near-infrared (NIR) absorbance. An NIR-II dye can be attached to melanin via a facile method, and applying a melanin-dye-based nanoprobe could be an excellent choice for the elimination of superficial laryngeal cancer while avoiding total laryngectomy. Methods : In this work, a promising nanoprobe was constructed using a facile EDC/NHS strategy involving an NIR-II dye and melanin nanoparticles. Results : The nanoprobe exhibited good water solubility, dispersibility, strong NIR-II fluorescence and photoacoustic (PA) signals, and higher photothermal performance. Cellular studies showed that the nanoprobe had low toxicity, excellent biocompatibility, and significantly enhanced imaging properties. After the nanoprobe was intravenously injected into Hep-2 laryngeal xenografts, superior dual-modal images were obtained at various time points, which revealed that the optimal photothermal treatment time was 8 h. Subsequently, PTT was carried out in vivo, and laryngeal tumors were completely eliminated after laser irradiation without any obvious side effects. Conclusion : These results indicate the immense potential of nanoprobes for the NIR-II fluorescence/PA imaging-guided photothermal therapy of laryngeal cancer.

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Wang Z et al.

Chemodynamic/photothermal synergistic therapy based on Ce-doped Cu-Al layered double hydroxides

NanoCancerPreclinicalMSOT

The combination of chemodynamic therapy (CDT) with photothermal therapy (PTT) is an efficacious strategy in cancer treatment to acquire satisfactory therapy efficiency in the endogenous redox reaction and external laser induction. In this work, we have designed Ce doped Cu-Al layered double hydroxide (CAC-LDH) ultrathin them through a bottom-up synthesis method, and further loaded them with indocyanine green (ICG). The synthesized ICG/CAC-LDH was used as a Fenton-catalyst and photothermal agent. With the Fenton activity, the ICG/CAC-LDH nanosheets could decompose H2O2 and exhibit a low KM value (1.57 mM) and an ultra-high Vmax (4.88 × 10-6 M s-1) value. Due to the presence of oxidized metal ions, ICG/CAC-LDH could induce intracellular GSH depletion and reduce Cu2+ and Ce4+ to Cu+ and Ce3+, respectively. The generated Cu+ and Ce3+ further reacted with local H2O2 to generate toxic hydroxyl radicals (˙OH) via the Fenton reaction. Owing to the obviously enhanced absorption of ICG/CAC-LDH at 808 nm, the photothermal efficiency of ICG/CAC-LDH increased significantly compared with ICG (ΔT = 34.7 °C vs. 28.3 °C). In vitro studies substantiate the remarkable CDT/PTT efficacy, with complete apoptosis of HepG2 cancer cells (the cell viability is less than 2%) treated with 25 μg mL-1 of ICG/CAC-LDH. Furthermore, ICG/CAC-LDH could also act as a contrast agent for cancer magnetic resonance imaging (MRI) and photoacoustic imaging (PAI). These results demonstrate the potential of ICG/CAC-LDH as an integrated agent for dual-modal imaging and synergistic CDT/PTT.

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Wang Z et al.

Chemodynamic/photothermal synergistic therapy based on Ce-doped Cu-Al layered double hydroxides

CancerPreclinicalMSOT

The combination of chemodynamic therapy (CDT) with photothermal therapy (PTT) is an efficacious strategy in cancer treatment to acquire satisfactory therapy efficiency in the endogenous redox reaction and external laser induction. In this work, we have designed Ce doped Cu-Al layered double hydroxide (CAC-LDH) ultrathin them through a bottom-up synthesis method, and further loaded them with indocyanine green (ICG). The synthesized ICG/CAC-LDH was used as a Fenton-catalyst and photothermal agent. With the Fenton activity, the ICG/CAC-LDH nanosheets could decompose H2O2 and exhibit a low KM value (1.57 mM) and an ultra-high Vmax (4.88 × 10-6 M s-1) value. Due to the presence of oxidized metal ions, ICG/CAC-LDH could induce intracellular GSH depletion and reduce Cu2+ and Ce4+ to Cu+ and Ce3+, respectively. The generated Cu+ and Ce3+ further reacted with local H2O2 to generate toxic hydroxyl radicals (˙OH) via the Fenton reaction. Owing to the obviously enhanced absorption of ICG/CAC-LDH at 808 nm, the photothermal efficiency of ICG/CAC-LDH increased significantly compared with ICG (ΔT = 34.7 °C vs. 28.3 °C). In vitro studies substantiate the remarkable CDT/PTT efficacy, with complete apoptosis of HepG2 cancer cells (the cell viability is less than 2%) treated with 25 μg mL-1 of ICG/CAC-LDH. Furthermore, ICG/CAC-LDH could also act as a contrast agent for cancer magnetic resonance imaging (MRI) and photoacoustic imaging (PAI). These results demonstrate the potential of ICG/CAC-LDH as an integrated agent for dual-modal imaging and synergistic CDT/PTT.

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Zheng D et al.

Her2-Targeted Multifunctional Nano-Theranostic Platform Mediates Tumor Microenvironment Remodeling and Immune Activation for Breast Cancer Treatment

NanoCancerPreclinicalMSOT

Purpose : The treatment of breast cancer is often ineffective due to the protection of the tumor microenvironment and the low immunogenicity of tumor cells, leading to a poor therapeutic effect. In this study, we designed a nano-theranostic platform for these obstacles: a photothermal effect mediated by a gold shell could remodel the tumor microenvironment by decreasing cancer-associated fibroblasts (CAFs) and promote the release of doxorubicin (DOX) from nanoparticles. In addition, it could realize photoacoustic (PA)/MRI dual-model imaging for diagnose breast cancer and targeted identification of Her2-positive breast cancer. Methods : Her2-DOX-superparamagnetic iron oxide nanoparticles (SPIOs)@Poly (D, L-lactide-co-glycolide) acid (PLGA)@Au nanoparticles (Her2-DSG NPs) were prepared based on a single emulsion oil-in-water (O/W) solvent evaporation method, gold seed growing method, and carbon diimide method. The size distribution, morphology, PA/MRI imaging, drug loading capacity, and drug release were investigated. Cytotoxicity, antitumor effect, cellular uptake, immunogenic cell death (ICD) effect, and targeted performance on human Her2-positive BT474 cell line were investigated in vitro. BT474/Adr cells were constructed and the antitumor effect of NPs on it was evaluated in vitro. Moreover, chemical-photothermal therapy effect, PA/MRI dual-model imaging, ICD effect induced by NPs, and tumor microenvironment remodeling in human BT474 breast cancer nude mice model were also investigated. Results : Nanoparticles were spherical, uniform in size and covered with a gold shell. NPs had a photothermal effect, and can realize photothermal-controlled drug release in vitro. Chemical-photothermal therapy had a good antitumor effect on BT474/Adr cells and on BT474 cells in vitro. The targeting evaluation in vitro showed that Her2-DSG NPs could actively target and identify Her2-positive tumor cells. The PA/MRI imaging was successfully validated in vitro/vivo. Similarly, NPs could enhance the ICD effect in vitro/vivo, which could activate an immune response. Immunofluorescence results also proved that photothermal effect could decrease CAFs to remodel the tumor microenvironment and enhance the accessibility of NPs to tumor cells. According to the toxicity results, targeted drug delivery combined with photothermal-responsive drug release proved that NPs had good biosafety in vivo. Chemical-photothermal therapy of Her2-targeted NPs has a good antitumor effect in the BT474 nude mice model. Conclusion : Our study showed that chemical-photothermal therapy combined with tumor microenvironment remodeling and immune activation based on the Her2-DSG NPs we developed are very promising for Her2-positive breast cancer.

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Zheng D et al.

Her2-Targeted Multifunctional Nano-Theranostic Platform Mediates Tumor Microenvironment Remodeling and Immune Activation for Breast Cancer Treatment

CancerPreclinicalMSOT

Purpose : The treatment of breast cancer is often ineffective due to the protection of the tumor microenvironment and the low immunogenicity of tumor cells, leading to a poor therapeutic effect. In this study, we designed a nano-theranostic platform for these obstacles: a photothermal effect mediated by a gold shell could remodel the tumor microenvironment by decreasing cancer-associated fibroblasts (CAFs) and promote the release of doxorubicin (DOX) from nanoparticles. In addition, it could realize photoacoustic (PA)/MRI dual-model imaging for diagnose breast cancer and targeted identification of Her2-positive breast cancer. Methods : Her2-DOX-superparamagnetic iron oxide nanoparticles (SPIOs)@Poly (D, L-lactide-co-glycolide) acid (PLGA)@Au nanoparticles (Her2-DSG NPs) were prepared based on a single emulsion oil-in-water (O/W) solvent evaporation method, gold seed growing method, and carbon diimide method. The size distribution, morphology, PA/MRI imaging, drug loading capacity, and drug release were investigated. Cytotoxicity, antitumor effect, cellular uptake, immunogenic cell death (ICD) effect, and targeted performance on human Her2-positive BT474 cell line were investigated in vitro. BT474/Adr cells were constructed and the antitumor effect of NPs on it was evaluated in vitro. Moreover, chemical-photothermal therapy effect, PA/MRI dual-model imaging, ICD effect induced by NPs, and tumor microenvironment remodeling in human BT474 breast cancer nude mice model were also investigated. Results : Nanoparticles were spherical, uniform in size and covered with a gold shell. NPs had a photothermal effect, and can realize photothermal-controlled drug release in vitro. Chemical-photothermal therapy had a good antitumor effect on BT474/Adr cells and on BT474 cells in vitro. The targeting evaluation in vitro showed that Her2-DSG NPs could actively target and identify Her2-positive tumor cells. The PA/MRI imaging was successfully validated in vitro/vivo. Similarly, NPs could enhance the ICD effect in vitro/vivo, which could activate an immune response. Immunofluorescence results also proved that photothermal effect could decrease CAFs to remodel the tumor microenvironment and enhance the accessibility of NPs to tumor cells. According to the toxicity results, targeted drug delivery combined with photothermal-responsive drug release proved that NPs had good biosafety in vivo. Chemical-photothermal therapy of Her2-targeted NPs has a good antitumor effect in the BT474 nude mice model. Conclusion : Our study showed that chemical-photothermal therapy combined with tumor microenvironment remodeling and immune activation based on the Her2-DSG NPs we developed are very promising for Her2-positive breast cancer.

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Cai W et al.

NIR-II FL/PA dual-modal imaging long-term tracking of human umbilical cord-derived mesenchymal stem cells labeled with melanin nanoparticles and visible HUMSC-based liver regeneration for acute liver failure

Other ApplicationsPreclinicalMSOT

Acetaminophen (APAP) has been widely used for relieving pain and fever, whilst overdose would lead to the occurrence of acute liver failure (ALF). Currently, few effective treatments are available for ALF in clinic, especially for severe, advanced- or end-stage patients who need liver transplantation. Human umbilical cord-derived mesenchymal stem cells (hUMSCs), as one of the mesenchymal stem cells, not only contribute to relieving hepatotoxicity and promoting hepatocyte regeneration due to their self-renewing, multi-differentiation potential, anti-inflammatory, immunomodulatory and paracrine properties, but possess lower immunomodulatory effects, faster self-renewal properties and noncontroversial ethical concerns, which may play a better role in the treatment of ALF. In this work, hUMSCs were rapidly labeled with near-infrared II fluorescent dye-modified melanin nanoparticles (MNP-PEG-H2), which could realize long-term tracking of hUMSCs by NIR-II fluorescent (FL)/photoacoustic (PA) dual-modal imaging and could visualize hUMSC-based liver regeneration in ALF. The nanoparticles exhibited good dispersibility and biocompatibility, high labeling efficiency for hUMSCs and excellent NIR-II FL/PA imaging performance. Moreover, the MNP-PEG-H2 labeled hUMSCs could be continuously traced in vivo for up to 21 days. After intravenous delivery, the NIR-II FL and PA images revealed that labeled hUMSCs were able to engraft in the injured liver and repair damaged tissue in ALF mice. Therefore, the hUMSCs labeled with endogenous melanin nanoparticles solve the key tracing problem of MSC-based regenerative medicine and realize the visualization of the treatment process, which may provide an efficient, safe and potential choice for ALF.

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Liu F et al.

Synergistic non-bonding interactions based on diketopyrrolo-pyrrole for elevated photoacoustic imaging-guided photothermal therapy

NanoCancerPreclinicalMSOT

Conjugated polymers have excellent properties and can be used in photothermal therapy (PTT). Nevertheless, the concept to design and optimize the photothermal performance by cooperative non-bonding interactions is still in its infancy. Herein, a series of diketopyrrolopyrrole (DPP) derivatives containing chalcogen and fluorine atoms were synthesized to reveal how intra- and intermolecular interactions affect the therapeutic performance of cancer in vitro and in vivo. The synergistic π-π and FH interactions facilitate fluorine and selenium-substituted DPP-SeF to elevate their photothermal conversion efficiency up to 62% from 32% without fluorine and selenium-substituted DPP-SS, and the half-maximal inhibitory concentration drops to ∼8.36 μg mL-1 for DPP-SeF from 15.14 μg mL-1 for DPP-SS on A549 cells under 808 nm light irradiation. More interestingly, efficient tumor killing ability and magnificent biocompatibility on an animal model of A549 transplanted tumor reassert that DPP-SeF nanoagents have immense potential as photoacoustic/PTT agents. Thus, this work presents an efficient phototherapeutic agent, and meanwhile demonstrates the facile concept of accessing the synergistic effect of non-bonding interactions to promote antitumor efficiency by ingenious molecular engineering.

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Cai W et al.

NIR-II FL/PA dual-modal imaging long-term tracking of human umbilical cord-derived mesenchymal stem cells labeled with melanin nanoparticles and visible HUMSC-based liver regeneration for acute liver failure

ToxicityPreclinicalMSOT

Acetaminophen (APAP) has been widely used for relieving pain and fever, whilst overdose would lead to the occurrence of acute liver failure (ALF). Currently, few effective treatments are available for ALF in clinic, especially for severe, advanced- or end-stage patients who need liver transplantation. Human umbilical cord-derived mesenchymal stem cells (hUMSCs), as one of the mesenchymal stem cells, not only contribute to relieving hepatotoxicity and promoting hepatocyte regeneration due to their self-renewing, multi-differentiation potential, anti-inflammatory, immunomodulatory and paracrine properties, but possess lower immunomodulatory effects, faster self-renewal properties and noncontroversial ethical concerns, which may play a better role in the treatment of ALF. In this work, hUMSCs were rapidly labeled with near-infrared II fluorescent dye-modified melanin nanoparticles (MNP-PEG-H2), which could realize long-term tracking of hUMSCs by NIR-II fluorescent (FL)/photoacoustic (PA) dual-modal imaging and could visualize hUMSC-based liver regeneration in ALF. The nanoparticles exhibited good dispersibility and biocompatibility, high labeling efficiency for hUMSCs and excellent NIR-II FL/PA imaging performance. Moreover, the MNP-PEG-H2 labeled hUMSCs could be continuously traced in vivo for up to 21 days. After intravenous delivery, the NIR-II FL and PA images revealed that labeled hUMSCs were able to engraft in the injured liver and repair damaged tissue in ALF mice. Therefore, the hUMSCs labeled with endogenous melanin nanoparticles solve the key tracing problem of MSC-based regenerative medicine and realize the visualization of the treatment process, which may provide an efficient, safe and potential choice for ALF.

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Liu F et al.

Synergistic non-bonding interactions based on diketopyrrolo-pyrrole for elevated photoacoustic imaging-guided photothermal therapy

CancerPreclinicalMSOT

Conjugated polymers have excellent properties and can be used in photothermal therapy (PTT). Nevertheless, the concept to design and optimize the photothermal performance by cooperative non-bonding interactions is still in its infancy. Herein, a series of diketopyrrolopyrrole (DPP) derivatives containing chalcogen and fluorine atoms were synthesized to reveal how intra- and intermolecular interactions affect the therapeutic performance of cancer in vitro and in vivo. The synergistic π-π and FH interactions facilitate fluorine and selenium-substituted DPP-SeF to elevate their photothermal conversion efficiency up to 62% from 32% without fluorine and selenium-substituted DPP-SS, and the half-maximal inhibitory concentration drops to ∼8.36 μg mL-1 for DPP-SeF from 15.14 μg mL-1 for DPP-SS on A549 cells under 808 nm light irradiation. More interestingly, efficient tumor killing ability and magnificent biocompatibility on an animal model of A549 transplanted tumor reassert that DPP-SeF nanoagents have immense potential as photoacoustic/PTT agents. Thus, this work presents an efficient phototherapeutic agent, and meanwhile demonstrates the facile concept of accessing the synergistic effect of non-bonding interactions to promote antitumor efficiency by ingenious molecular engineering.

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Hua S et al.

Multistage-responsive clustered nanosystem to improve tumor accumulation and penetration for photothermal/enhanced radiation synergistic therapy

NanoCancerPreclinicalMSOT

Developing new strategies to overcome biological barriers and achieve efficient delivery of therapeutic nanoparticles (NPs) is the key to achieve positive therapeutic outcomes in nanomedicine. Herein, a multistage-responsive clustered nanosystem is designed to systematically resolve the multiple tumor biological barriers conflict between the enhanced permeability retention (EPR) effect and spatially uniform penetration of the nanoparticles. The nanosystem with desirable diameter (initial size of ~50 nm), which is favorable for long blood circulation and high propensity of extravasation through tumor vascular interstices, can accumulate effectively around the tumor tissue through the EPR effect. Then, these pH-responsive nanoparticles are conglomerated to form large-sized aggregates (~1000 nm) in the tumor under the acidic microenvironment, and demonstrated great tumor retention. Subsequently, the photothermal treatment disperses the aggregates to be ultrasmall gold nanoclusters (~5 nm), thereby improving their tumor penetration ability, and enhancing the radiotherapeutic effect by radiosensitizer. In 4T1 tumor model, this nanosystem shows great tumor accumulation and penetration, and the tumor growth and the lung/liver metastasis in particle/PTT/RT treated mice is significantly inhibited. As a photoacoustic/fluorescence imaging agent and PT/RT synergistic agent, this pH-/laser-triggered size multistage-responsive nanosystem displayes both great tumor accumulation and penetration abilities, and shows excellent potential in tumor therapy.

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Hua S et al.

Multistage-responsive clustered nanosystem to improve tumor accumulation and penetration for photothermal/enhanced radiation synergistic therapy

CancerPreclinicalMSOT

Developing new strategies to overcome biological barriers and achieve efficient delivery of therapeutic nanoparticles (NPs) is the key to achieve positive therapeutic outcomes in nanomedicine. Herein, a multistage-responsive clustered nanosystem is designed to systematically resolve the multiple tumor biological barriers conflict between the enhanced permeability retention (EPR) effect and spatially uniform penetration of the nanoparticles. The nanosystem with desirable diameter (initial size of ~50 nm), which is favorable for long blood circulation and high propensity of extravasation through tumor vascular interstices, can accumulate effectively around the tumor tissue through the EPR effect. Then, these pH-responsive nanoparticles are conglomerated to form large-sized aggregates (~1000 nm) in the tumor under the acidic microenvironment, and demonstrated great tumor retention. Subsequently, the photothermal treatment disperses the aggregates to be ultrasmall gold nanoclusters (~5 nm), thereby improving their tumor penetration ability, and enhancing the radiotherapeutic effect by radiosensitizer. In 4T1 tumor model, this nanosystem shows great tumor accumulation and penetration, and the tumor growth and the lung/liver metastasis in particle/PTT/RT treated mice is significantly inhibited. As a photoacoustic/fluorescence imaging agent and PT/RT synergistic agent, this pH-/laser-triggered size multistage-responsive nanosystem displayes both great tumor accumulation and penetration abilities, and shows excellent potential in tumor therapy.

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Gao Y et al.

Terselenophene Regioisomer Conjugated Polymer Materials for High-Performance Cancer Phototheranostics

CancerPreclinicalMSOT

Molecular isomerization is a fundamental issue in the development of functional materials, with a crucial impact on photophysical properties. However, up to now, their effect on photothermal conversion is rarely investigated. Here, two near-infrared (NIR)-absorbing regioisomer conjugated polymers integrated with cis/trans-terselenophenes are designed and synthesized as efficient photothermal agents to enhance cancer phototheranostics. It is demonstrated that enhanced quinoidal resonance of trans-terselenophenes allows the resulting trans-CP to possess more planar backbone to further increase the effective conjugation length and result in the strong absorption spectra at 808 nm. Characterization of photophysical properties has proved that the photothermal conversion efficiency of trans-CP nanoparticles is up to 61.4%, and they are 210% as strong as cis-CP nanoparticles (29.4%). Further in vitro and in vivo works demonstrate efficient photothermal therapeutic effects with the guidance of photoacoustic imaging. This work affords a new understanding of the molecular isomerization into the development of conjugated materials for high-performance cancer phototheranostics.

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Serkova NJ et al.

Preclinical Applications of Multi-Platform Imaging in Animal Models of Cancer

CancerPreclinicalMSOT

In animal models of cancer, oncologic imaging has evolved from a simple assessment of tumor location and size to sophisticated multi-modality exploration of molecular, physiological, genetic, immunological and biochemical events at microscopic to macroscopic levels, performed non-invasively and sometimes in real time. We briefly review animal imaging technology and molecular imaging probes together with selected applications from recent literature. Fast and sensitive optical imaging is primarily used to track luciferase-expressing tumor cells, image molecular targets with fluorescent probes, and report on metabolic and physiological phenotypes using smart switchable luminescent probes. MicroPET/ SPECT have proven to be two of the most translational modalities for molecular and metabolic imaging of cancers: Immuno-PET is a promising and rapidly evolving area of imaging research. Sophisticated MRI techniques provide high-resolution images of small metastases, tumor inflammation, perfusion, oxygenation and acidity. Disseminated tumors to the bone and lung are easily detected by microCT, while ultrasound provides real-time visualization of tumor vasculature and perfusion. Recently available photoacoustic imaging provides real time evaluation of vascular patency, oxygenation, and nanoparticle distributions. New hybrid instruments such as PET-MRI promise more convenient combination of the capabilities of each modality, enabling enhanced research efficacy and throughput.

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Gao Y et al.

Terselenophene Regioisomer Conjugated Polymer Materials for High-Performance Cancer Phototheranostics

CancerPreclinicalMSOT

Molecular isomerization is a fundamental issue in the development of functional materials, with a crucial impact on photophysical properties. However, up to now, their effect on photothermal conversion is rarely investigated. Here, two near-infrared (NIR)-absorbing regioisomer conjugated polymers integrated with cis/trans-terselenophenes are designed and synthesized as efficient photothermal agents to enhance cancer phototheranostics. It is demonstrated that enhanced quinoidal resonance of trans-terselenophenes allows the resulting trans-CP to possess more planar backbone to further increase the effective conjugation length and result in the strong absorption spectra at 808 nm. Characterization of photophysical properties has proved that the photothermal conversion efficiency of trans-CP nanoparticles is up to 61.4%, and they are 210% as strong as cis-CP nanoparticles (29.4%). Further in vitro and in vivo works demonstrate efficient photothermal therapeutic effects with the guidance of photoacoustic imaging. This work affords a new understanding of the molecular isomerization into the development of conjugated materials for high-performance cancer phototheranostics.

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Serkova NJ et al.

Preclinical Applications of Multi-Platform Imaging in Animal Models of Cancer

CancerPreclinicalMSOT

In animal models of cancer, oncologic imaging has evolved from a simple assessment of tumor location and size to sophisticated multi-modality exploration of molecular, physiological, genetic, immunological and biochemical events at microscopic to macroscopic levels, performed non-invasively and sometimes in real time. We briefly review animal imaging technology and molecular imaging probes together with selected applications from recent literature. Fast and sensitive optical imaging is primarily used to track luciferase-expressing tumor cells, image molecular targets with fluorescent probes, and report on metabolic and physiological phenotypes using smart switchable luminescent probes. MicroPET/ SPECT have proven to be two of the most translational modalities for molecular and metabolic imaging of cancers: Immuno-PET is a promising and rapidly evolving area of imaging research. Sophisticated MRI techniques provide high-resolution images of small metastases, tumor inflammation, perfusion, oxygenation and acidity. Disseminated tumors to the bone and lung are easily detected by microCT, while ultrasound provides real-time visualization of tumor vasculature and perfusion. Recently available photoacoustic imaging provides real time evaluation of vascular patency, oxygenation, and nanoparticle distributions. New hybrid instruments such as PET-MRI promise more convenient combination of the capabilities of each modality, enabling enhanced research efficacy and throughput.

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Zhan C et al.

A dopamine-precursor-based nanoprodrug for in-situ drug release and treatment of acute liver failure by inhibiting NLRP3 inflammasome and facilitating liver regeneration

Other ApplicationsPreclinicalMSOT

Acute liver failure (ALF) is a severe liver disease with high mortality rate. Inflammasome is a newly-found and promising target for effective treatment of immunity-associated diseases including liver disease, and dopamine has recently been proved as an inhibitor for NLRP3 inflammasome. This work demonstrates a diselenide-based nanodrug for ALF treatment through inhibiting NLRP3 inflammasome activation and enhancing liver regeneration. A diselenide-containing molecule (DSeSeD) has been synthesized via covalently linking two l-Dopa molecules to a diselenide linker, and the resultant molecules form stable nanoparticles in aqueous media and encapsulate SW033291 (an inhibitor of prostaglandin-degrading enzyme that hampers liver regeneration) to produce the nanodrug (SW@DSeSeD). As a nanoscale prodrug, SW@DSeSeD protects its payloads from decomposition in bloodstream upon administration, accumulates in liver of ALF mice, then responds to the overexpressed ROS and thereby releases SW033291 as well as a stable dopamine precursor that can transform into dopamine in hepatic cells, thus achieving significant therapeutic efficacy against ALF through inhibiting NLRP3 inflammasome activation and enhancing hepatic regeneration. Moreover, multiple contrast agents have been loaded onto the nanodrug to achieve fluorescence, optoacoustic and magnetic resonance imaging for nanodrug location and disease evaluation.

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Zheng Z et al.

Biodegradable Multifunctional Nanotheranostic Based on Ag2S-Doped Hollow BSA-SiO2 for Enhancing ROS-Feedback Synergistic Antitumor Therapy

NanoCancerPreclinicalMSOT

Stimuli-responsive silica nanoparticles are an attractive therapeutic agent for effective tumor ablation, but the responsiveness of silica nanoagents is limited by intrastimulation level and silica framework structure. Herein, a biodegradable hollow SiO2-based nanosystem (Ag2S-GOx@BHS NYs) is developed by a novel one-step dual-template (bovine serum albumin (BSA) and cetyltrimethylammonium bromide (CTAB)) synthetic strategy for image-guided therapy. The Ag2S-GOx@BHS NYs can be specifically activated in the tumor microenvironment via a self-feedback mechanism to achieve reactive oxygen species (ROS)-induced multistep therapy. In response to the inherent acidity and H2O2 at the tumor sites, Ag2S-GOx@BHS would accelerate the structural degradation while releasing glucose oxidase (GOx), which could efficiently deplete intratumoral glucose to copious amounts of gluconic acid and H2O2. More importantly, the sufficient H2O2 not only acts as a reactant to generate Ag+ from Ag2S for metal-ion therapy and improves the oxidative stress but also combines with gluconic acid results in the self-accelerating degradation process. Moreover, the released Ag2S nanoparticles can help the Ag2S-GOx@BHS NYs realize the second near-infrared window fluorescence (NIR-II FL) and photoacoustic (PA) imaging-guided precise photothermal therapy (PTT). Taken together, the development of a self-feedback nanosystem may open up a new dimension for a highly effective multistep tumor therapy.

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Zhan C et al.

A dopamine-precursor-based nanoprodrug for in-situ drug release and treatment of acute liver failure by inhibiting NLRP3 inflammasome and facilitating liver regeneration

ToxicityPreclinicalMSOT

Acute liver failure (ALF) is a severe liver disease with high mortality rate. Inflammasome is a newly-found and promising target for effective treatment of immunity-associated diseases including liver disease, and dopamine has recently been proved as an inhibitor for NLRP3 inflammasome. This work demonstrates a diselenide-based nanodrug for ALF treatment through inhibiting NLRP3 inflammasome activation and enhancing liver regeneration. A diselenide-containing molecule (DSeSeD) has been synthesized via covalently linking two l-Dopa molecules to a diselenide linker, and the resultant molecules form stable nanoparticles in aqueous media and encapsulate SW033291 (an inhibitor of prostaglandin-degrading enzyme that hampers liver regeneration) to produce the nanodrug (SW@DSeSeD). As a nanoscale prodrug, SW@DSeSeD protects its payloads from decomposition in bloodstream upon administration, accumulates in liver of ALF mice, then responds to the overexpressed ROS and thereby releases SW033291 as well as a stable dopamine precursor that can transform into dopamine in hepatic cells, thus achieving significant therapeutic efficacy against ALF through inhibiting NLRP3 inflammasome activation and enhancing hepatic regeneration. Moreover, multiple contrast agents have been loaded onto the nanodrug to achieve fluorescence, optoacoustic and magnetic resonance imaging for nanodrug location and disease evaluation.

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Zheng Z et al.

Biodegradable Multifunctional Nanotheranostic Based on Ag2S-Doped Hollow BSA-SiO2 for Enhancing ROS-Feedback Synergistic Antitumor Therapy

CancerPreclinicalMSOT

Stimuli-responsive silica nanoparticles are an attractive therapeutic agent for effective tumor ablation, but the responsiveness of silica nanoagents is limited by intrastimulation level and silica framework structure. Herein, a biodegradable hollow SiO2-based nanosystem (Ag2S-GOx@BHS NYs) is developed by a novel one-step dual-template (bovine serum albumin (BSA) and cetyltrimethylammonium bromide (CTAB)) synthetic strategy for image-guided therapy. The Ag2S-GOx@BHS NYs can be specifically activated in the tumor microenvironment via a self-feedback mechanism to achieve reactive oxygen species (ROS)-induced multistep therapy. In response to the inherent acidity and H2O2 at the tumor sites, Ag2S-GOx@BHS would accelerate the structural degradation while releasing glucose oxidase (GOx), which could efficiently deplete intratumoral glucose to copious amounts of gluconic acid and H2O2. More importantly, the sufficient H2O2 not only acts as a reactant to generate Ag+ from Ag2S for metal-ion therapy and improves the oxidative stress but also combines with gluconic acid results in the self-accelerating degradation process. Moreover, the released Ag2S nanoparticles can help the Ag2S-GOx@BHS NYs realize the second near-infrared window fluorescence (NIR-II FL) and photoacoustic (PA) imaging-guided precise photothermal therapy (PTT). Taken together, the development of a self-feedback nanosystem may open up a new dimension for a highly effective multistep tumor therapy.

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Wang L et al.

Exploiting Co Defects in CoFe-Layered Double Hydroxide (CoFe-LDH) Derivatives for Highly Efficient Photothermal Cancer Therapy

NanoCancerPreclinicalMSOT

Currently, two-dimensional materials are being actively pursued in catalysis and other fields due their abundance of defects, which results in enhanced performance relative to their bulk defect-free counterparts. To date, the exploitation of defects in two-dimensional materials to enhance photothermal therapies has received little attention, motivating a detailed investigation. Herein, we successfully fabricated a series of novel CoFe-based photothermal agents (CoFe-x) by heating CoFe-layered double hydroxide (CoFe-LDH) nanosheets at different temperatures (x) between 200-800 °C under a Ar atmosphere. The CoFe-x products differed in their particle size, cobalt defect concentration, and electronic structure, with the CoFe-500 product containing the highest concentration of Co2+ defects and most efficient photothermal performance under near-infrared (NIR, 808 nm) irradiation. Experiments and density functional theory (DFT) calculations revealed that Co2+ defects modify the electronic structure of CoFe-x, narrowing the band gap and thus increasing the nonradiative recombination rate, thereby improving the NIR-driven photothermal properties. In vitro and in vivo results demonstrated that CoFe-500 was an efficient agent for photothermal cancer treatment and also near-infrared (NIR) thermal imaging, magnetic resonance (MR) imaging, and photoacoustic (PA) imaging. This work provides valuable new insights about the role of defects in the rational design of nanoagents with optimized structures for improved cancer therapy.

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Li S et al.

Delicately Designed Cancer Cell Membrane-Camouflaged Nanoparticles for Targeted 19F MR/PA/FL Imaging-Guided Photothermal Therapy

NanoCancerPreclinicalMSOT

Our exploration of multimodal nanoprobes aims to combine photoacoustic (PA) imaging, 19F magnetic resonance (MR), and fluorescence (FL) imaging, which offers complementary advantages such as high spatial resolution, unlimited penetration, and high sensitivity to enable more refined images for accurate tumor diagnoses. In this research, perfluorocarbons (PFCs) and indocyanine green (ICG) are encapsulated by poly(lactic-co-glycolic acid) (PLGA) for intravital 19F MR/FL/PA tri-modal imaging-guided photothermal therapy. Then, it is coated with an A549 cancer cell membrane (AM) to fabricate versatile theranostic nanoprobes (AM-PP@ICGNPs). After systemic administration, FLI reveals time-dependent tumor homing of NPs with high sensitivity, 19F MRI provides tumor localization of NPs without background signal interference, and PAI illustrates the detailed distribution of NPs inside the tumor with high spatial resolution. What is more, AM-PP@ICGNPs accumulated in the tumor area exhibit a prominent photothermal effect (48.4 °C) under near infrared (NIR) laser irradiation and realize an enhanced antitumor response in vivo. These benefits, in combination with the excellent biocompatibility, make AM-PP@ICGNPs a potential theranostic nanoagent for accurate tumor localization and ultimately achieve superior cancer therapy.

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Li S et al.

Delicately Designed Cancer Cell Membrane-Camouflaged Nanoparticles for Targeted 19F MR/PA/FL Imaging-Guided Photothermal Therapy

CancerPreclinicalMSOT

Our exploration of multimodal nanoprobes aims to combine photoacoustic (PA) imaging, 19F magnetic resonance (MR), and fluorescence (FL) imaging, which offers complementary advantages such as high spatial resolution, unlimited penetration, and high sensitivity to enable more refined images for accurate tumor diagnoses. In this research, perfluorocarbons (PFCs) and indocyanine green (ICG) are encapsulated by poly(lactic-co-glycolic acid) (PLGA) for intravital 19F MR/FL/PA tri-modal imaging-guided photothermal therapy. Then, it is coated with an A549 cancer cell membrane (AM) to fabricate versatile theranostic nanoprobes (AM-PP@ICGNPs). After systemic administration, FLI reveals time-dependent tumor homing of NPs with high sensitivity, 19F MRI provides tumor localization of NPs without background signal interference, and PAI illustrates the detailed distribution of NPs inside the tumor with high spatial resolution. What is more, AM-PP@ICGNPs accumulated in the tumor area exhibit a prominent photothermal effect (48.4 °C) under near infrared (NIR) laser irradiation and realize an enhanced antitumor response in vivo. These benefits, in combination with the excellent biocompatibility, make AM-PP@ICGNPs a potential theranostic nanoagent for accurate tumor localization and ultimately achieve superior cancer therapy.

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Wang L et al.

Exploiting Co Defects in CoFe-Layered Double Hydroxide (CoFe-LDH) Derivatives for Highly Efficient Photothermal Cancer Therapy

CancerPreclinicalMSOT

Currently, two-dimensional materials are being actively pursued in catalysis and other fields due their abundance of defects, which results in enhanced performance relative to their bulk defect-free counterparts. To date, the exploitation of defects in two-dimensional materials to enhance photothermal therapies has received little attention, motivating a detailed investigation. Herein, we successfully fabricated a series of novel CoFe-based photothermal agents (CoFe-x) by heating CoFe-layered double hydroxide (CoFe-LDH) nanosheets at different temperatures (x) between 200-800 °C under a Ar atmosphere. The CoFe-x products differed in their particle size, cobalt defect concentration, and electronic structure, with the CoFe-500 product containing the highest concentration of Co2+ defects and most efficient photothermal performance under near-infrared (NIR, 808 nm) irradiation. Experiments and density functional theory (DFT) calculations revealed that Co2+ defects modify the electronic structure of CoFe-x, narrowing the band gap and thus increasing the nonradiative recombination rate, thereby improving the NIR-driven photothermal properties. In vitro and in vivo results demonstrated that CoFe-500 was an efficient agent for photothermal cancer treatment and also near-infrared (NIR) thermal imaging, magnetic resonance (MR) imaging, and photoacoustic (PA) imaging. This work provides valuable new insights about the role of defects in the rational design of nanoagents with optimized structures for improved cancer therapy.

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Hallasch S et al.

MSOT might be a helpful tool for noninvasive early diagnosis of psoriatic arthritis

InflammationClinicalMSOT

Currently used imaging methods for diagnosis of psoriatic arthritis (PsA) frequently come along with exposure to radiation and can often only show long-term effects of the disease. The aim of the study was to check the feasibility of a new optoacoustic imaging method to identify PsA. 22 psoriasis patients and 19 healthy volunteers underwent examination using multispectral optoacoustic tomography (MSOT). The presence of arthritis was assessed via quantification of optoacoustic signal intensity of the endogenous chromophores oxy- and deoxyhemoglobin. We conducted high-resolution real-time ultrasound images of the finger joints. The semi quantitative analysis of the optoacoustic signals for both hemoglobin species showed a significant higher blood content and oxygenation in PsA patients compared to healthy controls. Our results indicate that MSOT might allow detection of inflammation in an early stage. If the data is further confirmed, this technique might be a suitable tool to avoid delay of diagnosis of PsA.

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MacCuaig WM et al.

Development of Multispectral Optoacoustic Tomography as a Clinically Translatable Modality for Cancer Imaging

CancerClinicalMSOT

The use of optoacoustic imaging takes advantage of the photoacoustic effect to generate high-contrast, high-resolution medical images at penetration depths of up to 5 cm. Multispectral optoacoustic tomography (MSOT) is a type of optoacoustic imaging system that has seen promising preclinical success with a recent emergence into the clinic. Multiwavelength illumination of tissue allows for the mapping of multiple chromophores, which are generated endogenously or exogenously. However, translation of MSOT to the clinic is still in its preliminary stages. For successful translation, MSOT requires refinement of probes and data-acquisition systems to tailor to the human body, along with more intuitive, real-time visualization settings. The possibilities of optoacoustic imaging, namely MSOT, in the clinic are reviewed here.

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MacCuaig WM et al.

Development of Multispectral Optoacoustic Tomography as a Clinically Translatable Modality for Cancer Imaging

CancerClinicalMSOT

The use of optoacoustic imaging takes advantage of the photoacoustic effect to generate high-contrast, high-resolution medical images at penetration depths of up to 5 cm. Multispectral optoacoustic tomography (MSOT) is a type of optoacoustic imaging system that has seen promising preclinical success with a recent emergence into the clinic. Multiwavelength illumination of tissue allows for the mapping of multiple chromophores, which are generated endogenously or exogenously. However, translation of MSOT to the clinic is still in its preliminary stages. For successful translation, MSOT requires refinement of probes and data-acquisition systems to tailor to the human body, along with more intuitive, real-time visualization settings. The possibilities of optoacoustic imaging, namely MSOT, in the clinic are reviewed here.

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Joseph J et al.

DNA-Based Nanocarriers to Enhance the Optoacoustic Contrast of Tumors In Vivo

NanoCancerPreclinicalMSOT

Optoacoustic tomography (OT) enables non-invasive deep tissue imaging of optical contrast at high spatio-temporal resolution. The applications of OT in cancer imaging often rely on the use of molecular imaging contrast agents based on near-infrared (NIR) dyes to enhance contrast at the tumor site. While these agents afford excellent biocompatibility and minimal toxicity, they present limited optoacoustic signal generation capability and rapid renal clearance, which can impede their tumor imaging efficacy. In this work, a synthetic strategy to overcome these limitations utilizing biodegradable DNA-based nanocarrier (DNA-NC) platforms is introduced. DNA-NCs enable the incorporation of NIR dyes (in this case, IRDye 800CW) at precise positions to enable fluorescence quenching and maximize optoacoustic signal generation. Furthermore, these DNA-NCs show a prolonged blood circulation compared to the native fluorophores, facilitating tumor accumulation by the enhanced permeability and retention (EPR) effect. In vivo imaging of tumor xenografts in mice following intravenous administration of DNA-NCs reveals enhanced OT signals at 24 h when compared to free fluorophores, indicating promise for this method to enhance the optoacoustic signal generation capability and tumor uptake of clinically relevant NIR dyes.

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Joseph J et al.

DNA-Based Nanocarriers to Enhance the Optoacoustic Contrast of Tumors In Vivo

CancerPreclinicalMSOT

Optoacoustic tomography (OT) enables non-invasive deep tissue imaging of optical contrast at high spatio-temporal resolution. The applications of OT in cancer imaging often rely on the use of molecular imaging contrast agents based on near-infrared (NIR) dyes to enhance contrast at the tumor site. While these agents afford excellent biocompatibility and minimal toxicity, they present limited optoacoustic signal generation capability and rapid renal clearance, which can impede their tumor imaging efficacy. In this work, a synthetic strategy to overcome these limitations utilizing biodegradable DNA-based nanocarrier (DNA-NC) platforms is introduced. DNA-NCs enable the incorporation of NIR dyes (in this case, IRDye 800CW) at precise positions to enable fluorescence quenching and maximize optoacoustic signal generation. Furthermore, these DNA-NCs show a prolonged blood circulation compared to the native fluorophores, facilitating tumor accumulation by the enhanced permeability and retention (EPR) effect. In vivo imaging of tumor xenografts in mice following intravenous administration of DNA-NCs reveals enhanced OT signals at 24 h when compared to free fluorophores, indicating promise for this method to enhance the optoacoustic signal generation capability and tumor uptake of clinically relevant NIR dyes.

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Wagner AL et al.

Precision of handheld multispectral optoacoustic tomography for muscle imaging

Other ApplicationsClinicalMSOT

Photo-or optoacoustic imaging (OAI) allows quantitative imaging of target tissues. Using multi-wavelength illumination with subsequent ultrasound detection, it may visualize a variety of different chromophores at centimeter depth. Despite its non-invasive, label-free advantages, the precision of repeated measurements for clinical applications is still elusive. We present a multilayer analysis of n = 1920 imaging datasets obtained from a prospective clinical trial (NCT03979157) in n = 10 healthy adult volunteers. All datasets were analyzed for 13 single wavelengths (SWL) between 660 nm-1210 nm and five MSOT-parameters (deoxygenated/oxygenated/total hemoglobin, collagen and lipid) by a semi-automated batch mode software. Intraclass correlation coefficients (ICC) were good to excellent for intrarater (SWL: 0.82-0.92; MSOT-parameter: 0.72-0.92) and interrater reproducibility (SWL: 0.79-0.87; MSOT-parameter: 0.78-0.86), with the exception for MSOT-parameter lipid (interrater ICC: 0.56). Results were stable over time, but exercise-related effects as well as inter-and intramuscular variability were observed. The findings of this study provide a framework for further clinical OAI implementation.

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Wagner AL et al.

Precision of handheld multispectral optoacoustic tomography for muscle imaging

FibrosisClinicalMSOT

Photo-or optoacoustic imaging (OAI) allows quantitative imaging of target tissues. Using multi-wavelength illumination with subsequent ultrasound detection, it may visualize a variety of different chromophores at centimeter depth. Despite its non-invasive, label-free advantages, the precision of repeated measurements for clinical applications is still elusive. We present a multilayer analysis of n = 1920 imaging datasets obtained from a prospective clinical trial (NCT03979157) in n = 10 healthy adult volunteers. All datasets were analyzed for 13 single wavelengths (SWL) between 660 nm-1210 nm and five MSOT-parameters (deoxygenated/oxygenated/total hemoglobin, collagen and lipid) by a semi-automated batch mode software. Intraclass correlation coefficients (ICC) were good to excellent for intrarater (SWL: 0.82-0.92; MSOT-parameter: 0.72-0.92) and interrater reproducibility (SWL: 0.79-0.87; MSOT-parameter: 0.78-0.86), with the exception for MSOT-parameter lipid (interrater ICC: 0.56). Results were stable over time, but exercise-related effects as well as inter-and intramuscular variability were observed. The findings of this study provide a framework for further clinical OAI implementation.

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Ren W et al.

Development of concurrent magnetic resonance imaging and volumetric optoacoustic tomography - a phantom feasibility study

TechnologyPreclinicalMSOT

Optoacoustic tomography (OAT) and magnetic resonance imaging (MRI) provide highly complementary capabilities for anatomical and functional imaging of living organisms. Herein, we investigate on the feasibility of combining both modalities to render concurrent images. This was achieved by introducing a specifically-designed copper-shielded spherical ultrasound array into a preclinical MRI scanner. Phantom experiments revealed that the OAT probe caused minimal distortion in the MRI images, while synchronization of the laser and the MRI pulse sequence enabled defining artifact-free acquisition windows for OAT. Good dynamic OAT contrast from superparamagnetic iron oxide nanoparticles, a commonly used agent for MRI contrast enhancement, was also observed. The hybrid OAT-MRI system thus provides an excellent platform for cross-validating functional readings of both modalities. Overall, this initial study serves to establish the technical feasibility of developing a hybrid OAT-MRI system for biomedical research.

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Ren W et al.

Development of concurrent magnetic resonance imaging and volumetric optoacoustic tomography - a phantom feasibility study

TechnologyPreclinicalMSOT

Optoacoustic tomography (OAT) and magnetic resonance imaging (MRI) provide highly complementary capabilities for anatomical and functional imaging of living organisms. Herein, we investigate on the feasibility of combining both modalities to render concurrent images. This was achieved by introducing a specifically-designed copper-shielded spherical ultrasound array into a preclinical MRI scanner. Phantom experiments revealed that the OAT probe caused minimal distortion in the MRI images, while synchronization of the laser and the MRI pulse sequence enabled defining artifact-free acquisition windows for OAT. Good dynamic OAT contrast from superparamagnetic iron oxide nanoparticles, a commonly used agent for MRI contrast enhancement, was also observed. The hybrid OAT-MRI system thus provides an excellent platform for cross-validating functional readings of both modalities. Overall, this initial study serves to establish the technical feasibility of developing a hybrid OAT-MRI system for biomedical research.

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Dutta R et al.

Brilliant cresyl blue enhanced optoacoustic imaging enables non-destructive imaging of mammalian ovarian follicles for artificial reproduction

Other ApplicationsPreclinicalMSOT

In the field of reproductive biology, there is a strong need for a suitable tool capable of non-destructive evaluation of oocyte viability and function. We studied the application of brilliant cresyl blue (BCB) as an intra-vital exogenous contrast agent using multispectral optoacoustic tomography (MSOT) for visualization of porcine ovarian follicles. The technique provided excellent molecular sensitivity, enabling the selection of competent oocytes without disrupting the follicles. We further conducted in vitro embryo culture, molecular analysis (real-time and reverse transcriptase polymerase chain reaction) and DNA fragmentation analysis to comprehensively establish the safety of BCB-enhanced MSOT imaging in monitoring oocyte viability. Overall, the experimental results suggest that the method offers a significant advance in the use of contrast agents and molecular imaging for reproductive studies. Our technique improves the accurate prediction of ovarian reserve significantly and, once standardized for in vivo imaging, could provide an effective tool for clinical infertility management.

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Dutta R et al.

Brilliant cresyl blue enhanced optoacoustic imaging enables non-destructive imaging of mammalian ovarian follicles for artificial reproduction

OtherPreclinicalMSOT

In the field of reproductive biology, there is a strong need for a suitable tool capable of non-destructive evaluation of oocyte viability and function. We studied the application of brilliant cresyl blue (BCB) as an intra-vital exogenous contrast agent using multispectral optoacoustic tomography (MSOT) for visualization of porcine ovarian follicles. The technique provided excellent molecular sensitivity, enabling the selection of competent oocytes without disrupting the follicles. We further conducted in vitro embryo culture, molecular analysis (real-time and reverse transcriptase polymerase chain reaction) and DNA fragmentation analysis to comprehensively establish the safety of BCB-enhanced MSOT imaging in monitoring oocyte viability. Overall, the experimental results suggest that the method offers a significant advance in the use of contrast agents and molecular imaging for reproductive studies. Our technique improves the accurate prediction of ovarian reserve significantly and, once standardized for in vivo imaging, could provide an effective tool for clinical infertility management.

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Zhu C et al.

Full-spectrum responsive ZrO2-based phototheranostic agent for NIR-II photoacoustic imaging-guided cancer phototherapy

NanoCancerPreclinicalMSOT

Second near-infrared (NIR-II) window responsive phototheranostic agents have a precise spatiotemporal potential for the diagnosis and treatment of cancer. In this study, a full-spectrum responsive ZrO2-based phototheranostic agent was found to achieve NIR-II photoacoustic (PA) imaging-guided tumour-targeting phototherapy. Initially, the ZrO2-based phototheranostic agent was fabricated through NaBH4 reduction to form boron-doped oxygen-deficient zirconia (ZrO2-x-B), an amino-functionalised SiO2 shell and a further covalent connection with hyaluronic acid (HA), namely, ZrO2-x-B@SiO2-HA. In the ZrO2-x-B@SiO2-HA system, the oxygen vacancy and boron doping resulted in full-spectrum absorption, enabling a high NIR-II photothermal conversion, high-resolution PA imaging ability and a remarkable production of reactive oxygen species (ROS). The surface modification of HA provided ZrO2-x-B@SiO2-HA with water dispersibility and a targeting capability for CD44 overexpressed cancer cells. Furthermore, in vitro and in vivo experiments showed that NIR-II activated ZrO2-x-B@SiO2-HA had a targeted photothermal/photodynamic effect for cancer elimination under the real-time guidance of NIR-II PAs. Hence, ZrO2-x-B@SiO2-HA displays a precise NIR-II radiation-activated phototheranostic potential for PA imaging-guided cancer-targeting photothermal/photodynamic therapy.

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Zhu C et al.

Full-spectrum responsive ZrO2-based phototheranostic agent for NIR-II photoacoustic imaging-guided cancer phototherapy

CancerPreclinicalMSOT

Second near-infrared (NIR-II) window responsive phototheranostic agents have a precise spatiotemporal potential for the diagnosis and treatment of cancer. In this study, a full-spectrum responsive ZrO2-based phototheranostic agent was found to achieve NIR-II photoacoustic (PA) imaging-guided tumour-targeting phototherapy. Initially, the ZrO2-based phototheranostic agent was fabricated through NaBH4 reduction to form boron-doped oxygen-deficient zirconia (ZrO2-x-B), an amino-functionalised SiO2 shell and a further covalent connection with hyaluronic acid (HA), namely, ZrO2-x-B@SiO2-HA. In the ZrO2-x-B@SiO2-HA system, the oxygen vacancy and boron doping resulted in full-spectrum absorption, enabling a high NIR-II photothermal conversion, high-resolution PA imaging ability and a remarkable production of reactive oxygen species (ROS). The surface modification of HA provided ZrO2-x-B@SiO2-HA with water dispersibility and a targeting capability for CD44 overexpressed cancer cells. Furthermore, in vitro and in vivo experiments showed that NIR-II activated ZrO2-x-B@SiO2-HA had a targeted photothermal/photodynamic effect for cancer elimination under the real-time guidance of NIR-II PAs. Hence, ZrO2-x-B@SiO2-HA displays a precise NIR-II radiation-activated phototheranostic potential for PA imaging-guided cancer-targeting photothermal/photodynamic therapy.

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Lafci B et al.

Noninvasive multiparametric characterization of mammary tumors with transmission-reflection optoacoustic ultrasound

CancerPreclinicalMSOT

Development of imaging methods capable of furnishing tumor-specific morphological, functional, and molecular information is paramount for early diagnosis, staging, and treatment of breast cancer. Ultrasound (US) and optoacoustic (OA) imaging methods exhibit excellent traits for tumor imaging in terms of fast imaging speed, ease of use, excellent contrast, and lack of ionizing radiation. Here, we demonstrate simultaneous tomographic whole body imaging of optical absorption, US reflectivity, and speed of sound (SoS) in living mice. In vivo studies of 4T1 breast cancer xenografts models revealed synergistic and complementary value of the hybrid imaging approach for characterizing mammary tumors. While neovasculature surrounding the tumor areas were observed based on the vascular anatomy contrast provided by the OA data, the tumor boundaries could be discerned by segmenting hypoechoic structures in pulse-echo US images. Tumor delineation was further facilitated by enhancing the contrast and spatial resolution of the SoS maps with a full-wave inversion method. The malignant lesions could thus be distinguished from other hypoechoic regions based on the average SoS values. The reported findings corroborate the strong potential of the hybrid imaging approach for advancing cancer research in small animal models and fostering development of new clinical diagnostic approaches.

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Lafci B et al.

Noninvasive multiparametric characterization of mammary tumors with transmission-reflection optoacoustic ultrasound

CancerPreclinicalMSOT

Development of imaging methods capable of furnishing tumor-specific morphological, functional, and molecular information is paramount for early diagnosis, staging, and treatment of breast cancer. Ultrasound (US) and optoacoustic (OA) imaging methods exhibit excellent traits for tumor imaging in terms of fast imaging speed, ease of use, excellent contrast, and lack of ionizing radiation. Here, we demonstrate simultaneous tomographic whole body imaging of optical absorption, US reflectivity, and speed of sound (SoS) in living mice. In vivo studies of 4T1 breast cancer xenografts models revealed synergistic and complementary value of the hybrid imaging approach for characterizing mammary tumors. While neovasculature surrounding the tumor areas were observed based on the vascular anatomy contrast provided by the OA data, the tumor boundaries could be discerned by segmenting hypoechoic structures in pulse-echo US images. Tumor delineation was further facilitated by enhancing the contrast and spatial resolution of the SoS maps with a full-wave inversion method. The malignant lesions could thus be distinguished from other hypoechoic regions based on the average SoS values. The reported findings corroborate the strong potential of the hybrid imaging approach for advancing cancer research in small animal models and fostering development of new clinical diagnostic approaches.

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Nafiujjaman M et al.

Biodegradable Hollow Manganese Silicate Nanocomposites to Alleviate Tumor Hypoxia toward Enhanced Photodynamic Therapy

NanoCancerPreclinicalMSOT

Photodynamic therapy (PDT) has been extensively explored as a minimally invasive treatment strategy for malignant cancers. It works with the help of a photosensitizer located within cancer cells that is irradiated by near-infrared light to produce potent toxins and singlet oxygen (1O2) and induce cell death. However, reactive oxygen species can be overexpressed in tumor tissue because of the rapid metabolic activity in cancer cells, and the insufficient oxygenation (hypoxia) can lead to low production of singlet oxygen (1O2) during PDT. In this study, we developed nanocomposites composed of a hollow manganese silicate (HMnOSi) nanoparticle and a photosensitizer (Ce6) that can generate significant amounts of O2 to relieve tumor hypoxia and enhance the therapeutic efficacy of PDT. Our nanocomposites were characterized by UV–vis, fluorescence spectroscopy, transmission electron microscopy (TEM), energy-dispersive X-ray, and dynamic light scattering. Our particles’ hollow mesoporous structures were shown to retain large amounts of Ce6 on the particle surface with high loading capacity (33%). TEM imaging showed that the nanoparticles could be biodegradable over time in simulated body fluid, which can imply clinical potentials. Significant H2O2 quenching capabilities to alleviate hypoxic conditions in a solid tumor were also presented. For breast cancer cells, the nanocomposite-treated group revealed that 91% of cells were dead under laser activation compared to 51% for the control group (free Ce6). In an animal study, our nanocomposites showed almost fourfold tumor growth inhibition versus the control and more than twofold over free Ce6 in orthotopic tumor xenografts. In addition, the oxygen saturation contrast inside tumors was evaluated by photoacoustic imaging to demonstrate the alleviated hypoxia in vivo. Our works provide a smart nanosystem to ameliorate the hypoxic tumor microenvironment and augment the efficacy of PDT in a targeted cancer treatment.

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Nafiujjaman M et al.

Biodegradable Hollow Manganese Silicate Nanocomposites to Alleviate Tumor Hypoxia toward Enhanced Photodynamic Therapy

CancerPreclinicalMSOT

Photodynamic therapy (PDT) has been extensively explored as a minimally invasive treatment strategy for malignant cancers. It works with the help of a photosensitizer located within cancer cells that is irradiated by near-infrared light to produce potent toxins and singlet oxygen (1O2) and induce cell death. However, reactive oxygen species can be overexpressed in tumor tissue because of the rapid metabolic activity in cancer cells, and the insufficient oxygenation (hypoxia) can lead to low production of singlet oxygen (1O2) during PDT. In this study, we developed nanocomposites composed of a hollow manganese silicate (HMnOSi) nanoparticle and a photosensitizer (Ce6) that can generate significant amounts of O2 to relieve tumor hypoxia and enhance the therapeutic efficacy of PDT. Our nanocomposites were characterized by UV–vis, fluorescence spectroscopy, transmission electron microscopy (TEM), energy-dispersive X-ray, and dynamic light scattering. Our particles’ hollow mesoporous structures were shown to retain large amounts of Ce6 on the particle surface with high loading capacity (33%). TEM imaging showed that the nanoparticles could be biodegradable over time in simulated body fluid, which can imply clinical potentials. Significant H2O2 quenching capabilities to alleviate hypoxic conditions in a solid tumor were also presented. For breast cancer cells, the nanocomposite-treated group revealed that 91% of cells were dead under laser activation compared to 51% for the control group (free Ce6). In an animal study, our nanocomposites showed almost fourfold tumor growth inhibition versus the control and more than twofold over free Ce6 in orthotopic tumor xenografts. In addition, the oxygen saturation contrast inside tumors was evaluated by photoacoustic imaging to demonstrate the alleviated hypoxia in vivo. Our works provide a smart nanosystem to ameliorate the hypoxic tumor microenvironment and augment the efficacy of PDT in a targeted cancer treatment.

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Kalashnikova I et al.

Ceria-based nanotheranostic agent for rheumatoid arthritis

InflammationPreclinicalMSOT

Rheumatoid arthritis (RA) is an autoimmune disease that affects 1-2% of the human population worldwide, and effective therapies with targeted delivery for local immune suppression have not been described. We address this problem by developing a novel theranostic nanoparticle for RA and assessed its therapeutic and targeting effects under image-guidance. Methods : Albumin-cerium oxide nanoparticles were synthesized by the biomineralization process and further conjugated with near-infrared, indocyanine green (ICG) dye. Enzymatic-like properties and reactive oxygen species (ROS) scavenging activities, as well as the ability to reprogram macrophages, were determined on a monocyte cell line in culture. The therapeutic effect and systemic targeting potential were evaluated in collagen-induced arthritis (CIA) mouse model using optical/optoacoustic tomographic imaging. Results : Small nanotheranostics with narrow size distribution and high colloidal stability were fabricated and displayed high ROS scavenging and enzymatic-like activity, as well as advanced efficacy in a converting pro-inflammatory macrophage phenotype into anti-inflammatory phenotype. When administrated into affected animals, these nanoparticles accumulated in inflamed joints and revealed a therapeutic effect similar to the gold-standard therapy for RA, methotrexate. Conclusions : The inflammation-targeting, inherent contrast and therapeutic activity of this new albumin-cerium oxide nanoparticle may make it a relevant agent for assessing severity in RA, and other inflammatory diseases, and controlling inflammation with image-guidance. The design of these nanotheranostics will enable potential clinical translation as systemic therapy for RA.

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Kalashnikova I et al.

Ceria-based nanotheranostic agent for rheumatoid arthritis

InflammationPreclinicalMSOT

Rheumatoid arthritis (RA) is an autoimmune disease that affects 1-2% of the human population worldwide, and effective therapies with targeted delivery for local immune suppression have not been described. We address this problem by developing a novel theranostic nanoparticle for RA and assessed its therapeutic and targeting effects under image-guidance. Methods : Albumin-cerium oxide nanoparticles were synthesized by the biomineralization process and further conjugated with near-infrared, indocyanine green (ICG) dye. Enzymatic-like properties and reactive oxygen species (ROS) scavenging activities, as well as the ability to reprogram macrophages, were determined on a monocyte cell line in culture. The therapeutic effect and systemic targeting potential were evaluated in collagen-induced arthritis (CIA) mouse model using optical/optoacoustic tomographic imaging. Results : Small nanotheranostics with narrow size distribution and high colloidal stability were fabricated and displayed high ROS scavenging and enzymatic-like activity, as well as advanced efficacy in a converting pro-inflammatory macrophage phenotype into anti-inflammatory phenotype. When administrated into affected animals, these nanoparticles accumulated in inflamed joints and revealed a therapeutic effect similar to the gold-standard therapy for RA, methotrexate. Conclusions : The inflammation-targeting, inherent contrast and therapeutic activity of this new albumin-cerium oxide nanoparticle may make it a relevant agent for assessing severity in RA, and other inflammatory diseases, and controlling inflammation with image-guidance. The design of these nanotheranostics will enable potential clinical translation as systemic therapy for RA.

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Lu T et al.

LV-GAN: A deep learning approach for limited-view optoacoustic imaging based on hybrid datasets

TechnologyPreclinicalMSOT

The optoacoustic imaging (OAI) methods are rapidly evolving for resolving optical contrast in medical imaging applications. In practice, measurement strategies are commonly implemented under limited-view conditions due to oversized image objectives or system design limitations. Data acquired by limited-view detection may impart artifacts and distortions in reconstructed optoacoustic (OA) images. We propose a hybrid data-driven deep learning approach based on generative adversarial network (GAN), termed as LV-GAN, to efficiently recover high quality images from limited-view OA images. Trained on both simulation and experiment data, LV-GAN is found capable of achieving high recovery accuracy even under limited detection angles less than 60° . The feasibility of LV-GAN for artifact removal in biological applications was validated by ex vivo experiments based on two different OAI systems, suggesting high potential of a ubiquitous use of LV-GAN to optimize image quality or system design for different scanners and application scenarios.

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Lu T et al.

LV-GAN: A deep learning approach for limited-view optoacoustic imaging based on hybrid datasets

TechnologyPreclinicalMSOT

The optoacoustic imaging (OAI) methods are rapidly evolving for resolving optical contrast in medical imaging applications. In practice, measurement strategies are commonly implemented under limited-view conditions due to oversized image objectives or system design limitations. Data acquired by limited-view detection may impart artifacts and distortions in reconstructed optoacoustic (OA) images. We propose a hybrid data-driven deep learning approach based on generative adversarial network (GAN), termed as LV-GAN, to efficiently recover high quality images from limited-view OA images. Trained on both simulation and experiment data, LV-GAN is found capable of achieving high recovery accuracy even under limited detection angles less than 60° . The feasibility of LV-GAN for artifact removal in biological applications was validated by ex vivo experiments based on two different OAI systems, suggesting high potential of a ubiquitous use of LV-GAN to optimize image quality or system design for different scanners and application scenarios.

