Multispectral Optoacoustic Tomography Research Articles

Application of Multispectral Optoacoustic Tomography for Lower Limb Musculoskeletal Sports Injuries in Adults

Compositional changes in relation to musculoskeletal injuries are difficult to measure non-invasively. This study aims to use non-invasive label-free imaging with Multispectral Optoacoustic Tomography (MSOT) to evaluate compositional changes with injury.Five different patient groups were examined, covering diagnoses of Achilles or patellar tendinopathy, Achilles tendon rupture and gastrocnemius muscle strain injury. Injured and contralateral limbs were imaged using a commercial MSOT device. Hemoglobin, collagen, and lipid contents were estimated. Some patients were examined before and after exercise.Hemoglobin measures had high reproducibility and displayed systematic changes in response to exercise. The content and exercise response of hemoglobin was equal on both limbs. In contrast, collagen and lipid measures were inconsistent and did not display the expected distribution.In conclusion, MSOT is applicable to imaging of hemoglobin in musculoskeletal injuries, providing complimentary information to conventional ultrasound, but applicability to other components like collagen and lipids could not be shown.

Enhancing eMSOT with nonlinear mixed model approaches for precise blood oxygenation imaging in tissues

Multispectral optoacoustic tomography (MSOT) utilizes multiple wavelengths to illuminate tissue, producing a series of optoacoustic images rich in spectral information. This approach offers a more comprehensive spectral profile compared to conventional optoacoustic techniques. Contrasted with single-wavelength optoacoustic images, the spectral information can be amalgamated with endogenous chromophores or exogenous dyes within biological organisms, thereby unveiling physiological, cellular, and subcellular functions. The development of eigenspectral optoacoustic tomography (eMSOT), grounded in the linear mixture model (LMM), along with its various derivative methods, facilitates label-free imaging of tissue oxygen saturation in deep-seated structures. However, the effectiveness of the LMM may diminish in the presence of multiple scattering effects or inter-substance interactions, thereby impairing the performance of the eMSOT method in heterogeneous tissues. To address this issue, we propose incorporating a nonlinear model to enhance the eMSOT technique, which we refer to as NL-eMSOT (non-linear eMSOT). This model employs the Hadamard product as a nonlinear component of the LMM, effectively characterizing the interactions between photons and both oxygenated and deoxygenated hemoglobin within the near-infrared spectral window. This innovation resolves the nonlinear unmixing problem inherent in optoacoustic imaging. Our approach, validated through numerical simulations, phantom experiments, and in vivo studies, improves the accuracy of quantitative oxygen saturation estimation in heterogeneous tissues by accounting for inter-substance interactions. Consequently, it necessitates the consideration of more complex mixing models to adequately address nonlinear interactions.

Non-invasive optoacoustic imaging of glycogen-storage and muscle degeneration in late-onset Pompe disease

Pompe disease (PD) is a rare autosomal recessive glycogen storage disorder that causes proximal muscle weakness and loss of respiratory function. While enzyme replacement therapy (ERT) is the only effective treatment, biomarkers for disease monitoring are scarce. Following ex vivo biomarker validation in phantom studies, we apply multispectral optoacoustic tomography (MSOT), a laser- and ultrasound-based non-invasive imaging approach, in a clinical trial (NCT05083806) to image the biceps muscles of 10 late-onset PD (LOPD) patients and 10 matched healthy controls. MSOT is compared with muscle magnetic resonance imaging (MRI), ultrasound, spirometry, muscle testing and quality of life scores. Next, results are validated in an independent LOPD patient cohort from a second clinical site. Our study demonstrates that MSOT enables imaging of subcellular disease pathology with increases in glycogen/water, collagen and lipid signals, providing higher sensitivity in detecting muscle degeneration than current methods. This translational approach suggests implementation in the complex care of these rare disease patients.

Imaging-Guided Metabolic Radiosensitization of Pediatric Rhabdoid Tumors.

