Multispectral Optoacoustic Tomography Research Articles

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

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. 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. Scanning revealed a 46% decrease in TBV and a 25% decrease in sO2 in the diabetic iBAT with respect to the healthy control. 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.

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

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.

Osteopontin-targeted probe detects orthotopic breast cancers using optoacoustic imaging

ABSTRACT 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.

Correction to Preventing Plasmon Coupling between Gold Nanorods Improves the Sensitivity of Photoacoustic Detection of Labeled Stem Cells in Vivo.

Gold nanorods are excellent contrast agents for imaging technologies which rely on near-infrared absorption such as photoacoustic imaging. For cell tracking applications, the cells of interest are labeled with the contrast agent prior to injection. However, after uptake into cells by endocytosis, the confinement and high concentration in endosomes leads to plasmon band broadening and reduced absorbance. This would limit the potential of multispectral optoacoustic tomography in terms of spectral processing and, consequently, sensitivity. Here, we show that steric hindrance provided by silica coating of the nanorods leads to the preservation of their spectral properties and improved photoacoustic sensitivity. This strategy allowed the detection and monitoring of as few as 2 × 104 mesenchymal stem cells in mice over a period of 15 days with a high spatial resolution. Importantly, the silica-coated nanorods did not affect the viability or differentiation potential of the transplanted mesenchymal stem cells.

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

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.

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

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.

Applying dynamic contrast enhanced MSOT imaging to intratumoral pharmacokinetic modeling

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).

Abstract 3727: Dual acidic pH targeted mesoporous silica nanoparticles for noninvasive detection of triple negative breast cancer

Abstract Purpose: Current screening methods for triple negative breast cancer suggest the presence and size of tumor, but do not identify the tumor microenvironment. The inability to determine precise tumor location and position following diagnosis impedes medical confidence in surgical resection and radiation therapy. Theranostic nanoparticles can be targeted for dye and drug delivery to facilitate non-invasive characterization and treatment of malignancies. Combinational use of nanomedicine and Multispectral Optoacoustic Tomography (MSOT) renders high resolution images through ultrasonic detection of thermoelastic dye expansion (the optoacoustic effect). Approaches in nanomedicine are steadily growing, but clinical evaluation relies on minimizing off-target accumulation and controlling cargo release. We evaluated a mesoporous silica nanoparticles with pH-sensitive chitosan gatekeeper and tumor targeting V3 pH low-insertion peptide (V3 pHLIP) conjugation (V3-CMSN-780) for dual acidic pH targeted delivery to triple negative breast cancer. Methods: Mesoporous silica nanoparticles were synthesized around a structural skeleton of hexadecyltrimethylammonium bromide (CTAB). CTAB was removed from the particles through repeated dialysis. Subsequent particles were characterized with digital light scattering (DLS) and zetasizer to confirm particle size and zeta potential. Mesoporous nanoparticles were then coated with chitosan for extracellular acidic pH selectivity and functionalized with variant 3 pH low-insertion peptide (V3 pHLIP) to promote anchoring of the particle to tumor cells. Functionalized nanoparticles (V3-CMSN) were loaded with NIR 780 (5 mg/mL) and delivered to MDA-MB-231 and MDA-MB-468 malignant cell lines at pH 7.4, 6.8, and 6.6 to confirm pH-sensitive dye release into the cells with Near Infrared fluorescent imaging. V3-CMSN treated cells were inserted into tissue mimicking phantoms which were evaluated using MSOT. Results: The size of V3-CMSN-780 was 35 d. nm with a zeta potential of 25 mV. V3-CMSN were loaded with 780 dye with a dye loading efficiency of 77%. Cellular uptake of V3-CMSN-780 within MDA-MB-231 cells was 2152 a.u., 5242 a.u., and 3639 a.u. at pHs 7.4, 6.8, and 6.6, respectively, based NIR fluorescent imaging. Treatment of MDA-MB-231 cells with V3-CMSN-780 within tissue mimicking phantoms also confirmed acidic pH selectivity of the particles with a 6X and 4X accumulation of particles at pH 6.8 and 6.6 as compared to pH 7.4. While similar results were observed in MDA-MB-468 cells with NIR fluorescent imaging, MSOT imaging indicated that MDA-MB-468 cells treated at pH 6.8 and 6.6 had increased 780 signal, 110X and 16X, incomparison to pH 7.4. Conclusion: Successful dual targeting of breast tumor cells provides a foundation for later in vivo and ex vivo studies using V3-780-CMSNs to deliver diagnostic and therapeutic cargo to malignant breast tissue. Citation Format: Joshua T. Hayes, Abhilash Samykutty, Molly McNally, Alexandra Thomas, Akiko Chiba, William Grizzle, Karen M. Winkfield, Lacey R. McNally. Dual acidic pH targeted mesoporous silica nanoparticles for noninvasive detection of triple negative breast cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 3727.