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Roberts S et al.

Optoacoustic imaging of Glucagon-like Peptide 1 Receptor with a near-infrared exendin-4 analog

CancerPreclinicalMSOT

Limitations in current imaging tools have long challenged the imaging of small pancreatic islets in animal models. Here, we report the first development and in vivo validation testing of a broad spectrum and high absorbance near infrared optoacoustic contrast agent, E4x12-Cy7. Our near infrared tracer (E4x12-Cy7) is based on the amino acid sequence of exendin-4 and targets the glucagon-like peptide-1 receptor (GLP-1R). Cell assays confirmed that E4x12-Cy7 has a high binding affinity (IC50 = 4.6 ± 0.8 nM). Using the multi-spectral optoacoustic tomography (MSOT), we imaged E4x12-Cy7 and optoacoustically visualized β-cell insulinoma xenografts in vivo for the first time. In the future, similar optoacoustic tracers that are specific for β-cells and combines optoacoustic and fluorescence imaging modalities could prove to be important tools for monitoring the pancreas for the progression of diabetes.

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Roberts S et al.

Optoacoustic imaging of Glucagon-like Peptide 1 Receptor with a near-infrared exendin-4 analog

CancerPreclinicalMSOT

Limitations in current imaging tools have long challenged the imaging of small pancreatic islets in animal models. Here, we report the first development and in vivo validation testing of a broad spectrum and high absorbance near infrared optoacoustic contrast agent, E4x12-Cy7. Our near infrared tracer (E4x12-Cy7) is based on the amino acid sequence of exendin-4 and targets the glucagon-like peptide-1 receptor (GLP-1R). Cell assays confirmed that E4x12-Cy7 has a high binding affinity (IC50 = 4.6 ± 0.8 nM). Using the multi-spectral optoacoustic tomography (MSOT), we imaged E4x12-Cy7 and optoacoustically visualized β-cell insulinoma xenografts in vivo for the first time. In the future, similar optoacoustic tracers that are specific for β-cells and combines optoacoustic and fluorescence imaging modalities could prove to be important tools for monitoring the pancreas for the progression of diabetes.

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Huang R et al

Artificial Metalloprotein Nanoanalogues: In Situ Catalytic Production of Oxygen to Enhance Photoimmunotherapeutic Inhibition of Primary and Abscopal Tumor Growth

NanoCancerPreclinicalMSOT

Photoimmunotherapy (PIT) has shown enormous potential in not only eliminating primary tumors, but also inhibiting abscopal tumor growth. However, the efficacy of PIT is greatly limited by tumor hypoxia, which causes the attenuation of phototherapeutic efficacy and is a feature of the immunosuppressive tumor microenvironment (TME). In this study, one type of brand-new artificial metalloprotein nanoanalogues is developed via reasonable integration of a “phototherapy-enzymatic” RuO2 and a model antigen, ovalbumin (OVA) for enhanced PIT of cancers, namely, RuO2 -hybridized OVA nanoanalogues (RuO2 @OVA NAs). The RuO2 @OVA NAs exhibit remarkable photothermal/photodynamic capabilities under the near-infrared light irradiation. More importantly, the photoacoustic imaging and immunofluorescence staining confirm that RuO2 @OVA NAs can remarkably alleviate hypoxia via in situ catalysis of hydrogen peroxide overexpressed in the TME to produce oxygen (O2 ). This ushers a prospect of concurrently enhancing photodynamic therapy and reversing the immunosuppressive TME. Also, OVA, as a supplement to the immune stimulation induced by phototherapy, can activate immune responses. Finally, further combination with the cytotoxic T-lymphocyte-associated protein 4 checkpoint blockade is reported to effectively eliminate the primary tumor and inhibit distant tumor growth via the abscopal effect of antitumor immune responses, prolonging the survival.

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Huang R et al

Artificial Metalloprotein Nanoanalogues: In Situ Catalytic Production of Oxygen to Enhance Photoimmunotherapeutic Inhibition of Primary and Abscopal Tumor Growth

CancerPreclinicalMSOT

Photoimmunotherapy (PIT) has shown enormous potential in not only eliminating primary tumors, but also inhibiting abscopal tumor growth. However, the efficacy of PIT is greatly limited by tumor hypoxia, which causes the attenuation of phototherapeutic efficacy and is a feature of the immunosuppressive tumor microenvironment (TME). In this study, one type of brand-new artificial metalloprotein nanoanalogues is developed via reasonable integration of a “phototherapy-enzymatic” RuO2 and a model antigen, ovalbumin (OVA) for enhanced PIT of cancers, namely, RuO2 -hybridized OVA nanoanalogues (RuO2 @OVA NAs). The RuO2 @OVA NAs exhibit remarkable photothermal/photodynamic capabilities under the near-infrared light irradiation. More importantly, the photoacoustic imaging and immunofluorescence staining confirm that RuO2 @OVA NAs can remarkably alleviate hypoxia via in situ catalysis of hydrogen peroxide overexpressed in the TME to produce oxygen (O2 ). This ushers a prospect of concurrently enhancing photodynamic therapy and reversing the immunosuppressive TME. Also, OVA, as a supplement to the immune stimulation induced by phototherapy, can activate immune responses. Finally, further combination with the cytotoxic T-lymphocyte-associated protein 4 checkpoint blockade is reported to effectively eliminate the primary tumor and inhibit distant tumor growth via the abscopal effect of antitumor immune responses, prolonging the survival.

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Yang Y et al.

NIR/photoacoustic imaging of multitype gallbladder cancer using carboxyl/amino functionalized polymer dots

NanoCancerPreclinicalMSOT

Gallbladder cancer has high incidence and mortality and a low early diagnosis rate and requires rapid and efficient diagnosis. Herein, carboxyl/amino functionalized polymer dots (Pdots) were designed to enhance cellular internalization and tumor accumulation. The prepared Pdots were 40-50 nm in diameter, contained no toxic metal, exhibited long circulation time and high stability, and produced strong NIR emission and photoacoustic signals. Different cellular uptake and distribution of functionalized Pdots in eight gallbladder cell lines were quantitatively investigated using flow cytometry and super-resolution microscopy. In vivo NIR fluorescence imaging showed that the functional Pdots had high accumulation in the tumor after 30 minutes of injection and remained there for up to 6 days. In addition, photoacoustic imaging found that the abundant blood vessels around the tumor microenvironment and Pdots entered the tumor through the blood vessels. Furthermore, a high heterogeneity of vascular networks was visualized in real-time and high resolution by probe-based confocal laser endomicroscopy imaging. These results offer a new avenue for the development of functional Pdots as a probe for multi-modal and multi-scale imaging of gallbladder cancer in small animals.

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Yang Y et al.

NIR/photoacoustic imaging of multitype gallbladder cancer using carboxyl/amino functionalized polymer dots

CancerPreclinicalMSOT

Gallbladder cancer has high incidence and mortality and a low early diagnosis rate and requires rapid and efficient diagnosis. Herein, carboxyl/amino functionalized polymer dots (Pdots) were designed to enhance cellular internalization and tumor accumulation. The prepared Pdots were 40-50 nm in diameter, contained no toxic metal, exhibited long circulation time and high stability, and produced strong NIR emission and photoacoustic signals. Different cellular uptake and distribution of functionalized Pdots in eight gallbladder cell lines were quantitatively investigated using flow cytometry and super-resolution microscopy. In vivo NIR fluorescence imaging showed that the functional Pdots had high accumulation in the tumor after 30 minutes of injection and remained there for up to 6 days. In addition, photoacoustic imaging found that the abundant blood vessels around the tumor microenvironment and Pdots entered the tumor through the blood vessels. Furthermore, a high heterogeneity of vascular networks was visualized in real-time and high resolution by probe-based confocal laser endomicroscopy imaging. These results offer a new avenue for the development of functional Pdots as a probe for multi-modal and multi-scale imaging of gallbladder cancer in small animals.

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Wu J et al.

Ultrathin Transition Metal Chalcogenide Nanosheets Synthesized via Topotactic Transformation for Effective Cancer Theranostics

NanoCancerPreclinicalMSOT

Ultrathin transition metal chalcogenide (TMC) nanosheets with ultrahigh photothermal conversion efficiency (η) and excellent stability are strongly desired in the application of photothermal therapy (PTT). However, the current synthetic methods of ultrathin TMC nanosheets have issues in obtaining uniform morphology, good dispersion, and satisfactory PTT behavior. Herein, ultrathin nanosheets of CoFe-selenide (CFS) with a finely controlled structure were prepared via a topological structural transformation process from an ultrathin CoFe-layered double hydroxide (LDH) precursor, followed by surface modification with poly(ethylene glycol) (PEG). The as-prepared CFS-PEG nanosheets inherit the ultrathin morphology of CoFe-LDH and exhibit an outstanding photothermal performance with a η of 74.5%, which is the first rank level of reported two-dimensional (2D) TMC nanosheet materials. The CFS-PEG nanosheets possess a satisfactory photoacoustic (PA) imaging capability with an ultralow detection limit (5 ppm) and simultaneously superior T2 magnetic resonance imaging (MRI) performance with a large transverse MR relaxivity value (r2) of 347.7 mM-1 s-1. Moreover, in vitro and in vivo assays verify superior anticancer activity with a dramatic photoinduced cancer cell apoptosis and tumor ablation. Therefore, a successful paradigm is provided for rational design and preparation of ultrathin TMC nanosheets in this work, holding enormous potential in cancer theranostics.

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Han R et al.

Ag2S nanoparticle-mediated multiple ablations reinvigorates the immune response for enhanced cancer photo-immunotherapy

NanoCancerPreclinicalMSOT

Photothermal therapy (PTT) has been widely used in cancer treatment in recent years. However, it is difficult to completely eliminate tumors by single PTT, and the effects of single dose of PTT frequency on the therapeutic outcome of PTT and the multiple PTT-induced immune response in cancer therapy also remain unclear. Here, water-soluble Ag2S nanoparticles (NPs) with optimal particle size (~15 nm) were synthesized and used as the PTT agents. The in vitro and in vivo results demonstrated that Ag2S NPs had good photothermal conversion in response to the irradiation of an 808 nm laser, and the results indicated that the NPs have potential as contrast agents for photoacoustic imaging as well as good biocompatibility. The in vivo results further revealed that the frequency of the Ag2S NP-mediated PTT affected the cancer therapeutic outcome. The increase of frequency efficiently reduced the primary tumor recurrence and alleviated metastasis. The present study suggested that the mechanism involves multiple PTT cycles inhibiting the proliferation of primary tumor cells and stimulating the systematic immune response in the mouse breast cancer model. Therefore, frequency optimization in photothermal ablation may provide a promising strategy to enhance the therapeutic outcome in cancer therapy.

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Han R et al.

Ag2S nanoparticle-mediated multiple ablations reinvigorates the immune response for enhanced cancer photo-immunotherapy

CancerPreclinicalMSOT

Photothermal therapy (PTT) has been widely used in cancer treatment in recent years. However, it is difficult to completely eliminate tumors by single PTT, and the effects of single dose of PTT frequency on the therapeutic outcome of PTT and the multiple PTT-induced immune response in cancer therapy also remain unclear. Here, water-soluble Ag2S nanoparticles (NPs) with optimal particle size (~15 nm) were synthesized and used as the PTT agents. The in vitro and in vivo results demonstrated that Ag2S NPs had good photothermal conversion in response to the irradiation of an 808 nm laser, and the results indicated that the NPs have potential as contrast agents for photoacoustic imaging as well as good biocompatibility. The in vivo results further revealed that the frequency of the Ag2S NP-mediated PTT affected the cancer therapeutic outcome. The increase of frequency efficiently reduced the primary tumor recurrence and alleviated metastasis. The present study suggested that the mechanism involves multiple PTT cycles inhibiting the proliferation of primary tumor cells and stimulating the systematic immune response in the mouse breast cancer model. Therefore, frequency optimization in photothermal ablation may provide a promising strategy to enhance the therapeutic outcome in cancer therapy.

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Wu J et al.

Ultrathin Transition Metal Chalcogenide Nanosheets Synthesized via Topotactic Transformation for Effective Cancer Theranostics

CancerPreclinicalMSOT

Ultrathin transition metal chalcogenide (TMC) nanosheets with ultrahigh photothermal conversion efficiency (η) and excellent stability are strongly desired in the application of photothermal therapy (PTT). However, the current synthetic methods of ultrathin TMC nanosheets have issues in obtaining uniform morphology, good dispersion, and satisfactory PTT behavior. Herein, ultrathin nanosheets of CoFe-selenide (CFS) with a finely controlled structure were prepared via a topological structural transformation process from an ultrathin CoFe-layered double hydroxide (LDH) precursor, followed by surface modification with poly(ethylene glycol) (PEG). The as-prepared CFS-PEG nanosheets inherit the ultrathin morphology of CoFe-LDH and exhibit an outstanding photothermal performance with a η of 74.5%, which is the first rank level of reported two-dimensional (2D) TMC nanosheet materials. The CFS-PEG nanosheets possess a satisfactory photoacoustic (PA) imaging capability with an ultralow detection limit (5 ppm) and simultaneously superior T2 magnetic resonance imaging (MRI) performance with a large transverse MR relaxivity value (r2) of 347.7 mM-1 s-1. Moreover, in vitro and in vivo assays verify superior anticancer activity with a dramatic photoinduced cancer cell apoptosis and tumor ablation. Therefore, a successful paradigm is provided for rational design and preparation of ultrathin TMC nanosheets in this work, holding enormous potential in cancer theranostics.

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Fredman G et al.

Skin tags imaged by reflectance confocal microscopy, optical coherence tomography and multispectral optoacoustic tomography at the bedside

NanoCancerClinicalMSOT

Background : Skin tags are common and mostly benign, but occasionally contain skin cancers. This study analysed skin tags by combining three advanced optical imaging technologies: reflectance confocal microscopy (RCM), optical coherence tomography (OCT) and multispectral optoacoustic imaging (MSOT) supplemented by dermoscopy MATERIALS AND METHODS: A prospective clinical study recruiting patients with skin tags from a university hospital clinic over a 2-week period. OCT, RCM and MSOT imaging were performed prior to excisional biopsies. Image features such as pigmentation, cell types and skin architecture, angiographic information demonstrating vascular pattern were captured, analysed, and compared to melanin and haemoglobin content in MSOT as well as histopathology. Results : Six patients with dermal naevi (2); compound naevi (3); neurofibroma (1) were included. All skin tags except the neurofibroma were pigmented (5/6), with sparse (5/6) and dense (4/6) hyperreflective nests and band-like collagen in dermis in 6/6 lesions on RCM. Dermoscopy showed dots (5/6) and coiled vessels (5/6). Linear vertical vessels were present in all OCT images. MSOT images consisted of a compact shell-like superficial melanin area, same shape and size as the skin tag, dermal vessels were visible in 4/5 naevi, HbO2 signal clearly demarcated blood vessels located below the melanin signal. Conclusion : OCT showed linear vessels in all lesions. Pigmentation was identified by RCM as benign nests of melanocytes. MSOT supplemented with spatial distribution of melanin and HbO2 that indicated all skin tags were benign with no infiltration of vessels inside the melanin signal. Each advanced method proved indispensable for fast diagnosis. Larger studies are warranted for validation.

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Fredman G et al.

Skin tags imaged by reflectance confocal microscopy, optical coherence tomography and multispectral optoacoustic tomography at the bedside

CancerClinicalMSOT

Background : Skin tags are common and mostly benign, but occasionally contain skin cancers. This study analysed skin tags by combining three advanced optical imaging technologies: reflectance confocal microscopy (RCM), optical coherence tomography (OCT) and multispectral optoacoustic imaging (MSOT) supplemented by dermoscopy MATERIALS AND METHODS: A prospective clinical study recruiting patients with skin tags from a university hospital clinic over a 2-week period. OCT, RCM and MSOT imaging were performed prior to excisional biopsies. Image features such as pigmentation, cell types and skin architecture, angiographic information demonstrating vascular pattern were captured, analysed, and compared to melanin and haemoglobin content in MSOT as well as histopathology. Results : Six patients with dermal naevi (2); compound naevi (3); neurofibroma (1) were included. All skin tags except the neurofibroma were pigmented (5/6), with sparse (5/6) and dense (4/6) hyperreflective nests and band-like collagen in dermis in 6/6 lesions on RCM. Dermoscopy showed dots (5/6) and coiled vessels (5/6). Linear vertical vessels were present in all OCT images. MSOT images consisted of a compact shell-like superficial melanin area, same shape and size as the skin tag, dermal vessels were visible in 4/5 naevi, HbO2 signal clearly demarcated blood vessels located below the melanin signal. Conclusion : OCT showed linear vessels in all lesions. Pigmentation was identified by RCM as benign nests of melanocytes. MSOT supplemented with spatial distribution of melanin and HbO2 that indicated all skin tags were benign with no infiltration of vessels inside the melanin signal. Each advanced method proved indispensable for fast diagnosis. Larger studies are warranted for validation.

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Meng T et al.

Matrix metalloproteinase-initiated aggregation of melanin nanoparticles as highly efficient contrast agent for enhanced tumor accumulation and dual-modal imaging

NanoCancerPreclinicalMSOT

Ultrasmall melanin nanoparticles (MNPs) have great application potential in medical imaging, owing to its satisfactory biodegradation, intrinsic photoacoustic (PA) property and natural chelating ability with metal ions for magnetic resonance imaging (MRI). Because of its ultrasmall particle size, it was easily metabolized by the kidney, but had relatively limited tumor retention according to our previous study. To further improve the intensities of MRI and PA signals for precise diagnosis, it is vital to enhance its tumor accumulation and prolong the retention time. In this study, we developed a matrix metalloproteinase-2 (MMP-2) activatable nanoprobe (PEG-PepMMP2-MNP-Gd), which was composed of water-insoluble gadolinium-chelated melanin (MNP-Gd), MMP-2 cleaved peptide and enzymatic detachable polyethylene glycol (PEG). In the presence of MMP-2 activity, PEG-coating on the surface was peeled off and the “hidden” hydrophobic segment was then exposed, which initiated the aggregation and size increase of nanoprobes. We demonstrated that the hydrodynamic size of the MMP-2 activatable nanoprobe increased from 17.1 nm to 90.2 nm after in vitro incubation with MMP-2. Moreover, the in vivo T1-weighted MRI and PA signals in tumors were both dramatically enhanced and extended after the PEG-PepMMP2-MNP-Gd nanoparticles were intravenously injected into mice. This could be attributed to the changed size selectively activated by highly expressed MMP-2 in tumors, and allowing nanoparticles to possess higher tumor accumulation and longer retention. In short, MMP2-initiated size-changeable PEG-PepMMP2-MNP-Gd could meet the paradoxical demand for size-leading permeability and retention in solid tumors, suggesting its promising applications as a highly efficient MRI/PA contrast agent for precise tumor diagnosis.

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Meng T et al.

Matrix metalloproteinase-initiated aggregation of melanin nanoparticles as highly efficient contrast agent for enhanced tumor accumulation and dual-modal imaging

CancerPreclinicalMSOT

Ultrasmall melanin nanoparticles (MNPs) have great application potential in medical imaging, owing to its satisfactory biodegradation, intrinsic photoacoustic (PA) property and natural chelating ability with metal ions for magnetic resonance imaging (MRI). Because of its ultrasmall particle size, it was easily metabolized by the kidney, but had relatively limited tumor retention according to our previous study. To further improve the intensities of MRI and PA signals for precise diagnosis, it is vital to enhance its tumor accumulation and prolong the retention time. In this study, we developed a matrix metalloproteinase-2 (MMP-2) activatable nanoprobe (PEG-PepMMP2-MNP-Gd), which was composed of water-insoluble gadolinium-chelated melanin (MNP-Gd), MMP-2 cleaved peptide and enzymatic detachable polyethylene glycol (PEG). In the presence of MMP-2 activity, PEG-coating on the surface was peeled off and the “hidden” hydrophobic segment was then exposed, which initiated the aggregation and size increase of nanoprobes. We demonstrated that the hydrodynamic size of the MMP-2 activatable nanoprobe increased from 17.1 nm to 90.2 nm after in vitro incubation with MMP-2. Moreover, the in vivo T1-weighted MRI and PA signals in tumors were both dramatically enhanced and extended after the PEG-PepMMP2-MNP-Gd nanoparticles were intravenously injected into mice. This could be attributed to the changed size selectively activated by highly expressed MMP-2 in tumors, and allowing nanoparticles to possess higher tumor accumulation and longer retention. In short, MMP2-initiated size-changeable PEG-PepMMP2-MNP-Gd could meet the paradoxical demand for size-leading permeability and retention in solid tumors, suggesting its promising applications as a highly efficient MRI/PA contrast agent for precise tumor diagnosis.

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Bao J et al.

Multifunctional Hf/Mn-TCPP Metal-Organic Framework Nanoparticles for Triple-Modality Imaging-Guided PTT/RT Synergistic Cancer Therapy

NanoCancerPreclinicalMSOT

Background : Recent studies have validated and confirmed the great potential of nanoscale metal-organic framework (NMOF) in the biomedical field, especially in improving the efficiency of cancer diagnosis and therapy. However, most previous studies only utilized either the metal cluster or the organic ligand of the NMOF for cancer treatments and merely reported limited theranostic functions, which may not be optimized. As a highly designable and easily functionalized material, prospective rational design offers a powerful way to extract the maximum benefit from NMOF for cancer theranostic applications. Materials and methods : A NMOF based on hafnium (Hf) cluster and Mn(III)-porphyrin ligand was rational designed and synthesized as a high-performance multifunctional theranostic agent. The folic acid (FA) was modified on the NMOF surface to enhance the cancer targeting efficacy. The proposed “all-in-one” FA-Hf-Mn-NMOF (fHMNM) was characterized and identified using various analytical techniques. Then, in vitro and in vivo studies were performed to further explore the effects of fHMNM both as the magnetic resonance imaging (MRI)/computed tomography (CT)/photoacoustic imaging (PAI) contrast agent and as the photothermal therapy (PTT)/radiotherapy (RT) agent. Results : A tumour targeting multifunctional fHMNM was successfully synthesized with high performance for MRI/CT/PAI enhancements and image-guided PTT/RT synergistic therapy properties. Compared with the current clinical CT and MR contrast agents, the X-ray attenuation and T1 relaxation rate of this integrated nanosystem increased 1.7-fold and 3-5-fold, respectively. More importantly, the catalase-like Mn(III)-porphyrin ligand can decompose H2O2 into O2 in tumour microenvironments to improve the synergistic treatment efficiency of PTT and RT. Significant tumour growth inhibition was achieved in mouse cancer models without obvious damage to the other organs. Conclusion : This work highlights the potential of fHMNM as an easily designable material for biomedical applications, could be an effective tool for in vivo detection and subsequent treatment of tumour.

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Bao J et al.

Multifunctional Hf/Mn-TCPP Metal-Organic Framework Nanoparticles for Triple-Modality Imaging-Guided PTT/RT Synergistic Cancer Therapy

CancerPreclinicalMSOT

Background : Recent studies have validated and confirmed the great potential of nanoscale metal-organic framework (NMOF) in the biomedical field, especially in improving the efficiency of cancer diagnosis and therapy. However, most previous studies only utilized either the metal cluster or the organic ligand of the NMOF for cancer treatments and merely reported limited theranostic functions, which may not be optimized. As a highly designable and easily functionalized material, prospective rational design offers a powerful way to extract the maximum benefit from NMOF for cancer theranostic applications. Materials and methods : A NMOF based on hafnium (Hf) cluster and Mn(III)-porphyrin ligand was rational designed and synthesized as a high-performance multifunctional theranostic agent. The folic acid (FA) was modified on the NMOF surface to enhance the cancer targeting efficacy. The proposed “all-in-one” FA-Hf-Mn-NMOF (fHMNM) was characterized and identified using various analytical techniques. Then, in vitro and in vivo studies were performed to further explore the effects of fHMNM both as the magnetic resonance imaging (MRI)/computed tomography (CT)/photoacoustic imaging (PAI) contrast agent and as the photothermal therapy (PTT)/radiotherapy (RT) agent. Results : A tumour targeting multifunctional fHMNM was successfully synthesized with high performance for MRI/CT/PAI enhancements and image-guided PTT/RT synergistic therapy properties. Compared with the current clinical CT and MR contrast agents, the X-ray attenuation and T1 relaxation rate of this integrated nanosystem increased 1.7-fold and 3-5-fold, respectively. More importantly, the catalase-like Mn(III)-porphyrin ligand can decompose H2O2 into O2 in tumour microenvironments to improve the synergistic treatment efficiency of PTT and RT. Significant tumour growth inhibition was achieved in mouse cancer models without obvious damage to the other organs. Conclusion : This work highlights the potential of fHMNM as an easily designable material for biomedical applications, could be an effective tool for in vivo detection and subsequent treatment of tumour.

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Nitkunanantharajah S et al.

Three-dimensional optoacoustic imaging of nailfold capillaries in systemic sclerosis and its potential for disease differentiation using deep learning

Other ApplicationsClinicalRSOM

The autoimmune disease systemic sclerosis (SSc) causes microvascular changes that can be easily observed cutaneously at the finger nailfold. Optoacoustic imaging (OAI), a combination of optical and ultrasound imaging, specifically raster-scanning optoacoustic mesoscopy (RSOM), offers a non-invasive high-resolution 3D visualization of capillaries allowing for a better view of microvascular changes and an extraction of volumetric measures. In this study, nailfold capillaries of patients with SSc and healthy controls are imaged and compared with each other for the first time using OAI. The nailfolds of 23 patients with SSc and 19 controls were imaged using RSOM. The acquired images were qualitatively compared to images from state-of-the-art imaging tools for SSc, dermoscopy and high magnification capillaroscopy. The vascular volume in the nailfold capillaries were computed from the RSOM images. The vascular volumes differ significantly between both cohorts (0.216 ± 0.085 mm3 and 0.337 ± 0.110 mm3; p < 0.0005). In addition, an artificial neural network was trained to automatically differentiate nailfold images from both cohorts to further assess whether OAI is sensitive enough to visualize anatomical differences in the capillaries between the two cohorts. Using transfer learning, the model classifies images with an area under the ROC curve of 0.897, and a sensitivity of 0.783 and specificity of 0.895. In conclusion, this study demonstrates the capabilities of RSOM as an imaging tool for SSc and establishes it as a modality that facilitates more in-depth studies into the disease mechanisms and progression.

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Nitkunanantharajah S et al.

Three-dimensional optoacoustic imaging of nailfold capillaries in systemic sclerosis and its potential for disease differentiation using deep learning

Other ApplicationsFibrosisClinicalRSOM

The autoimmune disease systemic sclerosis (SSc) causes microvascular changes that can be easily observed cutaneously at the finger nailfold. Optoacoustic imaging (OAI), a combination of optical and ultrasound imaging, specifically raster-scanning optoacoustic mesoscopy (RSOM), offers a non-invasive high-resolution 3D visualization of capillaries allowing for a better view of microvascular changes and an extraction of volumetric measures. In this study, nailfold capillaries of patients with SSc and healthy controls are imaged and compared with each other for the first time using OAI. The nailfolds of 23 patients with SSc and 19 controls were imaged using RSOM. The acquired images were qualitatively compared to images from state-of-the-art imaging tools for SSc, dermoscopy and high magnification capillaroscopy. The vascular volume in the nailfold capillaries were computed from the RSOM images. The vascular volumes differ significantly between both cohorts (0.216 ± 0.085 mm3 and 0.337 ± 0.110 mm3; p < 0.0005). In addition, an artificial neural network was trained to automatically differentiate nailfold images from both cohorts to further assess whether OAI is sensitive enough to visualize anatomical differences in the capillaries between the two cohorts. Using transfer learning, the model classifies images with an area under the ROC curve of 0.897, and a sensitivity of 0.783 and specificity of 0.895. In conclusion, this study demonstrates the capabilities of RSOM as an imaging tool for SSc and establishes it as a modality that facilitates more in-depth studies into the disease mechanisms and progression.

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Zhu Y et al.

Multicomponent Transition Metal Dichalcogenide Nanosheets for Imaging-Guided Photothermal and Chemodynamic Therapy

NanoCancerPreclinicalMSOT

Transition metal dichalcogenides (TMDs) have received considerable attention due to their strong absorption in the near-infrared (NIR) region, strong spin-orbit coupling, and excellent photothermal conversion efficiency (PCE). Herein, CoFeMn dichalcogenide nanosheets (CFMS NSs) are prepared via facile vulcanization of a lamellar CoFeMn-layered double hydroxide (LDH) precursor followed by polyvinyl pyrrolidone modification (to give CFMS-PVP NSs), and found to show excellent photoacoustic (PA) imaging and synergistic photothermal/chemodynamic therapy (PTT/CDT) performance. The as-prepared CFMS-PVP NSs inherit the ultrathin morphology of the CoFeMn-LDH precursor and exhibit an outstanding photothermal performance with a η of 89.0%, the highest PCE reported to date for 2D TMD materials. Moreover, 50% of maximum catalytic activity (Michaelis-Menten constant, K m) is attained by CFMS-PVP NSs with 0.26 × 10-3 m H2O2 at 318 K, markedly lower than the endogenous concentration of H2O2 inside tumor cells. In addition, complete apoptosis of HepG2 cancer cells and complete tumor elimination in vivo are observed after treatment with CFMS-PVP NSs at a low dose, substantiating the NSs’ remarkable PTT/CDT efficacy. This work provides a new and facile approach for the synthesis of high-quality multicomponent TMD nanosheets with precise process control, the potential for mass production, and outstanding performance, providing great promise in cancer theranostics.

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Shrestha B et al.

Gold nanorods enable noninvasive longitudinal monitoring of hydrogels in vivo with photoacoustic tomography

Other ApplicationsPreclinicalMSOT

Longitudinal in vivo monitoring is essential for the design and evaluation of biomaterials. An ideal method would provide three-dimensional quantitative information, high spatial resolution, deep tissue penetration, and contrast between tissue and material structures. Photoacoustic (PA) or optoacoustic imaging is a hybrid technique that allows three-dimensional imaging with high spatial resolution. In addition, photoacoustic imaging allows for imaging of vascularization based on the intrinsic contrast of hemoglobin. In this study, we investigated photoacoustic computed tomography (PACT) as a tool for longitudinal monitoring of an implanted hydrogel in a small animal model. Hydrogels were loaded with gold nanorods to enhance contrast and imaged weekly for 8 weeks. PACT allowed non-invasive three-dimensional, quantitative imaging of the hydrogels over the entire 8 weeks. Quantitative volume analysis was used to evaluate the in vivo degradation kinetics of the implants which deviated slightly from in vitro predictions. Multispectral imaging allowed for the simultaneous analysis of hydrogel degradation and local vascularization. These results provide support for the substantial potential of PACT as a tool for insight into biomaterial performance in vivo.

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Zhu Y et al.

Multicomponent Transition Metal Dichalcogenide Nanosheets for Imaging-Guided Photothermal and Chemodynamic Therapy

CancerPreclinicalMSOT

Transition metal dichalcogenides (TMDs) have received considerable attention due to their strong absorption in the near-infrared (NIR) region, strong spin-orbit coupling, and excellent photothermal conversion efficiency (PCE). Herein, CoFeMn dichalcogenide nanosheets (CFMS NSs) are prepared via facile vulcanization of a lamellar CoFeMn-layered double hydroxide (LDH) precursor followed by polyvinyl pyrrolidone modification (to give CFMS-PVP NSs), and found to show excellent photoacoustic (PA) imaging and synergistic photothermal/chemodynamic therapy (PTT/CDT) performance. The as-prepared CFMS-PVP NSs inherit the ultrathin morphology of the CoFeMn-LDH precursor and exhibit an outstanding photothermal performance with a η of 89.0%, the highest PCE reported to date for 2D TMD materials. Moreover, 50% of maximum catalytic activity (Michaelis-Menten constant, K m) is attained by CFMS-PVP NSs with 0.26 × 10-3 m H2O2 at 318 K, markedly lower than the endogenous concentration of H2O2 inside tumor cells. In addition, complete apoptosis of HepG2 cancer cells and complete tumor elimination in vivo are observed after treatment with CFMS-PVP NSs at a low dose, substantiating the NSs’ remarkable PTT/CDT efficacy. This work provides a new and facile approach for the synthesis of high-quality multicomponent TMD nanosheets with precise process control, the potential for mass production, and outstanding performance, providing great promise in cancer theranostics.

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Shrestha B et al.

Gold nanorods enable noninvasive longitudinal monitoring of hydrogels in vivo with photoacoustic tomography

OtherPreclinicalMSOT

Longitudinal in vivo monitoring is essential for the design and evaluation of biomaterials. An ideal method would provide three-dimensional quantitative information, high spatial resolution, deep tissue penetration, and contrast between tissue and material structures. Photoacoustic (PA) or optoacoustic imaging is a hybrid technique that allows three-dimensional imaging with high spatial resolution. In addition, photoacoustic imaging allows for imaging of vascularization based on the intrinsic contrast of hemoglobin. In this study, we investigated photoacoustic computed tomography (PACT) as a tool for longitudinal monitoring of an implanted hydrogel in a small animal model. Hydrogels were loaded with gold nanorods to enhance contrast and imaged weekly for 8 weeks. PACT allowed non-invasive three-dimensional, quantitative imaging of the hydrogels over the entire 8 weeks. Quantitative volume analysis was used to evaluate the in vivo degradation kinetics of the implants which deviated slightly from in vitro predictions. Multispectral imaging allowed for the simultaneous analysis of hydrogel degradation and local vascularization. These results provide support for the substantial potential of PACT as a tool for insight into biomaterial performance in vivo.

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Liapis E et al.

Resolution of spatial and temporal heterogeneity in bevacizumab-treated breast tumors by eigenspectra multispectral optoacoustic tomography

CancerPreclinicalMSOT

Understanding temporal and spatial hemodynamic heterogeneity as a function of tumor growth or therapy impacts the development of novel therapeutic strategies. In this study, we employed eigenspectra multispectral optoacoustic tomography (eMSOT) as a next-generation optoacoustic method to impart high accuracy in resolving tumor hemodynamics during bevacizumab therapy in two types of breast cancer xenografts (KPL-4, MDA-MB-468). Patterns of tumor total hemoglobin concentration (THb) and oxygen saturation (sO2) were imaged in control and bevacizumab-treated tumors over the course of 58d (KPL-4) and 16d (MDA-MB-468), and the evolution of functional vasculature “normalization” was resolved macroscopically. An initial sharp drop in tumor sO2 and THb content shortly after the initiation of bevacizumab treatment was followed by a recovery in oxygenation levels. Rim-core subregion analysis revealed steep spatial oxygenation gradients in growing tumors that were reduced after bevacizumab treatment. Critically, eMSOT imaging findings were validated directly by histopathologic assessment of hypoxia (pimonidazole) and vascularity (CD31). These data demonstrate how eMSOT brings new abilities for accurate observation of entire tumor responses to challenges at spatial and temporal dimensions not available by other techniques today.

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Liapis E et al.

Resolution of spatial and temporal heterogeneity in bevacizumab-treated breast tumors by eigenspectra multispectral optoacoustic tomography

CancerPreclinicalMSOT

Understanding temporal and spatial hemodynamic heterogeneity as a function of tumor growth or therapy impacts the development of novel therapeutic strategies. In this study, we employed eigenspectra multispectral optoacoustic tomography (eMSOT) as a next-generation optoacoustic method to impart high accuracy in resolving tumor hemodynamics during bevacizumab therapy in two types of breast cancer xenografts (KPL-4, MDA-MB-468). Patterns of tumor total hemoglobin concentration (THb) and oxygen saturation (sO2) were imaged in control and bevacizumab-treated tumors over the course of 58d (KPL-4) and 16d (MDA-MB-468), and the evolution of functional vasculature “normalization” was resolved macroscopically. An initial sharp drop in tumor sO2 and THb content shortly after the initiation of bevacizumab treatment was followed by a recovery in oxygenation levels. Rim-core subregion analysis revealed steep spatial oxygenation gradients in growing tumors that were reduced after bevacizumab treatment. Critically, eMSOT imaging findings were validated directly by histopathologic assessment of hypoxia (pimonidazole) and vascularity (CD31). These data demonstrate how eMSOT brings new abilities for accurate observation of entire tumor responses to challenges at spatial and temporal dimensions not available by other techniques today.

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Chen X et al.

Mitochondria-Targeted Fluorescent and Photoacoustic Imaging of Hydrogen Peroxide in Inflammation

InflammationPreclinicalMSOT

Hydrogen peroxide (H2O2) is a prominent reactive oxygen species with relative stability, which makes it a potential diagnostic marker for pathological states. Excessive H2O2 in mitochondria leads to oxidative stress and inflammation. However, precisely monitoring the level of H2O2 at specific organelles (e.g., mitochondria) in vivo is still of urgent necessity. Therefore, we rationally designed a mitochondria-targeted near-infrared probe TPP-HCy-BOH for fluorescent/photoacoustic (FL/PA) dual-modal imaging of overproduced H2O2 in an inflamed mouse model. TPP-HCy-BOH had a low LOD (0.348 μM), which is comparable to those of recently reported probes for H2O2 detection. The high kinetic rate constant (kobs = 4.72 × 10-3 s-1) of TPP-HCy-BOH toward H2O2 is superior to recently reported H2O2 probes. Compared to control probe HCy-BOH without the mitochondrial targeting moiety, TPP-HCy-BOH successfully images exogenous or endogenous H2O2 in mitochondria with an additional 2.4-fold FL increase and 4.7-fold PA increase in HeLa cells or additional 2.1-fold FL increase and 3.3-fold PA increase in RAW 264.7 cells. In LPS-induced acute inflammation in vivo, TPP-HCy-BOH is more competent to image overproduced H2O2 with additional 1.6-fold higher sensitivity of FL in abdomen and 2.0-fold higher sensitivity of PA in liver and longer retention time of 0.5 h than HCy-BOH. We anticipate that TPP-HCy-BOH could be employed for the FL/PA dual-modal diagnosis of pathological inflammation in clinic in near future.

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Chen X et al.

Mitochondria-Targeted Fluorescent and Photoacoustic Imaging of Hydrogen Peroxide in Inflammation

InflammationPreclinicalMSOT

Hydrogen peroxide (H2O2) is a prominent reactive oxygen species with relative stability, which makes it a potential diagnostic marker for pathological states. Excessive H2O2 in mitochondria leads to oxidative stress and inflammation. However, precisely monitoring the level of H2O2 at specific organelles (e.g., mitochondria) in vivo is still of urgent necessity. Therefore, we rationally designed a mitochondria-targeted near-infrared probe TPP-HCy-BOH for fluorescent/photoacoustic (FL/PA) dual-modal imaging of overproduced H2O2 in an inflamed mouse model. TPP-HCy-BOH had a low LOD (0.348 μM), which is comparable to those of recently reported probes for H2O2 detection. The high kinetic rate constant (kobs = 4.72 × 10-3 s-1) of TPP-HCy-BOH toward H2O2 is superior to recently reported H2O2 probes. Compared to control probe HCy-BOH without the mitochondrial targeting moiety, TPP-HCy-BOH successfully images exogenous or endogenous H2O2 in mitochondria with an additional 2.4-fold FL increase and 4.7-fold PA increase in HeLa cells or additional 2.1-fold FL increase and 3.3-fold PA increase in RAW 264.7 cells. In LPS-induced acute inflammation in vivo, TPP-HCy-BOH is more competent to image overproduced H2O2 with additional 1.6-fold higher sensitivity of FL in abdomen and 2.0-fold higher sensitivity of PA in liver and longer retention time of 0.5 h than HCy-BOH. We anticipate that TPP-HCy-BOH could be employed for the FL/PA dual-modal diagnosis of pathological inflammation in clinic in near future.

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Karlas A et al.

Multispectral optoacoustic tomography of peripheral arterial disease based on muscle hemoglobin gradients - a pilot clinical study

VascularClinicalMSOT

Background : Current imaging assessment of peripheral artery disease (PAD) relies on anatomical cross-sectional visualizations of the affected arteries. Multispectral optoacoustic tomography (MSOT) is a novel molecular imaging technique that provides direct and label-free visualizations of soft tissue perfusion and oxygenation. Methods : MSOT was prospectively assessed in a pilot trial in healthy volunteers (group n1=4, mean age 31, 50% male and group n3=4, mean age 37.3, 75% male) and patients with intermittent claudication (group n2=4, mean age 72, 75% male, PAD stage IIb). We conducted cuff-induced ischemia (group n1) and resting state measurements (groups n2 and n3) over the calf region. Spatially resolved mapping of oxygenated (HbO2), deoxygenated (Hb) and total (THb) hemoglobin, as well as oxygen saturation (SO2), were measured via hand-held hybrid MSOT-Ultrasound based purely on hemoglobin contrast. Results : Calf measurements in healthy volunteers revealed distinct dynamics for HbO2, Hb, THb and SO2 under cuff-induced ischemia. HbO2, THb and SO2 levels were significantly impaired in PAD patients compared to healthy volunteers (P<0.05 for all parameters). Revascularization led to significant improvements in HbO2 of the affected limb. Conclusions : Clinical MSOT allows for non-invasive, label-free and real-time imaging of muscle oxygenation in health and disease with implications for diagnostics and therapy assessment in PAD.

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Karlas A et al.

Multispectral optoacoustic tomography of peripheral arterial disease based on muscle hemoglobin gradients - a pilot clinical study

IschemiaClinicalMSOT

Background : Current imaging assessment of peripheral artery disease (PAD) relies on anatomical cross-sectional visualizations of the affected arteries. Multispectral optoacoustic tomography (MSOT) is a novel molecular imaging technique that provides direct and label-free visualizations of soft tissue perfusion and oxygenation. Methods : MSOT was prospectively assessed in a pilot trial in healthy volunteers (group n1=4, mean age 31, 50% male and group n3=4, mean age 37.3, 75% male) and patients with intermittent claudication (group n2=4, mean age 72, 75% male, PAD stage IIb). We conducted cuff-induced ischemia (group n1) and resting state measurements (groups n2 and n3) over the calf region. Spatially resolved mapping of oxygenated (HbO2), deoxygenated (Hb) and total (THb) hemoglobin, as well as oxygen saturation (SO2), were measured via hand-held hybrid MSOT-Ultrasound based purely on hemoglobin contrast. Results : Calf measurements in healthy volunteers revealed distinct dynamics for HbO2, Hb, THb and SO2 under cuff-induced ischemia. HbO2, THb and SO2 levels were significantly impaired in PAD patients compared to healthy volunteers (P<0.05 for all parameters). Revascularization led to significant improvements in HbO2 of the affected limb. Conclusions : Clinical MSOT allows for non-invasive, label-free and real-time imaging of muscle oxygenation in health and disease with implications for diagnostics and therapy assessment in PAD.

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Chen F et al.

Activatable Magnetic/ Photoacoustic Nanoplatform for Redox-Unlocked Deep-tissue Molecular Imaging In Vivo via Prussian Blue Nanoprobe

NanoPharmacokineticsPreclinicalMSOT

Drug-induced hepatic damage has drawn great attention on public health problems. Drugs are biotransformed in liver by enzymatic processes, accompanied by the production of reactive free radicals, which is the main cause of drug-induced hepatotoxicity. However, the limited penetration of optics make the use of current luminescent imaging more difficult for acquiring free radicals mapping for lesion location, when applied to whole-body imaging in vivo. In this work, we develop an activatable nanoprobe based on Prussian Blue (PB) that can combine magnetic resonance imaging (MRI) and photoacoustic imaging (PAI) for deep-tissue ONOO- imaging. We discover that ONOO- can oxidize FeII within PB into FeIII and meanwhile destroy the crystal structure of PB, so that the strong absorption of PB at 710 nm originated from the electron transferring between FeII and FeIII is greatly diminished. As a result, the reduced photoacoustic imaging (PA) signal of PB is able to function as an indicator for sensing ONOO-. Importantly, after reaction with ONOO-, the reduced size of PB result in the decrease of rotational correlation time (τR), leading to the activatable MRI signal for sensing ONOO-. Finally, we demonstrated PB nanoprobe is successfully able to image the variation of ONOO- in drug-induced hepatotoxicity in vivo by PAI and MRI bimodal imaging. Notably, the complementarity of such dual-modality imaging could not only endow our probes with better accuracy and higher penetration depth for visualizing of ONOO- in drug-induced liver injury, but also provide anatomical structure to identify the injury area of livers.

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Chen F et al.

Activatable Magnetic/ Photoacoustic Nanoplatform for Redox-Unlocked Deep-tissue Molecular Imaging In Vivo via Prussian Blue Nanoprobe

ToxicityPreclinicalMSOT

Drug-induced hepatic damage has drawn great attention on public health problems. Drugs are biotransformed in liver by enzymatic processes, accompanied by the production of reactive free radicals, which is the main cause of drug-induced hepatotoxicity. However, the limited penetration of optics make the use of current luminescent imaging more difficult for acquiring free radicals mapping for lesion location, when applied to whole-body imaging in vivo. In this work, we develop an activatable nanoprobe based on Prussian Blue (PB) that can combine magnetic resonance imaging (MRI) and photoacoustic imaging (PAI) for deep-tissue ONOO- imaging. We discover that ONOO- can oxidize FeII within PB into FeIII and meanwhile destroy the crystal structure of PB, so that the strong absorption of PB at 710 nm originated from the electron transferring between FeII and FeIII is greatly diminished. As a result, the reduced photoacoustic imaging (PA) signal of PB is able to function as an indicator for sensing ONOO-. Importantly, after reaction with ONOO-, the reduced size of PB result in the decrease of rotational correlation time (τR), leading to the activatable MRI signal for sensing ONOO-. Finally, we demonstrated PB nanoprobe is successfully able to image the variation of ONOO- in drug-induced hepatotoxicity in vivo by PAI and MRI bimodal imaging. Notably, the complementarity of such dual-modality imaging could not only endow our probes with better accuracy and higher penetration depth for visualizing of ONOO- in drug-induced liver injury, but also provide anatomical structure to identify the injury area of livers.

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Lafci B et al.

Deep Learning for Automatic Segmentation of Hybrid Optoacoustic Ultrasound (OPUS) Images

TechnologyPreclinicalMSOT

The highly complementary information provided by multispectral optoacoustics and pulse-echo ultrasound have recently prompted development of hybrid imaging instruments bringing together the unique contrast advantages of both modalities. In the hybrid optoacoustic ultrasound (OPUS) combination, images retrieved by one modality may further be used to improve the reconstruction accuracy of the other. In this regard, image segmentation plays a major role as it can aid improving the image quality and quantification abilities by facilitating modeling of light and sound propagation through the imaged tissues and surrounding coupling medium. Here we propose an automated approach for surface segmentation in whole-body mouse OPUS imaging using a deep convolutional neural network (CNN). The method has shown robust performance, attaining accurate segmentation of the animal boundary in both optoacoustic and pulseecho ultrasound images, as evinced by quantitative performance evaluation using Dice coefficient metrics.

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Lafci B et al.

Deep Learning for Automatic Segmentation of Hybrid Optoacoustic Ultrasound (OPUS) Images

TechnologyPreclinicalMSOT

The highly complementary information provided by multispectral optoacoustics and pulse-echo ultrasound have recently prompted development of hybrid imaging instruments bringing together the unique contrast advantages of both modalities. In the hybrid optoacoustic ultrasound (OPUS) combination, images retrieved by one modality may further be used to improve the reconstruction accuracy of the other. In this regard, image segmentation plays a major role as it can aid improving the image quality and quantification abilities by facilitating modeling of light and sound propagation through the imaged tissues and surrounding coupling medium. Here we propose an automated approach for surface segmentation in whole-body mouse OPUS imaging using a deep convolutional neural network (CNN). The method has shown robust performance, attaining accurate segmentation of the animal boundary in both optoacoustic and pulseecho ultrasound images, as evinced by quantitative performance evaluation using Dice coefficient metrics.

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Hao Y et al.

Polymeric Nanoparticles with ROS-Responsive Prodrug and Platinum Nanozyme for Enhanced Chemophotodynamic Therapy of Colon Cancer

NanoCancerPreclinicalMSOT

The combination of chemotherapy and photodynamic therapy (PDT) has promising potential in the synergistic treatment of cancer. However, chemotherapy and photodynamic synergistic therapy are impeded by uncontrolled chemotherapeutics release behavior, targeting deficiencies, and hypoxia-associated poor PDT efficacy in solid tumors. Here, a platinum nanozyme (PtNP) loaded reactive oxygen species (ROS)-responsive prodrug nanoparticle (CPT-TK-HPPH/Pt NP) is created to overcome these limitations. The ROS-responsive prodrug consists of a thioketal bond linked with camptothecin (CPT) and photosensitizer-2-(1-hexyloxyethyl)-2-devinyl pyropheophorbide-a (HPPH). The PtNP in CPT-TK-HPPH/Pt NP can efficiently catalyze the decomposition of hydrogen peroxide (H2O2) into oxygen to relieve hypoxia. The production of oxygen can satisfy the consumption of HPPH under 660 nm laser irradiation to attain the on-demand release of CPT and ensure enhanced photodynamic therapy. As a tumor diagnosis agent, the results of photoacoustic imaging and fluorescence imaging for CPT-TK-HPPH/Pt NP exhibit desirable long circulation and enhanced in vivo targeting. CPT-TK-HPPH/Pt NPs effectively inhibit tumor proliferation and growth in vitro and in vivo. CPT-TK-HPPH/Pt NP, with its excellent ROS-responsive drug release behavior and enhanced PDT efficiency can serve as a new cancer theranostic agent, and will further promote the research of chemophotodynamic synergistic cancer therapy.

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Hao Y et al.

Polymeric Nanoparticles with ROS-Responsive Prodrug and Platinum Nanozyme for Enhanced Chemophotodynamic Therapy of Colon Cancer

CancerPreclinicalMSOT

The combination of chemotherapy and photodynamic therapy (PDT) has promising potential in the synergistic treatment of cancer. However, chemotherapy and photodynamic synergistic therapy are impeded by uncontrolled chemotherapeutics release behavior, targeting deficiencies, and hypoxia-associated poor PDT efficacy in solid tumors. Here, a platinum nanozyme (PtNP) loaded reactive oxygen species (ROS)-responsive prodrug nanoparticle (CPT-TK-HPPH/Pt NP) is created to overcome these limitations. The ROS-responsive prodrug consists of a thioketal bond linked with camptothecin (CPT) and photosensitizer-2-(1-hexyloxyethyl)-2-devinyl pyropheophorbide-a (HPPH). The PtNP in CPT-TK-HPPH/Pt NP can efficiently catalyze the decomposition of hydrogen peroxide (H2O2) into oxygen to relieve hypoxia. The production of oxygen can satisfy the consumption of HPPH under 660 nm laser irradiation to attain the on-demand release of CPT and ensure enhanced photodynamic therapy. As a tumor diagnosis agent, the results of photoacoustic imaging and fluorescence imaging for CPT-TK-HPPH/Pt NP exhibit desirable long circulation and enhanced in vivo targeting. CPT-TK-HPPH/Pt NPs effectively inhibit tumor proliferation and growth in vitro and in vivo. CPT-TK-HPPH/Pt NP, with its excellent ROS-responsive drug release behavior and enhanced PDT efficiency can serve as a new cancer theranostic agent, and will further promote the research of chemophotodynamic synergistic cancer therapy.

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Hacker L et al.

Photoacoustics resolves species-specific differences in hemoglobin concentration and oxygenation

CancerVascularPreclinicalMSOT

Significance : Photoacoustic imaging (PAI) enables the detection of blood hemoglobin (HB) concentration and oxygenation (sO2) with high contrast and resolution. Despite the heavy use of photoacoustically determined total hemoglobin (THb) and oxygenation (sO2) biomarkers in PAI research, their relationship with underlying biochemical blood parameters and the impact of intra- and interspecies genetic variability have yet to be established. Aim : To explore the relationship between THb and sO2 photoacoustic biomarkers and the underlying biochemical blood parameters in a species-specific manner. Approach : Experiments were performed on blood in vitro using tissue-mimicking agar phantoms. Blood was extracted from mouse, rat, human, and naked mole-rat (Heterocephalus glaber), anticoagulated in ethylenediaminetetraacetic acid, and measured within 48 h. THb and sO2 were measured using a commercial photoacoustic tomography system (InVision 128, iThera Medical GmBH). Biochemical blood parameters such as HB concentration (g/dL), hematocrit (HCT, %), and red blood cell (RBC) count (μL – 1) were assessed using a hematology analyzer (Mythic 18 Vet, Woodley Equipment). Results : A significant correlation was observed between THb and biochemical HB, HCT, and RBC in mouse and rat blood. Moreover, PAI accurately recapitulated interspecies variations in HB and HCT between mouse and rat blood and resolved differences in the oxygen dissociation curves measured using sO2 between human, mouse, and rat. With these validation data in hand, we applied PAI to studies of blood obtained from naked mole-rats and could confirm the high oxygen affinity of this species in comparison to other rodents of similar size. Conclusions : Our results demonstrate the high sensitivity of photoacoustically determined hemoglobin biomarkers toward species-specific variations in vitro.

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Hacker L et al.

Photoacoustics resolves species-specific differences in hemoglobin concentration and oxygenation

IschemiaPreclinicalMSOT

Significance : Photoacoustic imaging (PAI) enables the detection of blood hemoglobin (HB) concentration and oxygenation (sO2) with high contrast and resolution. Despite the heavy use of photoacoustically determined total hemoglobin (THb) and oxygenation (sO2) biomarkers in PAI research, their relationship with underlying biochemical blood parameters and the impact of intra- and interspecies genetic variability have yet to be established. Aim : To explore the relationship between THb and sO2 photoacoustic biomarkers and the underlying biochemical blood parameters in a species-specific manner. Approach : Experiments were performed on blood in vitro using tissue-mimicking agar phantoms. Blood was extracted from mouse, rat, human, and naked mole-rat (Heterocephalus glaber), anticoagulated in ethylenediaminetetraacetic acid, and measured within 48 h. THb and sO2 were measured using a commercial photoacoustic tomography system (InVision 128, iThera Medical GmBH). Biochemical blood parameters such as HB concentration (g/dL), hematocrit (HCT, %), and red blood cell (RBC) count (μL – 1) were assessed using a hematology analyzer (Mythic 18 Vet, Woodley Equipment). Results : A significant correlation was observed between THb and biochemical HB, HCT, and RBC in mouse and rat blood. Moreover, PAI accurately recapitulated interspecies variations in HB and HCT between mouse and rat blood and resolved differences in the oxygen dissociation curves measured using sO2 between human, mouse, and rat. With these validation data in hand, we applied PAI to studies of blood obtained from naked mole-rats and could confirm the high oxygen affinity of this species in comparison to other rodents of similar size. Conclusions : Our results demonstrate the high sensitivity of photoacoustically determined hemoglobin biomarkers toward species-specific variations in vitro.

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Tomaszewski MR

Vascular Changes in Cancer Treatment-Seeing Is Believing

CancerVascularPreclinicalMSOT

Understanding the effects of novel cancer drugs on the tumor microenvironment will be crucial for their successful use in patients. In this issue of Cancer Research, Ghosh and colleagues discuss the effect of two promising heme-targeting agents on the vascular network in mouse models of lung cancer, utilizing emerging optoacoustic imaging approaches. The findings demonstrating significant, dynamic modulation of tumor hypoxia with the heme-targeting drug treatments create important opportunities for image-guided combination therapy.

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Tomaszewski MR

Vascular Changes in Cancer Treatment-Seeing Is Believing

CancerPreclinicalMSOT

Understanding the effects of novel cancer drugs on the tumor microenvironment will be crucial for their successful use in patients. In this issue of Cancer Research, Ghosh and colleagues discuss the effect of two promising heme-targeting agents on the vascular network in mouse models of lung cancer, utilizing emerging optoacoustic imaging approaches. The findings demonstrating significant, dynamic modulation of tumor hypoxia with the heme-targeting drug treatments create important opportunities for image-guided combination therapy.

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Feng J et al.

End-to-end Res-Unet based reconstruction algorithm for photoacoustic imaging

TechnologyPreclinicalMSOT

Recently, deep neural networks have attracted great attention in photoacoustic imaging (PAI). In PAI, reconstructing the initial pressure distribution from acquired photoacoustic (PA) signals is a typically inverse problem. In this paper, an end-to-end Unet with residual blocks (Res-Unet) is designed and trained to solve the inverse problem in PAI. The performance of the proposed algorithm is explored and analyzed by comparing a recent model-resolution-based regularization algorithm (MRR) with numerical and physical phantom experiments. The improvement obtained in the reconstructed images was more than 95% in pearson correlation and 39% in peak signal-to-noise ratio in comparison to the MRR. The Res-Unet also achieved superior performance over the state-of-the-art Unet++ architecture by more than 18% in PSNR in simulation experiments.

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Feng J et al.

End-to-end Res-Unet based reconstruction algorithm for photoacoustic imaging

TechnologyPreclinicalMSOT

Recently, deep neural networks have attracted great attention in photoacoustic imaging (PAI). In PAI, reconstructing the initial pressure distribution from acquired photoacoustic (PA) signals is a typically inverse problem. In this paper, an end-to-end Unet with residual blocks (Res-Unet) is designed and trained to solve the inverse problem in PAI. The performance of the proposed algorithm is explored and analyzed by comparing a recent model-resolution-based regularization algorithm (MRR) with numerical and physical phantom experiments. The improvement obtained in the reconstructed images was more than 95% in pearson correlation and 39% in peak signal-to-noise ratio in comparison to the MRR. The Res-Unet also achieved superior performance over the state-of-the-art Unet++ architecture by more than 18% in PSNR in simulation experiments.

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Jia X et al.

Functionalized Graphene@Gold Nanostar/Lipid for Pancreatic Cancer Gene and Photothermal Synergistic Therapy under Photoacoustic/Photothermal Imaging Dual-Modal Guidance

NanoCancerPreclinicalMSOT

Nanomaterial-based pancreatic cancer treatment has received widespread attention and rapid development in the past few years. The major challenges include the poor combination of diagnosis and therapy, the difficulty in targeting therapy from the root and the unsatisfactory antitumor efficiency, which is accompanied by a great risk of relapse and metastasis. In this work, a positively charged lipid bilayer membrane is coated on reduced graphene oxide@gold nanostar (rGO@AuNS) for photoacoustic/photothermal dual-modal imaging-guided gene/photothermal synergistic therapy of pancreatic cancer. In addition, the cross-linking of folic acid on the surface of rGO@AuNS-lipid can specifically bind after recognizing folic acid receptors on the surface of cancer cells, and greatly improve the targeting ability of the nanomaterial and the performance of imaging diagnosis by receptor-mediated endocytosis. Moreover, the photothermal and gene (targeting G12V mutant K-Ras gene) synergistic therapy shows outstanding anticancer efficacy for pancreatic cancer tumor bearing mice, and it is noteworthy that the treatment groups have anti-liver metastasis of pancreatic cancer.

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Xie X et al.

An Activatable Nano-Prodrug for Treating Tyrosine-Kinase-Inhibitor-Resistant Non-Small Cell Lung Cancer and for Optoacoustic and Fluorescent Imaging

NanoCancerPreclinicalMSOT

Non-small cell lung cancer (NSCLC) is the most common type of lung cancer and the cause of high rate of mortality. The epidermal growth factor receptor (EGFR)-targeted tyrosine kinase inhibitors are used to treat NSCLC, yet their curative effects are usually compromised by drug resistance. This study demonstrates a nanodrug for treating tyrosine-kinase-inhibitor-resistant NSCLC through inhibiting upstream and downstream EGFR signaling pathways. The main molecule of the nanodrug is synthesized by linking a tyrosine kinase inhibitor gefitinib and a near-infrared dye (NIR) on each side of a disulfide via carbonate bonds, and the nanodrug is then obtained through nanoparticle formation of the main molecule in aqueous medium and concomitant encapsulation of a serine threonine protein kinase (Akt) inhibitor celastrol. Upon administration, the nanodrug accumulates at the tumor region of NSCLC-bearing mice and releases the drugs for tumor inhibition, and the dye for fluorescence and optoacoustic imaging. Through suppressing the phosphorylation of upstream EGFR and downstream Akt in the EGFR pathway by gefitinib and celastrol, respectively, the nanodrug exhibits high inhibition efficacy against orthotopic NSCLC in mouse models.

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Chen J et al.

Activatable Probe for Detecting Alcoholic Liver Injury via Multispectral Optoacoustic Tomography and Fluorescence Imaging

Other ApplicationsPreclinicalMSOT

A probe has been developed for imaging alcoholic liver injury through detecting the overexpressed cytochrome P450 reductase in hypoxia in the hepatic region. Upon response to the enzyme, the activated probe displays turn-on fluorescence and near-infrared absorption and generates prominent optoacoustic signals.

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Hindelang B et al.

Quantification of skin sensitivity to ultraviolet radiation using ultra-wideband optoacoustic mesoscopy

SkinClinicalRSOM

Phototesting is used to assess individual sensitivity to ultraviolet (UV) radiation in order to determine adequate UV dosage for phototherapy . In the standard procedure, small skin areas are exposed to increasing doses of UV radiation. The lowest UV dose that induces a delineated erythema at 24±2 h after UV exposure defines the minimal erythema dose (MED) . Visual assessment is the gold standard for MED determination; however, it is prone to observer variability . Optical methods have been considered to quantify the magnitude of erythema response. However, they are limited by light scattering therefore high-resolution is restricted to depths of <200 μm resulting in unreliable measurements.

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You Q et al.

Persistent Regulation of Tumor Hypoxia Microenvironment via a Bioinspired Pt-Based Oxygen Nanogenerator for Multimodal Imaging-Guided Synergistic Phototherapy

NanoCancerPreclinicalMSOT

Multifunctional nanoplatforms for imaging-guided synergistic antitumor treatment are highly desirable in biomedical applications. However, anticancer treatment is largely affected by the pre-existing hypoxic tumor microenvironment (TME), which not only causes the resistance of the tumors to photodynamic therapy (PDT), but also promotes tumorigenesis and tumor progression. Here, a continuous O2 self-enriched nanoplatform is constructed for multimodal imaging-guided synergistic phototherapy based on octahedral gold nanoshells (GNSs), which are constructed by a more facile and straightforward one-step method using platinum (Pt) nanozyme-decorated metal-organic frameworks (MOF) as the inner template. The Pt-decorated MOF@GNSs (PtMGs) are further functionalized with human serum albumin-chelated gadolinium (HSA-Gd, HGd) and loaded with indocyanine green (ICG) (ICG-PtMGs@HGd) to achieve a synergistic PDT/PTT effect and fluorescence (FL)/multispectral optoacoustic tomography (MSOT)/X-ray computed tomography (CT)/magnetic resonance (MR) imaging. The Pt-decorated nanoplatform endows remarkable catalase-like behavior and facilitates the continuous decomposition of the endogenous H2O2 into O2 to enhance the PDT effect under hypoxic TME. HSA modification enhances the biocompatibility and tumor-targeting ability of the nanocomposites. This TME-responsive and O2 self-supplement nanoparticle holds great potential as a multifunctional theranostic nanoplatform for the multimodal imaging-guided synergistic phototherapy of solid tumors.