Tumor hypoxia leads to increased resistance to radiation therapy (RT), resulting in markedly worse clinical outcomes in the treatment and management of pediatric malignant rhabdoid tumors (MRT). To alleviate hypoxia in MRT, we repurposed an FDA approved, mitochondrial oxidative phosphorylation (OXPHOS) inhibitor, Atovaquone (AVO), to inhibit oxygen consumption and thereby enhance the sensitivity of tumor cells to low dose RT in MRT by hypoxia alleviation. Additionally, to better understand the tumor response induced by AVO and optimize the combination with RT, we employed an emerging, noninvasive imaging modality, known as multispectral optoacoustic tomography (MSOT), to monitor and evaluate real-time dynamic changes in tumor hypoxia and vascular perfusion. Oxygen-Enhanced (OE)-MSOT could measure the change of tumor oxygenation in the MRT xenograft models after AVO and RT treatments, indicating its potential as a response biomarker. OE-MSOT showed that treating MRT mouse models with AVO resulted in a transient increase in oxygen saturation (ΔsO 2 ) in tumors when the mice were subjected to oxygen challenge, while RT or saline treated groups produced no change. In AVO+RT combination groups, the tumors showed an increase in ΔsO 2 after AVO administration followed by a significant decrease after RT, that correlated with a strong anti-tumor response, demarcated by complete regression of tumors, with no relapse on long-term monitoring. These observations were histologically validated. In MRT models of acquired AVO resistance, combination therapy failed to alleviate tumoral hypoxia and elicit any therapeutic benefit. Together, our data highlights the utility of repurposing anti-malarial AVO as an anticancer adjuvant for enabling low dose RT for pediatric patients.

Structurally Modulated Formation of Cyanine J-Aggregates with Sharp and Tunable Spectra for Multiplexed Optoacoustic and Fluorescence Bioimaging.

J-aggregation brings intriguing optical and electronic properties to molecular dyes and significantly expands their applicability across diverse domains, yet the challenge for rationally designing J-aggregating dyes persists. Herein, we developed a large number of J-aggregating dyes from scratch by progressively refining structure of a common heptamethine cyanine. J-aggregates with sharp spectral bands (full-width at half-maximum≤38 nm) are attained by introducing a branched structure featuring a benzyl and a trifluoroacetyl group at meso-position of dyes. Fine-tuning the benzyl group enables spectral regulation of J-aggregates. Analysis of single crystal data of nine dyes reveals a correlation between J-aggregation propensity and molecular arrangement within crystals. Some J-aggregates are successfully implemented in multiplexed optoacoustic and fluorescence imaging in animals. Notably, three-color multispectral optoacoustic tomography imaging with high spatiotemporal resolution is achieved, owing to the sharp and distinct absorption bands of the J-aggregates.

Structurally Modulated Formation of Cyanine J‐Aggregates with Sharp and Tunable Spectra for Multiplexed Optoacoustic and Fluorescence Bioimaging

AbstractJ‐aggregation brings intriguing optical and electronic properties to molecular dyes and significantly expands their applicability across diverse domains, yet the challenge for rationally designing J‐aggregating dyes persists. Herein, we developed a large number of J‐aggregating dyes from scratch by progressively refining structure of a common heptamethine cyanine. J‐aggregates with sharp spectral bands (full‐width at half‐maximum≤38 nm) are attained by introducing a branched structure featuring a benzyl and a trifluoroacetyl group at meso‐position of dyes. Fine‐tuning the benzyl group enables spectral regulation of J‐aggregates. Analysis of single crystal data of nine dyes reveals a correlation between J‐aggregation propensity and molecular arrangement within crystals. Some J‐aggregates are successfully implemented in multiplexed optoacoustic and fluorescence imaging in animals. Notably, three‐color multispectral optoacoustic tomography imaging with high spatiotemporal resolution is achieved, owing to the sharp and distinct absorption bands of the J‐aggregates.

Visualizing alpha-synuclein and iron deposition in M83 mouse model of Parkinson's disease in vivo.