Abstract 4122: Acidic tumor microenvironment targeted wormhole-shaped mesoporous silica nanoparticles to detect ovarian cancer by multispectral optoacoustic tomography

Abstract Purpose: The implementation of the innovative technologies remains the top priority for the development of potential modalities for the diagnosis and treatment of various cancers. Despite all the recent advances, ovarian cancer is considered as a lethal gynecologic malignancy in which vast majority of the cases are diagnosed at the late metastatic stage at which the prognosis is poor. Because of the few apparent early symptoms, significant effort was made for developing efficient methods to identify early progression of the disease. We demonstrated that the bioconjugation of the V7 peptide on 27nm wormhole mesoporous silica nanoparticles (V7-CWMSN) particles specifically release the IR780 imaging probe at the orthotopically implanted early-stage ovarian tumor to detect by multispectral optoacoustic imaging technology (MSOT). Methods: Wormhole mesoporous silica nanoparticles (WMSN) were synthesized by sol-gel chemistry. The WMSN were characterized by dynamic light scattering (DLS) and transmission electron microscopy (TEM). The surface of the WMSN particle was functionalized with pH sensitizer chitosan to obtain CWMSN. The CWMSN particle was loaded with propidium Iodide (PI) or IR780 infrared imaging dye. Further, the conjugation of the CWMSN with V7 pHLIP peptide (V7-CWMSN) developed pH sensitive cargo release from the nanoparticles. Female athymic mice were orthotopically implanted with ES-2 ovarian cancer cells. Following 10 days of orthotopic implantation of the tumor cells, mice were intravenously injected with V7-CWMSN particles containing IR780 dye and were imaged with MSOT. Results: In the current study, we have synthesized the wormhole-shaped mesoporous silica particles (WMSN) with the 27 nm diameter carrying IR780 imaging probes for the detection of early-stage ovarian cancer. The V7 peptide undergoes a conformational change upon contact with the acidic tumor microenvironment. Also, the chitosan crosslinking on the surface of the particles (V7-CWMSN) acts as a gatekeeper that is degradable upon contact with acidic pH tumor to prevent off-target release. As a model for ovarian cancer, we have used athymic mice orthotopically implanted with ovarian cancer cells. This model closely resembles the human ovarian cancer pathophysiology. Our results have demonstrated that the intravenous delivery of V7-CWMSN particles could detect the orthotopically implanted early-stage ovarian tumors (p&amp;lt;0.0001,n=5). Conclusion: The development of the distinct nanoformulations with potent imaging technology enables the visualization of early-stage ovarian tumors. Translating these modalities may allow clinicians to identify early-stage malignancies that are currently undetectable through conventional imaging techniques. Citation Format: Abhilash Samykutty, Molly W. McNally, William E. Grizzle, Akiko Chiba, Alexandra Thomas, Lacey R. McNally. Acidic tumor microenvironment targeted wormhole-shaped mesoporous silica nanoparticles to detect ovarian cancer by multispectral optoacoustic tomography [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 4122.