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Wu S et al.

Persistent luminescence-polypyrrole nanocomposite for dual-modal imaging and photothermal therapy of mammary cancer

NanoCancerPreclinicalMSOT

Multifunctional nanocomposites that possess imaging and high-performance therapeutic features are experiencing a surge in interest in the precision clinical anticancer treatment. In this work, we reported the fabrication and bio-application of a novel persistent luminescence-polypyrrole nanocomposite (LPLNP@SPP) for photoacoustic/persistent luminescence (PA/PL) dual-modal imaging guided photothermal therapy (PTT). The construction of LPLNP@SPP avoids the PL quenching of LPLNP-OH by the polypyrrole-coating, and thus enables the combination of PL and PTT. The LPLNP@SPP shows excellent biocompatibility, long lasting near-infrared (NIR) PL emitting without in situ excitation and high-contrast PA signals. Meanwhile, this nanocomposite exhibits strong NIR absorbance and exceptional photothermal conversion capability, which provides notable potential for imaging-guided antitumor therapy. Thus, our work highlights the dual-functional core-shell LPLNP@SPP as a feasible theranostic nanoplatform for cancer diagnosis and therapy.

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Fu W et al.

Stimuli-Responsive Small-on-Large Nanoradiosensitizer for Enhanced Tumor Penetration and Radiotherapy Sensitization

NanoCancerPreclinicalMSOT

Development of an efficient nanoradiosensitization system that enhances the radiation doses in cancer cells to sensitize radiotherapy (RT) while sparing normal tissues is highly desirable. Here, we construct a tumor microenvironment (TME)-responsive disassembled small-on-large molybdenum disulfide/hafnium dioxide (MoS2/HfO2) dextran (M/H-D) nanoradiosensitizer. The M/H-D can degrade and release the HfO2 nanoparticles (NPs) in TME to enhance tumor penetration of the HfO2 NPs upon near-infrared (NIR) exposure, which can solve the bottleneck of insufficient internalization of the HfO2 NPs. Simultaneously, the NIR photothermal therapy increased peroxidase-like catalytic efficiency of the M/H-D nanoradiosensitizer in TME, which selectively catalyzed intratumorally overexpressed H2O2 into highly oxidized hydroxyl radicals (·OH). The heat induced by PTT also relieved the intratumoral hypoxia to sensitize RT. Consequently, this TME-responsive precise nanoradiosensitization achieved improved irradiation effectiveness, potent oxygenation in tumor, and efficient suppression to tumor, which can be real-time monitored by computed tomography and photoacoustic imaging.

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Zheng Z et al.

Two-stage activated nano-truck enhanced specific aggregation and deep delivery for synergistic tumor ablation

NanoCancerPreclinicalMSOT

Although nanomedicines have shown high performance in tumor theranostics, their anticancer activity is still limited by the drug delivery capacity, especially lack of targeting capability, poor tumor accumulation, and insufficient tumor deep-penetration. To address this challenge, a high biocompatibility nano-truck (BMP NT) with a two-stage delivery mechanism is designed and developed to achieve the precision therapeutic efficacy of cancer. In view of the enhanced permeability retention (EPR) effect, the surface cleavable layer of BMP NTs can be selectively removed by the overexpressed MMP-2 in a tumor-microenvironment to expose the hydrophobic segments for an induced “braking effect” strategy, resulting in a significant increase in tumor accumulation. Once internalized into cancer cells with the overproduced glutathione (GSH) and H2O2, the BMP NTs undergo the second-stage “unloading process” to release Mn2+ ions and ultrasmall Bi2S3@BSA nanoparticles, and the obtained Mn2+ ions can act as a Fenton-like catalyst for continuously catalyzing the endogenous H2O2 into highly toxic hydroxyl radicals (˙OH) for CDT. The GSH depletion will in turn improve the Mn2+-H2O2 reaction, further enhancing CDT efficiency. Meanwhile, the ultrasmall Bi2S3@BSA endows BMP NTs with excellent photothermal conversion ability to generate local hyperthermia and accelerate the intratumoral Fenton process, thus leading to an effective tumor therapeutic outcome in the synergistic function of CDT/photothermal therapy (PTT). Moreover, the BMP NTs can be used for in situ self-generation magnetic resonance imaging (MRI) and photoacoustic (PA) imaging to guide precision cancer therapy.

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Zheng D et al.

Flexible Photothermal Assemblies with Tunable Gold Patterns for Improved Imaging-Guided Synergistic Therapy

NanoCancerPreclinicalMSOT

Self-assembly of gold nanoparticles demonstrates a promising approach to realize enhanced photoacoustic imaging (PAI) and photothermal therapy (PTT) for accurate diagnosis and efficient cancer therapy. Herein, unique photothermal assemblies with tunable patterns of gold nanoparticles (including arcs, rings, ribbons, and vesicles) on poly(lactic-co-glycolic acid) (PLGA) spheres are constructed taking advantage of emulsion-confined and polymer-directed self-assembly strategies. The influencing factors and formation mechanism to produce the assemblies are investigated in details. Both the emulsion structure and migration behaviors of amphiphilic block copolymer tethered gold nanoparticles are found to contribute to the formation of versatile photothermal assemblies. Hyaluronic acid-modified R-PLGA-Au (RPA) exhibits outstanding photothermal performances under NIR laser irradiation, which is induced by strong plasmonic coupling between adjacent gold nanoparticles. It is interesting that secondary assembly of RPA can be triggered by NIR laser irradiation. Prolonged residence time in tumors is achieved after RPA assemblies are fused into superstructures with larger sizes, realizing real-time monitoring of the therapeutic processes via PAI with enhanced photoacoustic signals. Notably, synergistic effect resulting from PTT-enhanced chemotherapy is realized to demonstrate high antitumor performance. This work provides a facile strategy to construct flexible photothermal assemblies with favorable properties for imaging-guided synergistic therapy.

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JP Fuenzalida Werner et al.

Challenging a Preconception: Optoacoustic Spectrum Differs from the Optical Absorption Spectrum of Proteins and Dyes for Molecular Imaging

TechnologyPreclinicalMSOT

Optoacoustic (photoacoustic) imaging has seen marked advances in detection and data analysis, but there is less progress in understanding the photophysics of common optoacoustic contrast agents. This gap blocks the development of novel agents and the accurate analysis and interpretation of multispectral optoacoustic images. To close it, we developed a multimodal laser spectrometer (MLS) to enable the simultaneous measurement of optoacoustic, absorbance, and fluorescence spectra. Herein, we employ MLS to analyze contrast agents (methylene blue, rhodamine 800, Alexa Fluor 750, IRDye 800CW, and indocyanine green) and proteins (sfGFP, mCherry, mKate, HcRed, iRFP720, and smURFP). We found that the optical absorption spectrum does not correlate with the optoacoustic spectrum for the majority of the analytes. We determined that for dyes, the transition underlying an aggregation state has more optoacoustic signal generation efficiency than the monomer transition. For proteins we found a favored optoacoustic relaxation that stems from the neutral or zwitterionic chromophores and unreported photoswitching behavior of tdTomato and HcRed. We then crystalized HcRed in its photoswitch optoacoustic state, confirming structurally the change in isomerization with respect to HcReds’ fluorescence state. Finally, on the example of the widely used label tdTomato and the dye indocyanine green, we show the importance of correct photophysical (e.g., spectral and kinetic) information as a prerequisite for spectral-unmixing for in vivo imaging.

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Zhang Z et al.

Zwitterionic Conjugated Polymer as the Single Component for Photoacoustic-Imaging-Guided Dual-Modal Near-Infrared Phototherapy

NanoCancerPreclinicalMSOT

Systems consisting of different functional components that synergistically increase the antitumor efficiency of different cancer therapies are in great demand. Here, we report the use of nanoparticles (NPs) composed of a zwitterionic conjugated polymer, generating reactive oxygen species (ROS) and heat. These NPs are more effective in antitumor than single photodynamic therapy (PDT) or photothermal therapy (PTT) and have an optimal absorbance ranging from 700 to 850 nm. Light in this range is capable of reaching tumors by penetrating deep into tissues. The simultaneous PDT and PTT using a single near-infrared (NIR) light can be monitored via photoacoustic imaging (PAI). Treatment of tumor-bearing nude mice with combined PDT and PTT following tail vein injection of NPs resulted in complete tumor remission. No tumor relapse was observed during a 20 day treatment. These zwitterionic conjugated polymeric NPs with the capability of generating ROS and heat show great potential for PAI-guided photodynamic/photothermal dual-modal therapy.

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Longo A et al.

Assessment of hessian-based Frangi vesselness filter in optoacoustic imaging

VascularPreclinicalMSOT

The Hessian-based Frangi vesselness filter is commonly used to enhance vasculature in optoacoustic (photoacoustic) images, but its accuracy and limitations have never been rigorously assessed. Here we validate the ability of the filter to enhance vessel-like structures in phantoms, and we introduce an experimental approach that uses measurements before and after the administration of gold nanorods (AuNRs) to examine filter performance in vivo. We evaluate the influence of contrast, filter scales, angular tomographic coverage, out-of-plane signals and light fluence on image quality, and gain insight into the performance of the filter. We observe the generation of artifactual structures that can be misinterpreted as vessels and provide recommendations to ensure appropriate use of Frangi and other vesselness filters and avoid misinterpretation of post-processed optoacoustic images.

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Deán-Ben XL et al.

Deep tissue volumetric optoacoustic tracking of individual circulating tumor cells in an intracardially perfused mouse model

CancerPreclinicalMSOT

Widespread metastasis is the major cause of death from melanoma and other types of cancer. At present, the dynamic aspects of the metastatic cascade remain enigmatic. The feasibility to track circulating melanoma cells deep within living intact organisms can greatly impact our knowledge on tumor metastasis, but existing imaging approaches lack the sensitivity, spatio-temporal resolution or penetration depth to capture flowing tumor cells over large fields of view within optically-opaque biological tissues. Vast progress with the development of optoacoustic tomography technologies has recently enabled two- and three-dimensional imaging at unprecedented frame rates in the order of hundreds of Hertz, effectively mapping up to a million image voxels within a single volumetric snapshot. Herein, we employ volumetric optoacoustic tomography for real-time visualization of passage and trapping of individual B16 melanoma cells in the whole mouse brain. Detection of individual circulating melanoma cells was facilitated by substituting blood with an artificial cerebrospinal fluid that removes the strong absorption background in the optoacoustic images. The approach can provide new opportunities for studying trafficking and accumulation of metastatic melanoma cells in different organs.

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Peng B et al.

A Ratiometric Photoacoustic Imaging Approach for Semi-Quantitative Determination of Aggregation Efficiency in vivo

NanoCancerPreclinicalMSOT

In vivo self-assembly not only endows dynamic supramolecules with various biological functions, but also realizes metabolic differences, and improves the level of diagnosis and treatment. However, the method of measuring aggregation efficiency in vivo is still challenging. In this work, we first proposed a ratiometric photoacoustic imaging method to measure the aggregation efficiency of molecules in vivo in real time and semi-quantitatively. Similar to the traditional fluorescence method, the ratiometric photoacoustic signal has a typical exponential relationship with the aggregation efficiency, which is defined as the percentage of aggregation molecules in the total molecules. Then, we proposed a ratiometric photoacoustic (PA) probe, which can be tailored by cathepsin E and self-assembled into nanofibers in situ inside pancreatic cancer cells. The maximum aggregation efficiency of 10-5 M PA probe was 58% after 2 hours of incubation. After intratumoral administration in xenografted pancreatic tumor mice, the highest aggregation efficiency was found to be 36% 6 hours after the injection. The ratiometric PA probe provides us with a real-time method to detect the aggregation efficiency in vivo, which is helpful to deepen the understanding of the dynamic assembly process and optimize the design of supramolecules.

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Min H et al.

A Graphdiyne Oxide-Based Iron Sponge with Photothermally Enhanced Tumor-Specific Fenton Chemistry

NanoCancerPreclinicalMSOT

Fenton reaction-mediated oncotherapy is an emerging strategy which uses iron ions to catalytically convert endogenous hydrogen peroxide into hydroxyl radicals, the most reactive oxygen species found in biology, for efficient cancer therapy. However, Fenton reaction efficiency in tumor tissue is typically limited due to restrictive conditions. One strategy to overcome this obstacle is to increase the temperature specifically at the tumor site. Herein, a tumor-targeting iron sponge (TTIS) nanocomposite based on graphdiyne oxide, which has a high affinity for iron is described. TTIS can accumulate in tumor tissue by decoration with a tumor-targeting polymer to enable tumor photoacoustic and magnetic resonance imaging. With its excellent photothermal conversion efficiency (37.5%), TTIS is an efficient photothermal therapy (PTT) agent. Moreover, the heat produced in the process of PTT can accelerate the release of iron ions from TTIS and simultaneously enhance the efficiency of the Fenton reaction, thus achieving a combined PTT and Fenton reaction-mediated cancer therapy. This work introduces a graphdiyne oxide-based iron sponge that exerts an enhanced antitumor effect through PTT and Fenton chemistry.

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Zhang Y et al.

Enhanced Radiotherapy Using Photothermal Therapy Based on Dual-Sensitizer of Gold Nanoparticles With Acid-Induced Aggregation

NanoCancerPreclinicalMSOT

The damaged DNA strands caused by radiotherapy (RT) can repair by themselves. A gold nanoparticles (GNPs) system with acid-induced aggregation was developed into a dual sensitizer owing to its high radioactive rays attenuation ability and enhanced photothermal heating efficiency after GNPs aggregation to achieve a combination therapy of RT and photothermal therapy (PTT). In this combination therapy, the formed GNP aggregates firstly showed a higher sensitize enhancement ratio (SER) value (1.52). Importantly, the self-repair of damaged DNA strands was inhibited by mild PTT through down-regulating the expression of DNA repair protein, thus resulting in a much higher SER value (1.68). Anti-tumor studies further demonstrated that this combination therapy exhibited ideal anti-tumor efficacy. Furthermore, the imaging signals of GNPs in computed tomography and photoacoustic were significantly improved following the GNPs aggregation. Therefore, a dual sensitizer with multimodal imaging was successfully developed and can be further applied as a new anti-tumor therapy.

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Liu HW et al.

Imaging of Peroxynitrite in Drug-Induced Acute Kidney Injury With a Near-Infrared Fluorescence and Photoacoustic Dual-Modal Molecular Probe

Other ApplicationsPreclinicalMSOT

A FRET-based probe for mapping the fluctuation of ONOO- in cisplatin-induced acute kidney injury was constructed. It exhibits ratiometric near infrared fluorescence and a dramatic decrease of its peak absorbance at 719 nm upon addition of ONOO- that is converted into remarkable signal changes in fluorescence and photoacoustic images respectively.

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Zhang R et al.

Acid-Induced In Vivo Assembly of Gold Nanoparticles for Enhanced Photoacoustic Imaging-Guided Photothermal Therapy of Tumors

NanoCancerPreclinicalMSOT

The complexity of biological systems poses a great challenge in the development of nanotheranostic agents with enhanced therapeutic efficacies. To systematically overcome a series of barriers during in vivo administration and achieve optimal antitumor activity, nanotheranostic agents that can self-adaptively change their properties in response to certain tumor-associated signals are highly preferable. Herein, gold nanoparticles with a mixed-charge zwitterionic surface (Au-MUA-TMA) is fabricated, which can undergo pH-triggered self-assembly for promoting tumor targeting and improving photoacoustic imaging (PAI)-guided photothermal tumor ablation. In blood and normal tissues, relatively small-sized Au-MUA-TMA can circulate stably, and upon arriving at the tumor sites, they quickly assemble into larger aggregates in an acidic tumor environment to ensure higher tumor accumulation and retention. Furthermore, the absorption band of Au-MUA-TMA can be remarkably shifted to the near-infrared (NIR) region, which effectively activates the photoacoustic (PA) signals of tumors and enhances photothermal therapy (PTT) with minimal side effects. This in vivo self-assembly strategy enables the nanotheranostic agents to better fulfill multiple requirements for in vivo application, thereby attaining advanced performances in cancer diagnosis and treatment.

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Yew YW et al.

Raster-scanning optoacoustic mesoscopy imaging as an objective disease severity tool in atopic dermatitis patients

InflammationClinicalRSOM

Background : Accurate assessment of disease severity in atopic dermatitis (AD) is important in guiding management. Objective : To evaluate the feasibility of raster-scanning optoacoustic mesoscopy (RSOM) imaging as an objective disease severity tool for AD. Methods : This prospective study included 69 AD patients and 22 healthy volunteers. All AD participants were assessed using the Scoring Atopic Dermatitis (SCORAD) instrument and all participants had RSOM imaging using RSOM Explorer C50 system (iThera Medical GmbH, Germany). From the RSOM images generated, epidermis thickness (ET), total blood volume (TBV), vessel diameter in the dermis (VD), ratio of low and high frequency signals (LHFR) in the dermis were computed. We trained a linear kernel-based support vector machine model for eczema classification based on ET, TBV and LHFR. A novel Eczema Vascular and Structural Index (EVSI) was then formulated to assess eczema severity. Results : EVSI accurately classified healthy and eczematous skin (p <0.0001). EVSI obtained a high cross-validated area under the curve of 0.921, accuracy of 0.872, with high sensitivity and specificity of 0.853 and 0.838 respectively. The Pearson’s correlation coefficient of EVSI and SCORAD was 0.768. Conclusion : RSOM provides an accurate, direct and objective assessment of the skin ultra-structures in a non-invasive manner.

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Chen Z et al.

Thermosensitive Nanoplatform for Photoacoustic Imaging and NIR Light Triggered Chemo-photothermal Therapy

NanoCancerPreclinicalMSOT

Temperature-sensitive liposomes (TSLs) have received constant attention due to the release of contents around the physiological temperature, which holds great potential in the treatment of tumors. However, the development of TSLs is limited by the long-term biotoxicity and low photothermal conversion efficiency of heat-generation materials. In this study, we develop a new D–A (donor–acceptor) structure NIR absorbing dye (C720) which exhibits a high photothermal conversion efficiency (62%), good photostability, and photothermal reproducibility. Then C720 is doped in the lipid bilayer and DOX (doxorubicin) is wrapped in the core of temperature sensitive liposomes to construct a C720 and DOX-loaded thermosensitive nanoplatform (CDTSL). The as-prepared CDTSL achieves NIR light controlled drug release and can be applied for photoacoustic imaging. In vitro and in vivo studies confirm that CDTSL exhibits high tumor suppressive efficiency by synergistic photothermal therapy and chemotherapy. Our research provides fundamental insights for the rational design and preparation of a promising nanoplatform for photoacoustic imaging and chemo-photothermal therapy.

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Novoselova MV et al.

Optical clearing for photoacoustic lympho- and angiography beyond conventional depth limit in vivo

NanoVascularSkinPreclinicalRSOM

Photoacoustic (PA) imaging (PAI) is an emerging powerful tool for noninvasive real-time mapping of blood and lymphatic vessels and lymph nodes in vivo to diagnose cancer, lymphedema and other diseases. Among different PAI instruments, commercially available raster-scanning optoacoustic mesoscopy (RSOM) (iThera Medical GmbH., Germany) is useful for high-resolution imaging of different tissues with high potential of clinical translation. However, skin light scattering prevents mapping vessels and nodes deeper than 1-2 mm, that limits diagnostic values of PAI including RSOM. Here we demonstrate that glycerol-based tissue optical clearing (TOC) overcomes this challenge by reducing light scattering that improves RSOM depth penetration. In preclinical model of mouse limb in vivo, the replacement of conventional acoustic coupling agents such as water on the mixture of 70 % glycerol and 30 % ultrasound (US) gel resulted in the increase of tissue imaging depth in 1.5-2 times with 3D visualization of vessels with diameter down to 20 μm. To distinguish blood and lymphatic networks, we integrated label-free PA angiography (i.e., imaging of blood vessels), which uses hemoglobin as endogenous contrast agent, with PA lymphography based on labeling of lymphatic vessels with exogenous PA contrast agents. Similar to well-established clinical lymphography, contrast agents were injected in tissue and taken up by lymphatic vessels within a few minutes that provided quick RSOM lymphography. Furthermore, co-injection of PA contrast dye and multilayer nanocomposites as potential low-toxic drug-cargo showed selective prolonged accumulation of nanocomposites in sentinel lymph nodes. Overall, our findings open perspectives for deep and high resolution 3D PA angio- and lymphography, and for PA-guided lymphatic drug delivery using new RSOM & TOC approach.

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Yan C et al.

Magnetic-Photoacoustic Dual-Mode Probe for the Visualization of H2S in Colorectal Cancer

NanoCancerPreclinicalMSOT

Techniques for the qualitative and quantitative detection of H2S in vivo have attracted considerable attention due to the key role of H2S in various physiological and pathological processes. However, in vivo detection strategies for H2S are mainly based on fluorescence imaging, which is limited by its poor tissue penetration. Moreover, the limitations of single-mode probes are amplified in complex physiological environments. Herein, a core-shell Fe3O4@Cu2O nanoparticle was constructed as a magnetic-photoacoustic dual-mode probe for H2S detection in vitro and in vivo based on the in situ response of Cu2O to endogenous H2S in colon tumors. This probe is expected to greatly improve the accuracy of H2S detection in vivo because it employs two detection methods with complementary advantages. The new probe was experimentally applied to the in vivo and in vitro visualization of H2S in mice with colorectal cancer, validating the in situ reaction-activated dual-detection method. This work establishes a simple and efficient dual-mode imaging method based on a novel trigger mechanism. The findings provide a new strategy for colon cancer detection based on the in situ reactions at tumor sites.

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Ghosh P et al.

Oxygen-enhanced optoacoustic tomography reveals the effectiveness of targeting heme and oxidative phosphorylation at normalizing tumor vascular oxygenation

CancerVascularPreclinicalMSOT

Multispectral optoacoustic tomography (MSOT) is an emerging noninvasive imaging modality that can detect real-time dynamic information about the tumor microenvironment (TME) in humans and animals. Oxygen enhanced (OE)-MSOT can monitor tumor vasculature and oxygenation during disease development or therapy. Here we used MSOT and OE-MSOT to examine in mice the response of human non-small cell lung cancer (NSCLC) xenografts to a new class of anti-tumor drugs, heme-targeting agents heme-sequestering peptide 2 (HSP2) and cyclopamine tartrate (CycT). HSP2 inhibits heme uptake while CycT inhibits heme synthesis in NSCLC cells, where heme is essential for ATP generation via oxidative phosphorylation. HSP2 and CycT can inhibit ATP generation and thereby suppress NSCLC cell tumorigenic functions. MSOT showed that treatment of NSCLC tumors with HSP2 or CycT reduced total hemoglobin, increased oxygen saturation, and enhanced the amplitude of response to oxygen gas breathing challenge. HSP2 and CycT normalized tumor vasculature and improved tumor oxygenation, where levels of several hypoxia markers in NSCLC tumors were reduced by treatment with HSP2 or CycT. Furthermore, treatment with HSP2 or CycT reduced levels of angiogenic factor VEGFA, its receptor VEGFR1, and vascular marker CD34. Together, our data show that heme-targeting drugs HSP2 and CycT elicit multiple tumor-suppressing functions, such as inhibiting angiogenic function, normalizing tumor vasculature, alleviating tumor hypoxia, and inhibiting oxygen consumption and ATP generation.

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Zhu Y et al.

Bioactive MOFs Based Theranostic Agent for Highly Effective Combination of Multimodal Imaging and Chemo-Phototherapy

NanoCancerPreclinicalMSOT

Bioactive metal-organic frameworks (bio-MOFs) built from biofunctional metal ions and linkers show a new strategy to construct multifunctional theranostic platforms. Herein, a bio-MOF is synthetized via the self-assembling of Fe3+ ions and doxorubicin hydrochloride (DOX) molecules. Then, through a stepwise assembly strategy, another bio-MOFs structure consisting of Gd3+ ions and 1,3,5-benzenetricarboxylic acid (H3 BTC) is wrapped on the surfaces of Fe-DOX nanoparticles, followed by adsorbing photosensitizer indocyanine green (ICG). Specifically, the Gd-MOF shell structure can not only act as a contrast agent for magnetic resonance imaging (MRI), but also provides protection for Fe-DOX cores, controlling the release of DOX. The photoacoustic and photothermal imaging (PAI and PTI) methods are successfully introduced to the platform by loading ICG, providing potential applications for multimodal biological imaging. The in vitro and in vivo outcomes indicate that the Fe-DOX@Gd-MOF-ICG nanoplatform exhibits outstanding synergistic antitumor performance via MR/PA/PT imaging guided chemotherapy, photothermal and photodynamic combination therapy. The work may encourage further exploration of bio-MOFs based multifunctional theranostic platforms for multimodal imaging guided compound antitumor therapy, which will open an avenue of MOFs toward biological applications.

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Mishra K et al.

Multiplexed Whole-Animal Imaging With Reversibly Switchable Optoacoustic Proteins

CancerPreclinicalMSOT

We introduce two photochromic proteins for cell-specific in vivo optoacoustic (OA) imaging with signal unmixing in the temporal domain. We show highly sensitive, multiplexed visualization of T lymphocytes, bacteria, and tumors in the mouse body and brain. We developed machine learning-based software for commercial imaging systems for temporal unmixed OA imaging, enabling its routine use in life sciences.

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Wu S et al.

Persistent Luminescence Nanoplatform With Fenton-like Catalytic Activity for Tumor Multimodal Imaging and Photoenhanced Combination Therapy

NanoCancerPreclinicalMSOT

Reactive oxygen species-mediated tumor chemodynamic therapy and photodynamic therapy have captured extensive attention in practical cancer combination therapies. However, the severe treatment conditions and the hypoxic microenvironment of solid tumors significantly limit the efficacy of these therapies. This work demonstrates the design and fabrication of a multifunctional persistent luminescence nanoplatform (PHFI, refers to PLNP-HSA-Fe3+-IR780) for cancer multimodal imaging and effective photoenhanced combination therapy. The near-infrared-emitted persistent luminescence nanoparticles (PLNP) was modified with human serum albumin (HSA) combined with an IR780 probe and Fe3+. The synthesized PHFI possesses high longitudinal relaxivity, obvious photoacoustic contrast signals, and long-lasting persistent luminescence, indicating that PHFI can be used for cancer magnetic resonance imaging, photoacoustic imaging, and persistent luminescence multimodal imaging. PHFI shows intrinsic photoenhanced Fenton-like catalytic activities as well as photodynamic and photothermal effects and thereby can effectively overcome severe treatment conditions for killing tumor cells. It is worth noting that PHFI serving as a rechargeable internal light source for photoenhanced combination therapy was first disclosed. We believe that our work shows the great potential of PHFI for cancer theranostics and will advance the development of PLNP-based nanoplatforms in tumor catalytic therapy.

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Jiang Y et al.

Polymerization-induced photothermy: A non-donor-acceptor approach to highly effective near-infrared photothermal conversion nanoparticles

NanoCancerPreclinicalMSOT

Photothermal conversion nanoagents based on conjugated polymers (CPs) are attracting increasing attention for in vivo disease theranostics and high-performing ones are in urgent pursuit. Herein, we report a new and non-donor-acceptor approach to photothermal conversion CPs that combine several merits including low bandgaps, strong near-infrared absorption, low intersystem crossing rate and non-emissive nature. Three CPs based on 6,7; 6′,7′-fused isoindigos (nIIDs), i.e., P2IIDV, P3IIDV and P4IIDV that have optical bandgaps of 1.30, 1.22 and 1.17 eV, respectively, are synthesized. The nanoparticles (NPs) of the CPs in water are prepared via nanocoprecipitation, which are non-fluorescent due to the rapid intramolecular twisting in the CP backbone within NPs, enabling most of the excitation energy flow to generate heat. The photothermal conversion efficiencies of the NPs as measured under irradiation at 808, 880 and 980 nm are 62.4%, 40.5% and 15.8% for P2IIDV, 65.1%, 41.0% and 38.9% for P3IIDV and 71.5%, 48.9% and 41.7% for P4IIDV, which are significantly higher than indocyanine green and many popularly reported photothermal conversion materials. In vivo studies using xenograft 4T1 tumor-bearing mouse model demonstrate that the P4IIDV NPs can serve as a rather effective photothermal conversion nanoagent for enhanced photoacoustic imaging and photothermal therapy of tumors.

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Shao L et al.

Complementary autophagy inhibition and glucose metabolism with rattle-structured polydopamine@mesoporous silica nanoparticles for augmented low-temperature photothermal therapy and in vivo photoacoustic imaging

NanoCancerPreclinicalMSOT

Rattle-structured nanoparticles with movable cores, porous shells and hollow interiors have shown great effectiveness in drug delivery and cancer theranostics. Targeting autophagy and glucose have provided alternative strategies for cancer intervention therapy. Herein, rattle-structured polydopamine@mesoporous silica nanoparticles were prepared for in vivo photoacoustic (PA) imaging and augmented low-temperature photothermal therapy (PTT) via complementary autophagy inhibition and glucose metabolism. Methods : The multifunctional rattle-structured nanoparticles were designed with the nanocore of PDA and the nanoshell of hollow mesoporous silica (PDA@hm) via a four-step process. PDA@hm was then loaded with autophagy inhibitor chloroquine (CQ) and conjugated with glucose consumer glucose oxidase (GOx) (PDA@hm@CQ@GOx), forming a corona-like structure nanoparticle. Results : The CQ and GOx were loaded into the cavity and decorated onto the surface of PDA@hm, respectively. The GOx-mediated tumor starvation strategy would directly suppress the expression of HSP70 and HSP90, resulting in an enhanced low-temperature PTT induced by PDA nanocore. In addition, autophagy inhibition by the released CQ made up for the loss of low-temperature PTT and starvation efficiencies by PTT- and starvation-activated autophagy, realizing augmented therapy efficacy. Furthermore, the PDA nanocore in the PDA@hm@CQ@GOx could be also used for PA imaging. Conclusion : Such a “drugs” loaded rattle-structured nanoparticle could be used for augmented low-temperature PTT through complementarily regulating glucose metabolism and inhibiting autophagy and in vivo photoacoustic imaging.

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Zheng Z et al.

A Continuous Stimuli-Responsive System for NIR-II fluorescence/photoacoustic Imaging Guided photothermal/gas Synergistic Therapy

NanoCancerPreclinicalMSOT

Nanosystems responsive to a tumor microenvironment (TME) have recently attracted great attention due to their potential in precision cancer theranostics. However, theranostic nanosystems with a TME-activated consecutive cascade for the accurate diagnosis and treatment of cancer have rarely been exploited. Herein, an activatable theranostic nanosystem (Bi2S3-Ag2S-DATS@BSA-N3 NYs) is designed and constructed on the basis of a one-pot biomineralization method and surface functional modification to improve second near-infrared (NIR-II) fluorescence/photoacoustic (PA) imaging-guided photothermal therapy (PTT)/gas therapy (GT). Based on enhanced penetration and retention (EPR) effect-mediated tumor accumulation, the tumor-overexpressed glutathione (GSH) can accelerate hydrogen sulfide (H2S) generation from the nanoparticles by reacting with the encapsulated diallyl trisulfide (DATS). Meanwhile, the in situ released H2S can be used not only for gas therapy, but also to start the reduction of -N3(-) to -NH2(+), thereby enhancing the tumor-specific aggregation of NYs. As a result, the activatable nanosystems with excellent tumor accumulation and biodistribution could achieve an accurate NIR-II/PA dual-modality imaging for guiding the synergistic anticancer efficacy (PTT/GT). Thus, this work provides a promising TME-mediated continuously responsive strategy for efficient anticancer therapy.

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Mc Larney B et al.

Monitoring of Stimulus Evoked Murine Somatosensory Cortex Hemodynamic Activity With Volumetric Multi-Spectral Optoacoustic Tomography

NeuroPreclinicalMSOT

Sensory stimulation is an attractive paradigm for studying brain activity using various optical-, ultrasound- and MRI-based functional neuroimaging methods. Optoacoustics has been recently suggested as a powerful new tool for scalable mapping of multiple hemodynamic parameters with rich contrast and previously unachievable spatio-temporal resolution. Yet, its utility for studying the processing of peripheral inputs at the whole brain level has so far not been quantified. We employed volumetric multi-spectral optoacoustic tomography (vMSOT) to non-invasively monitor the HbO, HbR, and HbT dynamics across the mouse somatosensory cortex evoked by electrical paw stimuli. We show that elevated contralateral activation is preserved in the HbO map (invisible to MRI) under isoflurane anesthesia. Brain activation is shown to be predominantly confined to the somatosensory cortex, with strongest activation in the hindpaw region of the contralateral sensorimotor cortex. Furthermore, vMSOT detected the presence of an initial dip in the contralateral hindpaw region in the delta HbO channel. Sensorimotor cortical activity was identified over all other regions in HbT and HbO but not in HbR. Pearson’s correlation mapping enabled localizing the response to the sensorimotor cortex further highlighting the ability of vMSOT to bridge over imaging performance deficiencies of other functional neuroimaging modalities.

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Yin T et al.

Simple Structural Indocyanine Green-Loaded Microbubbles for Dual-Modality Imaging and Multi-Synergistic Photothermal Therapy in Prostate Cancer

CancerPreclinicalMSOT

As problems with the overuse of radical prostate cancer (PCa) treatment are increasingly exposed, focal therapy represents the direction of low- or intermediate-risk PCa management in the future. However, inaccurate diagnosis and low controllability of focal therapy hinder its clinical translation. In this study, we develop simple structural cyclic arginine-glycine-aspartic (cRGD) peptide-modified and indocyanine green (ICG)-loaded microbubbles (cRGD-ICG-MBs) for ultrasound-photoacoustic imaging and multi-synergistic photothermal therapy (PTT) to address the above problems. Precise PCa diagnosis is achieved by molecular ultrasound imaging. cRGD-targeting and low-frequency ultrasound with an amplitude of 500 kPa convert MBs into nanoparticles for enhanced ICG delivery. A low-frequency 2500-kPa amplitude ultrasound enables temporary vasculature destruction, which minimizes heat loss during PTT. Specifically, ICG in the tumor region is 14-fold higher than the control, resulting in satisfactory PTT. Our study highlights that this theranostic strategy possesses considerable clinical translational potential, especially in mini-invasive and individualized PCa therapy.

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Ma P et al.

MnOx Nanospikes as Nanoadjuvants and Immuogenic Cell Death Drugs With Enhanced Antitumor Immunity and Antimetastatic Effect

NanoCancerPreclinicalMSOT

Despite the widespread applications of manganese oxide nanomaterials (MONs) in biomedicine, the intrinsic immunogenicity of MONs is still unclear. Herein, MnOx nanospikes (NSs) as tumor microenvironment (TME)-responsive nanoadjuvants and immuogenic cell death (ICD) drugs are proposed firstly for cancer nanovaccine-based immunotherapy. MnOx NSs with large mesopores structures show ultrahigh loading efficiencies for ovalbumin and tumor cell fragment. The combination of ICD via chemodynamic therapy and ferroptosis inductions as well as antigen stimulations presents a better synergistic immunopotentiation action. Furthermore, the obtained nanovaccines can not only achieve TME-responsive magnetic resonance/photoacoustic dual-mode imaging contrasts, but also effectively inhibit primary/distal tumor growth as well as tumor metastasis.

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Tian Q et al.

Ellagic acid–Fe nanoscale coordination polymer with higher longitudinal relaxivity for dual-modality T1-weighted magnetic resonance and photoacoustic tumor imaging

TechnologyPreclinicalMSOT

Dual-modality contrast agents for T1-weighted magnetic resonance imaging (MRI) and photoacoustic imaging have attracted substantial attention as they combine the advantages of unlimited penetration depth and high sensitivity. However, most of the reported agents are Gd-based materials that exhibit nephrotoxicity, and few studies have focused on Fe-based materials owing to their lower relaxivity. This work describes the development of an ellagic acid (EA)–Fe nanoscale coordination polymer with high longitudinal relaxivity and strong near-infrared absorption for dual-modality T1-weighted MRI and photoacoustic imaging. The longitudinal relaxivity (r1) of the prepared EA-Fe@BSA nanoparticles was 2.54 mM− s−1, an increase of 185% compared with previously reported gallic acid-Fe nanoparticles. Furthermore, in vitro and in vivo experiments demonstrate that the EA-Fe@BSA NPs are an excellent T1-weighted MRI and photoacoustic dual-modality contrast agent with the advantages of convenient synthesis and low toxicity, exhibiting great potential for clinical use in tumor imaging.

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Ozbek A et al.

Compressed Optoacoustic Sensing of Volumetric Cardiac Motion

TechnologyPreclinicalMSOT

The recently developed optoacoustic tomography systems have attained volumetric frame rates exceeding 100 Hz, thus opening up new venues for studying previously invisible biological dynamics. Further gains in temporal resolution can potentially be achieved via partial data acquisition, though a priori knowledge on the acquired data is essential for rendering accurate reconstructions using compressed sensing approaches. In this work, we suggest a machine learning method based on principal component analysis for high-frame-rate volumetric cardiac imaging using only a few tomographic optoacoustic projections. The method is particularly effective for discerning periodic motion, as demonstrated herein by non-invasive imaging of a beating mouse heart. A training phase enables efficiently compressing the heart motion information, which is subsequently used as prior information for image reconstruction from sparse sampling at a higher frame rate. It is shown that image quality is preserved with a 64-fold reduction in the data flow. We demonstrate that, under certain conditions, the volumetric motion could effectively be captured by relying on time-resolved data from a single optoacoustic detector. Feasibility of capturing transient (non-periodic) events not registered in the training phase is further demonstrated by visualizing perfusion of a contrast agent in vivo. The suggested approach can be used to significantly boost the temporal resolution of optoacoustic imaging and facilitate development of more affordable and data efficient systems.

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Han Y et al.

A Simple POM Clusters for in Vivo NIR-II Photoacoustic Imaging-Guided NIR-II Photothermal Therapy

NanoCancerPreclinicalMSOT

Photoacoustic (PA) imaging in the second near-infrared (NIR-II) window exhibits enhanced deep-tissue imaging capability. Likely, cancer therapy in the NIR-II window could provide deeper penetration depth and higher exposure to laser over NIR-I. However, the traditional application of excitation light is still in the NIR-I window. In view of the excellent imaging and therapeutic capabilities of NIR-II window, we have demonstrated a simple polyoxometalate (POM) clusters (molecular formula: (Na)n(PMo12O40) or (NH4+)n(PMo12O40)), which integrates NIR-II photoacoustic imaging and NIR-II photothermal therapy into an “all-in-one” theranostic nanoplatform, and could be used for PA imaging-guided photothermal therapy in the NIR-II window. In vivo experiments demonstrate that the POM clusters with good water solubility and biocompatibility were effective to kill tumor without recurrence and metastasis under 1064 nm laser illumination.

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Tong T et al.

Domain Transform Network for Photoacoustic Tomography from Limited-view and Sparsely Sampled Data

TechnologyPreclinicalMSOT

Medical image reconstruction methods based on deep learning have recently demonstrated powerful performance in photoacoustic tomography (PAT) from limited-view and sparse data. However, because most of these methods must utilize conventional linear reconstruction methods to implement signal-to-image transformations, their performance is restricted. In this paper, we propose a novel deep learning reconstruction approach that integrates appropriate data pre-processing and training strategies. The Feature Projection Network (FPnet) presented herein is designed to learn this signal-to-image transformation through data-driven learning rather than through direct use of linear reconstruction. To further improve reconstruction results, our method integrates an image post-processing network (U-net). Experiments show that the proposed method can achieve high reconstruction quality from limited-view data with sparse measurements. When employing GPU acceleration, this method can achieve a reconstruction speed of 15 frames per second.

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O'Kelly D et al.

Evaluating Online Filtering Algorithms to Enhance Dynamic Multispectral Optoacoustic Tomography

TechnologyPreclinicalMSOT

Multispectral optoacoustic tomography (MSOT) is an emerging imaging modality, which is able to capture data at high spatiotemporal resolution using rapid tuning of the excitation laser wavelength. However, owing to the necessity of imaging one wavelength at a time to the exclusion of others, forming a complete multispectral image requires multiple excitations over time, which may introduce aliasing due to underlying spectral dynamics or noise in the data. In order to mitigate this limitation, we have applied kinematic α and αβ filters to multispectral time series, providing an estimate of the underlying multispectral image at every point in time throughout data acquisition. We demonstrate the efficacy of these methods in suppressing the inter-frame noise present in dynamic multispectral image time courses using a multispectral Shepp-Logan phantom and mice bearing distinct renal cell carcinoma tumors. The gains in signal to noise ratio provided by these filters enable higher-fidelity downstream analysis such as spectral unmixing and improved hypothesis testing in quantifying the onset of signal changes during an oxygen gas challenge.

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Zeng L et al.

A one-pot synthesis of multifunctional Bi2S3 nanoparticles and the construction of core-shell Bi2S3@Ce6-CeO2 nanocomposites for NIR-triggered phototherapy

NanoCancerPreclinicalMSOT

As a direct thin band gap n-type semiconductor, bismuth sulfide (Bi2S3) nanomaterials possess great near-infrared (NIR)-triggered photothermal effects, photoacoustic (PA) and computed tomography (CT) imaging properties. Hence, Bi2S3 nanomaterials have become a research focal point in multiple domains, such as the construction of NIR-triggered nanosystems for cancer therapy. In this study, through a simple one-pot synthesis with the assistance of EDTA-2Na, we first obtained monodispersed spherical Bi2S3 of uniform particle sizes with fascinating photothermal and PA/CT imaging properties. Based on this, we introduced the photosensitizer Ce6 with photodynamic property and CeO2 with the O2-evolving characteristic, and thus designed a core-shell structure of the Bi2S3@Ce6-CeO2 nanocomposites (Bi2S3@Ce6-CeO2 NCs). The as-received Bi2S3@Ce6-CeO2 NCs exhibited a remarkable synergetic photothermal and photodynamic therapeutic effect both in vitro and in vivo, demonstrating its promising potential for cancer treatments. In the long term, the multifunctional PA/CT properties of both Bi2S3 NPs and Bi2S3@Ce6-CeO2 NCs in this study also supply a novel Bi2S3-based platform for constructing integrated diagnosis and treatment platforms.

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Ivankovic I et al.

Volumetric Optoacoustic Tomography Differentiates Myocardial Remodelling

VascularPreclinicalMSOT

Purpose : Myocardial healing following myocardial infarction (MI) is a complex process that is yet to be fully understood. Clinical attempts in regeneration of the injured myocardium using cardiac stem cells faced major challenges, calling for a better understanding of the processes involved at a more basic level in order to foster translation. Procedures : We examined the feasibility of volumetric optoacoustic tomography (VOT) in studying healing of the myocardium in different models of MI, including permanent occlusion (PO) of the left coronary artery, temporary occlusion (ischemia-reperfusion-I/R) and infarcted c-kit mutants, a genetic mouse model with impaired cardiac healing. Murine hearts were imaged at 100 Hz frame rate using 800 nm excitation wavelength, corresponding to the peak absorption of indocyanine green (ICG) in plasma and the isosbestic point of haemoglobin. Results : The non-invasive real-time volumetric imaging capabilities of VOT have allowed the detection of significant variations in the pulmonary transit time (PTT), a parameter affected by MI, across different murine models. Upon intravenous injection of ICG, we were able to track alterations in cardiac perfusion in I/R models, which were absent in wild-type (wt) PO or kitW/kitW-v PO mice. The wt-PO and I/R models further exhibited irregularities in their cardiac cycles. Conclusions : Clear differences in the PTT, ICG perfusion and cardiac cycle patterns were identified between the different models and days post MI. Overall, the results highlight the unique capacity of VOT for multi-parametric characterization of morphological and functional changes in murine models of MI.

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Wang M et al.

Au2Pt-PEG-Ce6 nanoformulation with dual nanozyme activities for synergistic chemodynamic therapy / phototherapy

NanoCancerPreclinicalMSOT

Although synergistic therapy for tumors has displayed significant promise for effective treatment of cancer, developing a simple and effective strategy to build a multi-functional nanoplatform is still a huge challenge. By virtue of the characteristics of tumor microenvironment, such as hypoxia, slight acidity and H2O2 overexpression, Au2Pt-PEG-Ce6 nanoformulation is constructed for collaborative chemodynamic/phototherapy of tumors. Specifically, the Au2Pt nanozymes with multiple functions are synthesized in one step at room temperature. The photosensitizer chlorin e6 (Ce6) is covalently linked to Au2Pt nanozymes for photodynamic therapy (PDT). Interestingly, the Au2Pt nanozymes possess catalase- and peroxidase-like activities simultaneously, which not only can generate O2 for relaxation of tumor hypoxia and enhancement of PDT efficiency but also can produce ∙OH for chemodynamic therapy (CDT). In addition, the high photothermal conversion efficiency (η = 31.5%) of Au2Pt-PEG-Ce6 nanoformulation provides the possibility for photoacoustic (PA) and photothermal (PT) imaging guided photothermal therapy (PTT). Moreover, the presence of high-Z elements (Au and Pt) in Au2Pt-PEG-Ce6 nanoformulation endows it with the ability to act as an X-ray computed tomography (CT) imaging contrast agent. All in all, the Au2Pt-PEG-Ce6 exhibits great potential in multimodal imaging-guided synergistic PTT/PDT/CDT with remarkably tumor specificity and enhanced therapy.

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Pan X et al.

Biodegradable Nanocomposite with Dual Cell‐Tissue Penetration for Deep Tumor Chemo‐Phototherapy

NanoCancerPreclinicalMSOT

Chemo-phototherapy, as a promising cancer combination therapy strategy, has attracted widespread attention. However, the complex tumor microenvironment restricts the penetration depth of chemo-phototherapy agents in the tumor region. Here, biodegradable amphiphilic gelatin (AG) wrapped nanocomposite (PRDCuS@AG) composed of doxorubicin and copper sulfide (CuS)-loaded dendrimer is designed for deep tumor chemo-phototherapy. PR in PRDCuS@AG represents arginine-conjugated polyamidoamine dendrimer. PRDCuS@AG can rapidly biodegrade into PRDCuS by matrix metalloproteinases under near-infrared light irradiation. The resulted PRDCuS harbors dual cell-tissue penetration ability, which can effectively penetrate deep into the tumor tissue. In particular, PRDCuS@AG achieves photoacoustic imaging-guided synergistic chemo-phototherapy with 97% of tumor inhibition rate. Moreover, PRDCuS@AG can further degrade into 3 nm ultrasmall CuS, which can be eliminated from the body after treatment to avoid side effects. This strategy provides an insight that the development of chemo-phototherapy agents with high penetration ability to overcome the limitation of current deep tumor therapy.

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Dinnyes A et al.

Integration of nano‐ and biotechnology for beta‐cell and islet transplantation in type‐1 diabetes treatment

NanoPreclinicalMSOT

Regenerative medicine using human or porcine β‐cells or islets has an excellent potential to become a clinically relevant method for the treatment of type‐1 diabetes. High‐resolution imaging of the function and faith of transplanted porcine pancreatic islets and human stem cell–derived beta cells in large animals and patients for testing advanced therapy medicinal products (ATMPs) is a currently unmet need for pre‐clinical/clinical trials. The iNanoBIT EU H2020 project is developing novel highly sensitive nanotechnology‐based imaging approaches allowing for monitoring of survival, engraftment, proliferation, function and whole‐body distribution of the cellular transplants in a porcine diabetes model with excellent translational potential to humans. We develop and validate the application of single‐photon emission computed tomography (SPECT) and optoacoustic imaging technologies in a transgenic insulin‐deficient pig model to observe transplanted porcine xeno‐islets and in vitro differentiated human beta cells. We are progressing in generating new transgenic reporter pigs and human‐induced pluripotent cell (iPSC) lines for optoacoustic imaging and testing them in transplantable bioartificial islet devices. Novel multifunctional nanoparticles have been generated and are being tested for nuclear imaging of islets and beta cells using a new, high‐resolution SPECT imaging device. Overall, the combined multidisciplinary expertise of the project partners allows progress towards creating much needed technological toolboxes for the xenotransplantation and ATMP field, and thus reinforces the European healthcare supply chain for regenerative medicinal products.

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Balasundaram G et al.

Optoacoustic characterization of breast conserving surgery specimens – A pilot study

Breast CancerClinicalMSOT

In this pilot study, we tested an ultrasound-guided optoacoustic tomography (US-OT) two-dimensional (2D) array scanner to understand the optoacoustic patterns of excised breastconserving surgery (BCS) specimens. We imaged 14 BCS specimens containing malignant tumors at eight wavelengths spanning 700-1100 nm. Spectral unmixing across multiple wavelengths allowed for visualizing major intrinsic chromophores in the breast tissue including hemoglobin and lipid up to a depth of 7 mm. We identified less/no lipid signals within the tumor and intense deoxy-hemoglobin (Hb) signals on the rim of the tumor as unique characteristics of malignant tumors in comparison to no tumor region. We also observed continuous broad lipid signals as features of negative margins and compromised lipid signals interrupted by vasculature as features of positive margins. These differentiating patterns can form the basis of US-OT to be explored as an alternate, fast and efficient intraoperative method for evaluation of tumor resection margins.

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Yang Z et al.

Albumin-Based Nanotheranostic Probe with Hypoxia Alleviating Potentiates Synchronous Multimodal Imaging and Phototherapy for Glioma

NanoCancerNeuroPreclinicalMSOT

Highly infiltrative and invasive glioma cells obscure the boundary between tumor and normal brain tissue, making it extremely difficult to precisely diagnose and completely remove. The combination of multimodal imaging with effective treatments to diagnose precisely and guide surgery and therapy accurately is desperately needed for glioma in the brain. Here, we report a biomimetic catalase-integrated-albumin phototheranostic nanoprobe (ICG/AuNR@BCNP) to realize multimodal imaging, amplify phototherapy, and guide surgery for glioma after penetrating the blood-brain barrier, accumulating into deep-seated glioma via albumin-binding protein mediated transportation. The phototheranostic nanoprobe enabled fluorescence, photoacoustic, and infrared thermal imaging with desirable detecting depth and high signal-to-background ratio for clearly differentiating brain tumors from surrounding tissues. Meanwhile, the nanoprobe could effectively induce local hyperthermia and promote the level of singlet oxygen based on alleviated hypoxic glioma microenvironment by decomposing endogenous hydrogen peroxide to oxygen to amplify phototherapy. Thus, significant inhibition of glioma growth, extended survival time, alleviated tumor hypoxia, improved apoptosis, and antiangiogenesis effects were exhibited in several animal models including the periphery and the brain through intravenous or intratumoral injection, meanwhile with low toxicity to normal tissue. The phototherapy was also guided by the assistance of external bioluminescence, magnetic resonance, and positron emission tomography imaging. Moreover, the nanoprobe could accurately guide the glioma resection. These results suggest that the phototheranostic nanoprobe is a promising nanoplatform specifically for glioma to achieve multimodal diagnosis, effective phototherapy, and accurate imaging-guided surgery.

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Hindelang B et al.

Optoacoustic mesoscopy shows potential to increase accuracy of allergy patch testing

VascularSkinClinicalRSOM

BACKGROUND: Differentiation between irritant and allergic skin reactions in epicutaneous patch testing is based largely on subjective clinical criteria, with the risk of high intra- and interobserver variability. Novel dermatological imaging using optoacoustic mesoscopy allows quantitative three-dimensional assessment of microvascular biomarkers. METHODS: We investigated the potential of optoacoustic imaging to improve the precision of patch test evaluation by examining 69 test reactions and 48 healthy skin sections in 52 patients with suspected type-IV-allergy. RESULTS: We identified biomarkers from the optoacoustic images. Allergic reactions were associated with higher fragmentation of skin vasculature than irritant reactions (19.5±9.7 vs. 14.3±3.7 fragments/100 pixels2 ; P≤.01), as well as lower ratio of low- to-high-frequency acoustic signals (1.6 ±0.5 vs. 2.0±0.6, P≤.0045). Allergic reactions graded “++” showed higher vessel fragmentation than reactions graded “+” (25.4±13.2 vs. 17.1±6.5 fragments/100 pixels2 ; P≤.0074). A linear model combining the biomarkers fragmentation and frequency ratio could differentiate allergic from irritant test reactions with an area under the receiving operator characteristic curve of 0.80 (95% CI 0.64-0.91), reaching a sensitivity of 81% and specificity of 63%. CONCLUSIONS: Optoacoustic mesoscopy shows potential to help in differentiating allergic and irritant test reactions based on novel biomarkers that may reflect vasodilation, vessel tortuosity and edema.

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Jia X et al.

Precise visual distinction of brain glioma from normal tissues via targeted photoacoustic and fluorescence navigation

CancerNeuroPreclinicalMSOT

The vexing difficulty in distinguishing glioma from normal tissues is a major obstacle to prognosis. In an attempt to solve this problem, we used a joint strategy that combined targeted-cancer stem cells nanoparticles with precise photoacoustic and fluorescence navigation. We showed that traditional magnetic resonance imaging (MRI) did not represent the true morphology of tumors. Targeted nanoparticles specifically accumulated in the tumor area. Glioma was precisely revealed at the cellular level. Tumors could be non-invasively detected through the intact skull by fluorescence molecular imaging (FMI) and photoacoustic tomography (PAT). Moreover, PAT can be used to excise deep gliomas. Histological correlation confirmed that FMI imaging accurately delineated scattered tumor cells. The combination of optical PAT and FMI navigation fulfilled the promise of precise visual imaging in glioma detection and resection. This detection method was deeper and more intuitive than the current intraoperative pathology.

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Yücel YH et al.

Age-related decline of lymphatic drainage from the eye: A noninvasive in vivo photoacoustic tomography study

VascularPreclinicalMSOT

We aim to determine whether lymphatic drainage from the eye changes with age. Using quantitative photoacoustic tomography, groups of young and older mice were studied in the live state. 10 CD-1 mice of 2-3 months (5M/5F) were studied in addition to 13 older mice of 12-13 months (6M/7F). In each of 23 mice, near-infrared tracer (a near-infrared dye, QC-1 conjugated with Bovine Serum Albumin) was injected into the right eye, and imaging of ipsilateral cervical lymph nodes was performed with laser pulses at 11 different wavelengths prior to and 20 min, 2, 4 and 6 h after injection. Mean pixel intensities (MPIs) of nodes were calculated at each imaging session. The areas under the curves (AUC) were calculated for both groups of mice and compared using the t-test. The slopes of MPI of each region of interest were compared using the linear mixed model before and after adjusting for sex, body weight and intraocular pressure of the right eye. The mean intraocular pressure of right eyes before injection was similar in older and younger groups (12.77 ± 2.01 mmHg and 12.90 ± 2.38 mmHg, respectively; p = 0.888). In each mouse, the photoacoustic signal was detected in the right cervical lymph nodes at the 2-h time point following tracer injection into the right eye. At the 4 and 6 h imaging times, a steady increase of tracer signal was observed. Areas under the curve in the right cervical nodes were decreased significantly in older mice compared to younger mice (p = 0.007). The slopes of MPI in the nodes were significantly decreased in old mice compared to young mice both before and after adjusting for sex, body weight and intraocular pressure of the right eye (p = 0.003). In conclusion, lymphatic drainage from the eye is significantly reduced in older eyes. This finding suggests that impaired lymphatic clearance of aqueous humor, proteins and antigens from the eye may contribute to age-related disease of the eye such as glaucoma and inflammatory eye disease.

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Liu Y et al.

Amplified Photoacoustic Signal and Enhanced Photothermal Conversion of Polydopamine-Coated Gold Nanobipyramids for Phototheranostics and Synergistic Chemotherapy

NanoCancerPreclinicalMSOT

Light-responsive nanoprobes were suffering from the threat of high-dose laser irradiation, and it was important for constructing new nanoprobes for safe and efficient phototheranostics. Here, polydopamine (PDA)-coated gold nanobipyramids (AuNBPs@PDA) were synthesized for amplified photoacoustic (PA) signal and enhanced photothermal conversion with low-dose laser irradiation and then doxorubicin (DOX)-loaded AuNBPs@PDA-DOX nanoprobes were constructed for PA imaging-guided synergistic photothermal therapy (PTT) and chemotherapy. The AuNBPs@PDA nanoparticles possessed higher photothermal conversion efficiency (42.07%) and stronger PA signal than those of AuNBP nanoparticles, and the AuNBPs@PDA-DOX nanoprobes showed dual-responsive DOX release of pH and photothermal stimulation. With low-dose laser irradiation (1.0 W/cm2) and low-concentration AuNBPs@PDA-DOX (60 μg/mL), the 4T1 cell viability was reduced to about 5%, owing to the combination of PTT and chemotherapy, compared with 42.3% of single chemotherapy and 25.3% of single PTT. Moreover, by modeling 4T1 tumor-bearing nude mice, in vivo PA imaging was achieved and the tumors were completely inhibited, demonstrating the excellent synergistic effect of PTT/chemotherapy. Therefore, the developed AuNBPs@PDA-DOX nanoprobes can be used for phototheranostics and synergistic chemotherapy, achieving low-dose laser irradiation and high-efficient visualized theranostics.

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Ding L et al.

Model-based reconstruction of large three-dimensional optoacoustic datasets

TechnologyPreclinicalMSOT

Iterative model-based algorithms are known to enable more accurate and quantitative optoacoustic (photoacoustic) tomographic reconstructions than standard back-projection methods. However, three-dimensional (3D) model-based inversion is often hampered by high computational complexity and memory overhead. Parallel implementations on a graphics processing unit (GPU) have been shown to efficiently reduce the memory requirements by on-the-fly calculation of the actions of the optoacoustic model matrix, but the high complexity still makes these approaches impractical for large 3D optoacoustic datasets. Herein, we show that the computational complexity of 3D model-based iterative inversion can be significantly reduced by splitting the model matrix into two parts: one maximally sparse matrix containing only one entry per voxel-transducer pair and a second matrix corresponding to cyclic convolution. We further suggest reconstructing the images by multiplying the transpose of the model matrix calculated in this manner with the acquired signals, which is equivalent to using a very large regularization parameter in the iterative inversion method. The performance of these two approaches is compared to that of standard back-projection and a recently introduced GPU-based model-based method using datasets from in vivo experiments. The reconstruction time was accelerated by approximately an order of magnitude with the new iterative method, while multiplication with the transpose of the matrix is shown to be as fast as standard back-projection.

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Chen M et al.

Evoking Photothermy by Capturing Intramolecular Bond Stretching Vibration-Induced Dark-State Energy

NanoCancerPreclinicalMSOT

Development of highly effective approaches to desirable photothermal conversion agents is particularly valuable. Herein, we report a concept, namely, bond stretching vibration-induced photothermy, that serves as a mechanism to construct advanced photothermal conversion agents. As a proof-of-concept, two compounds (DCP-TPA and DCP-PTPA) with donor-acceptor (D-A) structures were synthesized. The bond stretching vibration of the pyrazine-containing unit in these molecules is vigorous and insensitive to the external environmental restraint, which efficiently transforms the absorbed photons to dark-state heat energy. The nanoparticles (NPs) of DCP-TPA and DCP-PTPA show rather high photothermal conversion efficiency (52% and 59%) and stronger photoacoustic (PA) signal than commercial methylene blue and reported high-performance semiconducting polymer nanoparticles. The DCP-PTPA NPs perform better than DCP-TPA NPs in terms of photothermal conversion, PA signal production, and in vivo PA tumor imaging because of the increased bond stretching vibration in the former molecule.

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Giacalone G et al.

Bedside 3D Visualization of Lymphatic Vessels with a Handheld Multispectral Optoacoustic Tomography Device

VascularClinicalMSOT

Identification of lymphatics by Indocyanine Green (ICG) lymphography in patients with severe lymphedema is limited due to the overlying dermal backflow. Nor can the method detect deep and/or small vessels. Multispectral optoacoustic tomography (MSOT), a real-time three- dimensional (3D) imaging modality which allows exact spatial identification of absorbers in tissue such as blood and injected dyes can overcome these hurdles. However, MSOT with a handheld probe has not been performed yet in lymphedema patients. We conducted a pilot study in 11 patients with primary and secondary lymphedema to test whether lymphatic vessels could be detected with a handheld MSOT device. In eight patients, we could not only identify lymphatics and veins but also visualize their position and contractility. Furthermore, deep lymphatic vessels not traceable by ICG lymphography and lymphatics covered by severe dermal backflow, could be clearly identified by MSOT. In three patients, two of which had advanced stage lymphedema, only veins but no lymphatic vessels could be identified. We found that MSOT can identify and image lymphatics and veins in real-time and beyond the limits of near-infrared technology during a single bedside examination. Given its easy use and high accuracy, the handheld MSOT device is a promising tool in lymphatic surgery.

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Kimm MA et al.

Longitudinal imaging of T cell-based immunotherapy with multi-spectral, multi-scale optoacoustic tomography

CancerVascularPreclinicalMSOT

Most imaging studies of immunotherapy have focused on tracking labeled T cell biodistribution in vivo for understanding trafficking and homing parameters and predicting therapeutic efficacy by the presence of transferred T cells at or in the tumour mass. Conversely, we investigate here a novel concept for longitudinally elucidating anatomical and pathophysiological changes of solid tumours after adoptive T cell transfer in a preclinical set up, using previously unexplored in-tandem macroscopic and mesoscopic optoacoustic (photoacoustic) imaging. We show non-invasive in vivo observations of vessel collapse during tumour rejection across entire tumours and observe for the first time longitudinal tumour rejection in a label-free manner based on optical absorption changes in the tumour mass due to cellular decline. We complement these observations with high resolution episcopic fluorescence imaging of T cell biodistribution using optimized T cell labeling based on two near-infrared dyes targeting the cell membrane and the cytoplasm. We discuss how optoacoustic macroscopy and mesoscopy offer unique contrast and immunotherapy insights, allowing label-free and longitudinal observations of tumour therapy. The results demonstrate optoacoustic imaging as an invaluable tool in understanding and optimizing T cell therapy.

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Chang M et al.