Abnormal alpha-synuclein (αSyn) and iron accumulation in the brain play an important role in Parkinson's disease (PD). Herein, we aim to visualize αSyn inclusions and iron deposition in the brains of M83 (A53T) mouse models of PD in vivo. The fluorescent pyrimidoindole derivative THK-565 probe was characterized by means of recombinant fibrils and brains from 10- to 11-month-old M83 mice. Concurrent wide-field fluorescence and volumetric multispectral optoacoustic tomography (vMSOT) imaging were subsequently performed in vivo. Structural and susceptibility weighted imaging (SWI) magnetic resonance imaging (MRI) at 9.4 T as well as scanning transmission x-ray microscopy (STXM) were performed to characterize the iron deposits in the perfused brains. Immunofluorescence and Prussian blue staining were further performed on brain slices to validate the detection of αSyn inclusions and iron deposition. THK-565 showed increased fluorescence upon binding to recombinant αSyn fibrils and αSyn inclusions in post-mortem brain slices from patients with PD and M83 mice. Administration of THK-565 in M83 mice showed higher cerebral retention at 20 and 40 min post-intravenous injection by wide-field fluorescence compared to nontransgenic littermate mice, in congruence with the vMSOT findings. SWI/phase images and Prussian blue indicated the accumulation of iron deposits in the brains of M83 mice, presumably in the Fe3+ form, as evinced by the STXM results. In conclusion, we demonstrated in vivo mapping of αSyn by means of noninvasive epifluorescence and vMSOT imaging and validated the results by targeting the THK-565 label and SWI/STXM identification of iron deposits in M83 mouse brains ex vivo.

Unveiling Metabolic Similarities of Entheses in Patients with Psoriasis and Psoriatic Arthritis Using Noninvasive In Vivo Molecular Imaging: Results From a Cross-sectional Exploratory Study.

We assessed and compared molecular tissue changes at the entheses in patients with psoriasis (PsO) and psoriatic arthritis (PsA) and in healthy controls (HCs) in vivo using multispectral optoacoustic tomography (MSOT) and described their relationship with clinical and ultrasound findings of enthesitis. A cross-sectional study (MSOT and Arthrosonography in PsA) in biologic disease-modifying antirheumatic drug-naïve patients with PsA and PsO and HCs was performed. Participants underwent clinical, ultrasonographic, and MSOT examination of six entheses (lateral humeral epicondyle, distal patellar tendon attachment, and Achilles tendon attachment). MSOT-measured hemoglobin (Hb), oxygen saturation (SO2), collagen, and lipid levels were quantified, and mean differences between groups were calculated using linear mixed effects models. MSOT-measured analytes were compared between entheses with and without clinical and ultrasound anomalies. Ninety participants were included (30 PsO, 30 PsA, and 30 HCs), 540 entheses were clinically assessed, and 540 ultrasound and 830 MSOT scans were obtained. Patients with PsA and PsO showed increased oxygenated Hb (PsA: P = 0.003; PsO: P = 0.054) and SO2 (PsA: P < 0.001; PsO: P = 0.001) levels and decreased collagen signals (PsA: P < 0.001; PsO: P < 0.001) compared with HCs, with more pronounced changes in PsA. Significantly lower collagen levels (P = 0.01) and increased lipids (P = 0.03) were recorded in tender entheses compared with nontender ones. Erosions and enthesophytes on ultrasound were associated with significant differences in SO2 (P = 0.014) and lipid signals (P = 0.020), respectively. Patients with PsA and PsO exhibit an analogous metabolic pattern at the entheses that is exacerbated in the presence of inflammation. These findings support the notion of a psoriatic disease spectrum characterized by common immunometabolic tissue changes.