Abstract 4103: Utility of multispectral optoacoustic tomography in imaging pancreatic tumors using a uPA-probe

Abstract Background: Pancreatic cancer has the lowest 5-year survival rate of all cancer types. Current methods of pancreatic cancer screening, diagnosis and treatment have failed to improve outcome in the last few decades. Potential explanation for this failure may be explained by the hypovascularized nature of pancreatic cancer, making conventional chemotherapy and imaging modality suboptimal. There is a potential for improved imaging using a new imaging modality, multispectral optoacoustic tomography (MSOT). We hypothesize that a using urokinase plasminogen activator (uPA) contrast agent while using MSOT imaging would improve identification of orthotopic pancreatic cancer in xenografts. Methods: Expression of uPA receptor (uPAR) were evaluated in pancreatic tumor cell lines, Panc1, S2CP9, MiaPaca-2 and S2VP10 using western blot. A uPA targeted contrast agent was created using standard bioconjugation methods with the Hilite 750 near infrared (NIR) dye. Five SCID mice were orthotopically implanted with S2CP9 (1.5 x 105) and 5 additional SCID mice were implanted with MiaPaCa2 (2.0 x 106) pancreatic tumor cells. When tumor size reached 3mm, 200µL of 100 nM uPA-750 probe or 750 dye alone was injected into mice. Biodistribution and accumulation of the uPA-750 probe was visualized using MSOT imaged at 2-hour intervals for 8 hours and at 24 hours. Accumulation of uPA-750 probe was evaluated in the tumor, liver, and kidney using NIR fluorescent imaging. Results: All pancreatic cancer cell line expressed uPAR with the highest in S2CP9 cells (3.0x), S2VP10 (2.5x), Panc1 (1.77x) and MiaPaca-2 (1.3x). In vivo, peak intensity of uPA-750 probe was successfully detected using MSOT at 4 hours, within the pancreas tumor in slices from 37mm-41mm. uPA-750 probe was undetectable within the tumor after 8 hours. Using ex vivo NIR fluorescence imaging, uPA-probe signal was detected only within the pancreatic tumor, however, no signal was detected in the liver or kidney. Conclusion: This study demonstrated MSOT imaging using uPA-probe as a contract agent may lead to improved pancreatic cancer detection which may lead to improvement in overall outcome. Citation Format: Akiko Chiba, Abhilash Samykutty, Mary Smith, Lacey McNally. Utility of multispectral optoacoustic tomography in imaging pancreatic tumors using a uPA-probe [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 4103.

Abstract 4664: Enzymatically-responsive tumor-targeted mesoporous silica nanoparticle for identification of pancreatic cancer

Abstract Purpose: Pancreatic cancer remains an unsolved health issue, with its rapid progression and resistance to modern therapy leading to poor prognoses for most patients. The prevalence of metastasis in pancreatic cancer makes complete tumor location and removal rare, and those who do have resectable disease have only a 20% 5-year survival rate. In recent years, nanoparticles have been explored as targeted delivery agents for chemotherapeutic drugs and imaging dyes, however few have achieved clinical success due to overestimation of biological phenomena and reliance on passive targeting systems. In this work, an enzyme-responsive nanoparticle has been developed for increased active pancreatic tumor targeting and specific release at biologically-significant enzyme concentrations. Methods: Mesoporous silica nanoparticles were formed using a scaffold of hexadecyltrimethylammonium bromide (CTAB) at 80°C. The scaffold was removed to form wormhole-like pores using a series of dialysis procedures. Transmission electron microscopy (TEM) confirmed the 35 nm diameter and porous structure of the particles. The particles were then loaded with IR780 dye, and surfaces were functionalized with (3-aminopropyl) triethoxysilane (APTES). The loaded particles were then encapsulated with a combination of Type A and Type B gelatin, followed by a stabilizing polyvinylpyrrolidone (PVP) layer. Dynamic light scattering (DLS) and zeta potential were used to confirm coating. Coated particle samples were exposed to collagenase type IV (MMP-9) enzyme to test encapsulation efficiency and enzyme sensitivity. Enzyme-treated and intact samples were transferred to tissue phantoms, and Multispectral optoacoustic tomography (MSOT) was used for comparative analysis. Results: TEM confirmed the formation of stable 35 nm silica nanoparticles with a wormhole-like pore structure. Zeta potential decrease from 55 mV to 5 mV and DLS particle diameter increase from 35 nm to 334.5 nm indicated binding of gelatin and PVP to particle surfaces. MSOT imaging showed 10 X increased signals from untreated nanoparticles as compared to enzyme-treated nanoparticles, indicating that dye molecules remained inside the pores of coated particles and were released when exposed to MMP-9. Conclusion: Gelatin/PVP-coated mesoporous silica nanoparticles encapsulated dye and demonstrated MMP-9 activated dye release at biologically-relevant enzyme concentrations. Citation Format: Kylie Nairon, Abhilash Samykutty, Molly W. McNally, Girish Mishra, William E. Grizzle, Lacey R. McNally. Enzymatically-responsive tumor-targeted mesoporous silica nanoparticle for identification of pancreatic cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 4664.