Cu2 MoS4 /Au Heterostructures with Enhanced Catalase-Like Activity and Photoconversion Efficiency for Primary/Metastatic Tumors Eradication by Phototherapy-Induced Immunotherapy

NanoCancerPreclinicalMSOT

Photoimmunotherapy can not only effectively ablate the primary tumor but also trigger strong antitumor immune responses against metastatic tumors by inducing immunogenic cell death. Herein, Cu2 MoS4 (CMS)/Au heterostructures are constructed by depositing plasmonic Au nanoparticles onto CMS nanosheets, which exhibit enhanced absorption in near-infrared (NIR) region due to the newly formed mid-gap state across the Fermi level based on the hybridization between Au 5d orbitals and S 3p orbitals, thus resulting in more excellent photothermal therapy and photodynamic therapy (PDT) effect than single CMS upon NIR laser irradiation. The CMS and CMS/Au can also serve as catalase to effectively relieve tumor hypoxia, which can enhance the therapeutic effect of O2 -dependent PDT. Notably, the NIR laser-irradiated CMS/Au can elicit strong immune responses via promoting dendritic cells maturation, cytokine secretion, and activating antitumor effector T-cell responses for both primary and metastatic tumors eradication. Moreover, CMS/Au exhibits outstanding photoacoustic and computed tomography imaging performance owing to its excellent photothermal conversion and X-ray attenuation ability. Overall, the work provides an imaging-guided and phototherapy-induced immunotherapy based on constructing CMS/Au heterostructures for effectively tumor ablation and cancer metastasis inhibition.

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Haedicke K et al.

High-resolution optoacoustic imaging of tissue responses to vascular-targeted therapies

CancerVascularPreclinicalRSOM

The monitoring of vascular-targeted therapies using magnetic resonance imaging, computed tomography or ultrasound is limited by their insufficient spatial resolution. Here, by taking advantage of the intrinsic optical properties of haemoglobin, we show that raster-scanning optoacoustic mesoscopy (RSOM) provides high-resolution images of the tumour vasculature and of the surrounding tissue, and that the detection of a wide range of ultrasound bandwidths enables the distinction of vessels of differing size, providing detailed insights into the vascular responses to vascular-targeted therapy. Using RSOM to examine the responses to vascular-targeted photodynamic therapy in mice with subcutaneous xenografts, we observed a substantial and immediate occlusion of the tumour vessels followed by haemorrhage within the tissue and the eventual collapse of the entire vasculature. Using dual-wavelength RSOM, which distinguishes oxyhaemoglobin from deoxyhaemoglobin, we observed an increase in oxygenation of the entire tumour volume immediately after the application of the therapy, and a second wave of oxygen reperfusion approximately 24 h thereafter. We also show that RSOM enables the quantification of differences in neoangiogenesis that predict treatment efficacy.

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Yang H et al.

Soft ultrasound priors in optoacoustic reconstruction: Improving clinical vascular imaging

TechnologyVascularClinicalMSOT

Using the same ultrasound detector, hybrid optoacoustic-ultrasound (OPUS) imaging provides concurrent scans of tissue slices or volumes and visualizes complementary sound- and light-based contrast at similar resolutions. In addition to the benefit of hybrid contrast, spatial co-registration enables images from one modality to be employed as prior information for improving an aspect of the performance of the other modality. We consider herein a handheld OPUS system and utilize structural information from ultrasound images to guide regional Laplacian regularization-based reconstruction of optoacoustic images. Using phantoms and data from OPUS scans of human radial and carotid arteries, we show that ultrasound-driven optoacoustic inversion reduces limited-view artefacts and improves image contrast. In phantoms, prior-integrated reconstruction leads to a 50 % higher contrast-to-noise ratio (CNR) of the image than standard reconstruction, and a 17 % higher structural similarity (SSIM) index. In clinical data, prior-integrated reconstruction detects deep-seated radial arteries with higher CNR than the standard method at three different depths. In this way, the prior-integrated method offers unique insights into atherosclerotic carotid plaques in humans (with p<0.01 between patients and healthy volunteers), potentially paving the way for new abilities in vascular imaging and more generally in optoacoustic imaging.

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Cvjetinovic J et al.

Photoacoustic and fluorescence lifetime imaging of diatoms

Other ApplicationsPreclinicalRSOM

Photoacoustic and fluorescent methods are used intensely in biology and medicine. These approaches can also be used to investigate unicellular diatom algae that are extremely important for Earth’s ecology. They are enveloped within silica frustules (exoskeletons), which can be used in drug delivery systems. Here, we report for the first time the successful application of photoacoustic (PA) and fluorescent visualization of diatoms. Chlorophyll a and c and fucoxanthin were found likely to be responsible for the photoacoustic effect in diatoms. The PA signal was obtained from gel drops containing diatoms and was found to increase with the diatom concentration. The fluorescence lifetime of the diatom chromophores ranged from 0.5 to 2 ns. The dynamic light scattering, absorbance, and SEM characterization techniques were also applied. The results were considered in combination to elucidate the nature of the photoacoustic signal. Possible biotechnological applications are proposed for the remote photoacoustic monitoring of algae.

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Chen Y et al.

Near-Infrared Laser-Triggered In Situ Dimorphic Transformation of BF 2-Azadipyrromethene Nanoaggregates for Enhanced Solid Tumor Penetration

NanoCancerPreclinicalMSOT

The shape of a drug delivery system impacts its in vivo behavior such as circulation time, accumulation, and penetration. Considering the advantages of functional dyes in bioapplications, we synthesize a class of nanoaggregates based on BF2-azadipyrromethene (aza-BODIPY) dyes, which can realize long blood circulation and deep tumor penetration simultaneously in vivo through morphological transformation modulated by a near-infrared (NIR) laser. First, when the temperature increases, the wormlike nanofibers of the aza-BODIPY-1 aggregate, possessing a long blood circulation time, can be transformed into spherical nanoparticles, which are conducive to increasing the penetration in the solid tumor. Second, without any postmodification, the nanofibers exhibit an outstandingly narrow absorption band in the NIR spectral range, so that they possess ideal photothermal properties. Through 655 nm laser irradiation, the intrinsic photothermal effect causes a local temperature increase to ∼48 °C, realizing the transformation of 1-NFs to 1-NPs. Third, the morphological transformation is real-time detected by photoacoustic (PA) imaging. By monitoring the change of the PA signal at a specific wavelength, the in vivo deformation process of nanomaterials can be traced. Consequently, the in situ morphology transformation of aza-BODIPY-based nanomaterials can simultaneously realize long blood circulation and deep penetration, resulting in the enhanced antitumor outcome.

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Karlas A et al.

Multispectral Optoacoustic Tomography of Muscle Perfusion and Oxygenation Under Arterial and Venous Occlusion: A Human Pilot Study

VascularClinicalMSOT

Perfusion and oxygenation are critical parameters of muscle metabolism in health and disease. They have been both the target of many studies, in particular using near-infrared spectroscopy (NIRS). However, difficulties with quantifying NIRS signals have limited a wide dissemination of the method to the clinics. Our aim was to investigate whether clinical multispectral optoacoustic tomography (MSOT) could enable the label-free imaging of muscle perfusion and oxygenation under clinically relevant challenges: the arterial and venous occlusion. We employed a hybrid clinical MSOT/ultrasound system equipped with a hand-held scanning probe to visualize hemodynamic and oxygenation changes in skeletal muscle under arterial and venous occlusions. Four (N = 4) healthy volunteers were scanned over the forearm for both 3-minute occlusion challenges. MSOT-recorded pathophysiologically expected results during tests of disturbed blood flow with high resolution and without the need for contrast agents. During arterial occlusion, MSOT-extracted Hb-values showed an increase, while HbO2 – and total blood volume (TBV)-values remained roughly steady, followed by a discrete increase during the hyperemic period after cuff deflation. During venous occlusion, results showed a clear increase in intramuscular HbO2 , Hb and TBV within the segmented muscle area. MSOT was found to be capable of label-free non-invasive imaging of muscle hemodynamics and oxygenation under arterial and venous occlusion. We introduce herein MSOT as a novel modality for the assessment of vascular disorders characterized by disturbed blood flow, such as acute limb ischemia and venous thrombosis.

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Regensburger AP et al.

Shedding Light on Pediatric Diseases: Multispectral Optoacoustic Tomography at the Doorway to Clinical Applications

CancerBreast CancerMelanomaIBDVascularSkinClinicalMSOT

Optoacoustic imaging (OAI), or photoacoustic imaging (PAI), has fundamentally influenced basic science by providing high-resolution visualization of biological mechanisms. With the introduction of multispectral optoacoustic tomography (MSOT), these technologies have now moved closer to clinical applications. MSOT utilizes short-pulsed near-infrared laser light to induce thermoelastic expansion in targeted tissues. This results in acoustic pressure waves, which are used to resolve specific endo- and exogenous chromophores. Especially in the pediatric population, this non-invasive imaging approach might hold fundamental advantages compared to conventional cross-sectional imaging modalities. As this technology allows the visualization of quantitative molecular tissue composition at high spatial resolution non-invasively in sufficient penetration depth, it paves the way to personalized medicine in pediatric diseases.

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Wang H et al.

A Smart Theranostic Platform for Photoacoustic and Magnetic Resonance Dual-Imaging-Guided Photothermal-Enhanced Chemodynamic Therapy

NanoCancerPreclinicalMSOT

The use of smart theranostic agents in multimodal imaging and treatment is a promising strategy to overcome the limitations of single mode diagnosis and treatment, and can greatly improve the diagnosis and effects of treatment. In this study, a gold@manganese dioxide (Au@MnO2) core-shell nanostructure was designed as a glutathione (GSH)-triggered smart theranostic agent for photoacoustic and magnetic resonance (MR) dual-imaging-guided photothermal-enhanced chemodynamic therapy. Both in vitro and in vivo experiments demonstrated not only that the photoacoustic and MR imaging function of Au@MnO2 could be activated by a high endogenous GSH concentration, but also that after being triggered by the endogenous GSH, Au@MnO2 had an excellent synergistic treatment effect in photothermal-enhanced chemodynamic therapy under the guidance of photoacoustic and MR imaging. This study demonstrated that the use of GSH-triggered Au@MnO2 in photoacoustic and MR dual-imaging-guided photothermal-enhanced chemodynamic therapy is a smart theranostic nanoplatform for the accurate diagnosis and efficient treatment of cancer.

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Li W et al.

Fast Noninvasive Measurement of Brown Adipose Tissue in Living Mice by Near-Infrared Fluorescence and Photoacoustic Imaging

Other ApplicationsPharmacokineticsPreclinicalMSOT

Aberrant brown adipose tissue (BAT) metabolism is linked to obesity as well as other metabolic disorders. However, the paucity of imaging tools limits the study of in vivo BAT metabolism in animal models. The current work evaluated a heptamethine dye (CyHF-8) in living mice as a dual-modality BAT-avid molecular probe for two imaging approaches, including near-infrared fluorescence imaging (NIRF) and photoacoustic imaging (PAI). CyHF-8 exhibited favorable spectral properties in the near-infrared window (786/787/805 nm) and accumulated in the subcellular mitochondria of brown adipocytes. After intravenous injection of CyHF-8, NIRF and PAI were both capable of noninvasively detecting interscapular BAT at early time points in living mice. Quantitative analysis of NIRF and PAI images showed that CyHF-8 signals respond to dynamic BAT changes in mice stimulated by norepinephrine (NE) and in diabetic mice induced by streptozotocin (STZ). In summary, dual-modality NIRF/PAI probe CyHF-8 can be used for both NIRF and PAI to noninvasively assess BAT metabolism in living animals.

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Garza-Morales R et al.

Targeting Melanoma Hypoxia with the Food-Grade Lactic Acid Bacterium Lactococcus Lactis

CancerVascularPreclinicalMSOT

Melanoma is the most aggressive form of skin cancer. Hypoxia is a feature of the tumor microenvironment that reduces efficacy of immuno- and chemotherapies, resulting in poor clinical outcomes. Lactococcus lactis is a facultative anaerobic gram-positive lactic acid bacterium (LAB) that is Generally Recognized as Safe (GRAS). Recently, the use of LAB as a delivery vehicle has emerged as an alternative strategy to deliver therapeutic molecules; therefore, we investigated whether L. lactis can target and localize within melanoma hypoxic niches. To simulate hypoxic conditions in vitro, melanoma cells A2058, A375 and MeWo were cultured in a chamber with a gas mixture of 5% CO2, 94% N2 and 1% O2. Among the cell lines tested, MeWo cells displayed greater survival rates when compared to A2058 and A375 cells. Co-cultures of L. lactis expressing GFP or mCherry and MeWo cells revealed that L. lactis efficiently express the transgenes under hypoxic conditions. Moreover, multispectral optoacoustic tomography (MSOT), and near infrared (NIR) imaging of tumor-bearing BALB/c mice revealed that the intravenous injection of either L. lactis expressing β-galactosidase (β-gal) or infrared fluorescent protein (IRFP713) results in the establishment of the recombinant bacteria within tumor hypoxic niches. Overall, our data suggest that L. lactis represents an alternative strategy to target and deliver therapeutic molecules into the tumor hypoxic microenvironment.

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Yang L et al.

ICG-Conjugated and 125 I-Labeled Polymeric Micelles with High Biosafety for Multimodality Imaging-Guided Photothermal Therapy of Tumor

NanoCancerPharmacokineticsPreclinicalMSOT

Noninvasive multimodality imaging-guided precision photothermal therapy (PTT) is proven to be an effective strategy for tumor theranostics by integrating diagnostics and therapeutics in one nanoplatform. In this study, indocyanine green (ICG)-conjugated and radionuclide iodine-125 (125 I)-labeled polymeric micelles (PEG-PTyr(125 I)-ICG PMs) are strategically prepared by the self-assembly of the ICG-decorated amphiphilic diblock polymer poly(ethylene glycol)-poly(l-tyrosine-125 I)-(indocyanine green) (PEG-PTyr(125 I)-ICG). The as-prepared polymeric micelles exhibit favorable biocompatibility, excellent size/photo/radiolabel stability, a high-photothermal conversion efficiency, a passive tumor-targeting ability, and a fluorescence (FL)/photoacoustic (PA)/single photon emission computed tomography (SPECT) imaging property. After tail intravenous injection, the polymeric micelles can efficiently accumulate at the tumor site and present comprehensive FL/PA/SPECT images with a high sensitivity, excellent spatial resolution, and unlimited tissue penetration under near-infrared (NIR) irradiation. Upon 808 nm laser irradiation, the subsequent precision PTT of tumors can be achieved with minimal cumulative side effects. Thus, this capable multifunctional nanoplatform with simple components and preparation procedures for FL/PA/SPECT multimodality imaging-guided PTT can be a potential candidate for clinical tumor theranostics.

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Novoselova MV et al.

Multifunctional nanostructured drug delivery carriers for cancer therapy: Multimodal imaging and ultrasound-induced drug release

NanoCancerPreclinicalRSOM

Development of multimodal systems for therapy and diagnosis of neoplastic diseases is an unmet need in oncology. The possibility of simultaneous diagnostics, monitoring, and therapy of various diseases allows expanding the applicability of modern systems for drug delivery. We have developed hybrid particles based on biocompatible polymers containing magnetic nanoparticles (MNPs), photoacoustic (MNPs), fluorescent (Cy5 or Cy7 dyes), and therapeutic components (doxorubicin). To achieve high loading efficiency of MNP and Dox to nanostructured carriers, we utilized a novel freezing-induced loading technique. To reduce the systemic toxicity of antitumor drugs and increase their therapeutic efficacy, we can use targeted delivery followed by the remote control of drug release using high intensity-focused ultrasound (HIFU). Loading of MNPs allowed performing magnetic targeting of the carriers and enhanced optoacoustic signal after controlled destruction of the shell and release of therapeutics as well as MRI imaging. The raster scanning optoacoustic mesoscopy (PA, RSOM), MRI, and fluorescent tomography (FT) confirmed the ultrasound-induced release of doxorubicin from capsules: in vitro (in tubes and pieces of meat) and in vivo (after delivery to the liver). Disruption of capsules results in a significant increase of doxorubicin and Cy7 fluorescence initially quenched by magnetite nanoparticles that can be used for real-time monitoring of drug release in vivo. In addition, we explicitly studied cytotoxicity, intracellular localization, and biodistribution of these particles. Elaborated drug delivery carriers have a good perspective for simultaneous imaging and focal therapy of different cancer types, including liver cancer.

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Gehrung M et al.

Co-registration of optoacoustic tomography and magnetic resonance imaging data from murine tumour models

CancerTechnologyPreclinicalMSOT

As optoacoustic tomography (OT) emerges as a mainstream pre-clinical imaging modality, understanding the relationship between optoacoustic and other imaging biomarkers in the context of the underlying tissue biology becomes vitally important. Complementary insight into tumour vasculature and hypoxia can be gained using OT alongside magnetic resonance imaging (MRI)-based techniques. To evaluate the relationship between these metrics and the relative performance of the two modalities in assessment of tumour physiology, co-registration of their output imaging data is required. Unfortunately, this poses a significant challenge due to differences in animal positioning during imaging. Here, we present an integrated framework for registration of OT and MR image data in mice. Our framework combines a novel MR animal holder, to improve animal positioning during imaging, and a landmark-based software co-registration algorithm. We demonstrate that our protocol significantly improves registration of both body and tumour contours between these modalities, enabling more precise multi-modal tumour characterisation.

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Liu F et al.

A glutathione-depleting chemodynamic therapy agent with photothermal and photoacoustic properties for tumor theranostics

NanoCancerPreclinicalMSOT

Nowadays, Fenton reaction-based chemodynamic therapy (CDT) strategies have drawn extensive attention as tumor-specific nanomedicine-based therapy. Nevertheless, current existing CDTs normally suffer from therapeutic bottlenecks such as the scavenging of hydroxyl radical (˙OH) by intracellular antioxidants and unideal therapeutic outcome of single treatment modality. Herein, we constructed novel all-in-one AFP nanoparticles (NPs) as CDT agents through a one-pot process for multifunctional nanotheranostics. The as-constructed AFP NPs could simultaneously produce ˙OH through the Fenton reaction and scavenge intracellular glutathione, functioning as self-reinforced CDT agents to achieve tumor-triggered enhanced CDT (ECDT). In addition, the AFP NPs possessed the capability of H2O2 and acid-boosted photoacoustic imaging and photothermal therapy, enabling a precise and effective tumor therapeutic outcome with minimal nonspecific damage in combination with ECDT. Our novel nanoplatform would open new perspectives on multi-functional CDT agents for accurate and non-invasive tumor theranostics.

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Lin J et al.

A magnetism/laser-auxiliary cascaded drug delivery to pulmonary carcinoma

NanoCancerPreclinicalMSOT

Although high-efficiency targeted delivery is investigated for years, the efficiency of tumor targeting seems still a hard core to smash. To overcome this problem, we design a three-step delivery strategy based on streptavidin-biotin interaction with the help of c(RGDfK), magnetic fields and lasers. The ultrasmall superparamagnetic iron oxide nanoparticles (USIONPs) modified with c(RGDfK) and biotin are delivered at step 1, followed by streptavidin and the doxorubicin (Dox) loaded nanosystems conjugated with biotin at steps 2 and 3, respectively. The delivery systems were proved to be efficient on A549 cells. The co-localization of signal for each step revealed the targeting mechanism. The external magnetic field could further amplify the endocytosis of USPIONs based on c(RGDfK), and magnify the uptake distinctions among different test groups. Based on photoacoustic imaging, laser-heating treatment could enhance the permeability of tumor venous blood vessels and change the insufficient blood flow in cancer. Then, it was noticed in vivo that only three-step delivery with laser-heating and magnetic fields realized the highest tumor distribution of nanosystem. Finally, the magnetism/laser-auxiliary cascaded delivery exhibited the best antitumor efficacy. Generally, this study demonstrated the necessity of combining physical, biological and chemical means of targeting.

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Ovsepian SV et al.

Visualizing Cortical Response to Optogenetic Stimulation and Sensory Inputs Using Multispectral Handheld Optoacoustic Imaging

NeuroPreclinicalMSOT

To date, the vast majority of intra-vital neuroimaging systems applied in clinic and diagnostics is stationary with a rigid scanning element, requires specialized facilities and costly infrastructure. Here, we describe a simple yet radical approach for optoacoustic (photoacoustic) brain imaging in vivo using a light-weight handheld probe. It enables multispectral video-rate visualization of hemoglobin gradient changes in the cortex of adult rats induced by whisker and forelimb sensory inputs, as well as by optogenetic stimulation of intra-cortical connections. With superb penetration and molecular specificity, described here method holds major promises for future applications in research, routine ambulatory neuroimaging, and diagnostics.

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Goh Y et al.

Ultrasound Guided Optoacoustic Tomography in Assessment of Tumor Margins for Lumpectomies

CancerClinicalMSOT

PURPOSE: To determine the accuracy of a handheld ultrasound-guided optoacoustic tomography (US-OT) probe developed for human deep-tissue imaging in ex vivo assessment of tumor margins postlumpectomy.

METHODS: A custom-built two-dimensional (2D) US-OT-handheld probe was used to scan 15 lumpectomy breast specimens. Optoacoustic signals acquired at multiple wavelengths between 700 and 1100 nm were reconstructed using model linear algorithm, followed by spectral unmixing for lipid and deoxyhemoglobin (Hb). Distribution maps of lipid and Hb on the anterior, posterior, superior, inferior, medial, and lateral margins of the specimens were inspected for margin involvement, and results were correlated with histopathologic findings. The agreement in tumor margin assessment between US-OT and histopathology was determined using the Bland-Altman plot. Accuracy, sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of margin assessment using US-OT were calculated.

RESULTS: Ninety margins (6 × 15 specimens) were assessed. The US-OT probe resolved blood vessels and lipid up to a depth of 6 mm. Negative and positive margins were discriminated by marked differences in the distribution patterns of lipid and Hb. US-OT assessments were concordant with histopathologic findings in 87 of 89 margins assessed (one margin was uninterpretable and excluded), with diagnostic accuracy of 97.9% (kappa = 0.79). The sensitivity, specificity, PPV, and NPV were 100% (4/4), 97.6% (83/85), 66.7% (4/6), and 100% (83/83), respectively.

CONCLUSION: US-OT was capable of providing distribution maps of lipid and Hb in lumpectomy specimens that predicted tumor margins with high sensitivity and specificity, making it a potential tool for intraoperative tumor margin assessment.

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Shi Y et al.

Biodistribution Survey of Oxidized Single-Wall Carbon Nanohorns Following Different Administration Routes by Using Label-Free Multispectral Optoacoustic Tomography

NanoPharmacokineticsPreclinicalMSOT

Introduction: Though widely studied for biomedical applications, the lack of current systemic studies on the in vivo fate of single-walled carbon nanohorns (SWCNHs) largely restricts their further applications, as real-time monitoring of their biodistribution remains a big challenge. Here, we aim to customize a label-free multispectral optoacoustic tomography (MSOT) method and systematically survey the fate of oxidized SWCNHs (SWCNHox) following different exposure routes by whole body imaging.

Methods: Mice were given a suspension of SWCNHox with an average size of 136.4 nm via four different administration routes, and then imaged by MSOT.

Results: After oral gavage, SWCNHox were mainly distributed in the gastrointestinal tract then excreted through the gut. Compared with the observation post first dosing, the accumulation of SWCNHox in the gastrointestinal tract was not obvious even after four-time oral gavage. Almost no SWCNHox were found at detectable levels in kidney, liver, blood and spleen. Following intravenous (iv) injection, SWCNHox were mainly presented and persisted in the spleen and liver, while very little in the kidney and almost none detectable in the intestine. SWCNHox accumulated significantly in the liver and spleen after four IV administrations. Following hypodermic and intramuscular injections, almost no SWCNHox could cross biological barriers and transport to the spleen, kidney or liver, likely due to their very low absorption rate. Almost all SWCNHox remained around the injection sites. For the first time, we have systematically investigated the in vivo fate of SWCNHs in a label-free and real-time manner.

Conclusion: The findings of this study provide insights into the selection of appropriate exposure routes for potential biomedical applications of carbon nanomaterials.

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Regensburger AP et al.

Detection of collagens by multispectral optoacoustic tomography as an imaging biomarker for Duchenne muscular dystrophy

Other ApplicationsClinicalMSOT

Biomarkers for monitoring of disease progression and response to therapy are lacking for muscle diseases such as Duchenne muscular dystrophy. Noninvasive in vivo molecular imaging with multispectral optoacoustic tomography (MSOT) uses pulsed laser light to induce acoustic pressure waves, enabling the visualization of endogenous chromophores. Here we describe an application of MSOT, in which illumination in the near- and extended near-infrared ranges from 680-1,100 nm enables the visualization and quantification of collagen content. We first demonstrated the feasibility of this approach to noninvasive quantification of tissue fibrosis in longitudinal studies in a large-animal Duchenne muscular dystrophy model in pigs, and then applied this approach to pediatric patients. MSOT-derived collagen content measurements in skeletal muscle were highly correlated to the functional status of the patients and provided additional information on molecular features as compared to magnetic resonance imaging. This study highlights the potential of MSOT imaging as a noninvasive, age-independent biomarker for the implementation and monitoring of newly developed therapies in muscular diseases.

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Lu SZ et al.

Bacteria-Instructed In Situ Aggregation of AuNPs with Enhanced PA Signal for Bacterial Infection Bioimaging

Infectious DiseasePreclinicalMSOT

The emergence of drug-resistant bacteria is becoming the focus of global public health. Early-stage pathogen bioimaging will offer a unique perspective to obtain infection information in patients. A photoacoustic (PA) contrast agent based on functional peptide modified gold nanoparticles (AuNPs@P1) is developed. These nanoparticles can be specifically tailored surface peptides by bacterial overexpressed enzyme inducing in situ aggregation of the gold nanoparticles. In the meantime, the close aggregation based on the hydrogen bonding, π-π stacking, and hydrophobic interaction of the peptide residues on the surface of gold nanoparticles exhibits a typical redshifted and broadened plasmon band. In addition, this active targeting and following in situ stimuli-induced aggregation contribute to increased nanoparticle accumulation in the infected site. Finally, the dynamic aggregation of AuNPs@P1 results in dramatically enhanced photoacoustic signals for bioimaging bacterial infection in vivo with high sensitivity and specificity. It is envisioned that this PA contrast agent may provide a new approach for early detection of bacterial infection in vivo.

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Ouyang J et al.

Nanoaggregate for Detecting and Mapping Breast Cancer Metastasis via Multispectral Optoacoustic Tomography and Aggregation-induced Near-infrared Fluorescence-I and -II Imaging

NanoCancerPreclinicalMSOT

An activatable nanoprobe for imaging breast cancer metastases through near infrared-I (NIR-I)/NIR-II fluorescence imaging and multispectral optoacoustic tomography (MSOT) imaging was designed. With a dihydroxanthene moiety serving as the electron donor, quinolinium as the electron acceptor and nitrobenzyloxydiphenylamino as the recognition element, the probe can specifically respond to nitroreductase and transform into an activated D-π-A structure with a NIR emission band extending beyond 900 nm. The activated nanoprobe exhibits NIR emission enhanced by aggregation-induced emission (AIE) and produces strong optoacoustic signal. The nanoprobe was used to detect and image metastases from the orthotopic breast tumors to lymph nodes and then to lung in two breast cancer mouse models. Moreover, the nanoprobe can monitor the treatment efficacy during chemotherapeutic course through fluorescence and MSOT imaging.

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Chen Z et al.

An Optical/Photoacoustic Dual-Modality Probe: Ratiometric in/ex Vivo Imaging for Stimulated H2S Upregulation in Mice

Other ApplicationsPreclinicalMSOT

Tracking signaling H2S in live mice demands responsive imaging with fine tissue imaging depth and low interferences from tissue scattering/autofluorescence and probe concentration. With complementary advantages of fluorescence and photoacoustic (PA) imaging, optical/PA dual-modality imaging was suggested for in/ex vivo H2S imaging. Therefore, a meso-benzoyloxyltricarboheptamethine cyanine, HS-CyBz, was prepared as the first ratiometric optical/PA dual-modality probe for H2S, profiting from a keto-enol transition sensing mechanism. Tail intravenous injection of this probe leads to probe accumulation in the liver of mice, and the endogenous H2S upregulation triggered by S-adenosyl-l-methionine has been verified by ratiometric optical/PA imaging, suggesting the promising potential of this ratiometric dual-modality imaging.

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Agrawal S et al.

Light-Emitting-Diode-Based Multispectral Photoacoustic Computed Tomography System

CancerPreclinicalMSOT

Photoacoustic computed tomography (PACT) has been widely explored for non-ionizing functional and molecular imaging of humans and small animals. In order for light to penetrate deep inside tissue, a bulky and high-cost tunable laser is typically used. Light-emitting diodes (LEDs) have recently emerged as cost-effective and portable alternative illumination sources for photoacoustic imaging. In this study, we have developed a portable, low-cost, five-dimensional (x, y, z, t, λ ) PACT system using multi-wavelength LED excitation to enable similar functional and molecular imaging capabilities as standard tunable lasers. Four LED arrays and a linear ultrasound transducer detector array are housed in a hollow cylindrical geometry that rotates 360 degrees to allow multiple projections through the subject of interest placed inside the cylinder. The structural, functional, and molecular imaging capabilities of the LED-PACT system are validated using various tissue-mimicking phantom studies. The axial, lateral, and elevational resolutions of the system at 2.3 cm depth are estimated as 0.12 mm, 0.3 mm, and 2.1 mm, respectively. Spectrally unmixed photoacoustic contrasts from tubes filled with oxy- and deoxy-hemoglobin, indocyanine green, methylene blue, and melanin molecules demonstrate the multispectral molecular imaging capabilities of the system. Human-finger-mimicking phantoms made of a bone and blood tubes show structural and functional oxygen saturation imaging capabilities. Together, these results demonstrate the potential of the proposed LED-based, low-cost, portable PACT system for pre-clinical and clinical applications.

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Weidenfeld I et al.

Homogentisic acid-derived pigment as a biocompatible label for optoacoustic imaging of macrophages

Other ApplicationsTechnologyPreclinicalMSOT

Macrophages are one of the most functionally-diverse cell types with roles in innate immunity, homeostasis and disease making them attractive targets for diagnostics and therapy. Photo- or optoacoustics could provide non-invasive, deep tissue imaging with high resolution and allow to visualize the spatiotemporal distribution of macrophages in vivo. However, present macrophage labels focus on synthetic nanomaterials, frequently limiting their ability to combine both host cell viability and functionality with strong signal generation. Here, we present a homogentisic acid-derived pigment (HDP) for biocompatible intracellular labeling of macrophages with strong optoacoustic contrast efficient enough to resolve single cells against a strong blood background. We study pigment formation during macrophage differentiation and activation, and utilize this labeling method to track migration of pro-inflammatory macrophages in vivo with whole-body imaging. We expand the sparse palette of macrophage labels for in vivo optoacoustic imaging and facilitate research on macrophage functionality and behavior.

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Attia ABE et al.

A review of clinical photoacoustic imaging: Current and future trends

CancerClinicalMSOT

Photoacoustic imaging (or optoacoustic imaging) is an upcoming biomedical imaging modality availing the benefits of optical resolution and acoustic depth of penetration. With its capacity to offer structural, functional, molecular and kinetic information making use of either endogenous contrast agents like hemoglobin, lipid, melanin and water or a variety of exogenous contrast agents or both, PAI has demonstrated promising potential in a wide range of preclinical and clinical applications. This review provides an overview of the rapidly expanding clinical applications of photoacoustic imaging including breast imaging, dermatologic imaging, vascular imaging, carotid artery imaging, musculoskeletal imaging, gastrointestinal imaging and adipose tissue imaging and the future directives utilizing different configurations of photoacoustic imaging. Particular emphasis is placed on investigations performed on human or human specimens.

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Lin W et al.

Engineering pH-Responsive BODIPY Nanoparticles for Tumor Selective Multimodal Imaging and Phototherapy

CancerPreclinicalMSOT

It is a challenge to develop multifunctional theranostic agents in one molecule, which simultaneously possesses tumor imaging ability with a high signal-to-noise ratio and excellent therapeutic activity. In this work, we synthesized and screened a series of BODIPY (BDP) with various absorption and fluorescence. The interplay of the molecular structure, pH-sensitive absorption and emission, and photodynamic and photothermal activities was well studied in detail. Photoinduced electron transfer, intramolecular charge transfer, and heavy atom effect were leveraged to engineer BDP with tumor imaging and therapeutic functions. The BDP nanoparticle formulations possessed multifunctional biological features, including selective treatment of cancer cells, near-infrared fluorescence, photoacoustic and computed tomography imaging, and photodynamic and photothermal therapy, as validated by cellular and animal experiments. These results not only give a new horizon to multifunctional BDP for biological applications but also show a new way to design the organic dye for tumor imaging and phototherapy.

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Lin Y et al

An Unsymmetrical Squaraine-Based Activatable Probe for Imaging Lymphatic Metastasis by Responding to Tumor Hypoxia with MSOT and Aggregation-Enhanced Fluorescent Imaging

VascularPreclinicalMSOT

Optoacoustic imaging has great potential for preclinical research and clinical practice, and designing robust activatable optoacoustic probes for specific diseases is beneficial for its further development. Herein, an activatable probe has been developed for tumor hypoxia imaging. For this probe, indole and quinoline were linked on each side of an oxocyclobutenolate core to form an unsymmetrical squaraine. A triarylamine group was incorporated to endow the molecule with the aggregation enhanced emission (AEE) properties. In aqueous media, the squaraine chromophore aggregates into the nanoprobe, which specifically responds to nitroreductase and produces strong optoacoustic signals due to its high extinction coefficient, as well as prominent fluorescence emission as a result of its AEE feature. The nanoprobe was used to image tumor metastasis via the lymphatic system both optoacoustically and fluorescently. Moreover, both the fluorescence signals and three-dimensional multispectral optoacoustic tomography signals from the activated nanoprobe allow us to locate the tumor site and to map the metastatic route.

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Ovsepian SV et al.

Advances in Optoacoustic Neurotomography of Animal Models

NeuroPreclinicalMSOT

Unlike traditional optical methods, optoacoustic imaging is less sensitive to scattering of ballistic photons, so it is capable of high-resolution interrogation at a greater depth. By integrating video-rate visualization with multiplexing and sensing a range of endogenous and exogenous chromophores, optoacoustic imaging has matured into a versatile noninvasive investigation modality with rapidly expanding use in biomedical research. We review the principal features of the technology and discuss recent advances it has enabled in structural, functional, and molecular neuroimaging in small-animal models. In extending the boundaries of noninvasive observation beyond the reach of customary photonic methods, the latest developments in optoacoustics have substantially advanced neuroimaging inquiry, with promising implications for basic and translational studies.

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Anani T et al.

Quantitative, real-time in vivo tracking of magnetic nanoparticles using multispectral optoacoustic tomography (MSOT) imaging

NanoPreclinicalMSOT

The goal of this work was to demonstrate real-time tracking of in vivo nanoparticle concentrations utilizing multispectral optoacoustic tomography (MSOT). Combining the high contrast of optical imaging with the high resolution of ultrasound imaging, MSOT was utilized for non-invasive, real-time tomographic imaging of particles in mice and the results calibrated against analysis of tissue samples with electron paramagnetic resonance (EPR) spectroscopy. In a longitudinal study, the pharmacokinetics (pK) and biodistribution of Cyanine-7 (Cy7) conjugated superparamagnetic iron oxide nanoparticles (Cy7-SPIONs) were monitored after intravenous administration into the tail vein of healthy B6-albino mice. Concentrations of Cy7-SPIONs determined by MSOT image analysis of the liver, spleen, and kidneys showed excellent agreement with EPR data obtained on tissue samples ‒ validating MSOT’s ability to quantify SPION concentrations with high spatial resolution. Both methods of analysis indicated highest accumulation of Cy7-SPIONs in the liver followed by the spleen, and negligible accumulation in the kidneys; SPION accumulation in organs with high concentrations of mononuclear phagocytic system macrophages is typical. Additionally, our study observed that particles modified with a 2 kDa polyethylene glycol (PEG) demonstrated significantly prolonged half-life in circulation compared to particles with 5 kDa PEG. The study demonstrates the potential of Cy7-SPIONs and MSOT for quantitative localization of magnetic nanoparticles in vivo, which can potentially be used to study their toxicity, quantify the efficacy of targeted drug delivery (e.g. within tumors), and their use as a multi-modal diagnostic agent to monitor disease progression.

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Gehrung M et al.

Development of a blood oxygenation phantom for photoacoustic tomography combined with online pO2 detection and flow spectrometry

TechnologyPreclinicalMSOT

Photoacoustic tomography (PAT) is intrinsically sensitive to blood oxygen saturation (sO2) in vivo. However, making accurate sO2 measurements without knowledge of tissue- and instrumentation-related correction factors is extremely challenging. We have developed a low-cost flow phantom to facilitate validation of PAT systems. The phantom is composed of a flow circuit of tubing partially embedded within a tissue-mimicking material, with independent sensors providing online monitoring of the optical absorption spectrum and partial pressure of oxygen in the tube. We first test the flow phantom using two small molecule dyes that are frequently used for photoacoustic imaging: methylene blue and indocyanine green. We then demonstrate the potential of the phantom for evaluating sO2 using chemical oxygenation and deoxygenation of blood in the circuit. Using this dynamic assessment of the photoacoustic sO2 measurement in phantoms in relation to a ground truth, we explore the influence of multispectral processing and spectral coloring on accurate assessment of sO2. Future studies could exploit this low-cost dynamic flow phantom to validate fluence correction algorithms and explore additional blood parameters such as pH and also absorptive and other properties of different fluids.

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Zhang S et al.

Photoacoustic imaging of living mice enhanced with a low-cost contrast agent

Other ApplicationsPreclinicalMSOT

One of the advantages of photoacoustic imaging (PAI) is that its image contrast may come from exogenous agents. Such advantage leads to the development of a great number of exogenous probes. However, the biosafety of most of these contrast agents has not yet been confirmed, thus hindering their clinical translation. In this work, we report on the utilization of a clinically commonly used nutritional medicine, the Intralipid, as a new contrast agent for photoacoustic imaging. Intralipid consists of soybean oil, lecithin and glycerin and has long been adapted in clinical practices, mainly as a parenteral nutrition. In our study, we found that with Intralipid, the imaging sensitivity of PAI can be effectively enhanced, as demonstrated in in vivo imaging of different organs of nude mice. Further imaging studies on cancerous mice showed not only a twofold PA signal enhancement, but also a strong and long-lasting signal aggregation in the tumor region. Our result revealed the potential of Intralipid to be used in clinical PAI applications, since it is clinically safe, and can be easily prepared at very low cost.

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Knauer N et al.

Spatial Compounding of Volumetric Data Enables Freehand Optoacoustic Angiography of Large-Scale Vascular Networks

NanoCancerClinicalMSOT

Optoacoustic tomography systems have attained un-precedented volumetric imaging speeds, thus enabling insights into rapid biological dynamics and marking a milestone in the clinical translation of this modality. Fast imaging performance often comes at the cost of limited field-of-view, which may hinder potential applications looking at larger tissue volumes. The imaged field-of-view can potentially be expanded via scanning and using additional hardware to track the position of the imaging probe. However, this approach turns impractical for high-resolution volumetric scans performed in a freehand mode along arbitrary trajectories. We have developed an accurate framework for spatial compounding of time-lapse optoacoustic data. The method exploits the frequency-domain properties of vascular networks in optoacoustic images and estimates the relative motion and orientation of the imaging probe. This allows rapidly combining sequential volumetric frames into large area scans without additional tracking hardware. The approach is universally applicable for compounding volumetric data acquired with calibrated scanning systems but also in a freehand mode with up to six degrees of freedom. Robust performance is demonstrated for whole-body mouse imaging with spiral volumetric optoacoustic tomography and for freehand visualization of vascular networks in humans using volumetric imaging probes. The newly introduced capability for angiographic observations at multiple spatial and temporal scales is expected to greatly facilitate the use of optoacoustic imaging technology in pre-clinical research and clinical diagnostics. The technique can equally benefit other biomedical imaging modalities, such as scanning fluorescence microscopy, optical coherence tomography or ultrasonography, thus optimizing their trade-offs between fast imaging performance and field-of-view.

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Huang J et al.

An Activatable Near-Infrared Chromophore for Multispectral Optoacoustic Imaging of Tumor Hypoxia and for Tumor Inhibition

CancerPreclinicalMSOT

Hypoxia is a key hallmark of solid tumors and tumor hypoxia usually contributes to cancer progression, therapeutic resistance and poor outcome. Accurately detecting and imaging tumor hypoxia with high spatial resolution would be conducive to formulating optimized treatment plan and thus achieving better patient outcome. Methods : Tumor hypoxia can cleave the azo linker and release a NIR fluorophore (NR-NH2) and release the active drug as well. NR-NH2 shows a strong absorption band at around 680 nm and a strong fluorescence band at 710 nm, allowing for both multispectral optoacoustic tomography imaging (MSOT) and fluorescent imaging of tumor hypoxia in a tumor-bearing mouse model. Results : Liposome encapsulated with the activatable chromophore (NR-azo) for detecting/imaging tumor hypoxia and for tumor inhibition was demonstrated. For this chromophore, a xanthene-based NIR fluorophore acts as the optoacoustic and fluorescent reporter, an azo linker serves as the hypoxia-responsive moiety and a nitrogen mustard as the therapeutic drug. NR-azo shows an absorption at around 575 nm but exhibits negligible fluorescence due to the existence of the strong electron-withdrawing azo linker. Conclusion : We demonstrated an optoacoustic and fluorescent system for not only imaging tumor hypoxia in vivo but also achieving tumor inhibition.

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Lv R et al.

Degradable magnetic-response photoacoustic/up-conversion luminescence imaging-guided photodynamic/photothermal antitumor therapy

NanoCancerPreclinicalMSOT

In this research, a degradable uniform mesoporous platform was designed as an imaging-guided photothermal therapy (PTT)/photodynamic therapy (PDT) agent. Fe3O4 nanoparticles were prepared using the solvothermal method, and a layer of mesoporous SiO2 was coated onto them using sol-gel and etching processes, then these ultra-small up-conversion nanoparticles (UCNPs) were loaded into the porous structure through electrostatic conjunction and physical absorption. By adjusting the etching processes, Fe3O4@mSiO2 and mSiO2 with a high surface area as a carrier host could be obtained separately. Importantly, the platform could recognize the tumor cells with a magnetic-response and then present strong photoacoustic (PA) and up-conversion luminescence (UCL) signals, and Fe3O4@mSiO2 as drug carriers could be degraded by hydrolysis. Furthermore, under a single 808 nm laser, the temperature of Fe3O4@mSiO2@UCNPs rises much higher than that of the surrounding tissues, and produces a large amount of singlet oxygen because a strong crossover occurs between the emitted blue emission of the UCNPs and the absorbance region of Fe3O4. Therefore, the Fe3O4@mSiO2@UCNPs can be used as a magnetic-targeted dual-modal imaging guided PTT/PDT theranostic probe.

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Minhas AS et al.

Measuring Kidney Perfusion, pH, and Renal Clearance Consecutively Using MRI and Multispectral Optoacoustic Tomography

PharmacokineticsPreclinicalMSOT

To establish multi-modal imaging for the assessment of kidney pH, perfusion, and clearance rate using magnetic resonance imaging (MRI) and multispectral optoacoustic tomography (MSOT) in healthy mice. Kidney pH and perfusion values were measured on a pixel-by-pixel basis using the MRI acidoCEST and FAIR-EPI methods. Kidney filtration rate was measured by analyzing the renal clearance rate of IRdye 800 using MSOT. To test the effect of one imaging method on the other, a set of 3 animals were imaged with MSOT followed by MRI, and a second set of 3 animals were imaged with MRI followed by MSOT. In a subsequent study, the reproducibility of pH, perfusion, and renal clearance measurements were tested by imaging 4 animals twice, separated by 4 days. The contrast agents used for acidoCEST based pH measurements influenced the results of MSOT. Specifically, the exponential decay time from the kidney cortex, as measured by MSOT, was significantly altered when MRI was performed prior to MSOT. However, no significant difference in the cortex to pelvis area under the curve (AUC) was noted. When the order of experiments was reversed, no significant differences were noted in the pH or perfusion values. Reproducibility measurements demonstrated similar pH and cortex to pelvis AUC; however, perfusion values were significantly different with the cortex values being higher and the pelvic values being lower in the second imaging time. We demonstrate that using a combination of MRI and MSOT, physiological measurements of pH, blood flow, and clearance rates can be measured in the mouse kidney in the same imaging session.

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Chen Z et al.

Concurrent fluorescence and volumetric optoacoustic tomography of nanoagent perfusion and bio-distribution in solid tumors

NanoCancerPreclinicalMSOT

Intravenously administered liposomes and other nano-sized particles are known to passively accumulate in solid tumors via the enhanced permeability and retention (EPR) effect, which is extensively explored toward the improvement of diagnosis and drug delivery in oncology. Agent extravasation into tumors is often hampered by the mononuclear phagocytic and renal systems, which sequester and/or eliminate most of the nanoparticles from the body. Dynamic imaging of the tumor microcirculation and bolus perfusion can thus facilitate optimization of the nanoparticle delivery. When it comes to non-invasive visualization of rapid biological dynamics in whole tumors, the currently available pre-clinical imaging modalities are commonly limited by shallow penetration, lack of suitable contrast or otherwise insufficient spatial or temporal resolution. Herein, we demonstrate the unique capabilities of a combined epi-fluorescence and optoacoustic tomography (FLOT) system for characterizing contrast agent dynamics in orthotopic breast tumors in mice. A liposomal indocyanine green (Lipo-ICG) preparation was administered intravenously with the time-lapse data continuously acquired during and after the injection procedure. In addition to the highly sensitive detection of the fluorescence agent by the epi-fluorescence modality, the volumetric multi-spectral optoacoustic tomography readings further enabled resolving deep-seated vascular structures with high spatial resolution and hence provided accurate readings of the dynamic bio-distribution of nanoparticles in the entire tumor in 3D. The synergetic combination of the two modalities can become a powerful tool in cancer research and potentially aid the diagnosis, staging and treatment guidance of certain types of cancer in the clinical setting.

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Tao C et al.

Surface Plasmon Resonance-Enhanced Photoacoustic Imaging and Photothermal Therapy of Endogenous H2 S-Triggered Au@Cu2 O

NanoCancerPreclinicalMSOT

Smart theranostics agents triggered by endogenous H2 S with combined activated photoacoustic imaging and photothermal therapy can improve the diagnosis and treatment of colon cancer. However, the low theranostic performance of the current smart theranostics agents after the triggering step has limited their further application. In this work, the theranostic performance of endogenous H2 S-triggered Au@Cu2 O for the diagnosis and treatment of colon cancer, which is generated from the localized surface plasmon resonance coupling effect between a noble metal (Au) and a semiconductor (Cu2 O), is investigated. Compared with Cu2 O, the prepared H2 S-triggered Au@Cu2 O shows a significantly stronger absorption at the near-infrared region, such as a ≈2.1 times change at 808 nm, giving a photothermal conversion efficiency increase of ≈1.2 times. More importantly, Au@Cu2 O still exhibits good photoacoustic imaging contrast and photothermal properties for treatment of colon cancer in vivo even at very low injection doses. This work not only investigates an endogenous H2 S-triggered Au@Cu2 O theranostic agent with enhanced theranostic performance for colon cancer but also provides a novel strategy for designing high-performance theranostic agents.

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Berezhnoi A et al.

Optical features of human skin revealed by optoacoustic mesoscopy in the visible and short-wave infrared regions

SkinClinicalRSOM

Detailed assessment of skin conditions or the efficacy of skin treatments could greatly benefit from noninvasively assessing the distribution of cutaneous and subcutaneous structures and biomolecules. We considered ultrawideband raster scan optoacoustic mesoscopy with an extended wavelength range from visible to short-wave infrared and observed previously unseen high-resolution images of lipids colocalized with water, melanin, and hemoglobin distribution in human skin. Based on this contrast, the technique resolves subcutaneous fat, the pilosebaceous unit with complete hair strand and bulb, dermal microvasculature, and epidermal structures. We further visualize melanoidins that form via the Maillard reaction in the ultrathin stratum corneum layer, analyze their absorption spectrum, and separate them from the melanin layer. The suggested method may allow novel interrogation of skin conditions, possibly impacting diagnostics and medical and cosmetic treatments.

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Wang D et al.

Porphyrin-based covalent organic framework nanoparticles for photoacoustic imaging-guided photodynamic and photothermal combination cancer therapy

NanoCancerPreclinicalMSOT

Combination of photodynamic therapy (PDT) and photothermal therapy (PTT) generally requires different components to build a composite irradiated with different excitation lights. One component photoactive agent for enhanced combination of PDT and PTT under the excitation of a single wavelength light source is more urgent in tumor phototherapy via adjusting spatial arrangement of photoactive units. Herein, porphyrin-based covalent organic framework nanoparticles (COF-366 NPs) were synthesized to control the orderly spatial arrangement of the photoactive building units and firstly used for antitumor therapy in vivo. COF-366 NPs provide the simultaneous therapy of PDT and PTT under a single wavelength light source with the monitoring of photoacoustic (PA) imaging, which makes the operation simpler and more convenient. COF-366 NPs had achieved good phototherapy effect even in the face of large tumors. The prepared multifunctional COF-366 NPs open up a new avenue to phototherapeutic materials and expand the application range of covalent organic framework.

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Weber J et al.

An activatable cancer-targeted hydrogen peroxide probe for photoacoustic and fluorescence imaging

CancerPreclinicalMSOT

Reactive oxygen species play an important role in cancer, however, their promiscuous reactivity, low abundance and short-lived nature limits our ability to study them in real time in living subjects with conventional non-invasive imaging methods. Photoacoustic imaging is an emerging modality for in vivo visualization of molecular processes with deep tissue penetration and high spatio-temporal resolution. Here, we describe the design and synthesis of a targeted, activatable probe for photoacoustic imaging, which is responsive to one of the major and abundant reactive oxygen species, hydrogen peroxide (H2O2). This bifunctional probe, which is also detectable with fluorescence imaging, is composed of a heptamethine carbocyanine dye scaffold for signal generation, a 2-deoxyglucose cancer localization moiety and a boronic ester functionality that specifically detects and reacts to H2O2. The optical properties of the probe were characterized using absorption, fluorescence and photoacoustic measurements; upon addition of pathophysiological H2O2 concentrations, a clear increase in fluorescence and red-shift of the absorption and photoacoustic spectra were observed. Studies performed in vitro showed no significant toxicity and specific uptake of the probe into the cytosol in breast cancer cell lines. Importantly, intravenous injection of the probe led to targeted uptake and accumulation in solid tumors, which enabled non-invasive photoacoustic and fluorescence imaging of H2O2. In conclusion, the reported probe shows promise for the in vivo visualization of hydrogen peroxide.

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Kim JJ et al.

A NIR probe tracks and treats lung tumor initiating cells by targeting HMOX2

CancerPreclinicalMSOT

Tumor initiating cells (TIC) are resistant to conventional anti-cancer therapy and associated with metastasis and relapse in cancer. Although various TIC markers and their antibodies have been proposed, it is limited to use of antibodies for in vivo imaging or treatment of TIC. In this study, we discovered heme oxygenase 2 (HMOX2) as a novel biomarker for TIC and developed a selective small molecule probe TiNIR (Tumor Initiating cell probe with Near Infra-Red). TiNIR detects and enriches the functionally active TIC in human lung tumors, and through photoacoustic proper-ty, TiNIR also visualizes lung TIC in the patient-derived xenograft (PDX) model. Furthermore, we demonstrate that TiNIR inhibits tumor growth by blocking the function of HMOX2, resulting in significantly increased survival rates of the cancer model mice. The novel therapeutic target HMOX2 and its fluorescent ligand TiNIR will open a new path for molecular level of lung TIC diagnosis and treatment.

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Park SJ et al.

Visualizing Alzheimer’s Disease Mouse Brain with Multispectral Optoacoustic Tomography using a Fluorescent probe, CDnir7

NeuroPreclinicalMSOT

Alzheimer’s disease (AD) is now clinically considered as a chronic inflammation-based neurodegenerative disease. The CDnir7 probe was previously developed as an optical imaging probe to target macrophages in order to image mouse inflammation using in vivo optical imaging modalities such as In Vivo imaging system (IVIS) and fluorescent molecular tomography (FMT). Here, we demonstrate the application of CDnir7 in AD mouse brain imaging via multispectral optoacoustic tomography (MSOT). Longitudinal MSOT imaging of CDnir7 showed higher CDnir7 localization in AD mouse cerebral cortex compared to that of normal mice. MSOT signals of CDnir7 localization in mouse brain were verified by ex vivo near-infrared (NIR) imaging and immunohistochemistry. Histological evaluation showed strong CDnir7 staining in AD cerebral cortex, hippocampus, basal ganglia and thalamus area. Based on the supporting evidence, CDnir7 has great potential as a molecular imaging probe for AD brain imaging.

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Yang Y et al.

NIR-II Driven Plasmon-Enhanced Catalysis for Timely Supply of Oxygen to Overcome Hypoxia Induced Radiotherapy Tolerance

NanoCancerPreclinicalMSOT

Hypoxia, as a characteristic feature of solid tumor, can significantly adversely affect the outcomes of cancer radiotherapy (RT), photodynamical therapy or chemotherapy. In this study, we have developed a novel strategy to overcome tumor hypoxia induced radiotherapy tolerance. Specifically, a novel two-dimensional Pd@Au bimetallic core-shell nanostructures (TPAN) was employed for the sustainable and robust production of O2 in long-term via the catalysis of endogenous H2O2. Notably, the catalytic activity of TPAN could be enhanced via surface plasmon resonance (SPR) effect triggered by NIR-II laser irradiation, to enhance the O2 production and thereby relieve tumor hypoxia. Thus, TPAN could enhance radiotherapy outcomes by three aspects: (i) NIR-II laser triggered SPR enhanced the catalysis of TPAN to produce O2 for relieving tumor hypoxia; (ii) high-Z element effect arising from Au and Pd to capture X-ray energy within tumor; (iii) TPAN affording X-ray, photoacoustic and NIR-II laser derived photothermal imaging, for precisely guiding cancer therapy, so as to reduce the side effects from irradiation.

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Liu F et al.

A Tumor-Microenvironment-Activated Nanozyme-Mediated Theranostic Nanoreactor for Imaging-Guided Combined Tumor Therapy

NanoCancerPreclinicalMSOT

Activatable theranostic agents that can be activated by tumor microenvironment possess higher specificity and sensitivity. Here, activatable nanozyme-mediated 2,2′-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) loaded ABTS@MIL-100/poly(vinylpyrrolidine) (AMP) nanoreactors (NRs) are developed for imaging-guided combined tumor therapy. The as-constructed AMP NRs can be specifically activated by the tumor microenvironment through a nanozyme-mediated “two-step rocket-launching-like” process to turn on its photoacoustic imaging signal and photothermal therapy (PTT) function. In addition, simultaneously producing hydroxyl radicals in response to the high H2 O2 level of the tumor microenvironment and disrupting intracellular glutathione (GSH) endows the AMP NRs with the ability of enhanced chemodynamic therapy (ECDT), thereby leading to more efficient therapeutic outcome in combination with tumor-triggered PTT. More importantly, the H2 O2 -activated and acid-enhanced properties enable the AMP NRs to be specific to tumors, leaving the normal tissues unharmed. These remarkable features of AMP NRs may open a new avenue to explore nanozyme-involved nanoreactors for intelligent, accurate, and noninvasive cancer theranostics.

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Liu F et al.

Engineering an NIR rhodol derivative with spirocyclic ring-opening activation for high-contrast photoacoustic imaging

NanoPharmacokineticsPreclinicalMSOT

Molecular probes that enable high-contrast photoacoustic (PA) imaging of cellular processes are valuable tools for in vivo studies. Design of activatable PA probes with high contrast remains elusive. We develop a new NIR rhodol derivative, Rhodol-NIR, with a large extinction coefficient, low quantum yield and structural switching from a ‘ring-open’ form to a ‘closed’ spirolactone upon esterification. This structural transition, together with the ideal photophysical properties, enables the development of activatable probes for high-contrast PA imaging via a target-specific de-esterification reaction. This strategy is demonstrated using a PA probe designed for a tumor biomarker, human NAD(P)H: quinone oxidoreductase isozyme 1 (hNQO1), which affords high contrast and excellent sensitivity for PA detection and imaging of hNQO1 in living cells and animals. The strategy can provide a new paradigm for engineering activatable PA probes for high-contrast imaging.

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Aziz A et al.

Real-time optoacoustic tracking of single moving micro-objects in deep phantom and ex vivo tissues

NanoPreclinicalMSOT

Medical imaging plays an important role in diagnosis and treatment of multiple diseases. It is a field which seeks for improved sensitivity and spatiotemporal resolution to allow the dynamic monitoring of diverse biological processes that occur at the micro- and nanoscale. Emerging technologies for targeted diagnosis and therapy such as nanotherapeutics, microimplants, catheters, and small medical tools also need to be precisely located and monitored while performing their function inside the human body. In this work, we show for the first time the real-time tracking of moving single micro-objects below centimeter thick phantom tissue and ex vivo chicken breast, using multispectral optoacoustic tomography (MSOT). This technique combines the advantages of ultrasound imaging regarding depth and resolution with the molecular specificity of optical methods, thereby facilitating the discrimination between the spectral signatures of the micro-objects from those of intrinsic tissue molecules. The resulting MSOT signal is further improved in terms of contrast and specificity by coating the micro-objects’ surface with gold nanorods, possessing a unique absorption spectrum, which facilitate their discrimination from surrounding biological tissues when translated to future in vivo settings.

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Basak K et al.

Non-invasive determination of murine placental and foetal functional parameters with multispectral optoacoustic tomography

Other ApplicationsPreclinicalMSOT

Despite the importance of placental function in embryonic development, it remains poorly understood and challenging to characterize, primarily due to the lack of non-invasive imaging tools capable of monitoring placental and foetal oxygenation and perfusion parameters during pregnancy. We developed an optoacoustic tomography approach for real-time imaging through entire ~4 cm cross-sections of pregnant mice. Functional changes in both maternal and embryo regions were studied at different gestation days when subjected to an oxygen breathing challenge and perfusion with indocyanine green. Structural phenotyping of the cross-sectional scans highlighted different internal organs, whereas multi-wavelength acquisitions enabled non-invasive label-free spectroscopic assessment of blood-oxygenation parameters in foeto-placental regions, rendering a strong correlation with the amount of oxygen administered. Likewise, the placental function in protecting the embryo from extrinsically administered agents was substantiated. The proposed methodology may potentially further serve as a probing mechanism to appraise embryo development during pregnancy in the clinical setting.

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Fuenzalida Werner JP et al.

Structure-based mutagenesis of phycobiliprotein smURFP for optoacoustic imaging

Other ApplicationsPreclinicalMSOT

Photo- or optoacoustics (OA) imaging is increasingly being used as a non-invasive imaging method that can simultaneously reveal structure and function in deep tissue. However, the most frequent transgenic OA labels are current fluorescent proteins that are not optimized for OA imaging. Thus, they lack OA signal strength, and their absorption maxima are positioned at short wavelengths, thus giving small penetration depths and strong background signals. Here, we apply insights from our recent determination of the structure of the fluorescent phycobiliprotein smURFP to mutate a range of residues to promote the nonradiative decay pathway that generates the OA signal. We identified hydrophobic and aromatic substitutions within the chromophore-binding pocket that substantially increase the intensity of the OA signal and red-shift the absorption. Our results demonstrate the feasibility of structure-based mutagenesis to repurpose fluorescent probes for OA imaging, and they may provide structure-function insights for de novo engineering of transgenic OA probes.

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Sun Y et al.

Melanin-dot-mediated delivery of metallacycle for NIR-II/photoacoustic dual-modal imaging-guided chemo-photothermal synergistic therapy

NanoCancerPreclinicalMSOT

Discrete Pt(II) metallacycles have potential applications in biomedicine. Herein, we engineered a dual-modal imaging and chemo-photothermal therapeutic nano-agent 1 that incorporates discrete Pt(II) metallacycle 2 and fluorescent dye 3 (emission wavelength in the second near-infrared channel [NIR-II]) into multifunctional melanin dots with photoacoustic signal and photothermal features. Nano-agent 1 has a good solubility, biocompatibility, and stability in vivo. Both photoacoustic imaging and NIR-II imaging in vivo confirmed that 1 can effectively accumulate at tumor sites with good signal-to-background ratio and favorable distribution. Guided by precise dual-modal imaging, nano-agent 1 exhibits a superior antitumor performance and less severe side effects compared with a single treatment because of the high efficiency of the chemo-photothermal synergistic therapy. This study shows that nano-agent 1 provides a promising multifunctional theranostic platform for potential applications in biomedicine.

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Ji C et al.

From Dyestuff Chemistry to Cancer Theranostics: The Rise of Rylenecarboximides

NanoCancerPreclinicalMSOT

Fighting cancer with the means of chemistry remains a tremendous challenge and defines a pressing societal need. Compounds based on synthetic organic dyes have long been recognized as vital tools for cancer diagnosis and therapy (theranostics). Fluorescence and photoacoustic imaging of cancer as well as cancer treatment protocols such as photodynamic and photothermal therapy are all photobased technologies that require chromophores. However, a serious drawback of most chromophoric molecules is photobleaching over the course of their use in biological environments, which severely compromises the desired theranostic effects. At this point, rylenecarboximide (RI) dyes with ultrahigh photostability hold enormous promise. RI stands for a homologous series of dyes consisting of an aromatic core and carboximide auxochromic groups. They possess high molar extinction coefficients and finely tunable photophysical properties. RIs such as perylenebiscarboxylic acid monoimide (PMI), perylenetetracarboxylic acid diimide (PDI), terrylenetetracarboxylic acid diimide (TDI), and quaterrylene tetracarboxylic acid diimide (QDI) have attracted great scientific attention as colorants, components of organic photovoltaics and organic field-effect transistors, as well as tools for biological applications. PDI has appeared as one of the most widely studied RI dyes for fluorescence bioimaging. Our recent breakthroughs including chemotherapy with PDI-based DNA intercalators and photothermal therapy guided by photoacoustic imaging using PDI, TDI, or QDI, define urgent needs for further scientific research and clinical translation. In this Account, we tackle the relationship between chemical structures and photophysical and pharmacologic properties of RIs aiming at new contrast and anticancer agents, which then lay the ground for further biomedical applications. First, we introduce the design concepts for RIs with a focus on their structure-property relationships. Chemical structure has an enormous impact on the fluorescent, chemotoxic, photodynamic, and photothermal performance of RIs. Next, based on the resulting performance criteria, we employ RIs for fluorescence and photoacoustic cancer imaging as well as cancer therapies. When carrying electron donating substituents, PDIs and PMIs possess high fluorescence quantum yield and red-shifted emission which qualifies them for use in cancer fluorescence imaging. Also, some fluorescent PDIs are combined with chemodrugs or developed into DNA intercalators for chemotherapy. PDI-based photosensitizers are prepared by “heavy atom” substitution, showing potential for photodynamic therapy. Further, photothermal agents using PDI, TDI, and QDI with near-infrared absorption and excellent photothermal conversion efficiency offer high promise in photothermal cancer therapy monitored by photoacoustic imaging. Finally, looking jointly at the outstanding properties of RIs and the demands of current biomedicine, we offer an outlook toward further modifications of RIs as a powerful and practical platform for advanced cancer theranostics as well as treatment of other diseases.