Non-invasive optoacoustic imaging of dermal microcirculatory revascularization in diet-induced obese mice undergoing exercise intervention

Microcirculatory dysfunction has been observed in the dermal white adipose tissue (dWAT) and subcutaneous white adipose tissue (scWAT) of obese humans and has been proposed as an early prediction marker for cardio-metabolic disease progression. In-vivo visualization and longitudinal monitoring of microvascular remodeling in these tissues remains challenging. We compare the performance of two optoacoustic imaging methods, i.e. multi-spectral optoacoustic tomography (MSOT) and raster-scanning optoacoustic mesoscopy (RSOM) in visualizing lipid and hemoglobin contrast in scWAT and dWAT in a mouse model of diet-induced obesity (DIO) undergoing voluntary wheel running intervention for 32 weeks. MSOT visualized lipid and hemoglobin contrast in murine fat depots in a quantitative manner even at early stages of DIO. We show for the first time to our knowledge that RSOM allows precise visualization of the dWAT microvasculature and provides quantitative readouts of skin layer thickness and vascular density in dWAT and dermis. Combination of MSOT and RSOM resolved exercise-induced morphological changes in microvasculature density, tissue oxygen saturation, lipid and blood volume content in dWAT and scWAT. The combination of MSOT and RSOM may allow precise monitoring of microcirculatory dysfunction and intervention response in dWAT and scWAT in a mouse model for DIO. Our findings have laid out the foundation for future clinical studies using optoacoustic-derived vascular readouts from adipose tissues as a biomarker for monitoring microcirculatory function in metabolic disease.

Multispectral optoacoustic tomography of benign parotid tumors in vivo: a prospective observational pilot study

Parotid lumps are a heterogeneous group of mainly benign but also malignant tumors. Preoperative imaging does not allow a differentiation between tumor types. Multispectral optoacoustic tomography (MSOT) may improve the preoperative diagnostics. In this first prospective pilot trial the ability of MSOT to discriminate between the two most frequent benign parotid tumors, pleomorphic adenoma (PA) and Warthin tumor (WT) as well as to normal parotid tissue was explored. Six wavelengths (700, 730, 760, 800, 850, 900 nm) and the parameters deoxygenated (HbR), oxygenated (HbO2), total hemoglobin (HbT), and saturation of hemoglobin (sO2) were analyzed. Ten patients with PA and fourteen with WT were included (12/12 female/male; median age: 51 years). For PA, the mean values for all measured wave lengths as well as for the hemoglobin parameters were different for the tumors compared to the healthy parotid (all p < 0.05). The mean MSOT parameters were all significantly higher (all p < 0.05) in the WT compared to healthy parotid gland except for HbT and sO2. Comparing both tumors directly, the mean values of MSOT parameters were not different between PA and WT (all p > 0.05). Differences were seen for the maximal MSOT parameters. The maximal tumor values for 900 nm, HbR, HbT, and sO2 were lower in PA than in WT (all p < 0.05). This preliminary MSOT parotid tumor imaging study showed clear differences for PA or WT compared to healthy parotid tissue. Some MSOT characteristics of PA and WT were different but needed to be explored in larger studies.

Teachability of multispectral optoacoustic tomography.

To date, the appropriate training required for the reproducible operation of multispectral optoacoustic tomography (MSOT) is poorly discussed. Therefore, the aim of this study was to assess the teachability of MSOT imaging. Five operators (two experienced and three inexperienced) performed repositioning imaging experiments. The inexperienced received the following introductions: personal supervision, video meeting, or printed introduction. The task was to image the exact same position on the calf muscle for seven times on five volunteers in two rounds of investigations. In the first session, operators used ultrasound guidance during measurements while using only photoacoustic data in the second session. The performance comparison was carried out with full-reference image quality measures to quantitatively assess the difference between repeated scans. The study demonstrates that given a personal supervision and hybrid ultrasound real-time imaging in MSOT measurements, inexperienced operators are able to achieve the same level as experienced operators in terms of repositioning accuracy.

Homo-Dyad with Outer Hydration Layer Approach for Developing NIR-II Chromophore of High Stability and Water-Solubility as Injectable and Sprayable Optical Probe.