New cross-sectional imaging in IBD.

Cross-sectional imaging, namely ultrasound, CT and MR enterography, complements clinical and endoscopic monitoring of activity and complications in IBD, and emerging new radiological technologies may have clinical applications in the near future. This review offers an update on the potential role of these new imaging methods in the management of IBD. Specific MR techniques [diffusion-weighted imaging (DWI), diffusion kurtosis imaging (DKI) and magnetization transfer] allow accurate detection of inflammation (DWI and maybe DKI) and fibrosis (magnetization transfer) in Crohn's disease, without the need of intravenous gadolinium administration. ultrasonography developments (elastography, contrast-enhanced ultrasonography, small intestine contrast ultrasonography and multispectral optoacoustic tomography) are promising techniques for evaluation of fibrosis (elastography) and inflammation (contrast ultrasonography). Dose-reduction techniques in CT allow similar quality imaging and diagnostic accuracy with lower radiation exposure. Hybrid imaging (PET/MR and PET/CT) hold promise for grading inflammation in Crohn's disease. The potential benefits of new cross-sectional imaging techniques in IBD include better inflammation grading, such as identification of mild degree of activity, which may be relevant whenever assessing response to treatment and, of uttermost importance, accurate preoperative detection and grading of fibrosis in stricturing Crohn's disease, facilitating surgical vs. medical therapeutic decisions.

Abstract 4121: Differences in optoacoustic signal reflect different characteristics of the vasculature and response to antiangiogenic therapy in breast cancer models