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Stoffels I et al.

Assessment of Nonradioactive Multispectral Optoacoustic Tomographic Imaging With Conventional Lymphoscintigraphic Imaging for Sentinel Lymph Node Biopsy in Melanoma

MelanomaClinicalMSOT

Importance: The metastatic status of sentinel lymph nodes (SLNs) is the most relevant prognostic factor in breast cancer, melanoma, and other tumors. The conventional standard to label SLNs is lymphoscintigraphy with technetium Tc 99m. A worldwide shortage and known disadvantages of Tc 99m have intensified efforts to establish alternative, nonradioactive imaging techniques.

Objective: To assess a new nonradioactive method using multispectral optoacoustic tomographic (MSOT) imaging in comparison with conventional lymphoscintigraphic imaging for SLN biopsy (SLNB) in melanoma.

Design, Setting, and Participants: Analysis of a cross-sectional study was conducted at the University Hospital-Essen, Skin Cancer Center, Essen, Germany. Between June 2, 2014, and February 22, 2019, 83 patients underwent SLNB with an additional preoperative indocyanine green (ICG) application. Sentinel lymph node basins were preoperatively identified by MSOT imaging, and ICG-labeled SLNs were intraoperatively detected using a near-infrared camera. The surgeons were blinded to the lymphoscintigraphic imaging results in the beginning of the SLNB. Use of a γ probe was restricted until the SLNB procedure was attempted by the nonradioactive method.

Main Outcomes and Measures: Concordance of SLN basins and SLNs identified by MSOT imaging plus near-infrared camera vs lymphoscintigraphic imaging plus single-photon emission computed tomographic or computed tomographic imaging was assessed.

Results: Of the 83 patients (mean [SD] age, 54.61 [17.53] years), 47 (56.6%) were men. In 83 surgical procedures, 165 SLNs were excised. The concordance rate of ICG-labeled and Tc 99m-marked detected SLN basins was 94.6% (n = 106 of 112). Intraoperatively, 159 SLNs were detected using a near-infrared camera and 165 were detected by a γ probe, resulting in a concordance rate of 96.4%. Multispectral optoacoustic tomographic imaging visualized SLNs in all anatomic regions with high penetration depth (5 cm).

Conclusions and Relevance: The findings of this study suggest that nonradioactive SLN detection via MSOT imaging allows identification of SLNs at a frequency equivalent to that of the current radiotracer conventional standard. Multispectral optoacoustic tomographic imaging appears to be a viable nonradioactive alternative to detect SLNs in malignant tumors.

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Teng L et al.

Nitric Oxide-Activated "Dual-Key-One-Lock" Nanoprobe for In Vivo Molecular Imaging and High-Specificity Cancer Therapy

NanoCancerPreclinicalMSOT

Cancer treatments are confounded by severe toxic effects toward patients. To address these issues, activatable nanoprobes have been designed for specific imaging and destruction of cancer cells under the stimulation of specific cancer-associated biomarkers. Most activatable nanoprobes were usually activated by some single-factor stimulation, but this restricts therapeutic specificity between diseased and normal tissue; therefore, multifactor activation is highly desired. To this end, we herein develop a novel dual-stimuli responsive theranostic nanoprobe for simultaneously activatable cancer imaging and photothermal therapy under the coactivation of “dual-key” stimulation of “nitric oxide (NO)/acidity”, so as to further improve the therapeutic specificity. Specifically, we have integrated a weak electron acceptor (benzo[c][1,2,5]thiadiazole-5,6-diamine) into a donor-π-acceptor-π-donor type chromophore. When the weak acceptor was oxidized by NO in acidic conditions to form a stronger acceptor (5H-[1,2,3]triazolo[4,5-f]-2,1,3-benzothiadiazole), the molecule absorption was significantly increased in the near-infrared region, based on the intramolecular charge transfer (ICT) mechanism. Under the dual-key stimulation of NO/acidity within the tumor associated with inflammation, the nanoprobe can correspondingly output dual signals for ratiometric photoacoustic and photothermal imaging of cancer in vivo and do so with enhanced accuracy and specificity. Our novel nanoprobe exhibited higher photoacoustic signal enhancement under dual-factor activation at 9.8 times that of NO and 132 times that of acidity alone, respectively. Moreover, through such dual activation of NO/acidity, the nanoprobe produces more differentiation of hyperthermia between tumor and normal tissues, to afford satisfactory photothermal therapy with minimal toxic side effects. Thus, our work presents a promising strategy for significantly improving the precision and specificity of cancer imaging and therapy.

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Li C et al.

Self-destructive PEG-BODIPY nanomaterials for photodynamic and photothermal therapy

NanoCancerPreclinicalMSOT

Photoactive nanoparticles are an important platform for multimodal imaging and phototherapy of tumors. Herein, amphiphilic photosensitizers were made from boron dipyrromethene (BODIPY) and poly(ethylene glycol) (PEG2k) by using a thioketal linker, which is reactive oxygen species-responsive. The photosensitizers could form stable nanoparticles in aqueous solution. The resulting nanoparticles could simultaneously produce heat and reactive oxygen species upon irradiation to achieve combined photothermal and photodynamic therapy. The produced singlet oxygen could destroy the thioketal linker, and accelerate the destruction of nanoparticles. In addition, the near-infrared fluorescence and photoacoustic imaging ability of nanoparticles can reflect the biodistribution and destiny of nanoparticles. This work highlights the application of integrated diagnostic and therapeutic photosensitizers in carriers.

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Dean-Ben XL et al.

Optoacoustic image formation approaches - a clinical perspective

TechnologyClinicalMSOT

Clinical translation of optoacoustic imaging is fostered by the rapid technical advances in imaging performance as well as the growing number of clinicians recognizing the immense diagnostic potential of this technology. Clinical optoacoustic systems are available in multiple configurations, including hand-held and endoscopic probes as well as raster-scan approaches. The hardware design must be adapted to the accessible portion of the imaged region and other application-specific requirements pertaining the achievable depth, field of view or spatio-temporal resolution. Equally important is the adequate choice of signal and image processing approach, which is largely responsible for the resulting imaging performance. Thus, new image reconstruction algorithms are constantly evolving in parallel to the newly-developed set-ups. This review focuses on recent progress on optoacoustic image formation algorithms and processing methods in the clinical setting. Major reconstruction challenges include real-time image rendering in two and three dimensions, efficient hybridization with other imaging modalitites as well as accurate interpretation and quantification of bio-markers, herein discussed in the context of ongoing progress in clinical translation.

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Moustakidis S et al.

Fully Automated Identification of Skin Morphology in Raster-Scan Optoacoustic Mesoscopy using Artificial Intelligence

Other ApplicationsTechnologyClinicalRSOM

PURPOSE: Identification of morphological characteristics of skin lesions is of vital importance in diagnosing diseases with dermatological manifestations. This task is often performed manually or in an automated way based on intensity level. Recently, ultra-broadband raster-scan optoacoustic mesoscopy (UWB-RSOM) was developed to offer unique cross-sectional optical imaging of the skin. A machine learning (ML) approach is proposed here to enable, for the first time, automated identification of skin layers in UWB-RSOM data.

METHODS AND MATERIALS: The proposed method, termed SkinSeg, was applied to coronal UWB-RSOM images obtained from 12 human participants. SkinSeg is a multi-step methodology that integrates data processing and transformation, feature extraction, feature selection and classification. Various image features and learning models were tested for their suitability at discriminating skin layers including traditional machine learning along with more advanced deep learning algorithms. An SVM-based post-processing approach was finally applied to further improve the classification outputs.

RESULTS: Random forest proved to be the most effective technique, achieving mean classification accuracy of 86.89% evaluated based on a repeated leave-one-out strategy. Insights about the features extracted and their effect on classification accuracy are provided. The highest accuracy was achieved using a small group of 4 features and remained at the same level or was even slightly decreased when more features were included. Convolutional neural networks provided also promising results at a level of approximately 85%. The application of the proposed post-processing technique was proved to be effective in terms of both testing accuracy and 3D visualization of classification maps.

CONCLUSIONS: SkinSeg demonstrated unique potential in identifying skin layers. The proposed method may facilitate clinical evaluation, monitoring and diagnosis of diseases linked to skin inflammation, diabetes and skin cancer. This article is protected by copyright. All rights reserved.

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Brown E et al.

Photoacoustic imaging as a tool to probe the tumour microenvironment

CancerPreclinicalClinicalMSOT

The tumour microenvironment (TME) is a complex cellular ecosystem subjected to chemical and physical signals that play a role in shaping tumour heterogeneity, invasion and metastasis. Studying the roles of the TME in cancer progression would strongly benefit from non-invasive visualisation of the tumour as a whole organ in vivo, both preclinically in mouse models of the disease, as well as in patient tumours. Although imaging techniques exist that can probe different facets of the TME, they face several limitations, including limited spatial resolution, extended scan times and poor specificity from confounding signals. Photoacoustic imaging (PAI) is an emerging modality, currently in clinical trials, that has the potential to overcome these limitations. Here, we review the biological properties of the TME and potential of existing imaging methods that have been developed to analyse these properties non-invasively. We then introduce PAI and explore the preclinical and clinical evidence that support its use in probing multiple features of the TME simultaneously, including blood vessel architecture, blood oxygenation, acidity, extracellular matrix deposition, lipid concentration and immune cell infiltration. Finally, we highlight the future prospects and outstanding challenges in the application of PAI as a tool in cancer research and as part of a clinical oncologist’s arsenal.

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Nitkunanantharajah S et al.

Skin surface detection in 3D optoacoustic mesoscopy based on dynamic programming

Other ApplicationsTechnologyClinicalRSOM

Optoacoustic (photoacoustic) mesoscopy offers unique capabilities in skin imaging and resolves skin features associated with detection, diagnosis and management of disease. A critical first step in the quantitative analysis of clinical optoacoustic images is to identify the skin surface in a rapid, reliable and automated manner. Nevertheless, most common edge-and surface-detection algorithms cannot reliably detect the skin surface on 3D raster-scan optoacoustic mesoscopy (RSOM) images, due to discontinuities and diffuse interfaces in the image. We present herein a novel dynamic programming approach that extracts the skin boundary as a 2D surface in one single step, as opposed to consecutive extraction of several independent 1D contours. A domain-specific energy function is introduced, taking into account the properties of volumetric optoacoustic mesoscopy images. The accuracy of the proposed method is validated on scans of the volar forearm of 19 volunteers with different skin complexions, for which the skin surface has been traced manually to provide a reference. Additionally, the robustness and the limitations of the method are demonstrated on data where the skin boundaries are low-contrast or ill-defined. The automatic skin surface detection method can improve the speed and accuracy in the analysis of quantitative features seen on RSOM images and accelerate the clinical translation of the technique. Our method can likely be extended to identify other types of surfaces in RSOM and other imaging modalities.

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Yew YW et al.

Investigation of Morphological, Vascular and Biochemical Changes in the Skin of an Atopic Dermatitis (AD) Patient in Response to Dupilumab Using Raster Scanning Optoacoustic Mesoscopy (RSOM) and Handheld Confocal Raman Spectroscopy (CRS)

SkinClinicalRSOM

n/a

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Yu J et al.

Antimonene Nanoflakes: Extraordinary Photoacoustic Performance for High-Contrast Imaging of Small Volume Tumors

NanoCancerPreclinicalMSOT

Photoacoustic imaging (PAI) has evolved to a stage that high-performance exogeneous contrast agents are urgently needed for imminent biomedical and clinical applications. Given that a material meets the basic criteria of efficient photoacoustic conversion, high biocompatibility, and fast excretion, great effort has been devoted to evaluating various materials for developing advantageous contrast agents to explore the full potentials of PAI. One focus is through modification of the current agents to boost their PA performance; whilst the other focus is to develop novel agents. Antimonene (AM) has emerged as a promising candidate for next generation of electronics among 2D materials due to its outstanding properties. Herein, it is reported that liquid-phase exfoliated antimonene exhibits extraordinary photoacoustic performance, which is not only more advantageous than other 2D materials, such as black phosphorus, graphene oxide, and transition metal dichalcogenides, but also superior to the commonly used PA contrast agents, such as ICG and gold nanorods. An insight analysis reveals that the unique thermal property of AM, including intrinsic low thermal conductivity and the morphology-related high interfacial thermal conductivity, might interpret the high photothermal conversion efficiency, and thus the excellent photoacoustic performance. The prodigious performance allows sensitive monitoring of intracellular events and high-quality in vivo tumor imaging.

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Zhan C et al.

A Gold Nanocage/Cluster Hybrid Structure for Whole-Body Multispectral Optoacoustic Tomography Imaging, EGFR Inhibitor Delivery, and Photothermal Therapy

NanoCancerPreclinicalMSOT

Gold nanocages (AuNCs) and gold nanoclusters (AuClusters) are two classes of advantageous nanostructures with special optical properties, and many other attractive properties. Integrating them into one nanosystem may achieve greater and smarter performance. Herein, a hybrid gold nanostructure for fluorescent and optoacoustic tomography imaging, controlled release of drugs, and photothermal therapy (PTT) is demonstrated. For this nanodrug (EA-AB), an epidermal growth factor receptor (EGFR) inhibitor erlotinib (EB) is loaded into AuNCs, which are then capped and functionalized by biocompatible AuCluster@BSA (BSA = bovine serum albumin) conjugates via electrostatic interaction. Upon cell internalization, the lysosomal proteases and low pH cause the release of EB from EA-AB, and also induce fluorescence restoration of the AuCluster for imaging. Irradiation with near-infrared light further promotes the drug release and affords a PTT effect as well. The AuNC-based nanodrug is optoacoustically active, and its biodistribution and metabolic process have been successfully monitored by whole-body and 3D multispectral optoacoustic tomography imaging. Owing to the combined actions of PTT and EGFR pathway blockage, EA-AB exhibits marked tumor inhibition efficacy in vivo.

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Roberts S et al.

Acid specific dark quencher QC1 pHLIP for multi-spectral optoacoustic diagnoses of breast cancer

CancerPreclinicalMSOT

Breast cancer is the most common type of malignant growth in women. Early detection of breast cancer, as well as the identification of possible metastatic spread poses a significant challenge because of the structural and genetic heterogeneity that occurs during the progression of the disease. Currently, mammographies, biopsies and MRI scans are the standard of care techniques used for breast cancer diagnosis, all of which have their individual shortfalls, especially when it comes to discriminating tumors and benign growths. With this in mind, we have developed a non-invasive optoacoustic imaging strategy that targets the acidic environment of breast cancer. A pH low insertion peptide (pHLIP) was conjugated to the dark quencher QC1, yielding a non-fluorescent sonophore with high extinction coefficient in the near infrared that increases signal as a function of increasing amounts of membrane insertion. In an orthotopic murine breast cancer model, pHLIP-targeted optoacoustic imaging allowed us to differentiate between healthy and breast cancer tissues with high signal/noise ratios. In vivo, the sonophore QC1-pHLIP could detect malignancies at higher contrast than its fluorescent analog ICG-pHLIP, which was developed for fluorescence-guided surgical applications. PHLIP-type optoacoustic imaging agents in clinical settings are attractive due to their ability to target breast cancer and a wide variety of other malignant growths for diagnostic purposes. Intuitively, these agents could also be used for visualization during surgery.

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Ivankovic I et al.

Volumetric optoacoustic tomography enables non-invasive in vivo characterization of impaired heart function in hypoxic conditions

VascularPreclinicalMSOT

Exposure to chronic hypoxia results in pulmonary hypertension characterized by increased vascular resistance and pulmonary vascular remodeling, changes in functional parameters of the pulmonary vasculature, and right ventricular hypertrophy, which can eventually lead to right heart failure. The underlying mechanisms of hypoxia-induced pulmonary hypertension have still not been fully elucidated while no curative treatment is currently available. Commonly employed pre-clinical analytic methods are largely limited to invasive studies interfering with cardiac tissue or otherwise ex vivo functional studies and histopathology. In this work, we suggest volumetric optoacoustic tomography (VOT) for non-invasive assessment of heart function in response to chronic hypoxia. Mice exposed for 3 consecutive weeks to normoxia or chronic hypoxia were imaged in vivo with heart perfusion tracked by VOT using indocyanide green contrast agent at high temporal (100 Hz) and spatial (200 µm) resolutions in 3D. Unequivocal difference in the pulmonary transit time was revealed between the hypoxic and normoxic conditions concomitant with the presence of pulmonary vascular remodeling within hypoxic models. Furthermore, a beat-to-beat analysis of the volumetric image data enabled identifying and characterizing arrhythmic events in mice exposed to chronic hypoxia. The newly introduced non-invasive methodology for analysis of impaired pulmonary vasculature and heart function under chronic hypoxic exposure provides important inputs into development of early diagnosis and treatment strategies in pulmonary hypertension.

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Zhang Y et al.

Positive feedback nanoamplifier responded to tumor microenvironments for self-enhanced tumor imaging and therapy

NanoCancerPreclinicalMSOT

Targeted activation or enhancement is an attractive strategy in the design of nano-theranostics. However, the responsiveness of the nanoagents is restricted by the limited levels of intra-tumor stimuli. Herein, we constructed a positive feedback nanoamplifier by encapsulating glucose oxidase (GOx) in the ferric ions contained metal organic framework (MIL-100), and coating the nanoparticles with polydopamine modified hyaluronic acid (HA-PDA). The mechanism of action of the ensuing nanoamplifiers was three pronged: 1) the high intra-tumor acidity accelerated the release of GOx, which consumed endogenous glucose and “starved” the tumors, in addition to aggravating the local acidity and H2O2 levels; 2) the hydroxyl radicals (·OH) generated from the Fenton-like reaction between MIL-100 with H2O2 contributed to the chemodynamic tumor therapy and augmented the O2 microenvironment, which could be speeded up under acid condition; 3) the oxygen (O2) produced in the Fenton-like reaction relieved the intra-tumor hypoxia and ensured the enzymatic reaction of GOx, along with augmenting the photoacoustic signal of nanoamplifier. Preliminary experiments in tumor bearing mice showed that the nanoamplifier not only boosted the local acidity/H2O2/O2 levels in tumor site to successfully suppress the growth of tumors through the self-enhanced chemodynamic/starving therapy, but also achieved the photoacoustic imaging of tumors. Taken together, this novel nanoamplifier with the abilities of self-enhanced tumor imaging and therapy is a promising entrant in the field of anti-tumor theranostics.

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Huang Y et al.

Diagnosing Drug-induced Liver Injury by Multispectral Optoacoustic Tomography and Fluorescence Imaging Using a Leucine-Aminopeptidase-Activated Probe

Other ApplicationsPreclinicalMSOT

Drug-induced liver injury (DILI) is a frequent cause of hepatic dysfunction as well as the single most frequent reason for removing approved medications from the market, and multispectral optoacoustic tomography (MSOT) is an emerging and noninvasive imaging modality for diagnosing and monitoring diseases. Herein, we report an activatable optoacoustic probe for imaging DILI through detecting the activity of leucine aminopeptidase (LAP). In this probe, an N-terminal leucyl moiety serving as the LAP recognition element is linked with a chromene-benzoindolium chromophore via 4-aminobenzylalcohol group. The elevated expression of hepatic LAP as a result of DILI cleaves the leucyl moiety and causes the red-shift of the probe’s absorption band, thereby generating prominent optoacoustic signals for MSOT imaging. During this process, the probe also exhibits prominent NIR fluorescence, which can be utilized for fluorescent imaging. More importantly, by rendering stacks of cross-sectional images as maximal intensity projection (MIP) images, we could precisely locate the focus of drug-induced liver injury in mice. This probe is expected to serve a powerful tool for studying physiological and pathological processes related to LAP.

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Liang S et al.

Intelligent Hollow Pt-CuS Janus Architecture for Synergistic Catalysis-Enhanced Sonodynamic and Photothermal Cancer Therapy

NanoCancerPreclinicalMSOT

As a noninvasive treatment modality, ultrasound (US)-triggered sonodynamic therapy (SDT) shows broad and promising applications to overcome the drawbacks of traditional photodynamic therapy (PDT) in combating cancer. However, the SDT efficacy is still not satisfactory without oxygen (O2) assistance. In addition, there is also much space to explore the SDT-based synergistic therapeutic modalities. Herein, a novel Pt-CuS Janus composed of hollow semiconductor CuS and noble metallic Pt was rationally designed and successfully synthesized. The hollow CuS shows a large inner cavity for loading sonosensitizer molecules (tetra-(4-aminophenyl) porphyrin, TAPP) to implement SDT. Moreover, the deposition of Pt not only enhances photothermal performance compared with those of CuS nanoparticles (NPs) due to the effect of the local electric field enhancement but also possesses nanozyme activity for catalyzing decomposition of endogenous overexpressed hydrogen peroxide (H2O2) to produce O2 that can overcome tumor hypoxia and augment the SDT-induced highly toxic reactive oxygen species (ROS) production for efficient cancer cell apoptosis. Importantly, the generated heat of Pt-CuS by 808 nm laser irradiation can accelerate the catalytic activity of Pt and elevate the O2 level that further facilitates SDT efficacy. Interestingly, the thermally sensitive copolymer coated around the Janus can act as a smart switch to regulate the catalytic ability of Pt and control TAPP release that has a significant effect on modulating the therapeutic effect. The synergistic catalysis-enhanced SDT efficiency and highly photothermal effect almost realized complete tumor resection without obvious reoccurrence and simultaneously displayed a highly therapeutic biosafety. Furthermore, the high optical absorbance allows the as-synthesized Pt-CuS Janus for photoacoustic (PA) imaging and NIR thermal imaging. This work develops a versatile nanoplatform for a multifunctional theranostic strategy and broadens the biological applications by rationally designing their structure.

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Ron A et al.

Volumetric optoacoustic imaging unveils high-resolution patterns of acute and cyclic hypoxia in a murine model of breast cancer

CancerPreclinicalMSOT

Mapping tumor heterogeneity and hypoxia within a living intact organism is essential for understanding the processes involved in cancer progression and assessing long-term responses to therapies. Efficient investigations into tumor hypoxia mechanisms have been hindered by the lack of intravital imaging tools capable of multi-parametric probing of entire solid tumors with high spatial and temporal resolution. Here we exploit volumetric multi-spectral optoacoustic tomography (vMSOT) for accurate, label-free delineation of tumor heterogeneity and dynamic oxygenation behavior. Mice bearing orthotopic MDA-MB-231 breast cancer xenografts were imaged non-invasively during rest and oxygen stress challenge, attaining time-lapse 3D oxygenation maps across entire tumors with 100µm spatial resolution. Volumetric quantification of the hypoxic fraction rendered values of 3.9-21.2% whereas the oxygen saturation (sO2) rate declined at 1.7-2.3% per mm in all tumors when approaching their core. Three distinct functional areas (the rim, hypoxic, and normoxic cores) were clearly discernible based on spatial sO2 profiles and responses to oxygen challenge. Notably, while sO2 readings were responsive to the challenge, deoxyhemoglobin (HbR) trends exhibited little to no variations in all mice. Dynamic analysis further revealed the presence of cyclic hypoxia patterns with a 21% average discrepancy between cyclic fractions analyzed by sO2 (42.2±17.3%) and HbR fluctuations (63±14.1%) observed in the hypoxic core. These findings corroborate the strong potential of multi-spectral optoacoustic tomography for advancing pre-clinical imaging of cancer and informing clinical decisions on therapeutic interventions.

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Zhang K et al.

A Bacteriochlorin-Based Metal-Organic Framework Nanosheet Superoxide Radical Generator for Photoacoustic Imaging-Guided Highly Efficient Photodynamic Therapy

NanoCancerPreclinicalMSOT

Hypoxic tumor microenvironment is the bottleneck of the conventional photodynamic therapy (PDT) and significantly weakens the overall therapeutic efficiency. Herein, versatile metal-organic framework (MOF) nanosheets (DBBC-UiO) comprised of bacteriochlorin ligand and Hf6(µ3-O)4(µ3-OH)4 clusters to address this tricky issue are designed. The resulting DBBC-UiO enables numerous superoxide anion radical (O2 -•) generation via a type I mechanism with a 750 nm NIR-laser irradiation, part of which transforms to high toxic hydroxyl radical (OH•) and oxygen (O2) through superoxide dismutase (SOD)-mediated catalytic reactions under severe hypoxic microenvironment (2% O2), and the partial recycled O2 enhances O2 -• generation. Owing to the synergistic radicals, it realizes advanced antitumor performance with 91% cell mortality against cancer cells in vitro, and highly efficient hypoxic solid tumor ablation in vivo. It also accomplishes photoacoustic imaging (PAI) for cancer diagnosis. This DBBC-UiO, taking advantage of superb penetration depth of the 750 nm laser and distinct antihypoxia activities, offers new opportunities for PDT against clinically hypoxic cancer.

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Chang M et al.

Self-assembled CeVO4/Ag nanohybrid as photoconversion agents with enhanced solar-driven photocatalysis and NIR-responsive photothermal/photodynamic synergistic therapy performance

NanoCancerPreclinicalMSOT

The plasmonic cerium vanadate (CeVO4) semiconductor and plasmonic silver (Ag) metal exhibit a localized surface plasmon resonance (LSPR) effect in the visible (Vis)-light region; however, weak absorption in the near-infrared (NIR) region restricts their environmental remediation and biomedical application. Herein, CeVO4/Ag nanohybrids with self-assembled heterostructure and improved Vis/NIR light absorption were synthesized from CeVO4 nanosheets and AgNO3 solution, which could serve as potential solar-driven catalytic agents and near-infrared (NIR) light responsive anticancer agents. Oleic acid-stabilized CeVO4 nanosheets were modified with the HS-PEG1000-OH by the thiol-ene click reaction and presented self-assembly morphology in aqueous solution due to hydrophobic-hydrophobic interactions. Sulfhydryl (-SH) groups provided stable sites for Ag+ ions on the surface of CeVO4, and Ag+ ions could be directly reduced by Ce3+ ions to form CeVO4/Ag heterojunction nanocrystals (NCs). Due to the higher absorption in the Vis/NIR light region than CeVO4 nanosheets, CeVO4/Ag NCs led to the improved solar light responsive photocatalytic degradation of organic dyes. Upon the exposure of these NCs to an 808 nm laser, CeVO4/Ag NCs show high photothermal conversion efficiency, ROS generation ability and photoacoustic (PA) signal for implementing PA imaging-guided photothermal/photodynamic synergistic cancer therapy with better tumor inhibition effect.

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Liu L et al.

A fluorinated aza-BODIPY derivative for NIR fluorescence/PA/19F MR tri-modality in vivo imaging

CancerPreclinicalMSOT

A fluorinated aza-BODIPY derivative BDPF was developed as a small molecule contrast agent, which displayed highly efficient near infrared fluorescence/photoacoustic/19F MR tri-modality tumor imaging.

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Wang WL et al.

Receptor-Mediated and Tumor-Microenvironment Combination-Responsive Ru Nanoaggregates for Enhanced Cancer Phototheranostics

NanoCancerPreclinicalMSOT

Although phototherapy has been considered as an emerging and promising technology for cancer therapy, its therapeutic specificity and efficacy are severely limited by nonspecific uptake by normal tissues, tumor hypoxia, and so on. Herein, combination-responsive strategy (CRS) is applied to develop one kind of hyaluronic acid-hybridized Ru nanoaggregates (HA-Ru NAs) for enhanced cancer phototherapy via the reasonable integration of receptor-mediated targeting (RMT) and tumor-microenvironment responsiveness (TMR). In this nanosystem, the HA component endows HA-Ru NAs with RMT characteristic to selectively recognize CD44-overexpressing cancer cells, whereas the Ru nanocomponent makes HA-Ru NAs have TMR therapy activity. Specially, the Ru nanocomponent not only has near-infrared-mediated photothermal and photodynamic functions but also can catalyze H2O2 in tumor tissue to produce O2 for the alleviation of tumor hypoxia and toxic •OH for chemodynamic therapy. Benefitting from these, HA-Ru NAs can be considered as a promising kind of CRS nanoplatforms for synergistic photothermal/photodynamic/chemodynamic therapies of cancer, which will not only effectively improve the phototherapeutic specificity and efficacy but also simplify the therapeutic nanosystems. Meanwhile, HA-Ru NAs can serve as a photoacoustic and computed tomography imaging contrast agent to monitor tumors. Such CRS nanoplatforms hold significant potential in improving therapeutic specificity and efficacy for enhanced cancer phototheranostics.

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Gottschalk S et al.

Isolated Murine Brain Model for Large-Scale Optoacoustic Calcium Imaging

NeuroPreclinicalMSOT

Real-time visualization of large-scale neural dynamics in whole mammalian brains is hindered with existing neuroimaging methods having limited capacity when it comes to imaging large tissue volumes at high speeds. Optoacoustic imaging has been shown to be capable of real-time three-dimensional imaging of multiple cerebral hemodynamic parameters in rodents. However, optoacoustic imaging of calcium activity deep within the mammalian brain is hampered by strong blood absorption in the visible light spectrum as well as a lack of activity labels excitable in the near-infrared window. We have developed and validated an isolated whole mouse brain preparation labeled with genetically encoded calcium indicator GCaMP6f, which can closely resemble in vivo conditions. An optoacoustic imaging system coupled to a superfusion system was further designed and used for rapid volumetric monitoring of stimulus-evoked calcium dynamics in the brain. These new imaging setup and isolated preparation’s protocols and characteristics are described here in detail. Our new technique captures calcium fluxes as true three-dimensional information across the entire brain with temporal resolution of 10 ms and spatial resolution of 150 μm, thus enabling large-scale neural recording at penetration depths and spatio-temporal resolution scales not covered with any existing neuroimaging techniques.

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Li X et al.

Optoacoustic Mesoscopy Analysis and Quantitative Estimation of Specific Imaging Metrics in Fitzpatrick skin phototypes II to V

SkinClinicalRSOM

Raster Scanning Optoacoustic Mesoscopy (RSOM) is a novel optoacoustic imaging modality that offers non-invasive, label-free, high resolution (~7 μm axial, ~30 μm lateral) imaging up to 1-2 mm below the skin, providing novel quantitative insights into skin pathophysiology. As the RSOM image contrast mechanism is based on light absorption, it is expected that the amount of melanin present in the skin will affect RSOM images. However, the effect of skin tone in the performance of RSOM has not been addressed so far. Herein, we present the efficiency of RSOM for in vivo skin imaging of human subjects with Fitzpatrick (FP) skin types between II to V. RSOM images acquired from the volar forearms of the subjects were used to derive metrics used in RSOM studies, like total blood volume, vessel diameter, and melanin signal intensity. Our study shows that the melanin signal intensity derived from the RSOM images exhibited an excellent correlation with that obtained from a clinical colorimeter for the subjects of varying FP skin types. We could successfully estimate the vessel diameter at different depths of the dermis. Furthermore, our study shows that there is a need to compensate for total blood volume calculated for subjects with higher FP skin types due to the lower signal-to-noise ratio in dermis, owing to strong absorption of light by melanin. This study sheds light into how RSOM can be used for studying various skin conditions in populations with different skin phenotypes.

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Wen K et al.

Triplet Tellurophene-based Semiconducting Polymer Nanoparticles for Near-Infrared-mediated Cancer Theranostics

NanoCancerPreclinicalMSOT

Semiconducting polymer (SP) nanoparticles (NPs) have recently emerged as one of the most promising agents for photoacoustic imaging (PAI)-guided photothermal/photodynamic therapy (PTT/PDT). Herein, a triplet tellurophene-based SP (PNDI-2T) was synthesized with efficient tin-free direct heteroarylation polycondensation (DHAP). The PNDI-2T NPs display remarkable near-infrared (NIR) absorption and low cytotoxicity. In addition, PNDI-2T NPs can generate abundant reactive oxygen species (ROS) since tellurophene facilitates the intersystem crossing to generate triplet excited states. Remarkably, PNDI-2T NPs present a high photothermal conversion efficiency (η = 45%) and a high ROS yield (ΦΔ = 38.7%) under 808 nm laser irradiation. Furthermore, we showed that PNDI-2T NPs could be excellent PAI-guided PTT/PDT agents for cancer theranostics. This study provides a new route to developing highly efficient and low cytotoxic agents for PAI-guided PTT/PDT.

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Omar M et al.

Optoacoustic mesoscopy for biomedicine

Other ApplicationsTechnologyPreclinicalRSOM

Fuelled by innovation, optical microscopy plays a critical role in the life sciences and medicine, from basic discovery to clinical diagnostics. However, optical microscopy is limited by typical penetration depths of a few hundred micrometres for in vivo interrogations in the visible spectrum. Optoacoustic microscopy complements optical microscopy by imaging the absorption of light, but it is similarly limited by penetration depth. In this Review, we summarize progress in the development and applicability of optoacoustic mesoscopy (OPAM); that is, optoacoustic imaging with acoustic resolution and wide-bandwidth ultrasound detection. OPAM extends the capabilities of optical imaging beyond the depths accessible to optical and optoacoustic microscopy, and thus enables new applications. We explain the operational principles of OPAM, its placement as a bridge between optoacoustic microscopy and optoacoustic macroscopy, and its performance in the label-free visualization of tissue pathophysiology, such as inflammation, oxygenation, vascularization and angiogenesis. We also review emerging applications of OPAM in clinical and biological imaging.

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Zhang H et al.

Second near-infrared photodynamic therapy and chemotherapy of orthotopic malignant glioblastoma with ultra-small Cu2-xSe nanoparticles

NanoCancerPreclinicalMSOT

The treatment of malignant glioblastoma is a huge challenge due to the existence of the blood-brain barrier. Herein, we report the treatment of orthotopic malignant glioblastoma with imaging guided second near-infrared (NIR-II) photodynamic therapy and chemotherapy by using drug-loaded ultra-small Cu2-xSe theranostic nanoparticles (NPs). Ultra-small Cu2-xSe NPs possess a strong absorbance in the NIR-II window, and their absorption at 1064 nm is around 2 times that at 808 nm. Their strong NIR-II absorbance and the deeper-tissue penetration of NIR-II light ensure excellent photodynamic therapy performance under irradiation with a 1064 nm laser. We also demonstrate that ultra-small Cu2-xSe NPs can produce vast amounts of reactive oxygen species via electron transfer (for ˙OH generation) and energy transfer (for 1O2 generation) mechanisms under irradiation. In addition, these NPs can be effectively and locally transported into orthotopic malignant glioblastoma with the assistance of focused ultrasound. The deposited Cu2-xSe NPs can be used for photoacoustic imaging to guide the combined NIR-II photodynamic therapy and chemotherapy. The results show that the tumor growth can be significantly suppressed. This work demonstrates the great potential of drug-loaded ultra-small Cu2-xSe NPs as a promising therapeutic agent for the treatment of orthotopic malignant glioblastoma.

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Yang Q et al.

Photostable Iridium(III)-Cyanine Complex Nanoparticles for Photoacoustic Imaging Guided Near-Infrared Photodynamic Therapy in Vivo.

NanoCancerPreclinicalMSOT

The iridium(III)-cyanine complex (IrCy) was fabricated by conjugating an iridium(III) complex to a cyanine dye with an intense near-infrared (NIR) absorption. IrCy complex nanoparticles (NPs) with high water solubility and photostability were prepared by a solvent evaporation-induced self-assembly strategy. Considering their effective photacoustic (PA) imaging and generation of 1O2 property with 808 nm laser irradiation in aqueous solution, PA imaging guided NIR-driven photodynamic therapy in vivo was effectively conducted in the 4T1 xenograft model. We developed a real-time PA imaging methodology to investigate the pharmacokinetics, tumor targeting, and biodistribution of IrCy NPs. Taking advantage of the analysis of the PA signal of the common iliac vein, the blood circulation half-life of IrCy NPs in mice was calculated to be ∼18 h, and the enhanced permeability and retention effect of IrCy NPs offered the maximum targeting property in the tumor at about 24 h. The obvious change of PA imaging signal in kidney and bladder confirmed IrCy NPs should be excreted partially from the urine system, and the PA signal decreased from 12.5× to 2.8× in the liver, and from 28.8× to 9.4× in the spleen also confirmed the hepatic metabolic pathway.

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An L et al.

Macrophages-mediated Delivery of Small Gold Nanorods for Tumor Hypoxia Photoacoustic Imaging and Enhanced Photothermal Therapy

NanoCancerPreclinicalMSOT

Macrophage-mediated delivery of drugs or nanoparticles has great potential in cancer treatment because it can avoid interception by the immune system and cross the blood-vessel barriers to reach the hypoxic regions of tumors. However, macrophage-based delivery system still faces some great challenges such as low theranostics agent loading capacity and hypoxic regions tendency in vivo. Herein, small gold nanorods (AuNRs) were used as the model theranostics agent to design a macrophage-mediated delivery system with high loading quantity for tumor hypoxia photoacoustic (PA) imaging and enhanced photothermal therapy (PTT). AuNRs modified with various thiolated poly(ethylene glycol)s (HS-PEG) via ligand exchange were investigated for toxicity and cell uptake by macrophages. The tumor hypoxic regions tendency of macrophage-loaded Anionic-AuNRs (Anionic-AuNRs@RAW) were verified by in vivo PA imaging and tumor sections. In vivo systemic PTT demonstrated enhanced tumor inhibition of anionic-AuNRs@RAW. This macrophage-mediated delivery system with high loading capacity could be used to enhance the effectiveness of cancer treatment.

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Ren W et al.

Automated registration of magnetic resonance imaging and optoacoustic tomography data for experimental studies

NeuroPreclinicalMSOT

Multimodal imaging combining optoacoustic tomography (OAT) with magnetic resonance imaging (MRI) enables spatiotemporal resolution complementarity, improves accurate quantification, and thus yields more insights into physiology and pathophysiology. However, only manual landmark based coregistration of OAT-MRI has been used so far. We developed a toolbox (RegOA), which frames an automated registration pipeline to align OAT with high-field MR images based on mutual information. We assessed the performance of the registration method using images acquired on one phantom with fiducial markers and in vivo/ex vivo data of mouse heads/brain. The accuracy and robustness of the registration are improved using a two-step registration method with preprocessing of OAT and MRI data. The major advantages of our approach are minimal user input and quantitative assessment of the registration error. The registration with MR and standard reference atlas enables regional information extraction, facilitating the accurate, objective, and rapid analysis of large groups of rodent OAT and MR images.

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Lu G et al.

Antimonene with two-orders-of-magnitude improved stability for high-performance cancer theranostics

NanoCancerPreclinicalMSOT

Although the antimonene (AM) nanomaterial is recently emerging as a new photothermal therapy (PTT) agent, its rapid degradation in physiological medium immensely limits its direct utilization. To this end, we herein engineered AM by the cooperation of dimension optimization, size control, and cell membrane (CM) camouflage. Compared with traditional AM nanosheets, the resulting AM nanoparticles (∼55 nm) cloaked with the CM (denoted as CmNPs) exhibited significantly improved stability and increased photothermal efficacy as well as superior tumor targeting capacity. After intravenous injection, the CmNPs enabled satisfactory photoacoustic/photothermal multimodal imaging at tumor sites. Meanwhile, the PTT together with the newly explored function of photodynamic therapy (PDT) achieved a potent combination therapy with few side effects. The maximized theranostic performance thus strongly recommends CmNPs as a safe and highly reliable modality for anticancer therapy.

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Anal Chem. 2019 May 7;91(9):5470-5477.

Photo-Controllable Proteins for Optoacoustic Imaging

Other ApplicationsPreclinicalMSOT

Photocontrollable proteins revolutionized life-science imaging due to their contribution to subdiffraction-resolution optical microscopy. They might have yet another lasting impact on photo- or optoacoustic imaging (OA). OA combines optical contrast with ultrasound detection enabling high-resolution real-time in vivo imaging well-beyond the typical penetration depth of optical methods. While OA already showed numerous applications relying on endogenous contrast from blood hemoglobin or lipids, its application in the life-science was limited by a lack of labels overcoming the strong signal from the aforementioned endogenous absorbers. Here, a number of recent studies showed that photocontrollable proteins provide the means to overcome this barrier eventually enabling OA to image small cell numbers in a complete organism in vivo. In this Feature article, we introduce the key photocontrollable proteins, explain the basic concepts, and highlight achievements that have been already made.

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Sharkey J et al.

A Noninvasive Imaging Toolbox Indicates Limited Therapeutic Potential of Conditionally Activated Macrophages in a Mouse Model of Multiple Organ Dysfunction

Other ApplicationsPreclinicalMSOT

Cell-based regenerative medicine therapies require robust preclinical safety, efficacy, biodistribution, and engraftment data prior to clinical testing. To address these challenges, we have developed an imaging toolbox comprising multispectral optoacoustic tomography and ultrasonography, which allows the degree of kidney, liver, and cardiac injury and the extent of functional recovery to be assessed noninvasively in a mouse model of multiorgan dysfunction. This toolbox allowed us to determine the therapeutic effects of adoptively transferred macrophages. Using bioluminescence imaging, we could then investigate the association between amelioration and biodistribution. Macrophage therapy provided limited improvement of kidney and liver function, although not significantly so, without amelioration of histological damage. No improvement in cardiac function was observed. Biodistribution analysis showed that macrophages homed and persisted in the injured kidneys and liver but did not populate the heart. Our data suggest that the limited improvement observed in kidney and liver function could be mediated by M2 macrophages. More importantly, we demonstrate here the utility of the imaging toolbox for assessing the efficacy of potential regenerative medicine therapies in multiple organs.

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Karlas A et al.

Cardiovascular optoacoustics: From mice to men - A review

Other ApplicationsTechnologyClinicalMSOT

Imaging has become an indispensable tool in the research and clinical management of cardiovascular disease (CVD). An array of imaging technologies is considered for CVD diagnostics and therapeutic assessment, ranging from ultrasonography, X-ray computed tomography and magnetic resonance imaging to nuclear and optical imaging methods. Each method has different operational characteristics and assesses different aspects of CVD pathophysiology; nevertheless, more information is desirable for achieving a comprehensive view of the disease. Optoacoustic (photoacoustic) imaging is an emerging modality promising to offer novel information on CVD parameters by allowing high-resolution imaging of optical contrast several centimeters deep inside tissue. Implemented with illumination at several wavelengths, multi-spectral optoacoustic tomography (MSOT) in particular, is sensitive to oxygenated and deoxygenated hemoglobin, water and lipids allowing imaging of the vasculature, tissue oxygen saturation and metabolic or inflammatory parameters. Progress with fast-tuning lasers, parallel detection and advanced image reconstruction and data-processing algorithms have recently transformed optoacoustics from a laboratory tool to a promising modality for small animal and clinical imaging. We review progress with optoacoustic CVD imaging, highlight the research and diagnostic potential and current applications and discuss the advantages, limitations and possibilities for integration into clinical routine.

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Gottschalk S et al.

Rapid volumetric optoacoustic imaging of neural dynamics across the mouse brain

NeuroPreclinicalMSOT

Efforts to scale neuroimaging towards the direct visualization of mammalian brain-wide neuronal activity have faced major challenges. Although high-resolution optical imaging of the whole brain in small animals has been achieved ex vivo, the real-time and direct monitoring of large-scale neuronal activity remains difficult, owing to the performance gap between localized, largely invasive, optical microscopy of rapid, cellular-resolved neuronal activity and whole-brain macroscopy of slow haemodynamics and metabolism. Here, we demonstrate both ex vivo and non-invasive in vivo functional optoacoustic (OA) neuroimaging of mice expressing the genetically encoded calcium indicator GCaMP6f. The approach offers rapid, high-resolution three-dimensional snapshots of whole-brain neuronal activity maps using single OA excitations, and of stimulus-evoked slow haemodynamics and fast calcium activity in the presence of strong haemoglobin background absorption. By providing direct neuroimaging at depths and spatiotemporal resolutions superior to optical fluorescence imaging, functional OA neuroimaging bridges the gap between functional microscopy and whole-brain macroscopy.

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Liu S et al.

Molecular Motion in Aggregates: Manipulating TICT for Boosting Photothermal Theranostics

NanoCancerPreclinicalMSOT

Planar donor and acceptor (D-A) conjugated structures are generally believed to be the standard for architecting highly efficient photothermal theranostic agents, in order to restrict intramolecular motions in aggregates (nanoparticles). However, other channels of extra nonradiative decay may be blocked. Now this challenge is addressed by proposing an “abnormal” strategy based on molecular motion in aggregates. Molecular rotors and bulky alkyl chains are grafted to the central D-A core to lower intermolecular interaction. The enhanced molecular motion favors the formation of a dark twisted intramolecular charge transfer state, whose nonradiative decay enhances the photothermal properties. Result shows that small-molecule NIRb14 with long alkyl chains branched at the second carbon exhibits enhanced photothermal properties compared with NIRb6, with short branched chains, and much higher than NIR6, with short linear chains, and the commercial gold nanorods. Both in vitro and in vivo experiments demonstrate that NIRb14 nanoparticles can be used as nanoagents for photoacoustic imaging-guided photothermal therapy. Moreover, charge reversal poly(β-amino ester) makes NIRb14 specifically accumulate at tumor sites. This study thus provides an excited molecular motion approach toward efficient phototheranostic agents.

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Han X et al.

An Extendable Star-Like Nanoplatform for Functional and Anatomical Imaging-Guided Photothermal Oncotherapy

NanoCancerPreclinicalMSOT

Combining informative imaging methodologies with effective treatments to destroy tumors is of great importance for oncotherapy. Versatile nanotheranostic agents that inherently possess both diagnostic imaging and therapeutic capabilities are highly desirable to meet these requirements. Here, a simple but powerful nanoplatform based on polydopamine-coated gold nanostar (GNS@PDA), which can be easily diversified to achieve various function extensions, is designed to realize functional and anatomical imaging-guided photothermal oncotherapy. This nanoplatform intrinsically enables computed tomography/photoacoustic/two-photon luminescence/infrared thermal tetramodal imaging and can further incorporate fibroblast activation protein (FAP, a protease highly expressed in most of tumors) activatable near-infrared fluorescence imaging and Fe3+-based magnetic resonance imaging for comprehensive diagnosis. Moreover, GNS@PDA exhibits excellent photothermal performance and efficient tumor accumulation. Under the precise guidance of multimodal imaging, GNS@PDA conducts homogeneous photothermal ablation of bulky solid tumors (∼200 mm3) in a xenograft mouse model. These results suggest great promise of this extendable nanoplatform for cancer theranostics.

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Yang H et al.

Synthetic data framework to estimate the minimum detectable concentration of contrast agents for multispectral optoacoustic imaging of small animals

TechnologyPreclinicalMSOT

The concentrations of contrast agents for optoacoustic imaging of small animals must usually be optimized through extensive pilot experiments on a case-by-case basis. The present work describes a streamlined approach for determining the minimum detectable concentration (MDC) of a contrast agent given experimental conditions and imaging system parameters. The developed Synthetic Data Framework (SDF) allows estimation of MDCs of various contrast agents under different tissue conditions without extensive animal experiments. The SDF combines simulated optoacoustic signals from exogenously administered contrast agents with in vivo experimental signals from background tissue to generate realistic synthetic multispectral optoacoustic images. In this paper, the SDF is validated with in vivo measurements and demonstrates close agreement between SDF synthetic data and experimental data in terms of both image intensity and MDCs. Use of the SDF to estimate MDCs for fluorescent dyes and nanoparticles at different tissue depths and for imaging lesions of different sizes is illustrated. This article is protected by copyright. All rights reserved.

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Fan B et al.

Photoacoustic-imaging-guided therapy of functionalized melanin nanoparticles: combination of photothermal ablation and gene therapy against laryngeal squamous cell carcinoma

NanoCancerPreclinicalMSOT

Multimodality therapy under imaging-guidance is significant to improve the accuracy of cancer treatment. In this study, a photoacoustic imaging (PAI)-guided anticancer strategy based on poly-l-lysine functionalized melanin nanoparticles (MNP-PLL) was developed to treat laryngeal squamous cell carcinoma (LSCC). As a promising alternative to traditional therapies for LSCC, MNP-PLL/miRNA nanoparticles were combined with photothermal ablation against primary tumors and miR-145-5p mediated gene therapy for depleting the metastatic potential of tumor cells. Furthermore, taking advantage of the photoacoustic properties of melanin, PAI guided therapy could optimize the time point of NIR irradiation to maximize the efficacy of photothermal therapy (PTT). The in vitro and in vivo results proved that the combined treatments displayed the most significant tumor suppression compared with monotherapy. By integrating thermo-gene therapies into a theranostic nanoplatform, the MNP-PLL/miR-145-5p nanoparticles significantly suppressed the LSCC progression, indicating their great potential use for cancer therapy.

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Peters L et al.

Phototrophic purple bacteria as optoacoustic in vivo reporters of macrophage activity

CancerPreclinicalMSOT

Τhe morphology, physiology and immunology, of solid tumors exhibit spatial heterogeneity which complicates our understanding of cancer progression and therapy response. Understanding spatial heterogeneity necessitates high resolution in vivo imaging of anatomical and pathophysiological tumor information. We introduce Rhodobacter as bacterial reporter for multispectral optoacoustic (photoacoustic) tomography (MSOT). We show that endogenous bacteriochlorophyll a in Rhodobacter gives rise to strong optoacoustic signals >800 nm away from interfering endogenous absorbers. Importantly, our results suggest that changes in the spectral signature of Rhodobacter which depend on macrophage activity inside the tumor can be used to reveal heterogeneity of the tumor microenvironment. Employing non-invasive high resolution MSOT in longitudinal studies we show spatiotemporal changes of Rhodobacter spectral profiles in mice bearing 4T1 and CT26.WT tumor models. Accessibility of Rhodobacter to genetic modification and thus to sensory and therapeutic functions suggests potential for a theranostic platform organism.

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Roll W et al.

Multispectral optoacoustic tomography of benign and malignant thyroid disorders - a pilot study

CancerClinicalMSOT

This study aims at evaluating hybrid multispectral optoacoustic tomography (MSOT)/ultrasound for imaging of thyroid disorders, including Graves’ disease and thyroid nodules. The functional biomarkers and tissue parameters deoxygenated (HbR), oxygenated (HbO2) and total hemoglobin (HbT), saturation of hemoglobin (sO2), fat and water content were analyzed in thyroid lobes affected by Graves’ disease (n = 6), thyroid lobes with healthy thyroid tissue (n = 8), benign (n = 13) and malignant (n = 3) thyroid nodules. In Graves’ disease, significantly higher values for HbR (3.18 ± 0.52 vs. 2.13 ± 0.62; P = 0.0055) and HbT (8.34 ± 0.88 vs. 6.59 ± 1.16; P = 0.0084) and significantly lower values for fat (0.64 ± 0.37 vs. 1.69 ± 1.25; P = 0.0293) were found compared to healthy controls. Malignant thyroid nodules showed significantly lower sO2 (55.4% ± 2.6% vs. 60.8% ± 7.2%; P = 0.0393) and lower fat values (0.62 ± 0.19 vs. 1.46 ± 0.87; P = 0.1295) than benign nodules. This pilot study shows the applicability and the potential of hybrid MSOT/ultrasound to semi-quantitatively provide tissue characterization and functional parameters in thyroid disorders for improved non-invasive diagnostics of thyroid diseases.

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Jiang X et al.

Photoacoustic Imaging of Nanoparticle Transport in the Kidneys at High Temporal Resolution

Other ApplicationsNanoPreclinicalMSOT

Noninvasive monitoring of kidney elimination of engineered nanoparticles at high temporal and spatial resolution will not only significantly advance our fundamental understandings of nephrology at nano scale but also render engineered nanoparticles new functionalities in early detection of kidney disease, which is influencing more than 10% of population worldwide. Taking advantage of strong NIR absorption of the well‐defined Au25(SG)18 nanocluster, we successfully used photoacoustic (PA) imaging to in‐situ visualize its transport through the aorta to the renal parenchyma and its subsequent filtration into the renal pelvis at a temporal resolution down to 1s. High temporal and spatial resolution imaging of Au25(SG)18 kidney elimination allows us for the first time to accurately quantify glomerular filtration rate (GFR) of individual kidneys in normal and pathological conditions using PA method, broadening biomedical applications of engineered nanoparticles in preclinical kidney research as anew tool for interrogating kidney functions at high temporal resolution and the anatomic level.

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Gujrati V et al.

Bioengineered bacterial vesicles as biological nano-heaters for optoacoustic imaging

Other ApplicationsNanoPreclinicalMSOT

Advances in genetic engineering have enabled the use of bacterial outer membrane vesicles (OMVs) to deliver vaccines, drugs and immunotherapy agents, as a strategy to circumvent biocompatibility and large-scale production issues associated with synthetic nanomaterials. We investigate bioengineered OMVs for contrast enhancement in optoacoustic (photoacoustic) imaging. We produce OMVs encapsulating biopolymer-melanin (OMV Mel ) using a bacterial strain expressing a tyrosinase transgene. Our results show that upon near-infrared light irradiation, OMV Mel generates strong optoacoustic signals appropriate for imaging applications. In addition, we show that OMV Mel builds up intense heat from the absorbed laser energy and mediates photothermal effects both in vitro and in vivo. Using multispectral optoacoustic tomography, we noninvasively monitor the spatio-temporal, tumour-associated OMV Mel distribution in vivo. This work points to the use of bioengineered vesicles as potent alternatives to synthetic particles more commonly employed for optoacoustic imaging, with the potential to enable both image enhancement and photothermal applications.

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Ai X et al.

Multispectral optoacoustic imaging of dynamic redox correlation and pathophysiological progression utilizing upconversion nanoprobes

Other ApplicationsNanoPreclinicalMSOT

Precise and differential profiling of the dynamic correlations and pathophysiological implications of multiplex biological mediators with deep penetration and highly programmed precision remain critical challenges in clinics. Here we present an innovative strategy by tailoring a powerful multispectral optoacoustic tomography (MSOT) technique with a photon-upconverting nanoprobe (UCN) for simultaneous visualization of diversely endogenous redox biomarkers with excellent spatiotemporal resolution in living conditions. Upon incorporating two specific radicals-sensitive NIR cyanine fluorophores onto UCNs surface, such nanoprobes can orthogonally respond to disparate oxidative and nitrosative stimulation, and generate spectrally opposite optoacoustic signal variations, which thus achieves compelling superiorities for reversed ratiometric tracking of multiple radicals under dual independent wavelength channels, and significantly, for precise validating of their complex dynamics and correlations with redox-mediated pathophysiological procession in vivo.

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Olefir I et al.

Spatial and Spectral Mapping and Decomposition of Neural Dynamics and Organization of the Mouse Brain with Multispectral Optoacoustic Tomography

NeuroPreclinicalMSOT

In traditional optical imaging, limited light penetration constrains high-resolution interrogation to tissue surfaces. Optoacoustic imaging combines the superb contrast of optical imaging with deep penetration of ultrasound, enabling a range of new applications. We used multispectral optoacoustic tomography (MSOT) for functional and structural neuroimaging in mice at resolution, depth, and specificity unattainable by other neuroimaging modalities. Based on multispectral readouts, we computed hemoglobin gradient and oxygen saturation changes related to processing of somatosensory signals in different structures along the entire subcortical-cortical axis. Using temporal correlation analysis and seed-based maps, we reveal the connectivity between cortical, thalamic, and sub-thalamic formations. With the same modality, high-resolution structural tomography of intact mouse brain was achieved based on endogenous contrasts, demonstrating near-perfect matches with anatomical features revealed by histology. These results extend the limits of noninvasive observations beyond the reach of standard high-resolution neuroimaging, verifying the suitability of MSOT for small-animal studies.

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Mol Pharm. 2019 Mar 4;16(3):1367-1384.

NIR-Light-Triggered Anticancer Strategy for Dual-Modality Imaging-Guided Combination Therapy via a Bioinspired Hybrid PLGA Nanoplatform

NanoCancerPreclinicalMSOT

A promising approach toward cancer therapy is expected to integrate imaging and therapeutic agents into a versatile nanocarrier for achieving improved antitumor efficacy and reducing the side effects of conventional chemotherapy. Herein, we designed a poly(d,l-lactic- co-glycolic acid) (PLGA)-based theranostic nanoplatform using the double emulsion solvent evaporation method (W/O/W), which is associated with bovine serum albumin (BSA) modifications, to codeliver indocyanine green (ICG), a widely used near-infrared (NIR) dye, and doxorubicin (Dox), a chemotherapeutic drug, for dual-modality imaging-guided chemo-photothermal combination cancer therapy. The resultant ICG/Dox co-loaded hybrid PLGA nanoparticles (denoted as IDPNs) had a diameter of around 200 nm and exhibited excellent monodispersity, fluorescence/size stability, and biocompatibility. It was confirmed that IDPNs displayed a photothermal effect and that the heat induced faster release of Dox, which led to enhanced drug accumulation in cells and was followed by their efficient escape from the lysosomes into the cytoplasm and drug diffusion into the nucleus, resulting in a chemo-photothermal combinatorial therapeutic effect in vitro. Moreover, the IDPNs exhibited a high ability to accumulate in tumor tissue, owing to the enhanced permeability and retention (EPR) effect, and could realize real-time fluorescence/photoacoustic imaging of solid tumors with a high spatial resolution. In addition, the exposure of tumor regions to NIR irradiation could enhance the tumor penetration ability of IDPNs, almost eradicating subcutaneous tumors. In addition, the inhibition rate of IDPNs used in combination with laser irradiation against EMT-6 tumors in tumor-bearing nude mice (chemo-photothermal therapy) was approximately 95.6%, which was much higher than that for chemo- or photothermal treatment alone. Our study validated the fact that the use of well-defined IDPNs with NIR laser treatment could be a promising strategy for the early diagnosis and passive tumor-targeted chemo-photothermal therapy for cancer.

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Xing R et al.

Self-Assembling Endogenous Biliverdin as a Versatile Near-Infrared Photothermal Nanoagent for Cancer Theranostics

NanoCancerPreclinicalMSOT

Photothermal nanomaterials that integrate multimodal imaging and therapeutic functions provide promising opportunities for noninvasive and targeted diagnosis and treatment in precision medicine. However, the clinical translation of existing photothermal nanoagents is severely hindered by their unclear physiological metabolism, which makes them a strong concern for biosafety. Here, the utilization of biliverdin (BV), an endogenic near-infrared (NIR)-absorbing pigment with well-studied metabolic pathways, to develop photothermal nanoagents with the aim of providing efficient and metabolizable candidates for tumor diagnosis and therapy, is demonstrated. It is shown that BV nanoagents with intense NIR absorption, long-term photostability and colloidal stability, and high photothermal conversion efficiency can be readily constructed by the supramolecular multicomponent self-assembly of BV, metal-binding short peptides, and metal ions through the reciprocity and synergy of coordination and multiple noncovalent interactions. In vivo data reveal that the BV nanoagents selectively accumulate in tumors, locally elevate tumor temperature under mild NIR irradiation, and consequently induce efficient photothermal tumor ablation with promising biocompatibility. Furthermore, the BV nanoagents can serve as a multimodal contrast for tumor visualization through both photoacoustic and magnetic resonance imaging. BV has no biosafety concerns, and thereby offers a great potential in precision medicine by integrating multiple theranostic functions.

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Bell G et al.

Functionalised iron oxide nanoparticles for multimodal optoacoustic and magnetic resonance imaging

NanoCancerPreclinicalMSOT

The novel attachment of the optoacoustic (OA) molecules indocyanine green (ICG) and Flamma®774 to the core of an iron oxide (Fe3O4) nanoparticle has resulted in the facile synthesis of a multimodal imaging probe for both multispectral optoacoustic tomography (MSOT) imaging and magnetic resonance imaging (MRI). The nanoparticles have been analysed structurally, optically and magnetically to demonstrate the multimodal characteristics. The OA analysis of the dyes ICG and Flamma®774 showed that they have absorbance at the near IR wavelengths of 790 and 780 nm, respectively, when conjugated to an iron oxide core. These wavelengths are ideal for spectral unmixing of the probe intensity from any endogenous contrast, such as oxy-(HbO2) and deoxy-hemoglobin (Hb). MRI showed that citrate capped Fe3O4 exhibited a good r2 contrast of 230 mM-1 s-1, which is in line with literature values. Upon optoacoustic dye modification, the r2 relaxivity coefficient is comparable with that of Flamma®774 iron oxide nanoparticles (FeO-774) with r2 = 212 mM-1 s-1, showing that an OA dye attachment can have little to no effect on the MRI contrast. Indocyanine green functionalised iron oxide (FeO-ICG) nanoparticles showed an r2 contrast that was dramatically reduced with r2 = 5 mM-1 s-1. These results indicate that the facile synthesis of an effective dual modality MRI-MSOT probe can be developed using an iron oxide core and simple ligand coordination chemistry using an optoacoustic dye.

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Deng H at al.

A targeted and multifunctional technology for identification between hepatocellular carcinoma and liver cirrhosis

CancerPreclinicalMSOT

Continuously updated diagnostic methods and advanced imaging methods have led to an increase in the early detection rate of small liver cancer; however, even with current diagnosis methods, it is still challenging to accurately judge a nodule with a diameter less than 2 cm whether it is hepatocellular carcinoma or liver cirrhosis. To solve this issue, a new technology is needed to distinguish above two kinds of liver nodules. There is an emerging imaging method that improves tissue resolution and sensitivity to detect micronodules with diameters less than 2 cm. To detect micronodules, photoacoustic imaging was used to provide noninvasive images at depths of several centimeters with a resolution of approximately 100 μm. To improve specificity, we developed a probe that specifically targets hepatocellular carcinoma by recognizing the biomarker GPC3 on the hepatocellular carcinoma cell membrane. The probe not only has a strong photoacoustic signal but also has a magnetic resonance signal. Furthermore, the material owns photothermal effect that absorbs longer wavelength light and releases heat that effectively and accurately kills tumor cells, thus improving patient’s survival and postoperative quality of life. Herein, we present a new technology that uses photoacoustic imaging to image and target microhepatocellular carcinoma biological processes derived from liver cirrhosis with high spatial resolution.