Dyes with extended conjugate structures are the focus of extensive design and synthesis efforts, aiming to confer unique and improved optical and electronic properties. Such advancements render these dyes applicable across a wide spectrum of uses, ranging from second-window near-infrared (NIR-II) bioimaging to organic photovoltaics. Nevertheless, the inherent benefits of long conjugation are often accompanied by persistent challenges like aggregation, fluorescence quenching, absorption blueshift, and low stability and poor water solubility. Herein, a unique structural design strategy termed "homo-dyad with outer hydration layer" is introduced to address these inherent problems, tailored for the development of imaging probes exhibiting long absorption/emission wavelengths. This approach involves bringing two heptamethine cyanines together through a flexible linker, forming a homo-dyad structure, while strategically attaching four polyethylene glycol (PEG9) chains to the terminal heterocycles. This approach imparts excellent water solubility, biocompatibility, and enhanced chemical, photo-, and spectral stability for the dyes. Utilizing this strategy, a biomarker-activatable probe (HD-FL-4PEG9-N) for NIR-II fluorescent and 3D multispectral optoacoustic tomography imaging is developed, and its effectiveness in disease visualization. It can not only serve as an injectable probe for acute kidney injury imaging due to its high water solubility, but also a sprayable probe for imaging bacterial-infected wounds.

Abstract 4162: Peptide-targeted probe identifies pancreatic cancer using optoacoustic imaging

Abstract Introduction: Advanced pancreatic ductal adenocarcinoma (PDAC) suffers from inadequate early detection, inoperability, and poor outcomes. While tumor identication in an intraoperative setting largely utilize ultrasound, ultrasound suffers from insufficient resolution and lacks the ability to identify molecular features to differentiate tumor from non-tumor. To overcome these limitations, we utilized optoacoustic imaging combined with a pH-sensitive peptide-based probe, V3, to identify pancreatic cancer in orthotopic mouse models. Methods: The V3 peptide was synthesized using microwave chemistry which resulted in a peptide of &amp;gt;90% purity. The V3 peptide was conjugated to a fluorescent dye and dialyzed to make the V3-750 probe. S2VP10 cancer cell line was plated in a 6-well plate and acclimated to 7.4, 6.8, and 6.6 pH media to mimic a healthy microenvironment and the acidic tumor microenvironment found in pancreas cancer. Cells were treated with 1 micromolar of V3-750 probe for 1 hour, then imaged on the near-infrared fluorescence imager. Treated cells were loaded into tissue mimicking phantoms and imaged using multispectral optoacoustic tomography. Athymic mice were orthotopically implanted with S2VP10 cells and tumor grew to 3 mm. V3-750 was intraveneously injected and mice were imaged 3h after injection with MSOT. Results: Signal values for the samples displayed a trend that the V3-750 probe has higher signal values in the 6.8 and 6.6 pH as compared to the 7.4 pH. MSOT data supported this trend, with the signal values from the 6.8 and 6.6 pH being greater than the 7.4 pH by 10-fold (p&amp;lt;0.05). Biodistribution demonstrates peak tumor-specific uptake at 3h post injection (3.1 a.u., 0.003 a.u. liver, 0.002 a.u. kidney). Conclusion: The heightened signal values for the acidic pH’s from the fluorescence imaging and the MSOT suggest that the V3-750 probe can contrast acidic cancer cells from healthy cells because it targets the acidic cancer microenvironment. Citation Format: Emma Sanderson, Tereza Husarova, Lacey McNally. Peptide-targeted probe identifies pancreatic cancer using optoacoustic imaging [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 4162.

Abstract 4160: V7 targeted liposomes detect pancreatic adenocarcinoma via multispectral optoacoustic tomography