Abstract Optoacoustic imaging has the potential to monitor tumour neo-vascularization, essential for disease progression and also a target for therapy. While promising in some settings, anti-angiogenic therapy has yet to fulfil its promise and mechanisms of resistance are poorly understood. In breast cancer, for example, resistance has been linked to hormonal status, oxygen consumption and alternative mechanisms of neo-vasculogenesis, including vascular mimicry (VM). Here, we use two mouse xenograft models: estrogen-dependent MCF-7 and estrogen independent MDA-MB-231. We analyse their characteristics in vivo using Multispectral optoacoustic tomography (MSOT) to detect oxy- and deoxy- haemoglobin (Hb) during tumour growth. We also analysed their histological and biochemical characteristics for blood vessel density (CD31) and maturity (aSMA, PAS staining), tumour hypoxia (CAIX), angiogenesis, inflammation and VM. Anti-angiogenic therapy response was also tested using Bevacizumab (BV, 10 mg/Kg) in two cohorts. While MSOT reveals similar blood content in both tumours, estrogen-dependent MCF-7 tumours show higher blood oxygenation than estrogen-independent MDA-MB-231 (55.8±7.5 % vs. 45.6±5.1%, p=0.0008) with values similar to healthy tissue (55.8±7.5 % vs. 57.8±5.3%, p=0.917). Ex vivo histological analysis shows that while MDA-MB-231 tumours are more hypoxic compared to MCF-7, they have a higher blood vessel density, however, the vasculature of MCF-7 tumours is more mature (vessel wall thickness and aSMA coverage). Based on molecular biomarkers, MCF-7 presents a more pro-inflammatory endothelial-like response, marked by an increase of vascular endothelial growth factor (p&amp;lt;0.0001) of host origin (mVEGF), macrophage Nitric Oxide Sinthase (iNOS) and circulating NO, a mediator in inflammation and endothelial homeostasis (p=0.0031). VE-Cadherin of human origin is detectable in MDA-MB-231 tumours, which present CD31-absent blood vessels; together, these findings indicate presence of VM in MDA-MB-231 tumours. Interestingly, these 2 biological profiles respond differently to the anti-angiogenic drug BV: we observed a partial response in MDA-MB-231 tumours (CR=2/22, PR=3/22), but no effect in tumour size or survival was observed in MCF-7 tumours. While no change was observed in mVEGF upon BV treatment in any cohort, changes in optoacoustic signal of total Hb were observed in the MDA-MB-231 tumours after treatment. In conclusion, optoacoustic imaging delineates the vascular function of the blood vessel networks generated by angiogenesis and vascular mimicry respectively in our estrogen-dependent and estrogen-independent breast cancer xenografts. This study highlights the potential application of this technique in monitoring tumour vasculature development and in the future could be used to assess response to therapy. Citation Format: Isabel Quiros-Gonzalez, Michal Tomaszewski, Laura Ansel-Bollepalli, Sarah J. Aikten, Michael Gill, Sarah E. Bohndiek. Differences in optoacoustic signal reflect different characteristics of the vasculature and response to antiangiogenic therapy in breast cancer models [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 4121.

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

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.

A UCP1 Near-Infrared Reporter System for Monitoring Adipose “Browning” In Vivo Using Photoacoustic Imaging

Obesity has reached pandemic proportions in the developed world. The discovery that white adipocytes have the capacity to undergo browning to become metabolically-active beige cells has generated significant interest in the field of metabolic medicine. However, the study of adipose tissue browning has been hampered by a lack of imaging modalities that permit longitudinal and non-invasive monitoring of this process. To this end, we designed near infra-red (NIR) fluorescence protein iRFP720-Ucp1 reporter construct, in which the expression of iRFP720 is driven by a mini UCP1 promoter. Non-invasive assessment of adipose beiging during adrenergic stimulation was performed by viral transduction of mouse white adipocytes, followed by multi-spectral optoacoustic imaging technology with ultrasound tomography (MSOT-US). We observed increased iRFP720 fluorescence coupled with attenuated lipid signals upon stimulation. As proof of concept, we validated our approach against the hybrid positron emission tomography combined with magnetic resonance (PET/MR) imaging modality, and quantified the extent of adipose browning by MRI-guided segmentation of PET signals. Notably, the browning extent detected by the iRFP720 reporter system with MSOT-US and the 18-FDG uptake in PET/MR are well correlated with Ucp1 induction. Together, these systems provide platforms for preclinical screening of compounds aimed to promote adipose browning and facilitate the translation of these discoveries into pharmacological treatments for obesity. Disclosure D. Chan: None. S. Sugii: Stock/Shareholder; Self; Celligenics. W. Han: None.

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

.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.

Bacterial encapsulins as orthogonal compartments for mammalian cell engineering

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.

MSOT: materials selection optimization in the LEED v4 protocol - a case study with BIM

The availability of tools that assess the material sustainability in relation to the green protocols is scarce. The research proposes a tool and a methodology to support the materials selection in terms of sustainability whilst also comparing material choices with a quantification of the associated LEED.v4 BD+C MR credits. It assesses the design whilst providing advice to designers on material choice improvement both to achieve LEED maximum score and material sustainability. The quantification is achieved using parameters defined in the project’s BIM model. The methodology was applied in a case study. The extension of the research to include non-certified materials and the application of it to other case studies is recommended as some materials and products fall out of the current assessment system.

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

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.

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

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.