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Wood C et al.

Photoacoustic-based oxygen saturation assessment of murine femoral bone marrow in a preclinical model of leukemia

CancerPreclinicalMSOT

A variety of hematological diseases manifest in the bone marrow (BM), broadly characterized as BM failure (BMF). BMF can be caused by acute lymphoblastic leukemia (ALL), which results in an expansion of hypoxic regions in the BM. Because of this hypoxic presentation, there is potential for improved characterization of BMF through in vivo assessment of oxygenation in the BM cavity. Photoacoustic (PA) imaging can provide local assessment of intravascular oxygen saturation (SO2), which has been shown to correlate with pimonidazole-assessed hypoxia. This study introduces an optimized PA imaging technique to assess SO2 within the femoral BM cavity through disease progression in a murine model of ALL. Results show a statistically significant difference with temporal changes in SO2 (from baseline) between control and diseased cohorts, demonstrating the potential of PA imaging for noninvasive, label-free monitoring of BMF diseases.

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Zhao Z et al.

Highly efficient photothermal nanoagent achieved by harvesting energy via excited-state intramolecular motion within nanoparticles

NanoCancerPreclinicalMSOT

The exciting applications of molecular motion are still limited and are in urgent pursuit, although some fascinating concepts such as molecular motors and molecular machines have been proposed for years. Utilizing molecular motion in a nanoplatform for practical application has been scarcely explored due to some unconquered challenges such as how to achieve effective molecular motion in the aggregate state within nanoparticles. Here, we introduce a class of near infrared-absorbing organic molecules with intramolecular motion-induced photothermy inside nanoparticles, which enables most absorbed light energy to dissipate as heat. Such a property makes the nanoparticles a superior photoacoustic imaging agent compared to widely used methylene blue and semiconducting polymer nanoparticles and allow them for high-contrast photoacoustic imaging of tumours in live mice. This study not only provides a strategy for developing advanced photothermal/photoacoustic imaging nanoagents, but also enables molecular motion in a nanoplatform to find a way for practical application.

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Ivankovic I et al.

Real-time Volumetric Assessment of the Human Carotid Artery: Handheld Multispectral Optoacoustic Tomography

VascularClinicalMSOT

Background Multispectral optical imaging has the capability of resolving hemoglobin, lipid, and water. Volumetric multispectral optoacoustic tomography (MSOT) is a hybrid imaging technique that provides a unique combination of functional and molecular contrast with real-time handheld imaging. Purpose To investigate whether volumetric MSOT can provide real-time assessment of the anatomic and functional status of the human carotid artery bifurcation noninvasively. Materials and Methods Imaging of healthy volunteers (n = 16) was performed with a custom-designed handheld volumetric MSOT scanner capable of high-spatial-resolution (approximately 200 µm) and real-time (10 volumes/sec) three-dimensional imaging, while further providing spectroscopic capacity through fast tuning of the excitation light wavelength. For comparison and anatomic cross-validation, volunteers were also scanned with clinical B-mode US. Results Volumetric MSOT achieved real-time imaging and characterization of the entire carotid bifurcation area across three dimensions simultaneously captured in a single volumetric image frame. Analysis of the acquired data further showed that a higher contrast-to-noise ratio can be achieved for wavelengths corresponding to a high optical absorption of oxygenated hemoglobin. Conclusion The human carotid artery was visualized by using handheld volumetric multispectral optoacoustic tomography. This imaging approach is less prone to motion artifacts than are the conventional clinical imaging methods, holding promise for providing additional image-based biomarkers for noninvasive label-free assessment of carotid artery disease. © RSNA, 2019 Online supplemental material is available for this article. See also the editorial by Mezrich in this issue.

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Zhang K et al.

Cancer Cell Membrane Camouflaged Nanoprobe for Catalytic Ratiometric Photoacoustic Imaging of MicroRNA in Living Mice

NanoCancerPreclinicalMSOT

Herein, a cancer cell (MCF-7 cell) membrane-encapsulated dendritic mesoporous silica nanoparticle simultaneously functionalized with DNA-photoacoustic (DNA-PA) probes and glutathione (GSH)-responsive DNA fuel strands for PA imaging of tumor-related miRNA in living mice with signal amplification ability is developed. It is demonstrated that one target miRNA can trigger disassembly of multiple PA fluorophore probes from the quencher with the aid of GSH-responsive DNA fuel strands via the entropy-driven process, resulting remarkable amplified change of PA signal ratio. Using oncogenic miRNA-21 as a model, a linear relationship between miRNA-21 concentrations and PA ratio in a dynamic range from 10 × 10-12 m to 100 × 10-9 m and a limit of detection down to 11.69 × 10-12 m are established. The accurate PA signal observation related to miRNA-21s in the tumor area in living mice is demonstrated, and the PA signal ratio increases significantly via the injection of miRNA-21. It is anticipated that the catalytic ratiometric PA imaging system can be applied to an array of molecular detection in living system by rational detection probe design.

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Li X et al.

From one to all: self-assembled theranostic nanoparticles for tumor-targeted imaging and programmed photoactive therapy

NanoCancerPreclinicalMSOT

BACKGROUND: In recent years, multifunctional theranostic nanoparticles have been fabricated by integrating imaging and therapeutic moieties into one single nano-formulations. However, Complexity of production and safety issues limits their further application.

RESULTS: Herein, we demonstrated self-assembled nanoparticles with single structure as a “from one to all” theranostic platform for tumor-targeted dual-modal imaging and programmed photoactive therapy (PPAT). The nanoparticles were successfully developed through self-assembling of hyaluronic acid (HA)-cystamine-cholesterol (HSC) conjugate, in which IR780 was simultaneously incorporated (HSCI NPs). Due to the proper hydrodynamic size and intrinsic targeting ability of HA, the HSCI NPs could accumulate at the tumor site effectively after systemic administration. In the presence of incorporated IR780, in vivo biodistribution and accumulation behaviors of HSCI NPs could be monitored by photoacoustic imaging. After cellular uptake, the HSCI NPs would disintegrate resulting from cystamine reacting with over-expressed GSH. The released IR780 would induce fluorescence “turn-on” conversion, which could be used to image tumor sites effectively. Upon treatment with 808 nm laser irradiation, PPAT could be achieved in which generated reactive oxygen species (ROS) would produce photodynamic therapy (PDT), and subsequently the raised temperature would be beneficial to tumor photothermal therapy (PTT).

CONCLUSION: The self-assembled HSCI NPs could act as “from one to all” theranostic platform for high treatment efficiency via PPAT pattern, which could also real-time monitor NPs accumulation by targeted and dual-modal imaging in a non-invasive way.

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Dong L et al.

Renal Clearable Bi-Bi2S3 Heterostructure Nanoparticles for Targeting Cancer Theranostics

NanoCancerPreclinicalMSOT

Recent development of precise nanomedicine has aroused an overwhelming interest in integration of diagnosis and treatment for cancers. Designing renal-clearable and targeting nanoparticles (NPs) has specific cancer theranostic implications and remains a challenging task. In this work, the ultrasmall folic acid (FA) and bovine serum albumin-modified Bi-Bi2S3 heterostructure nanoparticles NPs (Bi-Bi2S3/BSA&FA NPs) with excellent computed tomography (CT) and photoacoustic imaging abilities and outstanding photothermal performances were synthesized in an aqueous phase route via a simple method. Bi-Bi2S3/BSA&FA NPs have the following criteria: (i) Bi-Bi2S3/BSA&FA NPs with heterostructure possess better stability than Bi NPs and higher Bi content than Bi2S3 NPs, which are conducive to the enhancement of CT imaging effect; (ii) Bi-Bi2S3/BSA&FA NPs with FA molecules on the surface could target the tumor site effectively; (iii) Bi-Bi2S3/BSA&FA NPs could inhibit tumor growth effectively under 808 nm laser irradiation; (iv) ultrasmall Bi-Bi2S3/BSA&FA NPs could be cleared through kidney and liver within a reasonable time, avoiding a long-term retention/toxicity. Therefore, the renal clearable Bi-Bi2S3/BSA&FA NPs are a promising agent for targeting cancer theranostics.

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Mercep et al.

Transmission-reflection optoacoustic ultrasound (TROPUS) computed tomography of small animals

TechnologyPreclinicalMSOT

Rapid progress in the development of multispectral optoacoustic tomography techniques has enabled unprecedented insights into biological dynamics and molecular processes in vivo and noninvasively at penetration and spatiotemporal scales not covered by modern optical microscopy methods. Ultrasound imaging provides highly complementary information on elastic and functional tissue properties and further aids in enhancing optoacoustic image quality. We devised the first hybrid transmission-reflection optoacoustic ultrasound (TROPUS) small animal imaging platform that combines optoacoustic tomography with both reflection- and transmission-mode ultrasound computed tomography. The system features full-view cross-sectional tomographic imaging geometry for concomitant noninvasive mapping of the absorbed optical energy, acoustic reflectivity, speed of sound, and acoustic attenuation in whole live mice with submillimeter resolution and unrivaled image quality. Graphics-processing unit (GPU)-based algorithms employing spatial compounding and bent-ray-tracing iterative reconstruction were further developed to attain real-time rendering of ultrasound tomography images in the full-ring acquisition geometry. In vivo mouse imaging experiments revealed fine details on the organ parenchyma, vascularization, tissue reflectivity, density, and stiffness. We further used the speed of sound maps retrieved by the transmission ultrasound tomography to improve optoacoustic reconstructions via two-compartment modeling. The newly developed synergistic multimodal combination offers unmatched capabilities for imaging multiple tissue properties and biomarkers with high resolution, penetration, and contrast.

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Yin L et al.

Quantitatively Visualizing Tumor-related Protease Activity In Vivo Using A Ratiometric Photoacoustic Probe

CancerPreclinicalMSOT

The abnormal expression of tumor-related proteases plays a critical role in cancer invasion, progression, and metastasis. Therefore, it is considerably meaningful to non-invasively assess the proteases’ activity in vivo for both tumor diagnosis and therapeutic evaluation. Herein, we report an activatable probe constructed with a near-infrared dye (Cy5.5) and a quencher (QSY21) covalently linked through a peptide substrate of matrix metalloproteinases-2 (MMP-2) that was chosen as a model for tumor-associated proteases. Upon cleavage with activated MMP-2, this probe emitted an MMP-2-concentration-dependent fluorescence. Quite unexpectedly, owing to the variation in the aggregation state of both the dye and its quencher as a consequence of the cleavage, the responsive probe presented a dramatic MMP-2-concentration-dependent absorption at around 680 nm, while that at around 730 nm was MMP-2 concentration independent. These features allowed detection of MMP-2 activity via both fluorescence and photoacoustic (PA) imaging in vitro, respectively. Moreover, taking the PA signal at 730 nm as an internal reference, the PA signal at 680 nm allowed quantitative detection of MMP-2 expression in breast cancer in vivo. We thus envision that our current approach would offer a useful tool for studying the malignant impacts of versatile tumor-associated proteases in vivo.

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Aguirre J et al.

Motion quantification and automated correction in clinical RSOM

TechnologyClinicalRSOM

Raster-scan optoacoustic mesoscopy (RSOM) offers high-resolution, non-invasive insights into skin pathophysiology, which holds promise for disease diagnosis and monitoring in dermatology and other fields. However, RSOM is quite vulnerable to vertical motion of the skin, which can depend on the part of the body being imaged. Motion correction algorithms have already been proposed, but they are not fully automated, they depend on anatomical segmentation pre-processing steps that might not be performed successfully, and they are not site-specific. Here we determined for the first time the magnitude of the micrometric vertical skin displacements at different sites on the body that affect RSOM. The quantification of motion allowed us to develop a site-specific correction algorithm. The algorithm is fully automated and does not need prior anatomical information. We found that the magnitude of the vertical motion depends strongly on the site of imaging and is caused by breathing, heart beating and arterial pulsation. The developed algorithm resulted in more than 2-fold improvement in the signal-to-noise ratio of the reconstructed images at every site tested. Proposing an effective automated motion correction algorithm paves the way for realizing the full clinical potential of RSOM.

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Lauri A et al.

Whole-Cell Photoacoustic Sensor Based on Pigment Relocalization

Other ApplicationsPreclinicalRSOM

Photoacoustic (optoacoustic) imaging can extract molecular information with deeper tissue penetration than possible by fluorescence microscopy techniques. However, there is currently still a lack of robust genetically controlled contrast agents and molecular sensors that can dynamically detect biological analytes of interest with photoacoustics. In a biomimetic approach, we took inspiration from cuttlefish who can change their color by relocalizing pigment-filled organelles in so-called chromatophore cells under neurohumoral control. Analogously, we tested the use of melanophore cells from Xenopus laevis, containing compartments (melanosomes) filled with strongly absorbing melanin, as whole-cell sensors for optoacoustic imaging. Our results show that pigment relocalization in these cells, which is dependent on binding of a ligand of interest to a specific G protein-coupled receptor (GPCR), can be monitored in vitro and in vivo using photoacoustic mesoscopy. In addition to changes in the photoacoustic signal amplitudes, we could furthermore detect the melanosome aggregation process by a change in the frequency content of the photoacoustic signals. Using bioinspired engineering, we thus introduce a photoacoustic pigment relocalization sensor (PaPiReS) for molecular photoacoustic imaging of GPCR-mediated signaling molecules.

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Wang Y et al.

A disassembling strategy overcomes the EPR effect and renal clearance dilemma of the multifunctional theranostic NPs for cancer therapy

NanoCancerPreclinicalMSOT

Despite multifunctional nanoparticles using for photothermal therapy can efficiently kill cancer cells, their further application is still hindered by the intrinsic high uptake in the reticuloendothelial system (RES) organs, causing the slow elimination from the body and potential toxicity to the body. Therefore, it is ideal to develop multifunctional nanoparticles which process the ability to effectively accumulate in tumors, while the nanoparticles can be rapidly excreted from the body via renal clearance after effective treatment. Herein, we report the multifunctional nanoparticles (FeTNPs) based on the coordination interaction of phenolic group and metal iron, which are composed of ferric iron, tannic acid (TA) and poly (glutamic acid)-graft-methoxypoly (ethylene glycol) (PLG-g-mPEG). FeTNPs exhibit the following highlighted features: (1) The effective accumulation in the tumor tissue is achieved based on EPR effect. (2) The dual photoacoustic (PA)/magnetic resonance (MR) imaging capacity can provide guidance for the photothermal therapy (PTT). (3) FeTNPs can be dynamically disassembled by deferoxamine mesylate (DFO) to accelerate elimination of the nanoparticles, thus reducing the potential toxicity for the body. The DFO triggered dynamic disassembling strategy may open a new avenue to overcome the dilemma between EPR effect and renal clearance.

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Cheng Y et al.

Ultrathin Tellurium Oxide/Ammonium Tungsten Bronze Nanoribbon for Multi-Modality Imaging and Second NIR Region PTT

NanoCancerPreclinicalMSOT

Developing nano-photothermal agents (PTAs) with satisfied photothermal conversion efficiency (PTCE) in the second NIR window (1000-1350 nm, NIR II) holds great promise for enhanced photothermal therapy (PTT) effect. Herein, we develop a NIR-II PTA with advanced PTCE, based on a new two-dimensional (2D) ultrathin tellurium oxide/ammonium tungsten bronze (TeO2/(NH4)xWO3) nanoribbons (TONW NRs). The doped ammonia ions mediated-free electrons injection into the LUMO band of WO3 combined with the electronic transitions between W6+ ions and the lone pair of electrons in Te atoms achieve excellent NIR absorption of TONW NRs resulted from localized surface plasmon resonance (LSPR). The polyethylene glycol functionalized TONW NRs (PEG-TONW NRs) exhibit good stability and biocompatibility, displaying a PTCE high to 43.6%, surpassing many previous nano-PTAs active in the NIR II region, leading to remarkable tumor ablation ability both in vitro and in vivo. Meanwhile, advanced X-ray computed tomography (CT) and photoacoustic (PA) imaging capability of PEG-TONW NRs were also realized. Given the admirable photothermal effect in NIR II region, good biocompatibility and advanced CT/PA imaging diagnosis capability, the novel PEG-TONW NRs is promising in future personalized medicine application.

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Helfen A et al.

Multispectral Optoacoustic Tomography: Intra- and Interobserver Variability Using a Clinical Hybrid Approach

Other ApplicationsClinicalMSOT

Multispectral optoacoustic tomography (MSOT) represents a new imaging approach revealing functional tissue information without extrinsic contrast agents. Using a clinical combined ultrasound (US)/MSOT device, we investigated the interindividual robustness and impact of intra- and interobserver variability of MSOT values in soft tissue (muscle and subcutaneous fat) of healthy volunteers. Semiquantitative MSOT values for deoxygenated (Hb), oxygenated (HbO₂) and total hemoglobin (HbT), as well as oxygen saturation (sO₂), were calculated for both forearms in transversal and longitudinal probe orientation (n = 3, 8 measurements per subject). For intraobserver reproducibility, the same examiner investigated three subjects twice. Mean values of left vs. right forearm and transversal vs. longitudinal probe orientation were compared using an unpaired Student’s t test. Bland Altmann plots with 95% limits of agreement for absolute averages and differences were calculated. Intraclass correlation coefficients (ICC 2,k) were computed for three different examiners. We obtained reproducible and consistent MSOT values with small-to-moderate deviation for muscle and subcutaneous fat tissue. Probe orientation and body side had no impact on calculated MSOT values (p > 0.05 each). Intraobserver reproducibility revealed equable mean values with small-to-moderate deviation. For muscular tissue, good ICC was obtained for sO₂. Measurements of subcutaneous tissue revealed good-to-excellent ICCs for all calculated values. Thus, in this preliminary study on healthy individuals, clinical MSOT provided consistent and reproducible functional soft tissue characterization, independent on the investigating personnel.

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Wu Y et al.

A Nanoprobe for Diagnosing and Mapping Lymphatic Metastasis of Tumor Using 3D Multispectral Optoacoustic Tomography Owing to Aggregation/Deaggregation Induced Spectral Change

NanoCancerPreclinicalMSOT

Lymphatic metastasis of tumor is one of leading causes of cancer‐related death, and diagnosing lymphatic metastasis is of significance in terms of optimal disease management and possible better outcomes for patients. Herein a turn‐on optoacoustic nanoprobe is reported for noninvasively diagnosing and locating lymphatic metastasis in vivo. A positively charged tricyanofuran‐containing polyene chromophore (TCHM) with high extinction coefficient is designed, synthesized, and allowed to form the nanoprobe with a negatively charged hyaluronan. The TCHMs take an aggregated state within the nanoprobe and exhibit weak absorption at 882 nm, the overexpressed hyaluronidase in cancer cells specifically degrades hyaluronan into small fragments and disaggregates TCHMs, thereby greatly enhancing the absorption at 882 nm and generating prominent optoacoustic signals. For multispectral optoacoustic tomography (MSOT) imaging in vivo, mice models with subcutaneous tumor and orthotopic bladder tumor are imaged first to demonstrate the nanoprobe’s capability for detecting HAase‐overexpressing tumors. A mouse model of lymphatic metastasis of tumor is then established and the lymphatic metastasis is successfully imaged and tracked optoacoustically. The imaging results were verified using multiple biochemical assays. Moreover, 3D MSOT renderings are obtained for precisely locating and tracking the metastasis of tumor in lymphatic system in a spatiotemporal manner.

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Zhang Y et al.

Enhanced Radiosensitization by Gold Nanoparticles with Acid-Triggered Aggregation in Cancer Radiotherapy

NanoCancerPreclinicalMSOT

An ideal radiosensitizer holding an enhanced tumor retention can play an incredible role in enhancing tumor radiotherapy. Herein, a strategy of acid-triggered aggregation of small-sized gold nanoparticles (GNPs) system within tumor is proposed and the resulting GNPs aggregates are applied as a radiosensitizer in vitro and in vivo. The GNPs system with the acid-triggered aggregation achieves an enhanced GNPs accumulation and retention in cancer cells and tumors in the form of the resulted GNPs aggregates. As a consequence, the radiosensitization effect shows significant improvement in cancer radiotherapy, which is shown in the studies of DNA breakage and the comet assay, and the sensitizer enhancement ratio (SER) value of the GNPs system (1.730) with MCF-7 cancer cells is much larger than that of the single GNPs (1.16). In vivo antitumor studies reveal that the GNPs system also enhances the sensitivity of MCF-7 tumor xenograft to radiotherapy. Furthermore, the GNPs aggregates improve the signal of small GNPs in vivo photoacoustic imaging. This study provides a new strategy and insights into fabricating nanoaggregates to magnify the radiosensitive efficiency of nanosystems in cancer radiotherapy.

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Guo T et al.

Manganese-phenolic network-coated black phosphorus nanosheets for theranostics combining magnetic resonance/photoacoustic dual-modal imaging and photothermal therapy

NanoCancerPreclinicalMSOT

In this work, we directly coated a layer of tannic acid (TA)-Mn2+ chelate networks on black phosphorus (BP) nanosheets (BPNSs) via a simple one-step method. The as-synthesized TA-Mn2+ chelate-coated BPNSs (BPNS@TA-Mn) have excellent T1 MRI contrast enhancement capability, good photoacoustic imaging performance, and high photothermal conversion efficiency, showing great potential in imaging-guided photothermal therapy.

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Song S et al.

One-Dimensional Fe2P Acted as Fenton Agent Response to NIR II Light and Ultrasound for Deep Tumor Synergetic Theranostic

NanoCancerPreclinicalMSOT

Stringent reaction condition of effective Fenton reaction (the pH range of 3-4) hinders its further application in cancer therapy. Therefore, how to improve the efficiency of Fenton reaction in tumor site has been the main obstacle of chemodynamic therapy (CDT). Herein, we report biocompatible one-dimensional (1D) ferrous phosphide nanorods (FP NRs) with ultrasound (US)- and photothermal (PT)-enhanced Fenton properties and excellent photothermal conversion efficiency (56.6%) in the NIR II window, showing remarkably synergistic therapeutic properties. Additionally, FP NRs can be used as excellent photoacoustic imaging (PAI) and magnetic resonance imaging (MRI) agents attributed to its high photothermal conversion efficiency and excellent traverse relaxivity (277.79 mM-1 s-1). And for all we know, this is the first report on exploiting metallic phosphide response to NIR II laser (1064 nm) and US to improve the CDT effect with high therapeutic effect and PA/MR imaging, which provides a new strategy for developing more effective CDT in future practical applications.

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Sun L et al.

A Turn-On Optoacoustic Probe for Imaging Metformin-Induced Upregulation of Hepatic Hydrogen Sulfide and Subsequent Liver Injury

PharmacokineticsPreclinicalMSOT

Metformin is currently the most prescribed oral agent for diabetes treatment; however the overdose or long-term use may cause some severe side effects such as liver injury. Researches indicate that metformin-induced liver injury is closely related to upregulation of hepatic H2S. Hence, monitoring hepatic H2S generation induced by metformin could be an effective approach for evaluating hepatoxicity of the drug. Methods: We present a novel turn-on and dual-mode probe for detecting and imaging metformin-induced liver injury by specifically tracking the upregulation of hepatic H2S with fluorescent and optoacoustic methods. After reaction with H2S, the strong electron-withdrawing group dinitrophenyl ether (which acts as both the recognition moiety and the fluorescence quencher) was cleaved and replaced by an electron-donating group hydroxyl. This correspondingly leads to the changes of the probe’s electronic state and absorption red-shifting as well as the subsequent turn-on fluorescent and optoacoustic signals. Results: The probe was applied to the colon tumor-bearing mice model and the metformin-induced liver injury mice model to achieve tumor imaging and liver injury assessment. The biosafety of the probe was verified by histological analysis (hematoxylin and eosin staining) and serum biochemical assays. Conclusion: The probe responds quickly to H2S in tumors and the liver, and MSOT imaging with the probe offers cross-secitonal and 3D spatial information of liver injury. This study may provide an effective approach for accessing medication side effects by tracking drug-metabolism-related products.

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Shao L et al.

Auto-fluorescent polymer nanotheranostics for self-monitoring of cancer therapy via triple-collaborative strategy

NanoCancerPreclinicalMSOT

Aberrant regulation of angiogenesis supply sufficient oxygen and nutrients to exacerbate tumor progression and metastasis. Taking this hallmark of cancer into account, reported here is a self-monitoring and triple-collaborative therapy system by auto-fluorescent polymer nanotheranostics which could be concurrently against angiogenesis and tumor cell growth by combining the benefits of anti-angiogenesis, RNA interfere and photothermal therapy (PTT). Auto-fluorescent amphiphilic polymer polyethyleneimine-polylactide (PEI-PLA) with positive charge can simultaneously load hydrophobic antiangiogenesis agent combretastatin A4 (CA4), NIR dye IR825 and absorb negatively charged heat shock protein 70 (HSP70) inhibitor (siRNA against HSP70) to construct self-monitoring nanotheranostics (NPICS). NPICS can effectively restrain the expression of HSP70 to reduce their endurance to the IR825-mediated PTT, leading to an enhanced photocytotoxicity. In a xenograft mouse tumor model, NPICS show an effect of inhibition of tumor angiogenesis and also display a highly synergistic anticancer efficacy with NIR laser irradiation. Significantly, based on its inherent auto-fluorescence, PEI-PLA not only serves as the drug carrier, but also as the self-monitor to real-time track NPICS biodistribution and tumor accumulation via fluorescence imaging. Moreover, IR825 endows NPICS could also be used as photoacoustic (PA) agents for in vivo PA imaging. This nanoplatform shows enormous potentials in cancer theranostics.

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Kellnberger S et al.

Optoacoustic microscopy at multiple discrete frequencies

TechnologyPreclinicalMSOT

Optoacoustic (photoacoustic) sensing employs illumination of transient energy and is typically implemented in the time domain using nanosecond photon pulses. However, the generation of high-energy short photon pulses requires complex laser technology that imposes a low pulse repetition frequency (PRF) and limits the number of wavelengths that are concurrently available for spectral imaging. To avoid the limitations of working in the time domain, we have developed frequency-domain optoacoustic microscopy (FDOM), in which light intensity is modulated at multiple discrete frequencies. We integrated FDOM into a hybrid system with multiphoton microscopy, and we examine the relationship between image formation and modulation frequency, showcase high-fidelity images with increasing numbers of modulation frequencies from phantoms and in vivo, and identify a redundancy in optoacoustic measurements performed at multiple frequencies. We demonstrate that due to high repetition rates, FDOM achieves signal-to-noise ratios similar to those obtained by time-domain methods, using commonly available laser diodes. Moreover, we experimentally confirm various advantages of the frequency-domain implementation at discrete modulation frequencies, including concurrent illumination at two wavelengths that are carried out at different modulation frequencies as well as flow measurements in microfluidic chips and in vivo based on the optoacoustic Doppler effect. Furthermore, we discuss how FDOM redefines possibilities for optoacoustic imaging by capitalizing on the advantages of working in the frequency domain.

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Cong Z et al.

Multispectral optoacoustic tomography (MSOT) for imaging the particle size-dependent intratumoral distribution of polymeric micelles

NanoCancerPreclinicalMSOT

Purpose: This study proposes the utilization of multispectral optoacoustic tomography (MSOT) to investigate the intratumoral distribution of polymeric micelles and effect of size on the biodistribution and antitumor efficacy (ATE).

Materials and methods: Docetaxel and/or optoacoustic agent-loaded polymeric micelles (with diameters of 22, 48, and 124 nm) were prepared using amphiphilic block copolymers poly (ethylene glycol) methyl ether-block-poly (D,L lactide) (PEG2000-PDLLAx). Subcutaneous 4T1 tumor-bearing mice were monitored with MSOT imaging and IVIS® Spectrum in vivo live imaging after tail vein injection of micelles. The in vivo results and ex vivo confocal imaging results were then compared. Next, ATE of the three micelles was found and compared.

Results: We found that MSOT imaging offers spatiotemporal and quantitative information on intratumoral distribution of micelles in living animals. All the polymeric micelles rapidly extravasated into tumor site after intravenous injection, but only the 22-nm micelle preferred to distribute into the inner tumor tissues, leading to a superior ATE than that of 48- and 124-nm micelles.

Conclusion: This study demonstrated that MSOT is theranostically a powerful imaging modality, offering quantitative information on size-dependent spatiotemporal distribution patterns after the extravasation of nanomedicine from tumor blood vessels.

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Costa MM et al.

Quantitative photoacoustic imaging study of tumours in vivo: baseline variations in quantitative measurements

CancerPreclinicalMSOT

Photoacoustic imaging (PAI) provides information on haemoglobin levels and blood oxygenation (sO2). To facilitate assessment of the variability in sO2 and haemoglobin in tumours, for example in response to therapies, the baseline variability of these parameters was evaluated in subcutaneous head and neck tumours in mice, using a PAI system (MSOTinVision-256TF). Tumours of anaesthetized animals (midazolam-fentanyl-medetomidine) were imaged for 75 min, in varying positions, and repeatedly over 6 days. An increasing linear trend for average tumoural haemoglobin and blood sO2 was observed, when imaging over 75 min. There were no significant differences in these temporal trends, when repositioning tumours. A negative correlation was found between the percent decrease in blood sO2 over 6 days and tumour growth rate. This paper shows the potential of PAI to provide baseline data for assessing the significance of intra- and inter-tumoural variations that may eventually have value for predicting and/or monitoring cancer treatment response.

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Zhang W et al.

Hybrid Nanomaterials of Conjugated Polymers and Albumin for Precise Photothermal Therapy

NanoCancerPreclinicalMSOT

Heretofore, conjugated polymers (CPs) attract considerable attention in photothermal therapy (PTT). Although various CPs with different structures have been reported, the suboptimal circulation persistence and biodistribution limit their efficacy in tumor treatment. Human serum albumin (HSA), an endogenous plasm protein, has been widely functioned as a carrier for therapeutic agents. Herein, we construct nanocomplexs C16 pBDP@HSA NPs from hydrophobic 4, 4-difluoro-4-bora-3a, 4adiaza-s-indacene (BODIPY)-containing CPs and HSA, which exhibit robust stability in physiological conditions and excellent photothermal activity upon irradiation. The high photothermal conversion efficiency of 37.5 %, higher than that of other reported PTT agents such as gold nanorods, phosphorus quantum dots and 2D materials, results in the potent photocytotoxicity towards cancer cells. Simultaneously, C16 pBDP@HSA NPs’ capabilities of near infrared fluorescence and photoacoustic imaging can provide guidance to the PTT. The outstanding inhibition of tumor growth results from great photothermal activity, the benefited accumulation in tumor and optimal timing of treatment. To the best of our knowledge, this is the first study which combines the BODIPY-based CPs and HSA in one nanostructure and finds application in cancer treatment. Moreover, this article also offers a new strategy for other insoluble macromolecules to explore more biomedical applications.

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Scarfe L et al.

Non-invasive imaging reveals conditions that impact distribution and persistence of cells after in vivo administration

Other ApplicationsPreclinicalMSOT

Background Cell-based regenerative medicine therapies are now frequently tested in clinical trials. In many conditions, cell therapies are administered systemically, but there is little understanding of their fate, and adverse events are often under-reported. Currently, it is only possible to assess safety and fate of cell therapies in preclinical studies, specifically by monitoring animals longitudinally using multi-modal imaging approaches. Here, using a suite of in vivo imaging modalities to explore the fate of a range of human and murine cells, we investigate how route of administration, cell type and host immune status affect the fate of administered cells. Methods We applied a unique imaging platform combining bioluminescence, optoacoustic and magnetic resonance imaging modalities to assess the safety of different human and murine cell types by following their biodistribution and persistence in mice following administration into the venous or arterial system. Results Longitudinal imaging analyses (i) suggested that the intra-arterial route may be more hazardous than intravenous administration for certain cell types, (ii) revealed that the potential of a mouse mesenchymal stem/stromal cell (MSC) line to form tumours depended on administration route and mouse strain and (iii) indicated that clinically tested human umbilical cord (hUC)-derived MSCs can transiently and unexpectedly proliferate when administered intravenously to mice. Conclusions In order to perform an adequate safety assessment of potential cell-based therapies, a thorough understanding of cell biodistribution and fate post administration is required. The non-invasive imaging platform used here can expose not only the general organ distribution of these therapies, but also a detailed view of their presence within different organs and, importantly, tumourigenic potential. Our observation that the hUC-MSCs but not the human bone marrow (hBM)-derived MSCs persisted for a period in some animals suggests that therapies with these cells should proceed with caution.

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Landa FJO et al.

Four-dimensional optoacoustic monitoring of tissue heating with medium intensity focused ultrasound

TechnologyPreclinicalMSOT

Medium-intensity focused ultrasound (MIFU) concerns therapeutic ultrasound interventions aimed at stimulating physiological mechanisms to reinforce healing responses without reaching temperatures that can cause permanent tissue damage. The therapeutic outcome is strongly affected by the temperature distribution in the treated region and its accurate monitoring represents an unmet clinical need. In this work, we investigate on the capacities of four-dimensional optoacoustic tomography to monitor tissue heating with MIFU. Calibration experiments in a tissue-mimicking phantom have confirmed that the optoacoustically-estimated temperature variations accurately match the simultaneously acquired thermocouple readings. The performance of the suggested approach in real tissues was further shown with bovine muscle samples. Volumetric temperature maps were rendered in real time, allowing for dynamic monitoring of the ultrasound focal region, estimation of the peak temperature and the size of the heat-affected volume.

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Meng L et al.

Photoacoustic temperature imaging based on multi-wavelength excitation

TechnologyPreclinicalMSOT

Building further upon the high spatial resolution offered by ultrasonic imaging and the high optical contrast yielded by laser excitation of photoacoustic imaging, and exploiting the temperature dependence of photoacoustic signal amplitudes, this paper addresses the question whether the rich information given by multispectral optoacoustic tomography (MSOT) allows to obtain 3D temperature images. Numerical simulations and experimental results are reported on agarose phantoms containing gold nanoparticles and the effects of shadowing, reconstruction flaws, etc. on the accuracy are determined.

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Bhutiani N et al.

In vivo tracking of orally-administered particles within the gastrointestinal tract of murine models using multispectral optoacoustic tomography

NanoCancerPreclinicalMSOT

While particle carriers have potential to revolutionize disease treatment, using these carriers requires knowledge of spatial and temporal biodistribution. The goal of this study was to track orally administered particle uptake and trafficking through the murine gastrointestinal (GI) tract using multispectral optoacoustic tomography (MSOT).

Polylactic acid (PLA) particles encapsulating AlexaFluor 680 (AF680) dye conjugated to bovine serum albumin (BSA) were orally gavaged into mice. Particle uptake and trafficking were observed using MSOT imaging with subsequent confirmation of particle uptake via fluorescent microscopy. Mice treated with PLA-AF680-BSA particles exhibited MSOT signal within the small bowel wall at 1 and 6 h, colon wall at 6, 12, and 24 h, and mesenteric lymph node 24 and 48 h. Particle localization identified using MSOT correlated with fluorescence microscopy. Despite the potential of GI tract motion artifacts, MSOT allowed for teal-time tracking of particles within the GI tract in a non-invasive and real-time manner.

Future use of MSOT in conjunction with particles containing both protein-conjugated fluorophores as well as therapeutic agents could allow for non-invasive, real time tracking of particle uptake and drug delivery.

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Wu Y et al.

A conjugated-polymer-based ratiometric nanoprobe for evaluating in-vivo hepatotoxicity induced by herbal medicine via MSOT imaging

Other ApplicationsNanoPreclinicalMSOT

Herbal medicines are widely used around the world, while some of them are associated with adverse effects like herb-induced liver injury due to oxidative/nitrosative stress resulted from hepatically-generated ROS/RNS. It is of significance to accurately evaluate herbal-medicine-induced hepatotoxicity, since it would help provide effective monitoring method of the safety of herbal remedies. Herein we designed a ratiometric nanoprobe for in vivo imaging hepatic injury induced by herbal medicine (polygonum multiflorum, PM) via specifically responding to NO generated in liver by PM, and with MSOT imaging the precise location of liver injury can be identified. The liposomal nanoprobe consists of a responsive dye (IX-2NH2) which could specifically respond to NO and the diketopyrrolopyrrole-based conjugated polymer (DPP-TT) as the internal reference. Thus we can realize ratiometric optoacoustic detection of herbal-medicine-induced liver injury with 3D information in mouse model in a noninvasive way.

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Khattak S et al.

Non-invasive dynamic assessment of conjunctival melanomas by photoacoustic imaging

CancerPreclinicalMSOT

This study describes non-invasive photoacoustic imaging to detect and monitor the growth of conjunctival melanomas in vivo. Conjunctival melanomas were induced by injection of melanotic B16F10 cells into the subconjunctival space in syngeneic albino C57BL/6 mice. Non-invasive in vivo photoacoustic tomography was performed before, and after tumor induction up to 2 weeks. Spectral unmixing was performed to determine the location and to assess the distribution of melanin. The melanin photoacoustic signal intensity was quantified from the tumor-bearing and control eyes at all timepoints. For postmortem validation, total tumor and melanotic tumor volumes were measured using H&E stained tumor sections and were compared to in vivo photoacoustic imaging measurements. Photoacoustic imaging non-invasively detected eyes bearing conjunctival tumors of varying sizes. The melanin signal was detected as early as immediately following injection of melanotic tumor cells. Changes in tumor size over time were assessed with changes in the volume and intensity of the melanin signal. Four growing tumors and one regressing tumor were observed. Three tumors without significant change in signal intensity over time were observed, showing variable growth. Photoacoustic melanin signal on the last day of in vivo imaging correlated with postmortem total tumor volume (R2 = 0.81) and melanotic tumor volume (R2 = 0.80). The results of our study show that actively growing conjunctival melanomas can be quantified in a non-invasive manner using in vivo photoacoustic tomography. The photoacoustic melanin signal intensity correlated with total and melanotic tumor volume. This novel in vivo imaging platform may help to assess new treatment modalities to manage ocular tumors.

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Hindelang B et al.

Non-invasive imaging in dermatology and the unique potential of Raster-Scan Optoacoustic Mesoscopy (RSOM)

SkinClinicalRSOM

In recent years, several non-invasive imaging methods have been introduced to facilitate diagnostics and therapy monitoring in dermatology. The microscopic imaging methods are restricted in their penetration depth, while the mesoscopic methods probe deeper but provide only morphological, not functional, information. “Raster-scan optoacoustic mesoscopy” (RSOM), an emerging new imaging technique, combines deep penetration with contrast based on light absorption, which provides morphological, molecular, and functional information. Here we compare the capabilities and limitations of currently available dermatological imaging methods and highlight the principles and unique abilities of RSOM. We illustrate the clinical potential of RSOM, in particular for non-invasive, high-resolution diagnosis and monitoring of inflammatory and oncological skin diseases.

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Guo W et al.

Laser Induced Transformable BiS@HSA/DTX Multiple Nanorods for Photoacoustic/Computed Tomography Dual-Modal Imaging Guided Photothermal/Chemo Combinatorial Anticancer Therapy

NanoCancerPreclinicalMSOT

Sub-optimal intra-tumor accumulation and poorly controllable release of encapsulated drugs remain unresolved challenges hampering further advancement of nanomedicines on cancer therapy. Herein, we conceived near infrared (NIR) laser-triggered transformable BiS@HSA/DTX multiple nanorods (mNRs), which were made of small bundles of bismuth sulfide nanorods (BiS NRs) coated by docetaxel (DTX)-inlaid human serum albumin (HSA). The BiS@HSA/DTX mNRs had a lateral size of approximately 100 nm and efficiently accumulated in the tumor microenvironment upon systemic administration in tumor-bearing nude mice. NIR laser irradiation of the tumor area caused rapid disassembly of the BiS@HSA/DTX mNRs into individual HSA-coated BiS nanorods (BiS@HSA iNRs) and triggered the release of DTX from the HSA corona, due to the local temperature increase generated by BiS NRs via photothermal effect. The laser-induced transformation into BiS@HSA iNRs facilitated their penetration and increased the retention time in tumor. The spatiotemporal delivery behavior of the BiS@HSA/DTX mNRs could be monitored by photoacoustic/computed tomography dual-modal imaging in vivo. Furthermore, because of the excellent photothermal conversion properties of BiS NRs and laser-triggered DTX release from BiS@HSA/DTX mNRs, efficient tumor combinatorial therapy was achieved via concurrent hyperthermia and chemotherapy in mice treated with BiS@HSA/DTX mNRs upon NIR laser irradiation.

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Wang YY et al.

Combination-Responsive MoO3-x Hybridized Hyaluronic Acid Hollow Nanospheres for Cancer Phototheranostics

NanoCancerPreclinicalMSOT

It is of extreme importance to reduce side effects resulted from the nonspecific uptake of phototherapeutic agents by normal tissues. Currently, single responsive strategy still cannot entirely satisfy the requirements of practical applications. In this study, we developed one kind of combination-responsive phototherapeutic nanoplatforms, where oxygen deficient molybdenum oxide (MoO3-x) hybridized hyaluronic acid (HA) hollow nanospheres, namely MoO3-x@HA HNSs, were constructed via a facile one-step method. In MoO3-x@HA HNSs, the reasonable combination of actively targeted specificity endowed by HA component and tumor microenvironment-responsive phototherapy activity induced by MoO3-x component can effectively improve the precision of phototherapy. The results of in vitro and in vivo experiments confirm that MoO3-x@HA HNSs can selectively kill CD44-overexpressing cancer cells and inhibit tumor growth with irradiation from an 808 nm laser, revealing their remarkable synergistic photothermal therapy/photodynamic therapy effect with CD44 receptor-targeted specificity and pH-responsiveness in treating cancer. We also prove that MoO3-x@HA HNSs can be used as a contrast agent for the computed tomography/photoacoustic imaging imaging. Encouraged by these results, it is anticipated that the reasonable combination of active targeting and tumor microenvironment responsiveness can be promising strategy to develop phototherapeutic nanoplatforms for precise multi-modality cancer theranostics.

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Li Y et al.

Secretin-Activated Brown Fat Mediates Prandial Thermogenesis to Induce Satiation

VascularPreclinicalMSOT

The molecular mediator and functional significance of meal-associated brown fat (BAT) thermogenesis remains elusive. Here, we identified the gut hormone secretin as a non-sympathetic BAT activator mediating prandial thermogenesis, which consequentially induces satiation, thereby establishing a gut-secretin-BAT-brain axis in mammals with a physiological role of prandial thermogenesis in the control of satiation. Mechanistically, meal-associated rise in circulating secretin activates BAT thermogenesis by stimulating lipolysis upon binding to secretin receptors in brown adipocytes, which is sensed in the brain and promotes satiation. Chronic infusion of a modified human secretin transiently elevates energy expenditure in diet-induced obese mice. Clinical trials with human subjects showed that thermogenesis after a single-meal ingestion correlated with postprandial secretin levels and that secretin infusions increased glucose uptake in BAT. Collectively, our findings highlight the largely unappreciated function of BAT in the control of satiation and qualify BAT as an even more attractive target for treating obesity.

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Nassif IA et al.

Wavelength optimization in the multispectral photoacoustic tomography of the lymphatic drainage in mice

Other ApplicationsTechnologyPreclinicalMSOT

Multispectral photoacoustic tomography provides mapping of the tissue chromophore distributions using sets of tunable laser wavelengths. With the overall goal of studying the dynamics of cerebrospinal fluid in mice in vivo, our work aims to minimize the number of wavelengths to reduce scanning time, improve the temporal resolution, reduce the energy deposition and avoid the tracer photobleaching while maintaining high image quality. To select small sets of wavelengths we directly searched for the combinations of wavelengths providing the best and worst image quality in comparison with a reference image obtained using 131 closely spaced wavelengths between 680 and 940 nm in terms of the peak signal-to-noise ratio (PSNR). We have shown that using the PSNR optimization method, additional improvements could be achieved over the wavelength set selected using the method of the minimization of the extinction matrix condition number.

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Ron A et al.

Characterization of Brown Adipose Tissue in a Diabetic Mouse Model with Spiral Volumetric Optoacoustic Tomography

PharmacokineticsPreclinicalMSOT

PURPOSE : Diabetes is associated with a deterioration of the microvasculature in brown adipose tissue (BAT) and with a decrease in its metabolic activity. Multispectral optoacoustic tomography has been recently proposed as a new tool capable of differentiating healthy and diabetic BAT by observing hemoglobin gradients and microvasculature density in cross-sectional (2D) views. We report on the use of spiral volumetric optoacoustic tomography (SVOT) for an improved characterization of BAT. PROCEDURES : A streptozotocin-induced diabetes model and control mice were scanned with SVOT. Volumetric oxygen saturation (sO2) as well as total blood volume (TBV) in the subcutaneous interscapular BAT (iBAT) was quantified. Segmentation further enabled separating feeding and draining vessels from the BAT anatomical structure. RESULTS : Scanning revealed a 46 % decrease in TBV and a 25 % decrease in sO2 in the diabetic iBAT with respect to the healthy control. CONCLUSIONS : These results suggest that SVOT may serve as an effective tool for studying the effects of diabetes on BAT. The volumetric optoacoustic imaging probe used for the SVOT scans can be operated in a handheld mode, thus potentially providing a clinical translation route for BAT-related studies with this imaging technology.

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Laramie MD et al.

Small Molecule Optoacoustic Contrast Agents: An Unexplored Avenue for Enhancing In Vivo Imaging

NanoCancerNeuroPreclinicalMSOT

Almost every variety of medical imaging technique relies heavily on exogenous contrast agents to generate high-resolution images of biological structures. Organic small molecule contrast agents, in particular, are well suited for biomedical imaging applications due to their favorable biocompatibility and amenability to structural modification. PET/SPECT, MRI, and fluorescence imaging all have a large host of small molecule contrast agents developed for them, and there exists an academic understanding of how these compounds can be developed. Optoacoustic imaging is a relatively newer imaging technique and, as such, lacks well-established small molecule contrast agents; many of the contrast agents used are the same ones which have found use in fluorescence imaging applications. Many commonly-used fluorescent dyes have found successful application in optoacoustic imaging, but others generate no detectable signal. Moreover, the structural features that either enable a molecule to generate a detectable optoacoustic signal or prevent it from doing so are poorly understood, so design of new contrast agents lacks direction. This review aims to compile the small molecule optoacoustic contrast agents that have been successfully employed in the literature to bridge the information gap between molecular design and optoacoustic signal generation. The information contained within will help to provide direction for the future synthesis of optoacoustic contrast agents.

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Knights OB et al.

Gold Nanorods for Light-Based Lung Cancer Theranostics

NanoCancerPreclinicalMSOT

Gold nanorods (AuNRs) have the potential to be used in photoacoustic (PA) imaging and plasmonic photothermal therapy (PPTT) due to their unique optical properties, biocompatibility, controlled synthesis, and tuneable surface plasmon resonances (SPRs). Conventionally, continuous-wave (CW) lasers are used in PPTT partly due to their small size and low cost. However, if pulsed-wave (PW) lasers could be used to destroy tissue then combined theranostic applications, such as PA-guided PPTT, would be possible using the same laser system and AuNRs. In this study, we present the effects of AuNR size on PA response, PW-PPTT efficacy, and PA imaging in a tissue-mimicking phantom, as a necessary step in the development of AuNRs towards clinical use. At equivalent NP/mL, the PA signal intensity scaled with AuNR size, indicating that overall mass has an effect on PA response, and reinforcing the importance of efficient tumour targeting. Under PW illumination, all AuNRs showed toxicity at a laser fluence below the maximum permissible exposure to skin, with a maximum of 80% cell-death exhibited by the smallest AuNRs, strengthening the feasibility of PW-PPTT. The theranostic potential of PW lasers combined with AuNRs has been demonstrated for application in the lung.

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Clemmensen C et al.

Coordinated targeting of cold and nicotinic receptors synergistically improves obesity and type 2 diabetes

PharmacokineticsPreclinicalMSOT

Pharmacological stimulation of brown adipose tissue (BAT) thermogenesis to increase energy expenditure is progressively being pursued as a viable anti-obesity strategy. Here, we report that pharmacological activation of the cold receptor transient receptor potential cation channel subfamily M member 8 (TRPM8) with agonist icilin mimics the metabolic benefits of cold exposure. In diet-induced obese (DIO) mice, treatment with icilin enhances energy expenditure, and decreases body weight, without affecting food intake. To further potentiate the thermogenic action profile of icilin and add complementary anorexigenic mechanisms, we set out to identify pharmacological partners next to icilin. To that end, we specifically targeted nicotinic acetylcholine receptor (nAChR) subtype alpha3beta4 (α3β4), which we had recognized as a potential regulator of energy homeostasis and glucose metabolism. Combinatorial targeting of TRPM8 and nAChR α3β4 by icilin and dimethylphenylpiperazinium (DMPP) orchestrates synergistic anorexic and thermogenic pathways to reverse diet-induced obesity, dyslipidemia, and glucose intolerance in DIO mice.

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Wang X et al.

Amphiphilic redox-sensitive NIR BODIPY nanoparticles for dual-mode imaging and photothermal therapy

NanoPreclinicalMSOT

Theranostics, integrating tumor treatment and diagnosis concurrently, has become an emerging and meaningful strategy in cancer therapy. In this work, an amphiphilic redox-sensitive near-infrared (NIR) BODIPY dye, which could be formed into nanoparticles (PEG-SS-BDP NPs) by self-assembly, was synthesized and possessed good capability of photothermal therapy (PTT), near-infrared fluorescence (NIRF) imaging, photoacoustic (PA) imaging and drug loading. The stable nanoparticles could be dissociated to turn on NIRF due to the rift of embedded disulfide bonds by glutathione (GSH). The enhanced fluorescence in vitro could be observed via confocal laser scanning microscopy (CLSM) after adding GSH, confirming the redox-sensitivity of disulfide bonds. NIRF and PA imaging demonstrated active accumulation in tumor and good imaging effect. At last, PEG-SS-BDP NPs could significantly suppress tumor growth in vivo upon irradiation. The amphiphilic redox-sensitive BODIPY nanoparticles provide a promising design strategy to formulate multifunctional stimuli-responsive theranostic nanoplatforms.

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Li G et al.

Facile Approach to Synthesize Gold Nanorod@Polyacrylic Acid/Calcium Phosphate Yolk-Shell Nanoparticles for Dual-Mode Imaging and pH/NIR-Responsive Drug Delivery

NanoPreclinicalMSOT

A facile strategy to fabricate gold nanorod@polyacrylic acid/calcium phosphate (AuNR@PAA/CaP) yolk-shell nanoparticles (NPs) composed with a PAA/CaP shell and an AuNR yolk is reported. The as-obtained AuNR@PAA/CaP yolk-shell NPs possess ultrahigh doxorubicin (DOX) loading capability (1 mg DOX/mg NPs), superior photothermal conversion property (26%) and pH/near-infrared (NIR) dual-responsive drug delivery performance. The released DOX continuously increased due to the damage of the CaP shell at low pH values. When the DOX-loaded AuNR@PAA/CaP yolk-shell NPs were exposed to NIR irradiation, a burst-like drug release occurs owing to the heat produced by the AuNRs. Furthermore, AuNR@PAA/CaP yolk-shell NPs are successfully employed for synergic dual-mode X-ray computed tomography/photoacoustic imaging and chemo-photothermal cancer therapy. Therefore, this work brings new insights for the synthesis of multifunctional nanomaterials and extends theranostic applications.

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An L et al.

In situ sulfidation of Cu2O by endogenous H2S for colon cancer theranostics

CancerPreclinicalMSOT

Expression of a high concentration of H2S is closely related to the formation of colon cancer tumor. However, up to now, only few H2S triggered theranostics agents for colon cancer have been reported. Herein, a turn on theranostics agent was developed via utilizing the in situ reaction of Cu2O and endogenous H2S at colon tumor sites. Based on the In vitro and in vivo experiments, excellent photoacoustic imaging and photothermal therapy have both been confirmed by this in situ reaction activated colon cancer theranostics. Our work established a simple and efficient strategy for both diagnosis and treatment of colon cancer with a novel trigger mechanism, which provides a new route for colon cancer theranostics based on the in situ reactions at the tumor sites.

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Wang Z et al.

Application of polydopamine in tumor targeted drug delivery system and its drug release behavior

NanoCancerPreclinicalMSOT

Inspired by the bionics of marine mussels, polydopamine (PDA), a new polymer with unique physicochemical properties was discovered. Due to its simple preparation, good biocompatibility, unique drug-loading methods, PDA has attracted tremendous attentions in field of drug delivery and imaging, and the combination of chemotherapy and other therapies or diagnostic methods, such as photothermotherapy (PTT), photoacoustic imaging (PAI), magnetic resonance imaging (MRI), etc. As an excellent drug carrier in tumor targeted drug delivery system, the drug release behavior of drug-loaded PDA-based nanoparticles is also an important factor to be considered in the establishment of drug delivery systems. Therefore, the purpose of this review is to provide a comprehensive overview of the various applications of PDA in tumor targeted drug delivery systems and to gain insight into the release behavior of the drug-loaded PDA-based nanocarriers. A sufficient understanding and discussion of these aspects is expected to provide a better way to design more rational and effective PDA-based tumor nano-targeted delivery systems. Apart from this, the prospects for the future application of PDA in this field and some unique insights are listed at the end of the article.

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Kazmierczak PM et al.

Integrin-targeted quantitative optoacoustic imaging with MRI correlation for monitoring a BRAF/MEK inhibitor combination therapy in a murine model of human melanoma

MelanomaPreclinicalMSOT

PURPOSE: To investigate αvβ3-integrin-targeted optoacoustic imaging and MRI for monitoring a BRAF/MEK inhibitor combination therapy in a murine model of human melanoma.

MATERIALS AND METHODS: Human BRAF V600E-positive melanoma xenograft (A375)-bearing Balb/c nude mice (n = 10) were imaged before (day 0) and after (day 7) a BRAF/MEK inhibitor combination therapy (encorafenib, 1.3 mg/kg/d; binimetinib, 0.6 mg/kg/d, n = 5) or placebo (n = 5), respectively. Optoacoustic imaging was performed on a preclinical system unenhanced and 5 h after i. v. injection of an αvβ3-integrin-targeted fluorescent probe. The αvβ3-integrin-specific tumor signal was derived by spectral unmixing. For morphology-based tumor response assessments, T2w MRI data sets were acquired on a clinical 3 Tesla scanner. The imaging results were validated by multiparametric immunohistochemistry (ß3 -integrin expression, CD31 -microvascular density, Ki-67 -proliferation).

RESULTS: The αvβ3-integrin-specific tumor signal was significantly reduced under therapy, showing a unidirectional decline in all animals (from 7.98±2.22 to 1.67±1.30; p = 0.043). No significant signal change was observed in the control group (from 6.60±6.51 to 3.67±1.93; p = 0.500). Immunohistochemistry revealed a significantly lower integrin expression (ß3: 0.20±0.02 vs. 0.39±0.05; p = 0.008) and microvascular density (CD31: 119±15 vs. 292±49; p = 0.008) in the therapy group. Tumor volumes increased with no significant intergroup difference (therapy: +107±42 mm3; control +112±44mm3, p = 0.841). In vivo blocking studies with αvβ3-integrin antagonist cilengitide confirmed the target specificity of the fluorescent probe.

CONCLUSIONS: αvβ3-integrin-targeted optoacoustic imaging allowed for the early non-invasive monitoring of a BRAF/MEK inhibitor combination therapy in a murine model of human melanoma, adding molecular information on tumor receptor status to morphology-based tumor response criteria.

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Wu Y et al.

Activatable probes for diagnosing and positioning liver injury and metastatic tumors by multispectral optoacoustic tomography

CancerPreclinicalMSOT

Optoacoustic tomography (photoacoustic tomography) is an emerging imaging technology displaying great potential for medical diagnosis and preclinical research. Rationally designing activatable optoacoustic probes capable of diagnosing diseases and locating their foci can bring into full play the role of optoacoustic tomography (OAT) as a promising noninvasive imaging modality. Here we report two xanthene-based optoacoustic probes (C1X-OR1 and C2X-OR2) for temporospatial imaging of hepatic alkaline phosphatase (or β-galactosidase) for evaluating and locating drug-induced liver injury (or metastatic tumor). The probes rapidly respond to the disease-specific biomarkers by displaying red-shifted NIR absorption bands and generate prominent optoacoustic signals. Using multispectral optoacoustic tomography (MSOT), we can precisely localize the focus of drug-induced liver injury in mice using C1X-OR1, and the metastatic tumors using C2X-OR2. This work suggests that the activatable optoacoustic chromophores may potentially be applied for diagnosing and localizing disease foci, especially smaller and deeper ones.

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Samykutty A et al.

Osteopontin-targeted probe detects orthotopic breast cancers using optoacoustic imaging

Breast CancerPreclinicalMSOT

Improved detection of breast cancer using highly sensitive, tumor-specific imaging would facilitate diagnosis, surveillance and assessment of response to treatment. We conjugated osteopontin peptide to an infrared fluorescent dye to serve as a contrast agent for detection of breast cancer by multispectral optoacoustic tomography (MSOT). Selective binding of the osteopontin-based probe was identified using flow cytometry and near infrared fluorescent imaging in triple negative and HER2 positive breast cancer cell lines in vitro. Osteopontin-750 accumulation was evaluated in vivo using MSOT with secondary confirmation of signal accumulation using near infrared fluorescent imaging. The osteopontin-based probe demonstrated binding to breast cancer cells in vitro. Similarly, after intravenous administration of the osteopontin-750 probe, it accumulated preferentially in the subcutaneous breast tumor in nude mice (557 MSOT a.u. compared to untargeted organs such as kidney (53.7 MSOT a.u.) and liver (32.1 MSOT a.u.). At 2.5 h post-injection, signal intensity within the tumor was 9.7 and 17 times greater in the tumor bed than in the kidney or liver, respectively. Fluorescence imaging ex vivo comparing tumor signal to that of nontarget organs confirmed the results in vivo. MSOT imaging demonstrated selective accumulation of the fluorescent osteopontin targeting probe to tumor sites both in vitro and in vivo, and provided high-resolution images. Further development of this tool is promising for advanced diagnostic imaging, disease surveillance and therapeutic models that limit nontarget toxicity.

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Masthoff M et al.

Use of Multispectral Optoacoustic Tomography to Diagnose Vascular Malformations

VascularClinicalMSOT

Importance : Differential diagnosis of congenital vascular anomalies is challenging, and misdiagnosis is frequent. Vascular malformations are considered one of the most difficult vascular diseases to treat. A new imaging approach that visualizes anatomical features and quantitatively assesses molecular biomarkers noninvasively would aid diagnosis and monitoring of treatment response of vascular malformations.

Objective : To evaluate multispectral optoacoustic tomography (MSOT) for noninvasive assessment of molecular biomarkers for diagnosis and therapeutic monitoring of vascular malformations.

Design, Setting, and Participants : This pilot study examined 6 patients with arteriovenous malformation (AVM) and 6 patients with venous malformation (VM) diagnosed according to the classification system of the International Society for the Study of Vascular Anomalies. All patients underwent clinical hybrid MSOT/ultrasonographic (US) imaging before and after treatment at an interdisciplinary vascular malformations clinic by trained MSOT and US examiners. Examiners were blinded to the patient history and stage of disease. Data were collected from April 11 to 25, 2017, and analyzed from May 1 to October 31, 2017.

Interventions : Clinical hybrid MSOT/US imaging was performed before or within 1 week after endovascular embolization (for AVM) or percutaneous sclerotherapy (for VM).

Main Outcomes and Measures : Region-of-interest analysis of the lesion and contralateral healthy tissue revealed quantitative values for oxygenated (HbO2) and deoxygenated (HbR) hemoglobin by spectral unmixing of optoacoustic data acquired at multiple wavelengths. The HbO2:HbR ratio was calculated for healthy tissue and for AVM and VM before and after treatment.

Results : Twelve patients (9 female and 3 male; mean [SD] age, 23 [18] years; age range, 6-59 years) with vascular malformations (6 with AVMs and 6 with VMs) were included. Significantly higher HbO2:HbR ratios for AVMs (mean [SEM], 1.82 [0.08] vs 0.89 [0.03]; P < .001) and for VMs (mean [SEM], 1.12 [0.04] vs 0.89 [0.03]; P = .001) were found on MSOT tissue compared with healthy tissue. Significantly higher HbO2:HbR ratios for AVMs compared with VMs (mean [SEM], 1.82 [0.08] vs 1.12 [0.04]; P < .001) were also found. Therefore, MSOT provided intrinsic biomarker patterns to distinguish both vascular malformations. After therapy, the HbO2:HbR ratio dropped in correlation to treatment success validated by magnetic resonance imaging or angiography.

Conclusions and Relevance : This study suggests that different types of vascular malformations are clearly distinguished by MSOT-based, noninvasive assessment of hemoglobin levels in vascular malformations. The therapy effects found in this study could be instantly visualized, and this may offer a new tool for noninvasive diagnosis and monitoring of vascular malformations.

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Duan Y et al.

Photoacoustic and Magnetic Resonance Imaging Bimodal Contrast Agent Displaying Amplified Photoacoustic Signal

NanoPreclinicalMSOT

Progress in photoacoustic (PA) and magnetic resonance imaging (MRI) bimodal contrast agents has been achieved mainly by utilizing the imaging capability of single or multiple components and consequently realizing the desired application for both imaging modalities. However, the mechanism of the mutual influence between components within a single nanoformulation, which is the key to developing high-performance multimodal contrast agents, has yet to be fully understood. Herein, by integrating conjugated polymers (CPs) with iron oxide (IO) nanoparticles using an amphiphilic polymer, a bimodal contrast agent named CP-IO is developed, displaying 45% amplified PA signal intensity as compared to bare CP nanoparticle, while the performance of MRI is not affected. Further experimental and theoretical simulation results reveal that the addition of IO nanoparticles in CP-IO nanocomposites contributes to this PA signal amplification through a synergistic effect of additional heat generation and faster heat dissipation. Besides, the feasibility of CP-IO nanocomposites acting as PA-MRI bimodal contrast agents is validated through in vivo tumor imaging using mice models. From this study, it is demonstrated that a delicately designed structural arrangement of various components in a contrast agent could potentially lead to a superior performance in the imaging capability.