Abstract Purpose: Pancreatic ductal adenocarcinoma (PDA) remains one of the most aggressive malignancies with a 5-year survival rate of 9-10%. Insufficient early detection coupled with limitations in operating surgery renders PDA as one of the most challenging tumors to treat. Accurate localization of tumor margins can tremendously improve surgical treatment outcomes in patients. Recently, nanotechnology has emerged as a promising platform for theranostic applications in the field of drug discovery, although the clinical success is limited by their tumor-specific uptake. Hypoxia due to aberrant vascularization is a hallmark of PDA and can be exploited for active targeting. pH-low insertion peptide variant 7 (V7) is used as hypoxia and acidosis-dependent biomarker for selective targeting of pancreatic cancer tissue. This work is focused on using IR 780 contrast agent loaded, V7 peptide conjugated liposomes for the active targeting of PDA towards enhanced surgical outcomes. Methods: Liposomes encapsulating IR780 dye were prepared using thin film hydration technique. V7 peptide was conjugated to liposomes using an SMCC linker and liposomes were characterized for their size, polydispersity and surface potential. In-vitro uptake of IR780-V7-liposome by S2VP10 at pH 7.4, 6.8, and 6.6 was evaluated through NIR fluorescence imaging using an Odyssey Infrared System. Athymic mice were orthotopically implanted with S2VP10 cells. After tumors were 3 mm, V7-liposomes and untargeted liposomes (0.01 OD) were intravenously injected and biodistribution and tumor specific uptake was accessed using multispectral optoacoustic imaging (MSOT). Results: Dynamic light scattering (DLS) revealed the size of liposomes to be 109 nm with a polydispersity index of 0.198 and zeta potential of +35.8 mV. Surface conjugation of V7 peptide was confirmed using the zeta potential measurement. NIR fluorescence imaging in S2VP10 cells established enhanced tumor specific uptake of V7 conjugated liposomes than passively targeted liposomes (p&amp;lt;0.05). Biodistribution of V7-liposomes demonstrated tumor specific accumulation (PDAC tumor 23.7 a.u, liver 3.6 a.u., and kidney 1.1 a.u.) while untargeted liposomes had the greatest uptake in liver (PDAC tumor 2.1 a.u., liver 6.3 a.u., and kidney 0.7 a.u.) p&amp;lt;0.05. Conclusion: pH-specific actively targeted liposomes can be used to specifically target PDA with minimal off-target binding effects. V7-IR780-liposome formulation can be used to efficiently deliver contrast agent for imaging tumor margins and to expand the potential of MSOT towards clinical applications. Citation Format: Happy Agarwal, Phillip Chuong, William E. Grizzle, Barish H. Edil, Ajay Jain, Lacey R. McNally. V7 targeted liposomes detect pancreatic adenocarcinoma via multispectral optoacoustic tomography [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 4160.

Ultra-photostable small-molecule dyes facilitate near-infrared biophotonics

Long-wavelength, near-infrared small-molecule dyes are attractive in biophotonics. Conventionally, they rely on expanded aromatic structures for redshift, which comes at the cost of application performance such as photostability, cell permeability, and functionality. Here, we report a ground-state antiaromatic strategy and showcase the concise synthesis of 14 cationic aminofluorene dyes with mini structures (molecular weights: 299–504 Da) and distinct spectra covering 700–1600 nm. Aminofluorene dyes are cell-permeable and achieve rapid renal clearance via a simple 44 Da carboxylation. This accelerates optical diagnostics of renal injury by 50 min compared to existing macromolecular approaches. We develop a compact molecular sensing platform for in vivo intracellular sensing, and demonstrate the versatile applications of these dyes in multispectral fluorescence and optoacoustic imaging. We find that aromaticity reversal upon electronic excitation, as indicated by magnetic descriptors, not only reduces the energy bandgap but also induces strong vibronic coupling, resulting in ultrafast excited-state dynamics and unparalleled photostability. These results support the argument for ground-state antiaromaticity as a useful design rule of dye development, enabling performances essential for modern biophotonics.

Abstract 4163: Improving the dynamic range of pH low insertion peptides for targeted imaging of pancreatic tumors

Abstract Objective: Current intraoperative imaging modalities such as near-infrared fluorescent imaging (NIR) or ultrasound are limited due to operator experience and depth, and targeted imaging of pancreatic tumors would be beneficial. However, specific pancreatic tumor biomarkers available for targeting in a novel imaging protocol are lacking. As such, we focus on developing a novel targeted imaging paradigm utilizing multispectral optoacoustic imaging (MSOT) to target the acidic microenvironment of pancreatic tumors. Peptides know as pH low insertion peptides (pHLIPs) when bound to dye allow for contrasted imaging selectively based on pH using MSOT. We have identified the need for a pHLIP with improved dynamic range to improve imaging accuracy. Here, we synthesize the novel pHLIP V7FS for comparison to V3 with aims of improving the dynamic range of imaging with MSOT in pancreatic cancer. Methods: Using microwave chemistry, V7FS and V3 were synthesized with &amp;gt;90% purity. Peptides were conjugated to HiLyte 750 dye, and peptide-dye conjugation confirmed via spectroscopy. Intraoperative measurements of human pancreatic tumor and surrounding uninvolved tissue were obtained using a microsensor. Near-infrared fluorescent imaging was used to measure probe uptake in S2VP10 and S2013 pancreatic cancer cells lines grown in pH specific media (7.4, 6.8, 6.6) in replicates. MSOT was then used to image probes in phantoms mimicking tissue and then in mice with pancreatic tumors from orthotopically implanted S2VP10. Statistical analysis was performed using ANOVA. Results: Compared to surrounding uninvolved pancreatic tissue, human pancreatic tumor was more acidic with pH 6.2-6.7 vs 7.2-7.3 (p&amp;lt;0.01). Signal at pH 7.4, 6.8 and 6.6 was higher for V7FS-750 compared to V3-750 (p=0.0105). Signal for V7FS-750 was centered around pH 6.6 and signal for V3-750 centered around pH 6.8. Interaction between probe and pH did not reach significance (p=0.745). Peak uptake in orthotopic murine models was observed at 3 hours following intravenous injection. Conclusions: V7FS-750 was shown to have higher signal accumulation compared to V3-750 favoring a more acidic environment (pH 6.6 vs pH 6.8). This novel pHLIP was demonstrated to be viable for use in an imaging paradigm utilizing MSOT in an orthotopic murine model. Continued improvement in the dynamic range of these probes is promising for the use of pHLIPS in imaging of pancreatic cancer with MSOT. Citation Format: Ryan Bynum, Emma Sanderson, Barish H. Edil, Ajay Jain, Lacey R. McNally. Improving the dynamic range of pH low insertion peptides for targeted imaging of pancreatic tumors [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 4163.

Polysuccinimide-based nanoparticle: A nanocarrier with drug release delay and zero burst release properties for effective theranostics of cancer

We have developed a novel pH-responsive delivery system consisting of oleylamine-modified polysuccinimide (PSI) nanoparticles (NPs) whereby NPs remained stable and started to release bioactive agents after 8.5 h with maximal release acquired after 36 h under physiological pH. Our NPs did not exhibit any burst release of drug, which is a key advantage in anti-cancer targeted drug delivery system. Here, the NPs function as a carrier for bioactive agents such as Curcumin and IR-780 dye whereby the former exerts its intrinsic anti-cancer abilities, the latter confers photothermal treatment application and bimodal imaging ability using photoacoustic and fluorescence imaging. In vitro and in vivo results establish that administration of folate receptors targeting PSI-NPs in U87MG model effected in a substantial decrease in tumour and photothermal laser exposure at 808 nm further ablated tumours to an almost total eradication. Our dual loaded targeted NPs demonstrated selectivity through enhanced accumulation and retention in tumours as indicated by multi-spectral optoacoustic tomography (MSOT) and fluorescence imaging (FI). Loading of Curcumin and IR-780 into PSI-NPs improved its bioavailability, allowing Curcumin to be administered into the circulation system and retention in tumours which led to the simultaneous application for a successful targeted, synergistic photothermal treatment and bimodal imaging using MSOT and FI.

Multispectral Optoacoustic Tomography Enables In Vivo Anatomical and Functional Assessment of Human Tendons.