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Hsiao-Chun AL

Ultrafast Volumetric Optoacoustic Imaging of Whole Isolated Beating Mouse Heart

Other ApplicationsPreclinicalMSOT

The Langendorff-perfused heart technique has become the model of choice for multiparametric optical mapping of cardiac function and electrophysiology. However, photon scattering in tissues represents a significant drawback of the optical imaging approach, fundamentally limiting its mapping capacity to the heart surface. This work presents the first implementation of the optoacoustic approach for 4D imaging of the entire beating isolated mouse heart. The method combines optical excitation and acoustic detection to simultaneously render rich optical contrast and high spatio-temporal resolution at centimeter-scale depths. We demonstrate volumetric imaging of deeply located cardiac features, including the interventricular septum, chordae tendineae, and papillary muscles while further tracking the heart beat cycle and the motion of the pulmonary, mitral, and tricuspid valves in real time. The technique possesses a powerful combination between high imaging depth, fast volumetric imaging speed, functional and molecular imaging capacities not available with other imaging modalities currently used in cardiac research.

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Cell Metab. 2019 Mar 5;29(3):518-538.

Emerging Technologies to Image Tissue Metabolism

Other ApplicationsTechnologyPreclinicalClinicalMSOT

Due to the implication of altered metabolism in a large spectrum of tissue function and disease, assessment of metabolic processes becomes essential in managing health. In this regard, imaging can play a critical role in allowing observation of biochemical and physiological processes. Nuclear imaging methods, in particular positron emission tomography, have been widely employed for imaging metabolism but are mainly limited by the use of ionizing radiation and the sensing of only one parameter at each scanning session. Observations in healthy individuals or longitudinal studies of disease could markedly benefit from non-ionizing, multi-parameter imaging methods. We therefore focus this review on progress with the non-ionizing radiation methods of MRI, hyperpolarized magnetic resonance and magnetic resonance spectroscopy, chemical exchange saturation transfer, and emerging optoacoustic (photoacoustic) imaging. We also briefly discuss the role of nuclear and optical imaging methods for research and clinical protocols.

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Chuah SY et al.

Volumetric Multispectral Optoacoustic Tomography for 3-Dimensional Reconstruction of Skin Tumors: A Further Evaluation with Histopathologic Correlation

CancerPreclinicalMSOT

n/a

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Zheng X et al.

Biodegradable hypocrellin derivative nanovesicle as a near-infrared light-driven theranostic for dually photoactive cancer imaging and therapy

NanoCancerPreclinicalMSOT

Photoactive agents based on natural products have attracted substantial attention in clinical applications because of their distinct biological activity, molecular structure multiformity, and low biotoxicity. Herein, we initially modify hypocrellin B (HB) with 1,2-diamino-2-methyl propane to form near-infrared (NIR) light (>700 nm)-responsive amino-substituted HB derivative (DPAHB). The DPAHB exhibit broad absorption (400-800 nm), NIR emission (maximum emission peak at 710 nm), and high singlet oxygen (1O2) quantum yield (∼0.33) under NIR light (721 nm) irradiation. After self-assembly by using DPAHB with PEG-PLGA, the as-prepared nanovesicles (DPAHB NVs) retain efficient 1O2 generation, more interestingly, show high photothermal conversion efficiency (∼0.24) under NIR light (721 nm) irradiation for synergistic photodynamic therapy (PDT) and photothermal therapy toward hypoxic tumor. The DPAHB NVs can not only be as a fluorescence/photoacoustic imaging agent but also exhibit an even stronger PDT efficiency than that of chlorin e6 (a widely used classic photosensitizer). In vitro and in vivo studies demonstrate that DPAHB NVs possess high photothermal stability, enhanced tumor accumulation, and suitable biodegradation rate, thus, show a highly promising clinical potential as a new photoactive agent for cancer therapy.

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Lei P et al.

Ultrafast synthesis of ultrasmall polyethylenimine-protected AgBiS2 nanodots by "rookie method" for in vivo dual-modal CT/PA imaging and simultaneous photothermal therapy

NanoCancerPreclinicalMSOT

Developing a biocompatible nanotheranostic platform integrating diagnostic and therapeutic functions is a great prospect for cancer treatment. However, it is still a great challenge to synthesize nanotheranostic agents using an ultra-facile method. In the research reported here, ultrasmall polyethylenimine-protected silver bismuth sulfide (PEI-AgBiS2) nanodots were successfully synthesized using an ultra-facile and environmentally friendly strategy (1 min only at room temperature), which could be described as a “rookie method”. PEI-AgBiS2 nanodots show good monodispersity and biocompatibility. For the first time, PEI-AgBiS2 nanodots were reported as a powerful and safe nanotheranostic agent for cancer treatment. PEI-AgBiS2 nanodots exhibit excellent computed tomography (CT) and photoacoustic (PA) dual-modal imaging ability, which could effectively guide photothermal cancer therapy. Furthermore, PEI-AgBiS2 nanodots exhibit a high photothermal conversion efficiency (η = 35.2%). The photothermal therapy (PTT) results demonstrated a highly efficient tumor ablation ability. More importantly, the blood biochemistry and histology analyses verify that the PEI-AgBiS2 nanodots have negligible long-term toxicity. This work highlights that PEI-AgBiS2 nanodots produced using this extremely effective method are a high-performance and safe PTT agent. These findings open a new gateway for synthesizing nanotheranostic agents by using this ultra-facile method in the future.

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Cai Q et al.

Chemotaxis-Instructed Intracellular Staphylococcus aureus Infection Detection by a Targeting and Self-Assembly Signal-Enhanced Photoacoustic Probe

Infectious DiseasePreclinicalMSOT

Intracellular invasion and the survival of Staphylococcus aureus in phagocytic cells has been regarded as one of the mechanisms that leads to the treatment failure of S. aureus infection and potential antibiotic resistance. The detection of infected phagocytic cells plays an important role in guiding antibiotic treatment and in reducing drug resistance. The development of a sensitive and specific imaging probe to visualize the intracellular bacteria is quite challenging. In this work, we report a photoacoustic agent (MPC) that is able to detect intracellular S. aureus infection through a dynamic process, including (i) active targeting and internalization into macrophage cells, (ii) specific molecular tailoring by caspase-1 in infected macrophage cells, and (iii) enhancement of the photoacoustic (PA) signal owing to molecular self-assembly. The PA signal per area of the “stimuli-induced assembly” agent (MPC) increases more than 2-fold over that of the active targeting control agent (MPSC). Finally, based on this approach, the average PA signal in the infected site is enhanced by approximately 2.6-fold over that of the control site. We envision that this PA contrast agent may provide a new approach for the selective and sensitive diagnosis of an intracellular bacterial infection.

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Baumann KN et al.

An active DNA-based nanoprobe for photoacoustic pH imaging

NanoPreclinicalMSOT

We report an active DNA construct capable of probing pH through a photoacoustic (PA) ratiometric analysis approach. Our nanoprobe enables different PA readout in tissue mimicking phantoms in the range between pH 6.8 to 7.8 at physiologically relevant sodium concentrations. Thus, it represents a promising platform to probe pH values relevant to the tumor microenvironment using PA.

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Goh Y et al.

Multispectral Optoacoustic Tomography in Assessment of Breast Tumor Margins During Breast-Conserving Surgery: A First-in-human Case Study

Breast CancerClinicalMSOT

Clinical Practice Points

  • Multispectral optoacoustic tomography (MSOT) is an innovative state-of-the-art imaging modality that has gained popularity for in vivo breast imaging in recent years.
  • Combining high-resolution images with endogenous differentiation of biochemical contents, MSOT could be an accurate ex vivo imaging modality for assessment of tumor margins during breast-conserving surgery to reduce margin positivity rates.
  • Accurate intraoperative assessment of margins could lead to more precise surgery, allowing a smaller volume of breast tissue to be removed without compromising the resection margins.
  • To the authors’ knowledge, there has been no ex vivo study conducted to this day that uses MSOT in the assessment of breast tumor margins after lumpectomy. Hence, we would like to present the first case of breast tumor margin assessment using MSOT in a 55-year-old patient who underwent breast-conserving surgery for invasive ductal carcinoma.
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Tomaszewski MR et al.

Oxygen-enhanced and dynamic contrast-enhanced optoacoustic tomography provide surrogate biomarkers of tumour vascular function, hypoxia and necrosis

CancerPharmacokineticsPreclinicalMSOT

Measuring the functional status of tumour vasculature, including blood flow fluctuations and changes in oxygenation, is important in cancer staging and therapy monitoring. Current clinically approved imaging modalities suffer long procedure times and limited spatio-temporal resolution. Optoacoustic tomography (OT) is an emerging clinical imaging modality that overcomes these challenges. By acquiring data at multiple wavelengths, OT can interrogate haemoglobin concentration and oxygenation directly and resolve contributions from injected contrast agents. In this study, we tested whether two dynamic OT techniques, oxygenenhanced (OE) and dynamic contrast-enhanced (DCE)-OT, could provide surrogate biomarkers of tumour vascular function, hypoxia and necrosis. We found that vascular maturity led to changes in vascular function that affected tumour perfusion, modulating the DCE-OT signal. Perfusion in turn regulated oxygen availability, driving the OE-OT signal. In particular, we demonstrate for the first time a strong per-tumour and spatial correlation between imaging biomarkers derived from these in vivo techniques and tumour hypoxia quantified ex vivo. Our findings indicate that OT may offer a significant advantage for localised imaging of tumour response to vascular targeted therapies when compared to existing clinical DCE methods.

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Zhao Y et al.

In vivo therapeutic evaluation of polymeric nanomedicines: effect of different targeting peptides on therapeutic efficacy against breast cancer

NanoCancerPreclinicalMSOT

Targeted nanomedicines offer many advantages over macromolecular therapeutics that rely only on passive accumulation within the tumour environment. The aim of this work was to investigate the in vivo anticancer efficiency of polymeric nanomedicines that were conjugated with peptide aptamers that show high affinity for receptors on many cancer cells. In order to assess the ability for the nanomedicine to treat cancer and investigate how structure affected the behavior of the nanomedicine, three imaging modalities were utilized, including in vivo optical imaging, multispectral optoacoustic tomography (MSOT) and ex vivo confocal microscopy. An 8-mer (A8) or 13-mer (A13) peptide aptamer that have been shown to exhibit high affinity for heat shock protein 70 (HSP70) was covalently-bound to hyperbranched polymer (HBP) nanoparticles with the purpose of both cellular targeting, as well as the potential to impart some level of chemo-sensitization to the cells. Furthermore, doxorubicin was bound to the polymeric carrier as the anticancer drug, and Cyanine-5.5 (Cy5.5) was incorporated into the polymer as a monomeric fluorophore to aid in monitoring the behavior of the nanomedicine. Enhanced tumour regression was observed in nude mice bearing MDA-MB-468 xenografts when the nanocarriers were targeted using the peptide ligands, compared to control groups treated with free DOX or HBP without aptamer. The accumulated DOX level in solid tumours was 5.5 times higher in mice treated with the targeted therapeutic, than mice treated with free DOX, and 2.6 times higher than the untargeted nanomedicine that relied only on passive accumulation. The results suggest that aptamer-targeted therapeutics have great potential for improving accumulation of nanomedicines in tumours for therapy.

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Balasundaram G et al.

Noninvasive Anatomical and Functional Imaging of Orthotopic Glioblastoma Development and Therapy using Multispectral Optoacoustic Tomography

CancerNeuroPreclinicalMSOT

PURPOSE: Here we demonstrate the potential of multispectral optoacoustic tomography (MSOT), a new non-invasive structural and functional imaging modality, to track the growth and changes in blood oxygen saturation (sO2) in orthotopic glioblastoma (GBMs) and the surrounding brain tissues upon administration of a vascular disruptive agent (VDA).

METHODS: Nude mice injected with U87MG tumor cells were longitudinally monitored for the development of orthotopic GBMs up to 15 days and observed for changes in sO2 upon administration of combretastatin A4 phosphate (CA4P, 30 mg/kg), an FDA approved VDA for treating solid tumors. We employed a newly-developed non-negative constrained approach for combined MSOT image reconstruction and unmixing in order to quantitatively map sO2 in whole mouse brains.

RESULTS: Upon longitudinal monitoring, tumors could be detected in mouse brains using single-wavelength data as early as 6 days post tumor cell inoculation. Fifteen days post-inoculation, tumors had higher sO2 of 63 ± 11% (n = 5, P < .05) against 48 ± 7% in the corresponding contralateral brain, indicating their hyperoxic status. In a different set of animals, 42 days post-inoculation, tumors had lower sO2 of 42 ± 5% against 49 ± 4% (n = 3, P < .05) in the contralateral side, indicating their hypoxic status. Upon CA4P administration, sO2 in 15 days post-inoculation tumors dropped from 61 ± 9% to 36 ± 1% (n = 4, P < .01) within one hour, then reverted to pre CA4P treatment values (63 ± 6%) and remained constant until the last observation time point of 6 hours.

CONCLUSION: With the help of advanced post processing algorithms, MSOT was capable of monitoring the tumor growth and assessing hemodynamic changes upon administration of VDAs in orthotopic GBMs.

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Chang YX et al.

Synergistic Reducing Effect for Synthesis of Well-Defined Au Nanooctopods With Ultra-Narrow Plasmon Band Width and High Photothermal Conversion Efficiency

NanoPreclinicalMSOT

Branched Au nanoparticles have attracted intense interest owing to their remarkable properties and a wide variety of potential applications in surface-enhanced Raman spectroscopy (SERS), photothermal therapy, photoacoustic imaging, and biomedicines. The morphology and spatial arrangement of branches play the most crucial role in the determination of their properties and applications. However, it is still a synthetic challenge to control the exact arm numbers of branches with specific spatial arrangements. Here we report a facile method for the kinetically controlled growth of Au nanooctopods (NOPs) with a high yield (81%), monodispersity, and reproducibility by using the synergistic reducing effect of ascorbic acid and 1-methylpyrrolidine. The NOPs have eight arms elongated along <111> directions with uniform arm lengths. Due to their well-defined size and shape, NOPs show ultra-narrow surface plasmon band width with a full width at half maximum of only 76 nm (0.20 eV). Upon irradiation with laser, the NOPs possessed excellent photothermal conversion efficiencies up to 83.0% and photoacoustic imaging properties. This work highlights the future prospects of using NOPs with desired physicochemical properties for biomedical applications.

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Song X et al.

Novel GPC3-binding WS2-Ga3+-PEG-peptide nanosheets for in vivo bimodal imaging-guided photothermal therapy

NanoCancerPreclinicalMSOT

AIM: The diagnosis and treatment of hepatocarcinoma (HCC) is believed to be improved due to the development of specific targeting probes by molecular imaging methods. GPC3, which is a hepatocellular carcinoma (HCC)-specific tumor marker, anchors at most HCC cells. To target this cell membrane protein, we developed a novel nanoparticle by conjugating WS2-Ga3+-PEG and a short peptide with favorable specificity and affinity to the GPC3 protein.

MATERIALS & METHODS: In in vitro assay, several physical properties of the novel probe were evaluated. In in vivo assay, MRI, photoacoustic imaging and photothermal therapy were performed in the subcutaneous HepG2-bearing mice with the novel probe.

RESULTS & CONCLUSION: The effect of imaging and photothermal therapy was significant. We revealed that the novel nanosheet WS2-Ga3+-PEG-peptide is promising to detect and treat HCC-expressing GPC3.

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Peng L et al.

Phage Display-Derived Peptide-based Dual-Modality Imaging Probe for Bladder Cancer Diagnosis and Resection Post-Instillation: A Preclinical Study

CancerPreclinicalMSOT

Bladder cancer (BC) is a common human malignancy. Conventional ultrasound and white light cystoscopy are often used for BC diagnosis and resection, but insufficient specificity results in a high BC recurrence rate. New strategy for the diagnosis and resection of BC are needed. In this study, we developed a highly specific peptide-based probe for BC photoacoustic imaging (PAI) diagnosis and near-infrared (NIR)-imaging-guided resection post-instillation. A BC-specific peptide (PLSWT7) was selected by in vivo phage display technology and labeled with IRDye800CW to synthesize a BC-specific dual-modality imaging (DMI) probe (PLSWT7-DMI). The feasibility of PLSWT7-DMI-based dual-modality PAI-NIR imaging was assessed in vitro, in mouse models, and ex vivo human bladders. An air-pouch BC (APBC) model suitable for probe instillation was established to evaluate the probe-based BC PAI diagnosis and NIR-imaging-guided resection. Human bladders were used to assess whether PLSWT7-DMI-based DMI strategy is a translatable approach for BC detection and resection. The probe exhibited excellent selectivity and specificity both in vitro and in vivo. Post-instillation of the probe, tumors <3 mm were detectable by PAI, and NIR-imaging-guided tumor resection decreased the BC recurrence rate by 90% and increased the survival in the mouse model. Additionally, ex vivo NIR imaging of human bladders indicated that PLSWT7-DMI-based imaging would potentially allowed precise resection of BC in clinical settings. This PLSWT7-DMI-based DMI strategy was a translatable approach for BC diagnosis and resection and could potentially lower the BC recurrence rate.

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Vetschera P et al.

Characterization of reversibly switchable fluorescent proteins (rsFPs) in optoacoustic imaging

Other ApplicationsPreclinicalMSOT

Reversibly switchable fluorescent proteins (rsFPs) have had a revolutionizing effect on life science imaging due to their contribution to subdiffraction-resolution optical microscopy (nanoscopy). Initial studies showed that their use as labels could also be highly beneficial for emerging Photo- or Optoacoustic imaging. It could be shown that their use in Optoacoustics i) strongly improves the imaging CNR due to modulation and locked-in detection, ii) facilitates fluence calibration affording precise measurements of physiological parameters and finally iii) could boost spatial resolution following similar concepts as used for nanoscopy. However, rsFPs show different photophysical behavior in optoacoustics than in optical microscopy because optoacoustics requires pulsed illumination and depends on signal generation via non-radiative energy decay channels. This implies that rsFPs optimized for fluorescence imaging may not be ideal for optoacoustics. Here, we analyze the photophysical behavior of a broad range of rsFPs with optoacoustics and analyze how the experimental factors central to optoacoustic imaging influence the different types of rsFPs. Finally, we discuss how knowledge of the switching behavior can be exploited for various OA imaging approaches using sophisticate temporal unmixing schemes.

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Samykutty A et al.

Optoacoustic imaging identifies ovarian cancer using a microenvironment targeted theranostic wormhole mesoporous silica nanoparticle

NanoCancerPreclinicalMSOT

At the intersection of the newly emerging fields of optoacoustic imaging and theranostic nanomedicine, promising clinical progress can be made in dismal prognosis of ovarian cancer. An acidic pH targeted wormhole mesoporous silica nanoparticle (V7-RUBY) was developed to serve as a novel tumor specific theranostic nanoparticle detectable using multispectral optoacoustic tomographic (MSOT) imaging. We report the synthesis of a small, < 40 nm, biocompatible asymmetric wormhole pore mesoporous silica core particle that has both large loading capacity and favorable release kinetics combined with tumor-specific targeting and gatekeeping. V7-RUBY exploits the acidic tumor microenvironment for tumor-specific targeting and tumor-specific release. In vitro, treatment with V7-RUBY containing either paclitaxel or carboplatin resulted in increased cell death at pH 6.6 in comparison to drug alone (p < 0.0001). In orthotopic ovarian xenograft mouse models, V7-RUBY containing IR780 was specifically detected within the tumor 7X and 4X higher than the liver and >10X higher than in the kidney using both multispectral optoacoustic tomography (MSOT) imaging with secondary confirmation using near infrared fluorescence imaging (p < 0.0004). The V7-RUBY system carrying a cargo of either contrast agent or an anti-neoplastic drug has the potential to become a theranostic nanoparticle which can improve both diagnosis and treatment of ovarian cancer.

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Tang X et al.

Gold nanorods together with HSP inhibitor-VER-155008 micelles for colon cancer mild-temperature photothermal therapy

NanoCancerPreclinicalMSOT

Enhancing the heat-sensitivity of tumor cells provides an alternative solution to maintaining the therapeutic outcome of photothermal therapy (PTT). In this study, we constructed a therapeutic system, which was composed of methoxy-polyethylene-glycol-coated-gold-nanorods (MPEG-AuNR) and VER-155008-micelles, to evaluate the effect of VER-155008 on the sensitivity of tumor cells to heat, and further investigate the therapeutic outcome of MPEG-AuNR mediated PTT combined with VER-155008- micelles. VER-155008- micelles down-regulate the expression of heat shock proteins and attenuate the heat-resistance of tumor cell. The survival of HCT116 cells treated with VER-155008- micelles under 45 °C is equal to that treated with high temperature hyperthermia (55 °C) in vitro. Furthermore, we proved either the MPEG-AuNR or VER-155008- micelles can be accumulate in the tumor site by photoacoustic imaging and fluorescent imaging. In vivo anti-cancer evaluation showed that tumor size remarkably decreased (smaller than 100 mm3 or vanished) when treated with combing 45 °C mild PTT system, which contrasted to the tumor size when treated with individual 45 °C mild PTT (around 500 nm3) or normal saline as control (larger than 2000 nm3). These results proved that the VER-155008- micelles can attenuate the heat-resistance of tumor cells and enhance the therapeutic outcome of mild-temperature photothermal therapy.

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Zhang J et al.

Biocompatible semiconducting polymer nanoparticles as robust photoacoustic and photothermal agents revealing the effects of chemical structure on high photothermal conversion efficiency

NanoCancerPharmacokineticsPreclinicalMSOT

Understanding the relationship between polymer chemical structure and its performance of photoacoustic imaging (PAI) and photothermal therapy (PTT) is important for developing ideal PAI/PTT agents. In this report, four semiconducting polymer nanoparticles (SPNs) with different donor-acceptor architectures are self-assembled for highly effective PAI-guided PTT. In particular, SPN1 with the longest π-conjugation length and the highest mass extinction coefficient which are beneficial for intramolecular charge transfer as well as light harvesting, exhibits the highest photothermal conversion efficiency up to 52.6%. Moreover, the as-prepared SPN1 possess good water-dispersibility, robust size-stability and excellent photothermal properties. Furthermore, the SPN1 not only exhibits a remarkable cancer cell-killing ability but also shows a prominent tumor inhibition capacity. Finally, the as-prepared water-dispersible SPN1 displays good biocompatibility and biosafety, making it a promising candidate for future biomedical applications. Considering the plenty of near-infrared absorbing semiconducting polymer available, our work provides fundamental insights for rational design and preparation of highly efficient SPN-based PAI/PTT agents for cancer theranostics.

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Xiao TG et al.

Applying dynamic contrast enhanced MSOT imaging to intratumoral pharmacokinetic modeling

PharmacokineticsPreclinicalMSOT

Examining the dynamics of an agent in the tumor microenvironment can offer critical insights to the influx rate and accumulation of the agent. Intratumoral kinetic characterization in the in vivo setting can further elicudate distribution patterns and tumor microenvironment. Dynamic contrast-enhanced Multispectral Optoacoustic Tomographic imaging (DCE-MSOT) acquires serial MSOT images with the administration of an exogenous contrast agent over time. We tracked the dynamics of a tumor-targeted contrast agent, HypoxiSense 680 (HS680), in breast xenograft mouse models using MSOT. Arterial input function (AIF) approach with MSOT imaging allowed for tracking HS680 dynamics within the mouse. The optoacoustic signal for HS680 was quantified using the ROI function in the ViewMSOT software. A two-compartment pharmacokinetics (PK) model constructed in MATLAB to fit rate parameters. The contrast influx (kin) and outflux (kout) rate constants predicted are kin = 1.96 × 10−2 s-1 and kout = 9.5 × 10-3 s-1 (R = 0.9945).

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Zhang H et al.

Monitoring the Opening and Recovery of the Blood-Brain Barrier with Noninvasive Molecular Imaging by Biodegradable Ultrasmall Cu2- xSe Nanoparticles

NanoNeuroPreclinicalMSOT

The reversible and controllable opening and recovery of the blood-brain barrier (BBB) is crucial for the treatment of brain diseases, and it is a big challenge to noninvasively monitor these processes. In this article, dual-modal photoacoustic imaging and single-photon-emission computed tomography imaging based on ultrasmall Cu2- xSe nanoparticles (3.0 nm) were used to noninvasively monitor the opening and recovery of the BBB induced by focused ultrasound in living mice. The ultrasmall Cu2- xSe nanoparticles were modified with poly(ethylene glycol) to exhibit a long blood circulation time. Both small size and long blood circulation time enable them to efficiently penetrate into the brain with the assistance of ultrasound, which resulted in a strong signal at the sonicated site and allowed for photoacoustic and single-photon emission computed tomography imaging monitoring the recovery of the opened BBB. The results of biodistribution, blood routine examination, and histological staining indicate that the accumulated Cu2- xSe nanoparticles could be excreted from the brain and other major organs after 15 days without causing side effects. By the combination of the advantages of noninvasive molecular imaging and focused ultrasound, the ultrasmall biocompatible Cu2- xSe nanoparticles holds great potential for the diagnosis and therapeutic treatment of brain diseases.

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Ma T et al.

"Smart" Nanoprobes for Visualization of Tumor Microenvironments

NanoCancerPreclinicalMSOT

Physiological parameters in tumor microenvironments, including hypoxia, low extracellular pH, enzymes, reducing conditions, and so on, are closely associated with the proliferation, angiogenesis, invasion, and metastasis of cancer, and impact the therapeutic administrations. Therefore, monitoring the tumor microenvironment is significant for diagnosing tumors, predicting the invasion potential, evaluating therapeutic efficacy, planning the treatment, and cancer prognostics. Noninvasive molecular imaging technologies combined with novel “smart” nanoparticle-based activatable probes provide a feasible approach to visualize tumor-associated microenvironment factors. This review summarizes recent achievements in the designs of “smart” molecular imaging nanoprobes responding to the tumor microenvironment-related features, and highlights the state of the art in tumor heterogeneity imaging.

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Roberts S et al.

Sonophore-enhanced nanoemulsions for optoacoustic imaging of cancer

NanoCancerPreclinicalMSOT

Optoacoustic imaging offers the promise of high spatial resolution and, at the same time, penetration depths well beyond the conventional optical imaging technologies, advantages that would be favorable for a variety of clinical applications. However, similar to optical fluorescence imaging, exogenous contrast agents, known as sonophores, need to be developed for molecularly targeted optoacoustic imaging. Despite numerous optoacoustic contrast agents that have been reported, there is a need for more rational design of sonophores. Here, using a library screening approach, we systematically identified and evaluated twelve commercially available near-infrared (690–900 nm) and highly absorbing dyes for multi-spectral optoacoustic tomography (MSOT). In order to achieve more accurate spectral deconvolution and precise data quantification, we sought five practical mathematical methods, namely direct classical least squares based on UV-Vis (UV/Vis-DCLS) or optoacoustic (OA-DCLS) spectra, non-negative LS (NN-LS), independent component analysis (ICA) and principal component analysis (PCA). We found that OA-DCLS is the most suitable method, allowing easy implementation and sufficient accuracy for routine analysis. Here, we demonstrate for the first time that our biocompatible nanoemulsions (NEs), in combination with near-infrared and highly absorbing dyes, enable non-invasive in vivo MSOT detection of tumors. Specifically, we found that NE-IRDye QC1 offers excellent optoacoustic performance and detection compared to related near-infrared NEs. We demonstrate that when loaded with low fluorescent or dark quencher dyes, NEs represent a flexible and new class of exogenous sonophores suitable for non-invasive pre-clinical optoacoustic imaging.

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Masthoff M et al.

Multispectral optoacoustic tomography of systemic sclerosis

SkinClinicalMSOT

The study aimed to evaluate the clinical feasibility of hybrid ultrasound (US)/ multispectral optoacoustic tomography (MSOT) for assessing microvascular dysfunction in systemic sclerosis (SSc). A handheld US/MSOT imaging system was applied for imaging patients diagnosed with SSc (n=7) and healthy volunteers (n=8). Semiquantitative MSOT values for deoxygenated (HbR), oxygenated (HbO2 ) and total haemoglobin (HbT) were analysed for subcutaneous finger tissue of both hands (8 fingers per subject, 120 fingers in total) and used to assess disease activity (progressive vs. stable). Grouped data were compared by one-way nested ANOVA, Tukey post-hoc test as well as students t-test were used for statistical analysis. Subcutaneous finger tissue of patients with SSc provided significantly lower MSOT values for HbO2 (26.16±0.71 vs. 38.2±1.54, p=0.023) and HbT (55.92±1.62 vs. 72.46±1.90, p=0.018) compared to healthy volunteers. Patients with progressive SSc had significantly lower MSOT values compared to patients with stable disease and healthy volunteers. This pilot study shows the feasibility of MSOT imaging to resolve microvascular dysfunction in SSc as a marker of disease activity. By providing biological tissue properties not revealed by other imaging modalities, MSOT might help to grade SSc non-invasively and monitor early therapy response.

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Comenge J et al.

Multimodal cell tracking from systemic administration to tumour growth by combining gold nanorods and reporter genes

CancerPreclinicalMSOT

Understanding the fate of exogenous cells after implantation is important for clinical applications. Preclinical studies allow imaging of cell location and survival. Labelling with nanoparticles enables high sensitivity detection, but cell division and cell death cause signal dilution and false positives. By contrast, genetic reporter signals are amplified by cell division. Here, we characterise lentivirus-based bi-cistronic reporter gene vectors and silica-coated gold nanorods (GNRs) as synergistic tools for cell labelling and tracking. Co-expression of the bioluminescence reporter luciferase and the optoacoustic reporter near-infrared fluorescent protein iRFP720 enabled cell tracking over time in mice. Multispectral optoacoustic tomography (MSOT) showed immediate biodistribution of GNR-labelled cells after intracardiac injection and successive clearance of GNRs (day 1-15) with high resolution, while optoacoustic iRFP720 detection indicated tumour growth (day 10-40). This multimodal cell tracking approach could be applied widely for cancer and regenerative medicine research to monitor short- and long-term biodistribution, tumour formation and metastasis.

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Abeyakoon O et al.

Optoacoustic Imaging Detects Hormone-Related Physiological Changes of Breast Parenchyma

Breast CancerClinicalMSOT

PURPOSE : Optoacoustic imaging with ultrasound (OPUS) can assess in-vivo perfusion/oxygenation through surrogate measures of oxy, deoxy and total hemoglobin content in tissues. The primary aim of our study was to evaluate the ability of OPUS to detect physiological changes in the breast during the menstrual cycle and to determine qualitative/quantitative metrics of normal parenchymal tissue in pre-/post-menopausal women. The secondary aim was to assess the technique’s repeatability.

MATERIALS AND METHODS : We performed a prospective ethically approved study in volunteers using OPUS (700, 800 and 850 nm wavelengths) in the proliferative/follicular and secretory phase of the menstrual cycle. Regions of interest (ROIs) were drawn on the most superficial region of fibroglandular tissue and same-day intra-observer repeatability was assessed. We used t-tests to interrogate differences in the OPUS measurements due to hormonal changes and interclass correlation coefficients/Bland-Altman plots to evaluate the repeatability of mean ROI signal intensities.

RESULTS : 22 pre-menopausal and 8 post-menopausal volunteers were recruited. 21 participants underwent repeatability examinations. OPUS intensity values were significantly higher (p < 0.0001) at all excitation wavelengths in the secretory compared to the proliferative/follicular phase. Post-menopausal volunteers showed similar optoacoustic values to the proliferative/follicular phase of pre-menopausal volunteers. The repeatability of the technique was comparable to other handheld ultrasound modalities.

CONCLUSION : OPUS detects changes in perfusion/vascularity related to the menstrual cycle and menopausal status of breast parenchyma.

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Han Z et al.

An Innovation for Treating Orthotopic Pancreatic Cancer by Preoperative Screening and Imaging-Guided Surgery

CancerPreclinicalMSOT

PURPOSE : Pancreatic cancer is still associated with a poor outcome and low patient quality of life, which are mainly attributed to the late detection and requirement of distal pancreatectomy with extended resection of pancreatic tumors. Therefore, novel strategies for early screening and precise tumor resection are urgently needed. In this study, we evaluated the feasibility of a low-density lipoprotein receptor (LDLR)-targeted small-molecule contrast agent (peptide-22-Cy7) for early screening with photoacoustic tomography and near-infrared (NIR) imaging as guided surgical navigation to achieve precise resection.

PROCEDURE : Normal pancreatic cells (HPDE6-C7) and cancer cells (PANC-1) were respectively used in the in vitro targeting evaluations. The ability of peptide-22-Cy7 for preoperative in vivo pancreatic tumor detection was investigated in a mouse orthotopic pancreatic cancer model (n = 10) using photoacoustic tomography; 18 tumor-bearing mice were further divided into three groups for different treatments. After intravenous injection of peptide-22-Cy7, surgical navigation was conducted through laparotomy. Histopathological analysis was used to further confirm the tumor area and the state of surgical margins.

RESULTS : Flow cytometry demonstrated that peptide-22 is highly specific to pancreatic cancer cells, with a fluorescence intensity of approximately 87.3 %. Orthotopic pancreatic tumors with a size of 4 mm could be accurately detected by photoacoustic tomography. Surgical navigation effectively achieved R0 resection and minimized the range of resection, which led to increased body weight of the mice following surgery.

CONCLUSION : Overall, our newly developed targeted contrast agent facilitated the accurate positioning and resection of pancreatic tumors. Photoacoustic tomography and optical imaging-guided surgical navigation may be a novel direction for improving the survival, quality of life, and disease management of pancreatic cancer patients.

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Yücel YH et al.

Active Lymphatic Drainage From the Eye Measured by Noninvasive Photoacoustic Imaging of Near-Infrared Nanoparticles

VascularPreclinicalMSOT

Purpose : To visualize and quantify lymphatic drainage of aqueous humor from the eye to cervical lymph nodes in the dynamic state.

Methods : A near-infrared tracer was injected into the right eye anterior chamber of 10 mice under general anesthesia. Mice were imaged with photoacoustic tomography before and 20 minutes, 2, 4, and 6 hours after injection. Tracer signal intensity was measured in both eyes and right and left neck lymph nodes at every time point and signal intensity slopes were calculated. Slope differences between right and left eyes and right and left nodes were compared using paired t-test. Neck nodes were examined with fluorescence optical imaging and histologically for the presence of tracer.

Results : Following right eye intracameral injection of tracer, an exponential decrease in tracer signal was observed from 20 minutes to 6 hours in all mice. Slope differences of the signal intensity between right and left eyes were significant (P < 0.001). Simultaneously, increasing tracer signal was observed in the right neck node from 20 minutes to 6 hours. Slope differences of the signal intensity between right and left neck nodes were significant (P = 0.0051). Ex vivo optical fluorescence imaging and histopathologic examination of neck nodes confirmed tracer presence within submandibular nodes.

Conclusions : Active lymphatic drainage of aqueous from the eye to cervical lymph nodes was measured noninvasively by photoacoustic imaging of near-infrared nanoparticles. This unique in vivo assay may help to uncover novel drugs that target alternative outflow routes to lower IOP in glaucoma and may provide new insights into lymphatic drainage in eye health and disease.

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Neuschmelting V et al.

Dual-Modality Surface-Enhanced Resonance Raman Scattering and Multispectral Optoacoustic Tomography Nanoparticle Approach for Brain Tumor Delineation.

NanoCancerNeuroPreclinicalMSOT

Difficulty in visualizing glioma margins intraoperatively remains a major issue in the achievement of gross total tumor resection and, thus, better clinical outcome of glioblastoma (GBM) patients. Here, the potential of a new combined optical + optoacoustic imaging method for intraoperative brain tumor delineation is investigated. A strategy using a newly developed gold nanostar synthesis method, Raman reporter chemistry, and silication method to produce dual-modality contrast agents for combined surface-enhanced resonance Raman scattering (SERRS) and multispectral optoacoustic tomography (MSOT) imaging is devised. Following intravenous injection of the SERRS-MSOT-nanostars in brain tumor bearing mice, sequential MSOT imaging is performed in vivo and followed by Raman imaging. MSOT is able to accurately depict GBMs three-dimensionally with high specificity. The MSOT signal is found to correlate well with the SERRS images. Because SERRS enables uniquely sensitive high-resolution surface detection, it could represent an ideal complementary imaging modality to MSOT, which enables real-time, deep tissue imaging in 3D. This dual-modality SERRS-MSOT-nanostar contrast agent reported here is shown to enable high precision depiction of the extent of infiltrating GBMs by Raman- and MSOT imaging in a clinically relevant murine GBM model and could pave new ways for improved image-guided resection of brain tumors.

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O'Kelly D et al.

Tomographic breathing detection: a method to noninvasively assess in situ respiratory dynamics

Other ApplicationsPreclinicalMSOT

Physiological monitoring is a critical aspect of in vivo experimentation, particularly imaging studies. Physiological monitoring facilitates gated acquisition of imaging data and more robust experimental interpretation but has historically required additional instrumentation that may be cumbersome. As frame rates have increased, imaging methods have been able to capture ever more rapid dynamics, passing the Nyquist sampling rate of most physiological processes and allowing the capture of motion, such as breathing. With this transition, image artifacts have also changed their nature; rather than intraframe motion causing blurring and deteriorating resolution, interframe motion does not affect individual frames and may be recovered as useful information from an image time series. We demonstrate a method that takes advantage of interframe movement for detection of gross physiological motion in real-time image sequences. We further demonstrate the ability of the method, dubbed tomographic breathing detection to quantify the dynamics of respiration, allowing the capture of respiratory information pertinent to anesthetic depth monitoring. Our example uses multispectral optoacoustic tomography, but it will be widely relevant to other technologies.

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Sun J et al.

Ultrasmall endogenous biopolymer nanoparticles for magnetic resonance/photoacoustic dual-modal imaging-guided photothermal therapy

NanoCancerPreclinicalMSOT

Multi-modal imaging-guided photothermal therapy (PTT) has aroused extensive attention in biomedical research recently because it can provide more comprehensive information for accurate diagnosis and treatment. In this research, the manganese ion chelated endogenous biopolymer melanin nanoparticles were successfully prepared for magnetic resonance (MR)/photoacoustic (PA) dual-modal imaging-guided PTT. The obtained nanoparticles with an ultrasmall size of about 3.2 nm exhibited negligible cytotoxicity, high relaxivity for MRI, an excellent photothermal effect and PA activity. Moreover, in vivo MRI and PAI results all demonstrated that the nanoparticles began to diffuse in the blood after intratumoral injection into tumor-bearing mice and could spread throughout the whole tumor region at 3 h, indicating the optimal treatment time. The subsequent photothermal therapy of cancer cells in vivo was carried out and the result showed that tumor growth could be effectively inhibited without inducing any observed side effects. Besides, melanin as an endogenous biopolymer has native biocompatibility and biodegradability, and it can be excreted through both renal and hepatobiliary pathways after treatment. Therefore, the melanin-Mn nanoparticles may assist in better indicating the optimal treatment time, monitoring the therapeutic process and enhancing the therapeutic effect and showed great clinical translation potential for cancer diagnosis and therapy.

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Sigmund F et al.

Bacterial encapsulins as orthogonal compartments for mammalian cell engineering

Infectious DiseasePreclinicalMSOT

We genetically controlled compartmentalization in eukaryotic cells by heterologous expression of bacterial encapsulin shell and cargo proteins to engineer enclosed enzymatic reactions and size-constrained metal biomineralization. The shell protein (EncA) from Myxococcus xanthus auto-assembles into nanocompartments inside mammalian cells to which sets of native (EncB,C,D) and engineered cargo proteins self-target enabling localized bimolecular fluorescence and enzyme complementation. Encapsulation of the enzyme tyrosinase leads to the confinement of toxic melanin production for robust detection via multispectral optoacoustic tomography (MSOT). Co-expression of ferritin-like native cargo (EncB,C) results in efficient iron sequestration producing substantial contrast by magnetic resonance imaging (MRI) and allowing for magnetic cell sorting. The monodisperse, spherical, and iron-loading nanoshells are also excellent genetically encoded reporters for electron microscopy (EM). In general, eukaryotically expressed encapsulins enable cellular engineering of spatially confined multicomponent processes with versatile applications in multiscale molecular imaging, as well as intriguing implications for metabolic engineering and cellular therapy.

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Qi J et al.

Light-driven transformable optical agent with adaptive functions for boosting cancer surgery outcomes

CancerPreclinicalMSOT

Fluorescence and photoacoustic imaging have different advantages in cancer diagnosis; however, combining effects in one agent normally requires a trade-off as the mechanisms interfere. Here, based on rational molecular design, we introduce a smart organic nanoparticle whose absorbed excitation energy can be photo-switched to the pathway of thermal deactivation for photoacoustic imaging, or to allow opposed routes for fluorescence imaging and photodynamic therapy. The molecule is made of a dithienylethene (DTE) core with two surrounding 2-(1-(4-(1,2,2-triphenylvinyl)phenyl)ethylidene)malononitrile (TPECM) units (DTE-TPECM). The photosensitive molecule changes from a ring-closed, for photoacoustic imaging, to a ring-opened state for fluorescence and photodynamic effects upon an external light trigger. The nanoparticles’ photoacoustic and fluorescence imaging properties demonstrate the advantage of the switch. The use of the nanoparticles improves the outcomes of in vivo cancer surgery using preoperative photoacoustic imaging and intraoperative fluorescent visualization/photodynamic therapy of residual tumours to ensure total tumour removal.

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Ma X et al.

Multimodality Molecular Imaging-Guided Tumor Border Delineation and Photothermal Therapy Analysis Based on Graphene Oxide-Conjugated Gold Nanoparticles Chelated with Gd

NanoCancerPreclinicalMSOT

Tumor cell complete extinction is a crucial measure to evaluate antitumor efficacy. The difficulties in defining tumor margins and finding satellite metastases are the reason for tumor recurrence. A synergistic method based on multimodality molecular imaging needs to be developed so as to achieve the complete extinction of the tumor cells. In this study, graphene oxide conjugated with gold nanostars and chelated with Gd through 1,4,7,10-tetraazacyclododecane-N,N′,N,N′-tetraacetic acid (DOTA) (GO-AuNS-DOTA-Gd) were prepared to target HCC-LM3-fLuc cells and used for therapy. For subcutaneous tumor, multimodality molecular imaging including photoacoustic imaging (PAI) and magnetic resonance imaging (MRI) and the related processing techniques were used to monitor the pharmacokinetics process of GO-AuNS-DOTA-Gd in order to determine the optimal time for treatment. For orthotopic tumor, MRI was used to delineate the tumor location and margin in vivo before treatment. Then handheld photoacoustic imaging system was used to determine the tumor location during the surgery and guided the photothermal therapy. The experiment result based on orthotopic tumor demonstrated that this synergistic method could effectively reduce tumor residual and satellite metastases by 85.71% compared with the routine photothermal method without handheld PAI guidance. These results indicate that this multimodality molecular imaging-guided photothermal therapy method is promising with a good prospect in clinical application.

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Hupple CW et al.

A light-fluence-independent method for the quantitative analysis of dynamic contrast-enhanced multispectral optoacoustic tomography (DCE MSOT)

PharmacokineticsPreclinicalMSOT

MultiSpectral Optoacoustic Tomography (MSOT) is an emerging imaging technology that allows for data acquisition at high spatial and temporal resolution. These imaging characteristics are advantageous for Dynamic Contrast Enhanced (DCE) imaging that can assess the combination of vascular flow and permeability. However, the quantitative analysis of DCE MSOT data has not been possible due to complications caused by wavelength-dependent light attenuation and variability in light fluence at different anatomical locations. In this work we present a new method for the quantitative analysis of DCE MSOT data that is not biased by light fluence. We have named this method the two-compartment linear standard model (2C-LSM) for DCE MSOT.

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Mercep E et al.

Imaging of blood flow and oxygen state with a multi-segment optoacoustic ultrasound array

VascularClinicalMSOT

Changes in hemodynamic parameters are directly linked to biological function and physiological activity. Characterization of hemodynamics is commonly performed by Doppler ultrasound, which provides accurate measurements of blood flow velocity. Multi-spectral optoacoustic tomography is rapidly undergoing clinical translation fostered by its unique and complementary capacity for label-free mapping of the blood volume and the distribution of oxy- and deoxy-hemoglobin in blood. Here we report on a hybrid optoacoustic and ultrasound imaging approach that enables multi-modal imaging of blood flow and oxygen state using a multi-segment detector array. We further demonstrate rendering of multi-modal pulse-echo ultrasound, multi-spectral optoacoustic tomography, and color Doppler images from carotid artery of a healthy subject.

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Luís Dean-Ben X

Localization optoacoustic tomography

TechnologyPreclinicalMSOT

Localization-based imaging has revolutionized fluorescence optical microscopy and has also enabled unprecedented ultrasound images of microvascular structures in deep tissues. Herein, we introduce a new concept of localization optoacoustic tomography (LOT) that employs rapid sequential acquisition of three-dimensional optoacoustic images from flowing absorbing particles. We show that the new method enables breaking through the spatial resolution barrier of acoustic diffraction while further enhancing the visibility of structures under limited-view tomographic conditions. Given the intrinsic sensitivity of optoacoustics to multiple hemodynamic and oxygenation parameters, LOT may enable a new level of performance in studying functional and anatomical alterations of microcirculation.

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Chan XHD et al.

Multimodal imaging approach to monitor browning of adipose tissue in vivo

PharmacokineticsPreclinicalMSOT

The discovery that white adipocytes can undergo a browning process to become metabolically active beige cells has attracted significant interest in the fight against obesity. However, the study of adipose browning has been impeded by a lack of imaging tools that allow longitudinal and noninvasive monitoring of this process in vivo. Here, we report a preclinical imaging approach to detect development of beige adipocytes during adrenergic stimulation. In this approach, we expressed near-infrared fluorescent protein, iRFP720, driven under an uncoupling protein-1 (Ucp1) promoter in mice by viral transduction, and used multispectral optoacoustic imaging technology with ultrasound tomography (MSOT-US) to assess adipose beiging during adrenergic stimulation. We observed increased photoacoustic signal at 720 nm, coupled with attenuated lipid signals in stimulated animals. As a proof of concept, we validated our approach against hybrid positron emission tomography combined with magnetic resonance (PET/MR) imaging modality, and quantified the extent of adipose browning by MRI-guided segmentation of 2-deoxy-2-18F-fluoro-d-glucose uptake signals. The browning extent detected by MSOT-US and PET/MR are well correlated with Ucp1 induction. Taken together, these systems offer great opportunities for preclinical screening aimed at identifying compounds that promote adipose browning and translation of these discoveries into clinical studies of humans.

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Ni R et al.

Cortical hypoperfusion and reduced cerebral metabolic rate of oxygen in the arcAβ mouse model of Alzheimer’s disease

NeuroPreclinicalMSOT

The effect of cerebral amyloidosis on cerebral hemodynamics was investigated with photoacoustic tomography (PAT) and magnetic resonance imaging (MRI). First, the sensitivity and robustness of PAT for deriving metrics of vascular and tissue oxygenation in the murine brain was assessed in wild-type mice with a hyperoxia-normoxia challenge. Secondly, cerebral oxygenation was assessed in young and aged arcAβ mice and wild-type controls with PAT, while cerebral blood flow (CBF) was determined by perfusion MRI. The investigations revealed that PAT can sensitively and robustly detect physiological changes in vascular and tissue oxygenation. An advanced stage of cerebral amyloidosis in arcAβ mice is accompanied by a decreases in cortical CBF and the cerebral metabolic rate of oxygen (CMRO2), as oxygen extraction fraction (OEF) has been found unaffected. Thus, PAT constitutes a robust non-invasive tool for deriving metrics of tissue oxygenation, extraction and metabolism in the mouse brain under physiological and disease states.

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Sun M et al.

Tumour-homing chimeric polypeptide-conjugated polypyrrole nanoparticles for imaging-guided synergistic photothermal and chemical therapy of cancer

NanoCancerPreclinicalMSOT

Near-infrared (NIR)-absorbing conjugated polymer nanoparticles are interesting for imaging-guided combination therapy, especially for synergistic photothermal therapy and chemotherapy; however, most of them target tumours passively through the enhanced permeability and retention (EPR) effect, leading to low utilization efficiency. To address this problem, we report an active tumour-targeting strategy of tumour-homing chimeric polypeptide-conjugated NIR-absorbing conjugated-polymer nanoparticles as a new class of drug nanocarriers for imaging-guided combination therapy of cancer. Methods : A tumour-homing chimeric polypeptide C-ELP-F3 was genetically engineered, and chemoselectively conjugated to polypyrrole (PPy) nanoparticles via a facile thiol-maleimide coupling reaction to form ELP-F3 conjugated PPy (PPy-ELP-F3) nanoparticles. Doxorubicin (DOX) was physically adsorbed onto PPy-ELP-F3 nanoparticles to yield DOX-loaded PPy-ELP-F3 (DOX/PPy-ELP-F3) nanoparticles. The physicochemical properties of DOX/PPy-ELP-F3 were characterized. The pharmacokinetics of DOX/PPy-ELP-F3 was studied in a mouse model. The photoacoustic imaging and photothermal imaging of tumours were tested in a melanoma-bearing mouse model. The photothermal-chemical combination therapy of tumours was investigated by using melanoma cells in vitro and in a melanoma-bearing mouse model. Results : DOX/PPy-ELP-F3 nanoparticles showed enhanced cytotoxicity to melanoma cells in vitro and improved tumour-targeting efficiency in vivo, as compared with both DOX/PPy-ELP nanoparticles without the tumour-homing function and free DOX. The photothermal effect of DOX/PPy-ELP-F3 nanoparticles could accelerate the release of DOX from PPy-ELP-F3. Under the guidance of photoacoustic and photothermal imaging, the synergy of photothermal and chemical therapy could completely abolish tumours without detectable systemic toxicity. Conclusion : Tumour-homing chimeric polypeptide-conjugated NIR-absorbing conjugated-polymer nanoparticles are promising as a new multifunctional drug delivery platform for highly-efficient imaging guided combination therapy.

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Rabender CS et al.

Sepiapterin Enhances Tumor Radio- and Chemosensitivities by Promoting Vascular Normalization

CancerPreclinicalMSOT

Previously, we demonstrated that nitric oxide (NO) synthase (NOS) is uncoupled in a wide range of solid tumors and that restoring NOS coupling with the tetrahydrobiopterin precursor sepiapterin (SP) inhibits tumor progression. Endothelial dysfunction characterizes the poorly functional vasculature of solid tumors, and since NO is critical for regulation of endothelial function we asked whether SP, by recoupling NOS, improves tumor vasculature structure and function-enhancing chemotherapeutic delivery and response to radiotherapy. MMTV-neu mice with spontaneous breast tumors were treated with SP by oral gavage and evaluated by multispectral optoacoustic tomographic analysis of tumor HbO2 and by tissue staining for markers of hypoxia, blood perfusion, and markers of endothelial and smooth muscle proteins. Recoupling tumor NOS activity results in vascular normalization observed as reduced tumor hypoxia, improved tumor percentage of HbO2 and perfusion, as well as increased pericyte coverage of tumor blood vessels. The normalized vasculature and improved tumor oxygenation led to a greater than 2-fold increase in radiation-induced apoptosis compared with radiation or SP alone. High-performance liquid chromatography analysis of tumor doxorubicin levels showed a greater than 50% increase in doxorubicin uptake and a synergistic effect on tumor cell apoptosis. This study highlights for the first time the importance of NOS uncoupling and endothelial dysfunction in the development of tumor vasculature and presents a new approach for improving the tumoricidal efficacies of chemotherapy and radiotherapy.

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Quiros-Gonzalez I et al.

Optoacoustics delineates murine breast cancer models displaying angiogenesis and vascular mimicry

CancerPreclinicalMSOT

BACKGROUND : Optoacoustic tomography (OT) of breast tumour oxygenation is a promising new technique, currently in clinical trials, which may help to determine disease stage and therapeutic response. However, the ability of OT to distinguish breast tumours displaying different vascular characteristics has yet to be established. The aim of the study is to prove OT as a sensitive technique for differentiating breast tumour models with manifestly different vasculatures.

METHODS : Multispectral OT (MSOT) was performed in oestrogen-dependent (MCF-7) and oestrogen-independent (MDA-MB-231) orthotopic breast cancer xenografts. Total haemoglobin (THb) and oxygen saturation (SO2MSOT) were calculated. Pathological and biochemical evaluation of the tumour vascular phenotype was performed for validation.

RESULTS : MCF-7 tumours show SO2MSOT similar to healthy tissue in both rim and core, despite significantly lower THb in the core. MDA-MB-231 tumours show markedly lower SO2MSOT with a significant rim-core disparity. Ex vivo analysis revealed that MCF-7 tumours contain fewer blood vessels (CD31+) that are more mature (CD31+/aSMA+) than MDA-MB-231. MCF-7 presented higher levels of stromal VEGF and iNOS, with increased NO serum levels. The vasculogenic process observed in MCF-7 was consistent with angiogenesis, while MDA-MB-231 appeared to rely more on vascular mimicry.

CONCLUSIONS : OT is sensitive to differences in the vascular phenotypes of our breast cancer models.

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Berezhnoi A et al.

Assessing hyperthermia-induced vasodilation in human skin in vivo using optoacoustic mesoscopy

VascularClinicalRSOM

The aim of this study was to explore the unique imaging abilities of optoacoustic mesoscopy to visualize skin structures and microvasculature with the view of establishing a robust approach for monitoring heat-induced hyperemia in human skin in vivo. Using raster-scan optoacoustic mesoscopy (RSOM), we investigated whether optoacoustic (photoacoustic) mesoscopy can identify changes in skin response to local heating at microvasculature resolution in a cross-sectional fashion through skin in the human forearm. We visualized the heat-induced hyperemia for the first time with single-vessel resolution throughout the whole skin depth. We quantified changes in total blood volume in the skin and their correlation with local heating. In response to local heating, total blood volume increased 1.83- and 1.76-fold, respectively, in the volar and dorsal aspects of forearm skin. We demonstrate RSOM imaging of the dilation of individual vessels in the skin microvasculature, consistent with hyperemic response to heating at the skin surface. Our results demonstrate great potential of RSOM for elucidating the morphology, functional state and reactivity of dermal microvasculature, with implications for diagnostics and disease monitoring. Image: Cross-sectional view of skin microvasculature dilated in response to hyperthermia.

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Das A et al.

Impairment of an Endothelial NAD+-H2S Signaling Network Is a Reversible Cause of Vascular Aging

VascularPreclinicalMSOT

A decline in capillary density and blood flow with age is a major cause of mortality and morbidity. Understanding why this occurs is key to future gains in human health. NAD precursors reverse aspects of aging, in part, by activating sirtuin deacylases (SIRT1-SIRT7) that mediate the benefits of exercise and dietary restriction (DR). We show that SIRT1 in endothelial cells is a key mediator of pro-angiogenic signals secreted from myocytes. Treatment of mice with the NAD+ booster nicotinamide mononucleotide (NMN) improves blood flow and increases endurance in elderly mice by promoting SIRT1-dependent increases in capillary density, an effect augmented by exercise or increasing the levels of hydrogen sulfide (H2S), a DR mimetic and regulator of endothelial NAD+ levels. These findings have implications for improving blood flow to organs and tissues, increasing human performance, and reestablishing a virtuous cycle of mobility in the elderly.

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Nitkunanantharajah S et al.

Trackerless panoramic optoacoustic imaging: a first feasibility evaluation

TechnologyPreclinicalMSOT

PURPOSE : Optoacoustic imaging provides high spatial resolution and the possibility to image specific functional parameters in real-time, therefore positioning itself as a promising modality for various applications. However, despite these advantages, the applicability of real-time optoacoustic imaging is generally limited due to a relatively small field of view.

METHODS : With this work, we aim at presenting a path towards panoramic optoacoustic tomographic imaging without requiring additional sensors or position trackers. We propose a two-step seamless stitching method for the compounding of multiple datasets acquired with a real-time 3D optoacoustic imaging system within a panoramic scan. The employed workflow is specifically tailored to the image properties and respective challenges.

RESULTS : A comparison of the presented alignment on in-vivo data shows a mean error of [Formula: see text] compared to ground truth tracking data. The presented compounding scheme integrates the physical resolution of optoacoustic data and hence can provide improved contrast in comparison with other compounding approaches based on addition or averaging.

CONCLUSION : The proposed method can produce optoacoustic volumes with an enlarged field of view and improved quality compared to current methods in optoacoustic imaging. However, our study also shows challenges for panoramic scans. In this view, we discuss relevant properties, challenges, and opportunities and present an evaluation of the performance of the presented approach with different input data.

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Reber J et al.

Non-invasive Measurement of Brown Fat Metabolism Based on Optoacoustic Imaging of Hemoglobin Gradients

PharmacokineticsPreclinicalClinicalMSOT

Metabolism is a fundamental process of life. However, non-invasive measurement of local tissue metabolism is limited today by a deficiency in adequate tools for in vivo observations. We designed a multi-modular platform that explored the relation between local tissue oxygen consumption, determined by label-free optoacoustic measurements of hemoglobin, and concurrent indirect calorimetry obtained during metabolic activation of brown adipose tissue (BAT). By studying mice and humans, we show how video-rate handheld multi-spectral optoacoustic tomography (MSOT) in the 700-970 nm spectral range enables non-invasive imaging of BAT activation, consistent with positron emission tomography findings. Moreover, we observe BAT composition differences between healthy and diabetic tissues. The study consolidates hemoglobin as a principal label-free biomarker for longitudinal non-invasive imaging of BAT morphology and bioenergetics in situ. We also resolve water and fat components in volunteers, and contrast MSOT readouts with magnetic resonance imaging data.

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Ni R et al.

Noninvasive detection of acute cerebral hypoxia and subsequent matrix-metalloproteinase activity in a mouse model of cerebral ischemia using multispectral-optoacoustic-tomography

NeuroPreclinicalMSOT

Oxygen metabolism and matrix metalloproteinases (MMPs) play important roles in the pathophysiology of cerebral ischemia. Using multispectral optoacoustic tomography (MSOT) imaging, we visualized in vivo changes in cerebral tissue oxygenation during 1 h of transient middle cerebral artery occlusion (tMCAO) and at 48 h after reperfusion together with MMP activity using an MMP-activatable probe. The deoxyhemoglobin, oxyhemoglobin, and MMP signals were coregistered with structural magnetic resonance imaging data. The ipsi-/contralateral ratio of tissue oxygen saturation ([Formula: see text]) was significantly reduced during 1 h of tMCAO and recovered after 48 h of reperfusion in tMCAO compared with sham-operated mice ([Formula: see text] to 10 per group). A higher ipsi-/contralateral MMP signal ratio was detected at 48 h after reperfusion in the lesioned brain regions of tMCAO compared with the sham-operated animal ([Formula: see text] to 6 per group). Ex vivo near-infrared fluorescence imaging of MMP signal in brain slices was used to validate in vivo MSOT measurements. In conclusion, noninvasive MSOT imaging can provide visualization of hemodynamic alterations and MMP activity in a mouse model of cerebral ischemia.

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Yan C et al.

Concentration effect on large scale synthesis of high quality small gold nanorods and their potential role in cancer theranostics

NanoCancerPreclinicalMSOT

Cancer theranostics agents, such as gold nanorods, represent great potential in cancer therapy. However, the big size and the low yield of the gold nanorods reported previously have limited their clinical translation. Therefore, it is significant to develop a new method to prepare the small gold nanorods (width <8 nm) at larger scale. In this report, a modified seedless method was proposed based on the effect of precursor concentration assisted synthesis of high quality small gold nanorods at large scale. The obtained small gold nanorods exhibit high quality and dimension of (18 ± 5 nm) × (5 ± 1 nm). After modified with biological compatibility reagents, the small gold nanorods behave excellent photoacoustic imaging and photo-thermal therapy ability. These results manifest that the obtained small gold nanorods not only realize the improvements of previously limitations, also are thus supposed to pave the way to cancer theranostics in clinic application.

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Aguirre J et al.

Assessing nailfold microvascular structure with ultra-wideband raster-scan optoacoustic mesoscopy

VascularClinicalRSOM

Nailfold capillaroscopy, based on bright-field microscopy, is widely used to diagnose systemic sclerosis (SSc). However it cannot reveal information about venules and arterioles lying deep under the nailfold, nor can it provide detailed data about surface microvasculature when the skin around the nail is thick. These limitations reflect the fact that capillaroscopy is based on microscopy methods whose penetration depth is restricted to about 200 μm. We investigated whether ultra-wideband raster-scan optoacoustic mesoscopy (UWB-RSOM) can resolve small capillaries of the nailfold in healthy volunteers and compared the optoacoustic data to conventional capillaroscopy examinations. We quantified UWB-RSOM-resolved capillary density and capillary diameter as features that relate to SSc biomarkers, and we obtained the first three-dimensional, in vivo images of the deeper arterioles and venules. These results establish the potential of UWB-RSOM for analyzing SSc-relevant markers.

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Brannen A et al.

Correlation of 360-degree Surface Mapping In Vivo Bioluminescence with Multi-Spectral Optoacoustic Tomography in Human Xenograft Tumor Models

CancerPreclinicalMSOT

Pre-clinical monitoring of tumor growth and identification of distal metastasis requires a balance between accuracy and expediency. Bioluminescence imaging (BLI) is often used to track tumor growth but is primarily limited to planar 2-dimensional (2D) imaging. Consistent subject placement within a standard top-mounted, single-detector small animal imager is vital to reducing variability in repeated same-animal measures over time. Here, we describe a method for tracking tumor development using a multi-angle BLI and photo-acoustic workflow. We correlate serial caliper measurements and 2D BLI to 360° BLI and photo-acoustic datasets for the same animals. Full 360° BLI showed improved correlations with both volumes obtained from caliper measurements and photo-acoustic segmentation, as compared to planar BLI. We also determined segmented tumor volumes from photo-acoustic datasets more accurately reflects true excised tumors’ volumes compared to caliper measurements. Our results demonstrate the distinct advantages of both 360° surface mapping by BLI and photo-acoustic methodologies for non-invasive tracking of tumor growth in pre-clinical academic settings. Furthermore, our design is fully implementable in all top-mounted, single-detector imagers, thereby providing the opportunity to shift the paradigm away from planar BLI into rapid BLI tomography applications.

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Petrosyan T et al.

Rapid scanning wide-field clutter elimination in epi-optoacoustic imaging using comb LOVIT

TechnologyPreclinicalMSOT

Epi-style optoacoustic (OA) imaging provides flexibility by integrating the irradiation optics and ultrasound receiver, yet clutter generated by optical absorption near the probe obscures deep OA sources. Localised vibration tagging (LOVIT) retrieves OA signal from images that are acquired with and without a preceding ultrasonic pushing beam: Radiation force leads to a phase shift of signals coming from the focal area resulting in their visibility in a difference image, whereas clutter from outside the pushing beam is eliminated. Disadvantages of a single-focus approach are residual clutter from inside the pushing beam above the focus, and time-intensive scanning of the focus to retrieve a large field-of-view. To speed up acquisition, we propose to create multiple foci in parallel, forming comb-shaped ARF patterns. By subtracting OA images obtained with interleaved combs, this technique moreover results in greatly improved clutter reduction in phantoms mimicking optical, acoustic and elastic properties of breast tissue.