Tendon injuries resulting from accidents and aging are increasing globally. However, key tendon functional parameters such as microvascularity and oxygen perfusion remain inaccessible via the currently available clinical diagnostic tools, resulting in disagreements on optimal treatment options. Here, a new noninvasive method for anatomical and functional characterization of human tendons based on multispectral optoacoustic tomography (MSOT) is reported. Healthy subjects are investigated using a hand-held scanner delivering real-time volumetric images. Tendons in the wrist, ankle, and lower leg are imaged in the near-infrared optical spectrum to utilize endogenous contrast from Type I collagen. Morphology of the flexor carpi ulnaris, carpi radialis, palmaris longus, and Achilles tendons are reconstructed in full. The functional roles of the flexor digitorium longus, hallicus longus, and the tibialis posterior tendons have been visualized by dynamic tracking during toe extension-flexion motion. Furthermore, major vessels and microvasculature near the Achilles tendon are localized, and the global increase in oxygen saturation in response to targeted exercise is confirmed by perfusion studies. MSOT is shown to be a versatile tool capable of anatomical and functional tendon assessments. Future studies including abnormal subjects can validate the method as a viable noninvasive clinical tool for tendinopathy management and healing monitoring.

Preclinical multi-physiologic monitoring of immediate-early responses to diverse treatment strategies in breast cancer by optoacoustic imaging.

Optoacoustic imaging enables the measurement of tissue oxygen saturation (sO2) and blood perfusion while being utilized for detecting tumor microenvironments. Our aim was to employ multispectral optoacoustic tomography (MSOT) to assess immediate-early changes of hemoglobin level and sO2 within breast tumors during diverse treatments. Mouse breast cancer models were allocated into four groups: control, everolimus (EVE), paclitaxel (PTX), and photodynamic therapy (PDT). Hemoglobin was quantified daily, as well as sO2 and blood perfusion were verified by immunohistochemical (IHC) staining. MSOT showed a temporal window of enhanced oxygenation and improved perfusion in EVE and PTX groups, while sO2 consistently remained below baseline in PDT. The same results were obtained for the IHC. Therefore, MSOT can monitor tumor hypoxia and indirectly reflect blood perfusion in a non-invasive and non-labeled way, which has the potential to monitor breast cancer progression early and enable individualized treatment in clinical practice.

Local Magnetic Hyperthermia and Systemic Gemcitabine/Paclitaxel Chemotherapy Triggers Neo-Angiogenesis in Orthotopic Pancreatic Tumors without Involvement of Auto/Paracrine Tumor Cell VEGF Signaling and Hypoxia.

There is a growing interest in exploring the therapeutically mediated modulation of tumor vascularization of pancreatic cancer, which is known for its poorly perfused tumor microenvironment limiting the delivery of therapeutic agents to the tumor site. Here, we assessed how magnetic hyperthermia in combination with chemotherapy selectively affects growth, the vascular compartment of tumors, and the presence of tumor cells expressing key regulators of angiogenesis. To that purpose, a orthotopic PANC-1 (fluorescent human pancreatic adenocarcinoma) mouse tumor model (Rj:Athym-Foxn1nu/nu) was used. Magnetic hyperthermia was applied alone or in combination with systemic chemotherapy (gemcitabine 50 mg per kg body weight, nab-pacitaxel 30 mg/kg body weight) on days 1 and 7 following magnetic nanoparticle application (dose: 1 mg per 100 mm3 of tumor). We used ultrasound imaging, immunohistochemistry, multi-spectral optoacoustic tomography (MSOT), and hematology to assess the biological parameters mentioned above. We found that magnetic hyperthermia in combination with gemcitabine/paclitaxel chemotherapy was able to impact tumor growth (decreased volumes and Ki67 expression) and to trigger neo-angiogenesis (increased small vessel diameter) as a result of the therapeutically mediated cell damages/stress in tumors. The applied stressors activated specific pro-angiogenic mechanisms, which differed from those seen in hypoxic conditions involving HIF-1α, since (a) treated tumors showed a significant decrease of cells expressing VEGF, CD31, HIF-1α, and neuropilin-1; and (b) the relative tumor blood volume and oxygen level remained unchanged. Neo-angiogenesis seems to be the result of the activation of cell stress pathways, like MAPK pathways (high number of pERK-expressing tumor cells). In the long term, the combination of magnetic hyperthermia and chemotherapy could potentially be applied to transiently modulate tumor angiogenesis and to improve drug accessibility during oncologic therapies of pancreatic cancer.