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Wang M et al.

Rational Design of Multifunctional Fe@γ-Fe2 O3 @H-TiO2 Nanocomposites with Enhanced Magnetic and Photoconversion Effects for Wide Applications: From Photocatalysis to Imaging-Guided Photothermal Cancer Therapy

NanoCancerPreclinicalMSOT

Titanium dioxide (TiO2 ) has been widely investigated and used in many areas due to its high refractive index and ultraviolet light absorption, but the lack of absorption in the visible-near infrared (Vis-NIR) region limits its application. Herein, multifunctional Fe@γ-Fe2 O3 @H-TiO2 nanocomposites (NCs) with multilayer-structure are synthesized by one-step hydrogen reduction, which show remarkably improved magnetic and photoconversion effects as a promising generalists for photocatalysis, bioimaging, and photothermal therapy (PTT). Hydrogenation is used to turn white TiO2 in to hydrogenated TiO2 (H-TiO2 ), thus improving the absorption in the Vis-NIR region. Based on the excellent solar-driven photocatalytic activities of the H-TiO2 shell, the Fe@γ-Fe2 O3 magnetic core is introduced to make it convenient for separating and recovering the catalytic agents. More importantly, Fe@γ-Fe2 O3 @H-TiO2 NCs show enhanced photothermal conversion efficiency due to more circuit loops for electron transitions between H-TiO2 and γ-Fe2 O3 , and the electronic structures of Fe@γ-Fe2 O3 @H-TiO2 NCs are calculated using the Vienna ab initio simulation package based on the density functional theory to account for the results. The reported core-shell NCs can serve as an NIR-responsive photothermal agent for magnetic-targeted photothermal therapy and as a multimodal imaging probe for cancer including infrared photothermal imaging, magnetic resonance imaging, and photoacoustic imaging.

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Zheng H et al.

Tyrosinase-Based Reporter Gene for Photoacoustic Imaging of MicroRNA-9 Regulated by DNA Methylation in Living Subjects

CancerPreclinicalMSOT

MicroRNAs (miRNAs) are a class of negative regulators of gene expression and play critical roles in various biological processes. Conventional approaches for detecting miRNAs, such as northern blotting, microarray, and real-time PCR, usually require the lysis of cell samples and could not provide the in vivo information about miRNAs in living organisms. Here, we designed a tyrosinase (TYR)-based reporter to monitor miR-9 expression that is regulated by DNA methylation in living cells and animals. During DNA methylation of A549 cells treated by 5-aza-2′-deoxycytidine (5-Aza-dC), the CMV/TYR-3xTS reporter-transfected cells demonstrated a gradual decrease in melanin content, TYR activity, and photoacoustic signal because of the gradual activation of miR-9 expression. The miR-9-regulated repression of TYR activity also resulted in a significant decrease in photoacoustic signal from the flank of mice with 5-Aza-dC treatment, whereas the bioluminescence signal from internal control had no obvious change. The TYR-based miRNA reporter may serve as a new imaging probe for monitoring the dynamic expression of miRNAs during various cellular or disease progression in cells and living animals.

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Sun T et al.

Second Near-Infrared Conjugated Polymer Nanoparticles for Photoacoustic Imaging and Photothermal Therapy

NanoCancerPreclinicalMSOT

Photothermal conversion in the second near-infrared (NIR-II) window allows deeper penetration and higher exposure to lasers, but examples of NIR-II photothermal agents are mainly formulated by inorganic compounds. In view of the underlying influence of inorganic materials, a novel NIR-II photothermal nanoagent based on a narrow band gap D-A conjugated polymer (TBDOPV-DT) with 2,2-bithiophene as the donor and thiophene-fused benzodifurandione-based oligo( p-phenylenevinylene) as the acceptor has been developed. More importantly, TBDOPV-DT nanoparticles (TBDOPV-DT NPs) are demonstrated to combine excellent photoacoustic imaging (PAI) and photothermal therapy (PTT) ability. TBDOPV-DT NPs exhibit dramatic photostability and heating reproducibility with a photothermal conversion efficiency of 50%. Especially, the NPs possess a remarkable PTT effect toward cancer cells in vitro and can eliminate tumor cells completely in vivo under 1064 nm laser irradiation, while no appreciable side effects have been observed. This study achieves PAI-guided cancer therapy and sheds light on the future of using organic polymer NPs for the NIR-II PTT of cancer.

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Hu DR et al.

Oxygen-generating Hybrid Polymeric Nanoparticles with Encapsulated Doxorubicin and Chlorin e6 for Trimodal Imaging-Guided Combined Chemo-Photodynamic Therapy

NanoCancerPreclinicalMSOT

The combination of chemotherapy with photodynamic therapy (PDT) has attracted broad attention as it can overcome limitations of conventional chemo-treatment by using different modes of action. However, the efficacy of PDT to treat solid tumors is severely affected by hypoxia in tumors.

Methods : In this study, we developed oxygen-generating theranostic nanoparticles (CDM NPs) by hierarchically assembling doxorubicin (DOX), chlorin e6 (Ce6) and colloidal manganese dioxide (MnO2) with poly (ε-caprolactone-co-lactide)-b-poly (ethylene glycol)-b-poly (ε-caprolactone-co-lactide) for treating breast cancer. The in vitro and in vivo antitumor efficacy and imaging performance were investigated.

Results : The theranostic nanoparticles showed high stability and biocompatibility both in vitro and in vivo. MnO2 within the nanoparticles could trigger decomposition of excessive endogenous H2O2 in the tumor microenvironment to generate oxygen in-situ to relieve tumor hypoxia. With enhanced oxygen generation, the PDT effect was significantly improved under laser-irradiation. More importantly, this effect together with that of DOX was able to dramatically promote the combined chemotherapy-PDT efficacy of CDM NPs in an MCF-7 tumor-bearing mouse model. Furthermore, the real-time tumor accumulation of the nanocomposites could be monitored by fluorescence imaging, photoacoustic (PA) imaging and magnetic resonance imaging (MRI).

Conclusion : The designed CDM NPs are expected to provide an alternative way of improving antitumor efficacy by combined chemo-PDT further enhanced by oxygen generation, and would have broad applications in cancer theranostics.

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Zhang S et al.

acancy engineering of Cu2−xSe nanoparticles with tunable LSPR and magnetism for dual-modal imaging guided photothermal therapy of cancer

NanoCancerPreclinicalMSOT

The vacancies in the semiconductor nanocrystals not only induce unique properties, but also provide spaces for engineering them with multifunctions by the introduction of other elements. Herein, the vacancy of Cu2−xSe nanoparticles was tuned by doping with magnetic ferric ions (Fe3+) at room temperature, and the position and intensity of the near-infrared localized surface plasmon resonance (LSPR) in the resultant nanostructure can be finely controlled by altering the feeding amount of Fe3+ ions. The results of the density-functional theory (DFT) calculations show that both doping and replacement reactions are favourable. Owing to its tunable near-infrared absorption and magnetic property, the obtained hybrid nanostructure was demonstrated to be a novel nanotheranostic agent for effective deep-tissue photoacoustic imaging, magnetic resonance imaging, and photothermal therapy of cancer.

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Zhou P et al.

Photoacoustic-Enabled Self-Guidance in Magnetic-Hyperthermia Fe@Fe3 O4 Nanoparticles for Theranostics In Vivo

NanoPreclinicalMSOT

Magnetic nanoparticles have gained much interest for theranostics benefited from their intrinsic integration of imaging and therapeutic abilities. Herein, c(RGDyK) peptide PEGylated Fe@Fe 3 O 4 nanoparticles (RGD-PEG-MNPs) are developed for photoacoustic (PA)-enabled self-guidance in tumor-targeting magnetic hyperthermia therapy in vivo. In the α v β 3 -positive U87MG glioblastoma xenograft model, the PA signal of RGD-PEG-MNPs reaches its maximum in the tumor at 6 h after intravenous administration. This signal is enhanced by 2.2-folds compared to that of the preinjection and is also 2.2 times higher than that in the blocking group. It demonstrates the excellent targeting property of RGD-PEG-MNPs. With the guidance of the PA, an effective magnetic hyperthermia to tumor is achieved using RGD-PEG-MNPs.

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Duffy MJ et al.

Towards optimized naphthalocyanines as sonochromes for photoacoustic imaging in vivo

NanoPreclinicalMSOT

In this paper we establish a methodology to predict photoacoustic imaging capabilities from the structure of absorber molecules (sonochromes). The comparative in vitro and in vivo screening of naphthalocyanines and cyanine dyes has shown a substitution pattern dependent shift in photoacoustic excitation wavelength, with distal substitution producing the preferred maximum around 800 nm. Central ion change showed variable production of photoacoustic signals, as well as singlet oxygen photoproduction and fluorescence with the optimum for photoacoustic imaging being nickel(II). Our approach paves the way for the design, evaluation and realization of optimized sonochromes as photoacoustic contrast agents.

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Tan L et al.

Renal-clearable quaternary chalcogenide nanocrystal for photoacoustic/magnetic resonance imaging guided tumor photothermal therapy

NanoCancerPreclinicalMSOT

Ultrasmall Cu2ZnSnS4 (CZTS) nanocrystals with high near infrared (NIR) photothermal conversion abilities and peroxidase-mimic properties are synthesized and functionalized with bovine serum albumin (BSA) for rapid clearance multifunctional theranostic platform. Due to the presence of Cu (I) of CZTS@BSA, H2O2 could be decomposed to produce highly reactive oxygen species (ROS), catalyzed by intrinsic peroxidase like activity of CZTS. The CZTS@BSA possesses high NIR absorption and excellent photoacoustic (PA) imaging abilities. The as-prepared CZTS@BSA is also reported as an efficient T1 contrast agent for in vivo MR imaging. Therefore, in vivo distribution and rapid renal clearance of CZTS@BSA are successfully tracked by PA/MR dual-modal-imaging and further proved by ICP-MS analysis. Systemic acute toxicity evaluation indicates CZTS@BSA have good biocompatibility to normal tissues and blood. All results reveal that CZTS@BSA could act as a rapid clearance theranostic nanoplatform for dual-modal-imaging guided tumor PTT.

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Neuschmelting V et al.

WST11 Vascular Targeted Photodynamic Therapy Effect Monitoring by Multispectral Optoacoustic Tomography (MSOT) in Mice

CancerPreclinicalMSOT

Objective : Monitoring emerging vascular-targeted photodynamic therapy (VTP) and understanding the time-dynamics of treatment effects remains challenging. We interrogated whether handheld multispectral optoacoustic tomography (MSOT) could noninvasively monitor the effect of VTP using WST11, a vascular-acting photosensitizer, on tumor tissues over time using a renal cell cancer mouse model. We also investigated whether MSOT illumination can induce VTP, to implement a single-modality theranostic approach. Materials and Methods : Eight BalB/c mice were subcutaneously implanted with murine renal adenocarcinoma cells (RENCA) on the flank. Three weeks later VTP was performed (10 min continuous illumination at 753 nm following intravenous infusion using WST11 or saline as control. Handheld MSOT images were collected prior to VTP administration and subsequently thereafter over the course of the first hour, at 24 and 48 h. Data collected were unmixed for blood oxygen saturation in tissue (SO2) based on the spectral signatures of deoxy- and oxygenated hemoglobin. Changes in oxygen saturation over time, relative to baseline, were examined by paired t-test for statistical significance (p < 0.05). In-vivo findings were corroborated by histological analyses of the tumor tissue. Results : MSOT is shown to prominently resolve changes in oxygen saturation in tumors within the first 20 min post WST11-VTP treatment. Within the first hour post-treatment, SO2 decreased by more than 60% over baseline (p < 0.05), whereas it remained unchanged (p > 0.1) in the sham-treated group. Moreover, unlike in the control group, SO2 in treated tumors further decreased over the course of 24 to 48 h post-treatment, concomitant with the propagation of profound central tumor necrosis present in histological analysis. We further show that pulsed MSOT illumination can activate WST11 as efficiently as the continuous wave irradiation employed for treatment. Conclusion : Handheld MSOT non-invasively monitored WST11-VTP effects based on the SO2 signal and detected blood saturation changes within the first 20 min post-treatment. MSOT may potentially serve as a means for both VTP induction and real-time VTP monitoring in a theranostic approach.

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Dey S et al.

The vascular disrupting agent combretastatin A-4 phosphate causes prolonged elevation of proteins involved in heme flux and function in resistant tumor cells

CancerPreclinicalMSOT

Vascular disrupting agents (VDAs) represent a promising class of anti-cancer drugs for solid tumor treatment. Here, we aim to better understand the mechanisms underlying tumor reccurrence and treatment resistance following the administration of a VDA, combretastatin A-4 phosphate (CA4P). Firstly, we used photoacoustic tomography to noninvasively map the effect of CA4P on blood oxygen levels throughout subcutaneous non-small cell lung cancer (NSCLC) tumors in mice. We found that the oxygenation of peripheral tumor vessels was significantly decreased at 1 and 3 hours post-CA4P treatment. The oxygenation of the tumor core reduced significantly at 1 and 3 hours, and reached anoxia after 24 hours. Secondly, we examined the effect of CA4P on the levels of proteins involved in heme flux and function, which are elevated in lung tumors. Using immunohistochemistry, we found that CA4P substantially enhanced the levels of enzymes involved in heme biosynthesis, uptake, and degradation, as well as oxygen-utilizing hemoproteins. Furthermore, measurements of markers of mitochondrial function suggest that CA4P did not diminish mitochondrial function in resistant tumor cells. These results suggest that elevated levels of heme flux and function contribute to tumor regrowth and treatment resistance post-VDA administration.

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Napp J et al.

Fluorescence- and multispectral optoacoustic imaging for an optimized detection of deeply located tumors in an orthotopic mouse model of pancreatic carcinoma

CancerPreclinicalMSOT

A crucial point for the management of pancreatic ductal adenocarcinoma (PDAC) is the decrease of R1 resections. Our aim was to evaluate the combination of multispectral optoacoustic tomography (MSOT) with fluorescence guided surgery (FGS) for diagnosis and perioperative detection of tumor nodules and resection margins in a xenotransplant mouse model of human pancreatic cancer. The peptide cRGD, conjugated with the near infrared fluorescent (NIRF) dye IRDye800CW and with a trans-cyclooctene (TCO) tag for future click chemistry (cRGD-800CW-TCO), was applied to PDAC bearing immunodeficient nude mice; 27 days after orthotopic transplantation of human AsPC-1 cells into the head of the pancreas, mice were injected with cRGD-800CW-TCO and imaged with fluorescence- and optoacoustic devices before and 2, 6 and 24 hr after injection, before they were sacrificed and dissected with a guidance of FGS imaging system. Fluorescence imaging of cRGD-800CW-TCO allowed detection of the tumor area but without information about the depth, whereas MSOT allowed high resolution 3 D identification of the tumor area, in particular of small tumor nodules. Highly sensitive delineation of tumor burden was achieved during FGS in all mice. Imaging of whole-mouse cryosections, histopathological analysis and NIRF microscopy confirmed the localization of cRGD-800CW-TCO within the tumor tissue. In principle, all imaging modalities applied here were able to detect PDAC in vivo. However, the combination of MSOT and FGS provided detailed spatial information of the signal and achieved a complete overview of the distribution and localization of cRGD-800CW-TCO within the tumor before and during surgical intervention.

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Yang Q et al.

Porous Au@Pt Nanoparticles: Therapeutic Platform for Tumor Chemo-Photothermal Co-Therapy and Alleviating Doxorubicin-Induced Oxidative Damage

NanoCancerPreclinicalMSOT

Nanoparticle-based systems explore not only the delivery efficacy of drugs or contrast agents, but also additional capabilities like reducing the systemic toxicity, especially during cancer chemotherapy. Since some of the noble metal nanoparticles exhibit the catalysis properties which can scavenge the reactive oxygen species (ROS), they can be used as a promising drug delivery platform for reducing the oxidative stress damage in normal tissues caused by some chemotherapy drugs. Herein, in this study, we construct porous Au@Pt nanoparticles and further explore the properties of porous Au@Pt nanoparticles in relieving the oxidative stress damage as well as in tumor growth inhibition by chemo-photothermal co-therapy. The tunable surface pore structure of Au@Pt nanoparticle provides space for Doxorubicin (DOX) loading. cRGD peptide modification enable the DOX-loaded Au@Pt nanoparticles to improve drug delivery properties. The constructed nanocarrier (DOX/Au@Pt-cRGD) shows controlled drug release behavior. Meanwhile, the absorbance peak of the Au@Pt structure in the near-infrared (NIR) portion provides the capacity for in vivo photoacoustic imaging and the high photoconversion efficiency, which make Au@Pt nanoparticle a suitable carrier for photothermal therapy (PTT). Combined with chemotherapy, the nanosystem DOX/Au@Pt-cRGD shows enhanced anticancer therapeutic effects. More importantly, ROS-scavenging activity of Au@Pt alleviates the DOX-induced oxidative stress damage, especially the cardiomyopathy during chemotherapy. Herein, this nanosystem DOX/Au@Pt-cRGD could be explored as reactive oxygen scavenger and drug delivery system for side effects relieving chemo-photothermal combinational therapy.

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Stylogiannis A et al.

Continuous wave laser diodes enable fast optoacoustic imaging

TechnologyPreclinicalMSOT

Pulsed laser diodes may offer a smaller, less expensive alternative to conventional optoacoustic laser sources; however they do not provide pulse rates faster than a few tens of kHz and emit at wavelengths only within the near-infrared region. We investigated whether continuous wave (CW) laser diodes, which are available in visible and near-infrared regions, can be good optoacoustic light sources when overdriven with a peak current >40-fold higher than the CW absolute maximum. We found that overdriven CW diodes provided ∼10 ns pulses of ∼200 nJ/pulse and repetition rates higher than 600 kHz without being damaged, outperforming many pulsed laser diodes. Using this system, we obtained images of phantoms and mouse ear and human arm in vivo, confirming their use in optoacoustic imaging and sensing.

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Ovsepian SV et al.

Pushing the Boundaries of Neuroimaging with Optoacoustics

NeuroPreclinicalMSOT

With the central ability to visualize a variety of endogenous chromophores and biomarkers or exogenous contrast agents, optoacoustic (photoacoustic) imaging empowers new experimental capabilities for investigating brain mechanisms and functions. Here, the operational principles of optoacoustic neuroimaging are reviewed in conjunction with recent advances enabling high-resolution and real-time observation, which extend beyond the reach of optical imaging methods. Multiple implementations of optoacoustics for monitoring hemodynamics and neuro-vascular responses in the brain are showcased. The unique capabilities of optoacoustic imaging for multi-spectral cellular and molecular sensing are discussed with reference to recent application for visualizing healthy and diseased brains. Outstanding challenges in the field are considered in the context of current and future applications of optoacoustic neuroimaging for basic and translational neuroscience research. In pushing the boundaries of brain imaging, optoacoustic methods afford major insights into the neuronal mechanisms of brain functions and organization of behavior.

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Zhang M et al.

Precise synthesis of unique polydopamine/mesoporous calcium phosphate hollow Janus nanoparticles for imaging-guided chemo-photothermal synergistic therapy

NanoCancerPreclinicalMSOT

Multifunctional polymer–inorganic Janus nanoparticles (JNPs) that simultaneously have therapeutic and imaging functions are highly desired in biomedical applications. Here, we fabricated spherical polydopamine/mesoporous calcium phosphate hollow JNPs (PDA/mCaP H-JNPs) via a novel and facile approach. The obtained PDA/mCaP H-JNPs were further selectively functionalized with indocyanine green (ICG) and methoxy-poly(ethylene glycol)thiol (PEG-SH) on PDA domains to achieve a superior photoacoustic (PA) imaging capability and stability, while the other mCaP sides with hollow cavities served as storage spaces and passages for the anti-cancer drug, doxorubicin (DOX). The resultant PEG–ICG–PDA/mCaP H-JNPs possess excellent biocompatibility, a competent drug loading capability, high photothermal conversion efficiency, strong near-infrared (NIR) absorbance, and pH/NIR dual-responsive properties, enabling the H-JNPs to be applied for PA imaging-guided synergistic cancer chemo-phototherapy in vitro and in vivo. Furthermore, the synthetic approach could be extended to prepare PDA/various mesoporous inorganic H-JNPs with spherical shapes for specific applications.

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Chen L et al.

Biodegradable Nanoagents with Short Biological Half-Life for SPECT/PAI/MRI Multimodality Imaging and PTT Therapy of Tumors

NanoCancerPreclinicalMSOT

Rapid clearance of nanoagents is a critical criterion for their clinical translation. Herein, it is reported that biodegradable and renal clearable nanoparticles are potentially useful for image-guided photothermal therapy of tumors. The multifunctional nanoparticles with excellent colloidal stability are synthesized through coordination reactions between Fe3+ ions and gallic acid (GA)/polyvinyl pyrrolidone (PVP) in aqueous solution. Detailed characterization reveals that the resulting Fe3+ /GA/PVP complex nanoparticles (FGPNs) integrate strong near-infrared absorption with paramagnetism well. As a result, the FGPNs present outstanding performance for photoacoustic imaging and magnetic resonance imaging of tumors, and outstanding photothermal ablation effect for tumor therapy owing to their high photothermal conversion efficiency. More importantly, the pharmacokinetic behaviors of the FGPNs determined through 125 I labeling suggest that the FGPNs are readily degraded in vivo showing a short biological half-life, and the decomposition products are excreted through either renal clearance pathway or bowel elimination pathway via stomach, which highlights the characteristics of the current multifunctional theranostic agent and their potential in clinical translation.

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Dong L et al.

Multifunctional Cu-Ag2S nanoparticles with high photothermal conversion efficiency for photoacoustic imaging-guided photothermal therapy in vivo

NanoCancerPreclinicalMSOT

Photothermal therapy (PTT) has attracted increasing interest and become widely used in cancer therapy owing to its noninvasiveness and low level of systemic adverse effects. However, there is an urgent need to develop biocompatible and multifunctional PTT agents with high photothermal conversion efficiency. Herein, biocompatible Cu-Ag2S/PVP nanoparticles (NPs) with strong near-infrared absorption and high photothermal conversion efficiency were successfully synthesized for high-performance photoacoustic (PA) imaging-guided PTT in vivo. The novel Cu-Ag2S/PVP NPs feature high photothermal conversion efficiency (58.2%) under 808 nm light irradiation, noticeably higher than those of most reported PTT agents. Because of their good dispersibility, Cu-Ag2S/PVP NPs passively accumulate within tumors via the enhanced permeability and retention effect, which can be confirmed by PA imaging, photothermal performance, and biodistribution in vivo. Furthermore, Cu-Ag2S/PVP NPs are thoroughly cleared through feces and urine within seven days, indicating a high level of biosafety for further potential clinical translation.

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Ke K et al.

Copper Manganese Sulfide Nanoplates: A New Two-Dimensional Theranostic Nanoplatform for MRI/MSOT Dual-Modal Imaging-Guided Photothermal Therapy in the Second Near-Infrared Window

NanoCancerPreclinicalMSOT

Multifunctional nanoplatforms with integrated diagnostic and therapeutic functions have attracted tremendous attention. Especially, the second near-infrared (NIR-II) light response-based nanoplatforms hold great potential in cancer theranostic applications, which is because the NIR-II window provides larger tissue penetration depth and higher maximum permissible exposure (MPE) than that of the well-studied first near-infrared (NIR-I) window. Herein, we for the first time present a two-dimensional (2D)-nanoplatform based on Cu2MnS2 nanoplates (NPs) for magnetic resonance imaging (MRI)/multispectral optoacoustic tomography (MSOT) dual-modal imaging-guided photothermal therapy (PTT) of cancer in the NIR-II window. Methods: Cu2MnS2 NPs were synthesized through a facile and environmentally friendly process. A series of experiments, including the characterization of Cu2MnS2 NPs, the long-term toxicity of Cu2MnS2 NPs in BALB/c nude mice, the applications of Cu2MnS2 NPs for in vitro and in vivo MRI/MSOT dual-modal imaging and NIR-II PTT of cancer were carried out. Results: The as-synthesized Cu2MnS2 NPs exhibit low cytotoxicity, excellent biocompatibility as well as high photothermal conversion efficiency (~49.38%) and outstanding photostability. Together with their good T1-shortening effect and strong absorbance in the NIR-I and NIR-II region, the Cu2MnS2 NPs display high-contrast imaging performance both in MRI and MSOT (900 nm laser source). Moreover, the subsequent in vitro and in vivo results demonstrate that the Cu2MnS2 NPs possess excellent PTT efficacy under 1064 nm laser irradiation with a low power density (0.6 W cm-2). In addition, the detailed long-term toxicity studies further confirming the safety of Cu2MnS2 NPs in vivo. Conclusion: We have developed a new 2D Cu2MnS2 NPs as multifunctional theranostic agents for MRI/MSOT dual-modal imaging-guided PTT of cancer in the NIR-II window. Such biocompatible Cu2MnS2 NPs might provide a new perspective for exploring new 2D-based nanoplatforms with improved properties for clinical applications in the future.

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Guo Z et al.

Synthesis of BSA‐Coated BiOI@Bi2S3 Semiconductor Heterojunction Nanoparticles and Their Applications for Radio/Photodynamic/Photothermal Synergistic Therapy of Tumor

NanoCancerPreclinicalMSOT

Developing an effective theranostic nanoplatform remains a great challenge for cancer diagnosis and treatment. Here, BiOI@Bi2S3@BSA (bovine serum albumin) semiconductor heterojunction nanoparticles (SHNPs) for triple‐combination radio/photodynamic/photothermal cancer therapy and multimodal computed tomography/photoacoustic (CT/PA) bioimaging are reported. On the one hand, SHNPs possess strong X‐ray attenuation capability since they contain high‐Z elements, and thus they are anticipated to be a very competent candidate as radio‐sensitizing materials for radiotherapy enhancement. On the other hand, as a semiconductor, the as‐prepared SHNPs offer an extra approach for reactive oxygen species generation based on electron–hole pair under the irradiation of X‐ray through the photodynamic therapy process. This X‐ray excited photodynamic therapy obviously has better penetration depth in bio‐tissue. What’s more, the SHNPs also possess well photothermal conversion efficiency for photothermal therapy, because Bi2S3 is a thin band semiconductor with strong near‐infrared absorption that can cause local overheat. In vivo tumor ablation studies show that synergistic radio/photodynamic/photothermal therapy achieves more significant therapeutic effect than any single treatment. In addition, with the strong X‐ray attenuation and high near‐infrared absorption, the as‐obtained SHNPs can also be applied as a multimodal contrast agent in CT/PA imaging.

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Joseph J et al.

Distance dependent photoacoustics revealed through DNA nanostructures

NanoPreclinicalMSOT

Molecular rulers that rely on the Förster resonance energy transfer (FRET) mechanism are widely used to investigate dynamic molecular processes that occur on the nanometer scale. However, the capabilities of these fluorescence molecular rulers are fundamentally limited to shallow imaging depths by light scattering in biological samples. Photoacoustic tomography (PAT) has recently emerged as a high resolution modality for in vivo imaging, coupling optical excitation with ultrasound detection. In this paper, we report the capability of PAT to probe distance-dependent FRET at centimeter depths. Using DNA nanotechnology we created several nanostructures with precisely positioned fluorophore–quencher pairs over a range of nanoscale separation distances. PAT of the DNA nanostructures showed distance-dependent photoacoustic signal enhancement and demonstrated the ability of PAT to reveal the FRET process deep within tissue mimicking phantoms. Further, we experimentally validated these DNA nanostructures as a novel and biocompatible strategy to augment the intrinsic photoacoustic signal generation capabilities of small molecule fluorescent dyes.

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Chen Z et al.

Hybrid system for in vivo epifluorescence and 4D optoacoustic imaging

NeuroPreclinicalMSOT

Epifluorescence imaging is widely used in cell and molecular biology due to its excellent sensitivity, contrast, and ease of implementation. Optoacoustic imaging has been shown to deliver a highly complementary and unique set of capabilities for biological discovery, such as high spatial resolution in noninvasive deep tissue observations, fast volumetric imaging capacity, and spectrally enriched contrast. In this Letter, we report on a hybrid system combining planar fluorescence and real-time volumetric four-dimensional optoacoustic imaging by means of a fiberscope integrated within a handheld hemispherical ultrasound detection array. The in vivo imaging performance is demonstrated by non-invasive visualization of fast contrast agent perfusion through the mouse brain. The proposed synergistic combination of fluorescence and optoacoustic imaging can benefit numerous studies looking at multi-scale in vivo dynamics, such as functional neuroimaging, visualization of organ perfusion and contrast agent uptake, cell tracking, and pharmacokinetic and bio-distribution analysis.

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Lin HA et al.

Characterization of Cardiac Dynamics in an Acute Myocardial Infarction Model by Four-Dimensional Optoacoustic and Magnetic Resonance Imaging

Other ApplicationsPreclinicalMSOT

Extraction of murine cardiac functional parameters on a beat-by-beat basis is limited with the existing imaging modalities due to insufficient three-dimensional temporal resolution. Faster volumetric imaging methods enabling in vivo characterization of functional parameters are poised to advance cardiovascular research and provide a better understanding of the mechanisms underlying cardiac diseases. We present a new approach based on analyzing contrast-enhanced optoacoustic (OA) images acquired at high volumetric frame rate without using cardiac gating or other approaches for motion correction. We apply an acute murine myocardial infarction model optimized for acquisition of artifact-free optoacoustic imaging data to study cardiovascular hemodynamics. Infarcted hearts (n = 21) could be clearly differentiated from healthy controls (n = 9) based on a significantly higher pulmonary transit time (PTT) (2.25 [2.00-2.41] s versus 1.34 [1.25-1.67] s, p = 0.0235), while no statistically significant difference was observed in the heart rate (318 [252-361] bpm versus 264 [252-320] bpm, p = 0.3129). Nevertheless, nonlinear heartbeat dynamics was stronger in the healthy hearts, as evidenced by the third harmonic component in the heartbeat spectra. MRI data acquired from the same mice further revealed that the PTT increases with the size of infarction and similarly increases with reduced ejection fraction. Moreover, an inverse relationship between infarct PTT and time post-surgery was found, which suggests the occurrence of cardiac healing. In combination with the proven ability of optoacoustics to track targeted probes within the injured myocardium, our method can depict cardiac anatomy, function, and molecular signatures, with both high spatial and temporal resolution. Volumetric four-dimensional optoacoustic characterization of cardiac dynamics with supreme temporal resolution can capture cardiovascular dynamics on a beat-by-beat basis in mouse models of myocardial ischemia.

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Roberts S et al.

Calcium Sensor for Photoacoustic Imaging

Other ApplicationsPreclinicalMSOT

We introduce a selective and cell-permeable calcium sensor for photoacoustics (CaSPA), a versatile imaging technique that allows for fast volumetric mapping of photoabsorbing molecules with deep tissue penetration. To optimize for Ca2+-dependent photoacoustic signal changes, we synthesized a selective metallochromic sensor with high extinction coefficient, low quantum yield, and high photobleaching resistance. Micromolar concentrations of Ca2+ lead to a robust blueshift of the absorbance of CaSPA, which translated into an accompanying decrease of the peak photoacoustic signal. The acetoxymethyl esterified sensor variant was readily taken up by cells without toxic effects and thus allowed us for the first time to perform live imaging of Ca2+ fluxes in genetically unmodified cells and heart organoids as well as in zebrafish larval brain via combined fluorescence and photoacoustic imaging.

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Li D et al.

Investigating the Effect of Chemical Structure of Semiconducting Polymer Nanoparticle on Photothermal Therapy and Photoacoustic Imaging

NanoCancerPreclinicalMSOT

The donor-acceptor semiconducting polymers (SPs) have robust absorbance in near-infrared (NIR) region, great photostability, high photothermal conversion efficiency, and good biocompatibility. Thus, the SPs exhibit great potentials for photothermal therapy (PTT) and photoacoustic imaging (PAI). However, poor understanding of the underlying mechanisms and the correlation between the SP polymer chemical structures and their performances of PTT and PAI have significantly hindered their biomedical application. Herein, a series of acceptor-π-acceptor type (A1-π-A2) type SPs were synthesized. The diketopyrrolopyrrole (DPP) and thiophene are used as A1 electron accepting block and π-bridge, and the chemical structure of A2 unit was variable. The SPs were formulated into PEGylated nanoparticles, which ensured these SP-based nanoparticles (SP@NPs) exhibited similar size, shape, and physiological stability. Thus, the chemical structure of A2 unit was the only variable. The effects of the SP chemical structures are carefully and comprehensively evaluated through both in vitro and in vivo experiments. Our results demonstrated the chemical structure of A2 unit simultaneously impact their absorption spectra and photothermal (PT) conversion efficiency, which finally determined their PTT and PAI performances. Among these A2 acceptors, thieno[3,2-b]thiophene (TT) unit exhibited the best in vitro and in vivo anticancer efficacies and PAI performances. This study not only provides molecular insights into the design of efficient SPs for PTT and PAI but also highlights the flexibility and potential of SP@NPs for biomedical application. Thus, SP@NPs can act as a versatile nanoplatform for the development of novel light intensive imaging and therapeutic approaches.

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Cheng X et al.

Enhanced Radiotherapy using Bismuth Sulfide Nanoagents Combined with Photo-thermal Treatment

NanoCancerPreclinicalMSOT

Nanotechniques that can improve the effectiveness of radiotherapy (RT) by integrating it with multimodal imaging are highly desirable. Results In this study, we fabricated Bi2S3 nanorods that have attractive features such as their ability to function as contrast agents for X-ray computed tomography (CT) and photoacoustic (PA) imaging as well as good biocompatibility. Both in vitro and in vivo studies confirmed that the Bi2S3 nanoagents could potentiate the lethal effects of radiation via amplifying the local radiation dose and enhancing the anti-tumor efficacy of RT by augmenting the photo-thermal effect. Furthermore, the nanoagent-mediated hyperthermia could effectively increase the oxygen concentration in hypoxic regions thereby inhibiting the expression of hypoxia-inducible factor (HIF-1α). This, in turn, interfered with DNA repair via decreasing the expression of DNA repair-related proteins to overcome radio-resistance. Also, RT combined with nanoagent-mediated hyperthermia could substantially suppress tumor metastasis via down-regulating angiogenic factors. Conclusion In summary, we constructed a single-component powerful nanoagent for CT/PA imaging-guided tumor radiotherapy and, most importantly, explored the potential mechanisms of nanoagent-mediated photo-thermal treatment for enhancing the efficacy of RT in a synergistic manner. Keywords : multimodal imaging, radiation therapy, hypoxia, DNA repair, synergistic therapy.

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Diot G et al.

Multispectral Optoacoustic Tomography (MSOT) of Human Breast Cancer

Breast CancerClinicalMSOT

Purpose : In a pilot study, we introduce fast handheld multispectral optoacoustic tomography (MSOT) of the breast at 28 wavelengths, aiming to identify high-resolution optoacoustic (photoacoustic) patterns of breast cancer and noncancerous breast tissue. Experimental Design : We imaged 10 female patients ages 48-81 years with malignant nonspecific breast cancer or invasive lobular carcinoma. Three healthy volunteers ages 31-36 years were also imaged. Fast-MSOT was based on unique single-frame-per-pulse (SFPP) image acquisition employed to improve the accuracy of spectral differentiation over using a small number of wavelengths. Breast tissue was illuminated at the 700-970 nm spectral range over 0.56 seconds total scan time. MSOT data were guided by ultrasonography and X-ray mammography or MRI. Results : The extended spectral range allowed the computation of oxygenated hemoglobin (HBO2), deoxygenated hemoglobin (HB), total blood volume (TBV), lipid, and water contributions, allowing first insights into in vivo high-resolution breast tissue MSOT cancer patterns. TBV and Hb/HBO2 images resolved marked differences between cancer and control tissue, manifested as a vessel-rich tumor periphery with highly heterogeneous spatial appearance compared with healthy tissue. We observe significant TBV variations between different tumors and between tumors over healthy tissues. Water and fat lipid layers appear disrupted in cancer versus healthy tissue; however, offer weaker contrast compared with TBV images. Conclusions : In contrast to optical methods, MSOT resolves physiologic cancer features with high resolution and revealed patterns not offered by other radiologic modalities. The new features relate to personalized and precision medicine potential.

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Shah A et al.

Value of combining dynamic contrast enhanced ultrasound and optoacoustic tomography for hypoxia imaging

CancerPreclinicalMSOT

Optoacoustic imaging (OAI) can detect haemoglobin and assess its oxygenation. However, the lack of a haemoglobin signal need not indicate a lack of perfusion. This study uses a novel method to assist the co-registration of optoacoustic images with dynamic contrast enhanced ultrasound (DCE-US) images to demonstrate, in preclinical tumour models, the value of combining haemoglobin imaging with a perfusion imaging method, showing that a lack of a haemoglobin signal does not necessarily indicate an absence of perfusion. DCE-US was chosen for this particular experiment because US is extremely sensitive to microbubble contrast agents and because microbubbles, like red blood cells but unlike currently available optical contrast agents, do not extravasate. Significant spatial correlations were revealed between the DCE-US properties and tumour blood-oxygen saturation and haemoglobin, as estimated using OAI. It is speculated that DCE-US properties could be applied as surrogate biomarkers for hypoxia when planning clinical radiotherapy or chemotherapy.

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Schwarz M et al.

Motion correction in optoacoustic mesoscopy

TechnologyPreclinicalClinicalRSOM

Raster-scan optoacoustic mesoscopy (RSOM), also termed photoacoustic mesoscopy, offers novel insights into vascular morphology and pathophysiological biomarkers of skin inflammation in vivo at depths unattainable by other optical imaging methods. Using ultra-wideband detection and focused ultrasound transducers, RSOM can achieve axial resolution of 4 micron and lateral resolution of 20 micron to depths of several millimeters. However, motion effects may deteriorate performance and reduce the effective resolution. To provide high-quality optoacoustic images in clinical measurements, we developed a motion correction algorithm for RSOM. The algorithm is based on observing disruptions of the ultrasound wave front generated by the vertical movement of the melanin layer at the skin surface. From the disrupted skin surface, a smooth synthetic surface is generated, and the offset between the two surfaces is used to correct for the relative position of the ultrasound detector. We test the algorithm in measurements of healthy and psoriatic human skin and achieve effective resolution up to 5-fold higher than before correction. We discuss the performance of the correction algorithm and its implications in the context of multispectral mesoscopy.

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Mason RP

Oxygen breathing challenge- the simplest theranostic

CancerPreclinicalMSOT

Multispectral optoacoustic tomography provides insights into tumor vascular oxygenation with high temporal and spatial resolution non-invasively. New work indicates that a simple oxygen breathing challenge can reveal differences in tumor, potentially as a prognostic biomarker.

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Ju Y et al.

Monodisperse Au-Fe2C Janus Nanoparticles: An Attractive Multifunctional Material for Triple-Modal Imaging-Guided Tumor Photothermal Therapy

NanoCancerPharmacokineticsPreclinicalMSOT

Imaging-guided photothermal therapy (PTT) by combination of imaging and PTT has been emerging as a promising therapeutic method for precision therapy. However, the development of multicomponent nanoplatforms with stable structures for both PTT and multiple-model imaging remains a great challenge. Herein, we synthesized monodisperse Au-Fe2C Janus nanoparticles (JNPs) of 12 nm, which are multifunctional entities for cancer theranostics. Due to the broad absorption in the near-infrared range, Au-Fe2C JNPs showed a significant photothermal effect with a 30.2% calculated photothermal transduction efficiency under 808 nm laser irradiation in vitro. Owing to their excellent optical and magnetic properties, Au-Fe2C JNPs were demonstrated to be advantageous agents for triple-modal magnetic resonance imaging (MRI)/multispectral photoacoustic tomography (MSOT)/computed tomography (CT) both in vitro and in vivo. We found that Au-Fe2C JNPs conjugated with the affibody (Au-Fe2C-ZHER2:342) have more accumulation and deeper penetration in tumor sites than nontargeting JNPs (Au-Fe2C-PEG) in vivo. Meanwhile, our results verified that Au-Fe2C-ZHER2:342 JNPs can selectively target tumor cells with low cytotoxicity and ablate tumor tissues effectively in a mouse model. In summary, monodisperse Au-Fe2C JNPs, used as a multifunctional nanoplatform, allow the combination of multiple-model imaging techniques and high therapeutic efficacy and have great potential for precision theranostic nanomedicines.

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Landa FJO et al.

Volumetric Optoacoustic Temperature Mapping in Photothermal Therapy

TechnologyPreclinicalClinicalMSOT

Photothermal therapy and ablation are commonplace medical procedures employed for treatment of tumors, vascular and brain abnormalities as well as other disorders that require selective destruction of tissues. Yet, accurate mapping of the dynamic temperature field distribution in the treated region represents an unmet clinical need, strongly affecting the clinical outcome of these interventions. We introduce a fast three-dimensional temperature mapping method based on real-time optoacoustic sensing of the treated region coupled with a thermal-diffusion-based model of heat distribution in tissues. Deviations of the optoacoustic temperature readings provided at 40  ms intervals remained below 10% in tissue-mimicking phantom experiments for temperature elevations above 3 °C, as validated by simultaneous thermocouple measurements. Performance of the new method to dynamically estimate the volumetric temperature distribution was further showcased in post-mortem mouse imaging experiments. The newly discovered capacity to non-invasively measure the temperature map in an entire treated volume with both high spatial and temporal resolutions holds potential for improving safety and efficacy of light-based therapeutic interventions.

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Xiao W et al.

Normalizing Tumor Vessels To Increase the Enzyme-Induced Retention and Targeting of Gold Nanoparticle for Breast Cancer Imaging and Treatment

NanoCancerPreclinicalMSOT

Abnormal tumor vessels impede the transport and distribution of chemotherapeutics, resulting in low drug concentration at tumor sites and compromised drug efficacy. Normalizing tumor vessels can modulate tumor vascular permeability, alleviate tumor hypoxia, increase blood perfusion, attenuate interstitial fluid pressure, and improve drug delivery. Herein, a novel strategy combining cediranib, a tumor vessel normalizing agent, with an enzyme responsive size-changeable gold nanoparticle (AuNPs-A&C) was developed. In vivo photoacoustic and fluorescence imaging showed that oral pretreatment with 6 mg/kg/day of cediranib for two consecutive days significantly enhanced the retention of AuNPs-A&C in 4T1 tumor. In vivo photoacoustic imaging for hemoglobin (Hb) and oxyhemoglobin (HbO2), Evans blue assay, and immunofluorescence assay showed that cediranib pretreatment markedly increased tumor vascular permeability and tumor oxygenation, while distinctly decreased the tumor microvessel density, demonstrating normalized tumor vessels and favorably altered microenvironment. Additionally, the combination strategy considerably elevated the tumor targeting capacity of different nanoparticle formulations (AuNPs-PEG, AuNPs-A&C), while coadministration of cediranib and AuNPs-A&C achieved prevailing tumor targeting and antitumor efficacy in 4T1 tumor bearing mouse model. In conclusion, we report a novel combined administration strategy to further improve tumor diagnosis and treatment.

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Xie B et al.

Optoacoustic Detection of Early Therapy-Induced Tumor Cell Death Using a Targeted Imaging Agent

CancerPreclinicalMSOT

Purpose : The development of new treatments and their deployment in the clinic may be assisted by imaging methods that allow an early assessment of treatment response in individual patients. The C2A domain of Synaptotagmin-I (C2Am), which binds to the phosphatidylserine (PS) exposed by apoptotic and necrotic cells, has been developed as an imaging probe for detecting cell death. Multispectral optoacoustic tomography (MSOT) is a real-time and clinically applicable imaging modality that was used here with a near infrared (NIR) fluorophore-labeled C2Am to image tumor cell death in mice treated with a TNF-related apoptosis-inducing ligand receptor 2 (TRAILR2) agonist and with 5-fluorouracil (5-FU). Experimental Design : C2Am was labeled with a NIR fluorophore and injected intravenously into mice bearing human colorectal TRAIL-sensitive Colo205 and TRAIL-resistant HT-29 xenografts that had been treated with a potent agonist of TRAILR2 and in Colo205 tumors treated with 5-FU. Results : Three-dimensional (3D) MSOT images of probe distribution showed development of tumor contrast within 3 hours of probe administration and a signal-to-background ratio in regions containing dead cells of >10 after 24 hours. A site-directed mutant of C2Am that is inactive in PS binding showed negligible binding. Tumor retention of the active probe was strongly correlated (R2 = 0.97, P value < 0.01) with a marker of apoptotic cell death measured in histologic sections obtained post mortem. Conclusions : The rapid development of relatively high levels of contrast suggests that NIR fluorophore-labeled C2Am could be a useful optoacoustic imaging probe for detecting early therapy-induced tumor cell death in the clinic.

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Shah A et al.

Detecting human melanoma cell re-differentiation following BRAF or heat shock protein 90 inhibition using photoacoustic and magnetic resonance imaging

CancerPreclinicalMSOT

Targeted therapies specific to the BRAF-MEK-ERK signaling pathway have shown great promise in the treatment of malignant melanoma in the last few years, with these drugs now commonly used in clinic. Melanoma cells treated using these agents are known to exhibit increased levels of melanin pigment and tyrosinase activity. In this study we assessed the potential of non-invasive imaging approaches (photoacoustic imaging (PAI) and magnetic resonance imaging (MRI)) to detect melanin induction in SKMEL28 human melanoma cells, following inhibition of Hsp90 and BRAF signaling using 17-AAG and vemurafenib, respectively. We confirmed, using western blot and spectrophotometry, that Hsp90 or BRAF inhibitor-induced melanoma cell differentiation resulted in an upregulation of tyrosinase and melanin expression levels, in comparison to control cells. This post-treatment increase in cellular pigmentation induced a significant increase in PAI signals that are spectrally identifiable and shortening of the MRI relaxation times T 1 and [Formula: see text]. This proof-of-concept study demonstrates the potential of MRI and PAI for detecting the downstream cellular changes induced by Hsp90 and BRAF-MEK-targeted therapies in melanoma cells with potential significance for in vivo imaging.

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Becker A et al.

Multispectral optoacoustic tomography of the human breast: characterisation of healthy tissue and malignant lesions using a hybrid ultrasound-optoacoustic approach

Breast CancerClinicalMSOT

BACKGROUND AND AIM: Multispectral optoacoustic tomography (MSOT) represents a new in vivo imaging technique with high resolution (~250 μm) and tissue penetration (>1 cm) using the photoacoustic effect. While ultrasound contains anatomical information for lesion detection, MSOT provides functional information based on intrinsic tissue chromophores. We aimed to evaluate the feasibility of combined ultrasound/MSOT imaging of breast cancer in patients compared to healthy volunteers.

METHODS: Imaging was performed using a handheld MSOT system for clinical use in healthy volunteers (n = 6) and representative patients with histologically confirmed invasive breast carcinoma (n = 5) and ductal carcinoma in situ (DCIS, n = 2). MSOT values for haemoglobin and oxygen saturation were assessed at 0.5, 1.0 and 1.5 cm depth and selected wavelengths between 700 and 850 nm.

RESULTS: Reproducible signals were obtained in all wavelengths with consistent MSOT signals in superficial tissue in breasts of healthy individuals. In contrast, we found increased signals for haemoglobin in invasive carcinoma, suggesting a higher perfusion of the tumour and tumour environment. For DCIS, MSOT values showed only little variation compared to healthy tissue.

CONCLUSIONS: This preliminary MSOT breast imaging study provided stable, reproducible data on tissue composition and physiological properties, potentially enabling differentiation of solid malignant and healthy tissue.

KEY POINTS: • A handheld MSOT probe enables real-time molecular imaging of the breast. • MSOT of healthy controls provides a reproducible reference for pathology identification. • MSOT parameters allows for differentiation of invasive carcinoma and healthy tissue

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Brillant N et al.

Dynamic and accurate assessment of acetaminophen-induced hepatotoxicity by integrated photoacoustic imaging and mechanistic biomarkers in vivo

PharmacokineticsPreclinicalMSOT

The prediction and understanding of acetaminophen (APAP)-induced liver injury (APAP-ILI) and the response to therapeutic interventions is complex. This is due in part to sensitivity and specificity limitations of currently used assessment techniques. Here we sought to determine the utility of integrating translational non-invasive photoacoustic imaging of liver function with mechanistic circulating biomarkers of hepatotoxicity with histological assessment to facilitate the more accurate and precise characterization of APAP-ILI and the efficacy of therapeutic intervention. Perturbation of liver function and cellular viability was assessed in C57BL/6J male mice by Indocyanine green (ICG) clearance (Multispectral Optoacoustic Tomography (MSOT)) and by measurement of mechanistic (miR-122, HMGB1) and established (ALT, bilirubin) circulating biomarkers in response to the acetaminophen and its treatment with acetylcysteine (NAC) in vivo. We utilised a 60% partial hepatectomy model as a situation of defined hepatic functional mass loss to compared acetaminophen-induced changes to. Integration of these mechanistic markers correlated with histological features of APAP hepatotoxicity in a time-dependent manner. They accurately reflected the onset and recovery from hepatotoxicity compared to traditional biomarkers and also reported the efficacy of NAC with high sensitivity. ICG clearance kinetics correlated with histological scores for acute liver damage for APAP (i.e. 3h timepoint; r=0.90, P<0.0001) and elevations in both of the mechanistic biomarkers, miR-122 (e.g. 6h timepoint; r=0.70, P=0.005) and HMGB1 (e.g. 6h timepoint; r=0.56, P=0.04). For the first time we report the utility of this non-invasive longitudinal imaging approach to provide direct visualisation of the liver function coupled with mechanistic biomarkers, in the same animal, allowing the investigation of the toxicological and pharmacological aspects of APAP-ILI and hepatic regeneration.

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Deng X et al.

A Hollow‐Structured CuS@Cu2S@Au Nanohybrid: Synergistically Enhanced Photothermal Efficiency and Photoswitchable Targeting Effect for Cancer Theranostics

NanoCancerPreclinicalMSOT

It is of great importance in drug delivery to fabricate multifunctional nanocarriers with intelligent targeting properties, for cancer diagnosis and therapy. Herein, hollow‐structured CuS@Cu2S@Au nanoshell/satellite nanoparticles are designed and synthesized for enhanced photothermal therapy and photoswitchable targeting theranostics. The remarkably improved photothermal conversion efficiency of CuS@Cu2S@Au under 808 nm near‐infrared (NIR) laser irradiation can be explained by the reduced bandgap and more circuit paths for electron transitions for CuS and Cu2S modified with Au nanoparticles, as calculated by the Vienna ab initio simulation package, based on density functional theory. By modification of thermal‐isomerization RGD targeting molecules and thermally sensitive copolymer on the surface of nanoparticles, the transition of the shielded/unshielded mode of RGD (Arg‐Gly‐Asp) targeting molecules and shrinking of the thermally sensitive polymer by NIR photoactivation can realize a photoswitchable targeting effect. After loading an anticancer drug doxorubicin in the cavity of CuS@Cu2S@Au, the antitumor therapy efficacy is greatly enhanced by combining chemo‐ and photothermal therapy. The reported nanohybrid can also act as a photoacoustic imaging agent and an NIR thermal imaging agent for real‐time imaging, which provides a versatile platform for multifunctional theranostics and stimuli‐responsive targeted cancer therapy.

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Tomaszewski MR et al.

Oxygen Enhanced Optoacoustic Tomography (OE-OT) Reveals Vascular Dynamics in Murine Models of Prostate Cancer

CancerPreclinicalMSOT

Poor oxygenation of solid tumours has been linked with resistance to chemo- and radio-therapy and poor patient outcomes, hence non-invasive imaging of oxygen supply and demand in tumours could improve disease staging and therapeutic monitoring. Optoacoustic tomography (OT) is an emerging clinical imaging modality that provides static images of endogenous haemoglobin concentration and oxygenation. Here, we demonstrate oxygen enhanced (OE)-OT, exploiting an oxygen gas challenge to visualise the spatiotemporal heterogeneity of tumour vascular function. We show that tracking oxygenation dynamics using OE-OT reveals significant differences between two prostate cancer models in nude mice with markedly different vascular function (PC3 & LNCaP), which appear identical in static OT. LNCaP tumours showed a spatially heterogeneous response within and between tumours, with a substantial but slow response to the gas challenge, aligned with ex vivo analysis, which revealed a generally perfused and viable tumour with marked areas of haemorrhage. PC3 tumours had a lower fraction of responding pixels compared to LNCaP with a high disparity between rim and core response. While the PC3 core showed little or no dynamic response, the rim showed a rapid change, consistent with our ex vivo findings of hypoxic and necrotic core tissue surrounded by a rim of mature and perfused vasculature. OE-OT metrics are shown to be highly repeatable and correlate directly on a per-tumour basis to tumour vessel function assessed ex vivo. OE-OT provides a non-invasive approach to reveal the complex dynamics of tumour vessel perfusion, permeability and vasoactivity in real time. Our findings indicate that OE-OT holds potential for application in prostate cancer patients, to improve delineation of aggressive and indolent disease as well as in patient stratification for chemo- and radio-therapy.

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Karlas A et al.

Flow-mediated dilatation test using optoacoustic imaging: a proof-of-concept

VascularPreclinicalMSOT

Label-free multispectral optoacoustic tomography (MSOT) has recently shown superior performance in visualizing the morphology of human vasculature, especially of smaller vessels, compared to ultrasonography. Herein, we extend these observations towards MSOT interrogation of macrovascular endothelial function. We employed a real-time handheld MSOT scanner to assess flow-mediated dilatation (FMD), a technique used to characterize endothelial function. A data processing scheme was developed to quantify the dimensions and diameter changes of arteries in humans and determine wall distensibility parameters. By enabling high-resolution delineation of the blood-vessel wall in a cross-sectional fashion, the findings suggest MSOT as a capable alternative to ultrasonography for clinical FMD measurements.

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Lin YX et al.

"In vivo self-assembled" nanoprobes for optimizing autophagy-mediated chemotherapy

NanoCancerPharmacokineticsPreclinicalMSOT

Autophagic therapy is regarded as a promising strategy for disease treatment. Appropriate autophagy regulations in vivo play a crucial role in translating this new concept from benchside to bedside. So far, emerging technologies are required to spatially and quantitatively monitor autophagic process in vivo in order to minimize the cytotoxity concerns associated with autophagy-mediated therapy. We successfully demonstrate the “proof-of-concept” study on autophagy-mediated chemotherapy in mice. Here, we describe a photoacoustic (PA) nanoprobe based on “in vivo self-assembly” idea for real-time and quantitative detection of autophagy in mice for the first time. The purpurin-18 (P18) monomer is connected to hydrophilic poly(amidoamine) dendrimer (4th generation) through a peptide (GKGSFGFTG) that can be cleaved by an autophagy-specific enzyme, i.e., ATG4B, consequently resulting in aggregation of P18 and enhanced PA signals. Based on this aggregation-induced “turn-on” PA signals, we noninvasively determine the ATG4B activity for monitoring autophagy of tumor in vivo. According to the results of PA imaging, we could optimize chemotherapy efficacy through precisely modulating autophagy, which thereby decrease systemic toxicity from chemotherapeutics and autophagy inhibitors. We envision it will pave the way for developing autophagy-based treatment of diseases in the future.

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Tang J et al.

Dual-Mode Imaging-Guided Synergistic Chemo- and Magnetohyperthermia Therapy in a Versatile Nanoplatform To Eliminate Cancer Stem Cells

NanoCancerPharmacokineticsPreclinicalMSOT

Cancer stem cells (CSCs) have been identified as a new target for therapy in diverse cancers. Traditional therapies usually kill the bulk of cancer cells, but are often unable to effectively eliminate CSCs, which may lead to drug resistance and cancer relapse. Herein, we propose a novel strategy: fabricating multifunctional magnetic Fe3O4@PPr@HA hybrid nanoparticles and loading it with the Notch signaling pathway inhibitor N-[N-(3,5-difluorophenacetyl-l-alanyl)]-S-phenylglycinet-butylester (DAPT) to eliminate CSCs. Hyaluronic acid ligands greatly enhance the accumulation of the hybrid nanoparticles in the tumor site and in the CSCs. Both hyaluronase in the tumor microenvironment and the magnetic hyperthermia effect of the inner magnetic core can accelerate the release of DAPT. This controlled release of DAPT in the tumor site further enhances the ability of the combination of chemo- and magnetohyperthermia therapy to eliminate cancer stem cells. With the help of polypyrrole-mediated photoacoustic and Fe3O4-mediated magnetic resonance imaging, the drug release can be precisely monitored in vivo. This versatile nanoplatform enables effective elimination of the cancer stem cells and monitoring of the drugs.

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Du J et al.

Design of TPGS-functionalized Cu3BiS3 nanocrystals with strong absorption in the second near-infrared window for radiation therapy enhancement

NanoCancerPreclinicalMSOT

Integrating radiation therapy with high-depth photothermal therapy in the second near-infrared (NIR) window is highly required for efficient treatment of deep-seated tumor cells. Here, we constructed a multifunctional nano-theranostic with bimetallic chalcogenide nanocrystals (NCs) functionalized with amphiphilic D -α-tocopherol polyethylene glycol 1000 succinate (TPGS-Cu 3 BiS 3 ). Benefiting from the strong absorbance of both X-ray and NIR light in the second NIR window, TPGS-Cu 3 BiS 3 CNs can not only deposit more radiation dose to trigger enhanced radiation damage in vivo , but also conduct photo-induced hyperthermia for thermal ablation in the second NIR window and effective improvement of tumor oxygenation to overcome the hypoxia-associated radio-resistance of tumors. Moreover, copper ions on the surface of TPGS-Cu 3 BiS 3 NCs are capable of catalyzing the Fenton-like and Haber–Weiss reactions to produce highly reactive hydroxyl radicals, leading to the increase in the level of oxygen radicals and further enhance cancer cell destruction. Apart from their therapeutic application, by means of X-ray computer tomography imaging as well as multispectral optoacoustic tomography imaging, TPGS-Cu 3 BiS 3 NCs also have the potential as a nano-theranostic to offer remarkable therapeutic outcome for deep-seated tumor cells in imaging-guided synergistically enhanced radiation therapy.

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Yang C et al.

Multifunctional Bismuth Nanoparticles as Theranostic Agent for PA/CT Imaging and NIR Laser-Driven Photothermal Therapy

NanoCancerPharmacokineticsPreclinicalMSOT

“One-for-all” multifunctional theranostic agents are highly demanded in biomedical fields. However, their design and fabrication still face enormous challenges. Herein, we strategically design and fabricate 1,2-dilauroyl-sn-glycero-3-phosphocholine-modified (DLPC-modified) bismuth nanoparticles (denoted as Bi@DLPC NPs) with desirable size of 47 ± 3 nm as a theranostic agent for photoacoustic (PA) and X-ray computed tomography (CT) imaging guided photothermal therapy (PTT) in response to near-infrared (NIR) laser irradiation. Bi@DLPC NPs possess the excellent photothermal conversion efficiency of 35% and PA/CT imaging properties, which are attributed to the strong NIR absorption and high atomic number (83) of bismuth element. Moreover, it is demonstrated that Bi@DLPC NPs are effectively accumulated in the tumor region because of the enhanced permeability and retention (EPR) effect. With the PTT, the growth of cancer cells (MDA-MB-231 cells) can be remarkably ablated in vitro and in vivo; meanwhile no obvious damage and noticeable toxicity are detected to major organs. The antitumor mechanism of Bi@DLPC NPs is attributable to the mitochondrial dysfunction and change of cell membrane permeability of MDA-MB-231 cells caused by photothermal effects upon laser irradiation. On the basis of their high stability and excellent biocompatibility, Bi@DLPC NPs have great potential for the treatment of various types of tumors.

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Cao Y et al.

Near-infrared conjugated polymers for photoacoustic imaging-guided photothermal/chemo combination therapy

NanoCancerPharmacokineticsPreclinicalMSOT

Conjugated polymers (CPs) with intensive near-infrared (NIR) absorption and high photothermal conversion efficiency (PCE) have emerged as a new generation of photothermal therapy (PTT) and photoacoustic imaging (PAI) agents for cancer therapy. PTT + chemotherapy has been identified as a powerful modality to offer synergistic effects in the destruction and monitoring of cancer tissues. In this study, diketopyrrolopyrrole-based polymers (DPP) were designed through a combination of donor–acceptor moieties. Then, doxorubicin (DOX) and DPP were co-encapsulated in tocopheryl polyethylene-glycol-succinate-cholesterol (TPGS-CHO) copolymers to build a combined theranostic system for tumor treatment. These combined NPs with high PCE (∼50%) and strong (NIR) absorption exhibit excellent real-time photoacoustic imaging detection and synergistic cancer inhibition.

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Jia Q et al.

Biocompatible Iron Phthalocyanine-Albumin Assemblies as Photoacoustic and Thermal Theranostics in Living Mice

NanoCancerPharmacokineticsPreclinicalMSOT

Exploring novel and versatile nanomaterials for the construction of personalized multifunctional phototheranostics with significant potentials in bioimaging-guided tumor phototherapies has attracted considerable attention. Herein, the phototheranostic agent human serum albumin-iron (II) phthalocyanine FePc nanoparticles (HSA-FePc NPs) were fabricated for photoacoustic (PA) imaging-guided photothermal therapy (PTT) of cancer in vivo. The prepared HSA-FePc NPs exhibited high stability, efficient NIR absorption, good capability and stability of photothermal behavior with a high photothermal conversion efficiency of ∼44.4%, high contrast and spatial resolution of PA imaging, efficient cancer therapy, and low long-term toxicity. This potent multifunctional phototheranostic is, therefore, very promising and favorable for effective, precise, and safe antitumor treatment in clinical application.

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Attia ABE et al.

Noninvasive real-time characterization of non-melanoma skin cancers with handheld optoacoustic probes

CancerSkinClinicalMSOT

Currently, imaging technologies that enable dermsurgeons to visualize non-melanoma skin cancers (NMSC) in vivo preoperatively are lacking, resulting in excessive or incomplete removal. Multispectral optoacoustic tomography (MSOT) is a volumetric imaging tool to differentiate tissue chromophores and exogenous contrast agents, based on differences in their spectral signatures and used for high-resolution imaging of functional and molecular contrast at centimeter scale depth. We performed MSOT imaging with two- an