An integrated widefield imaging and spectroscopy system for contrast-enhanced, image-guided resection of tumors

An Explicit Estimated Baseline Model for Robust Estimation of Fluorophores Using Multiple-Wavelength Excitation Fluorescence Spectroscopy

Spectroscopy is a popular technique for identifying and quantifying fluorophores in fluorescent materials. However, quantifying the fluorophore of interest can be challenging when the material also contains other fluorophores (baseline), particularly if the emission spectrum of the baseline is not well-defined and overlaps with that of the fluorophore of interest. In this work, we propose a method that is free from any prior assumptions about the baseline by utilizing fluorescence signals at multiple excitation wavelengths. Despite the nonlinearity of the model, a closed-form expression of the least squares estimator is also derived. To evaluate our method, we consider the practical case of estimating the contributions of two forms of protoporphyrin IX (PpIX) in a fluorescence signal. This fluorophore of interest is commonly utilized in neuro-oncology operating rooms to distinguish the boundary between healthy and tumor tissue in a type of brain tumor known as glioma. Using a digital phantom calibrated with clinical and experimental data, we demonstrate that our method is more robust than current state-of-the-art methods for classifying pathological status, particularly when applied to images of simulated clinical gliomas. To account for the high variability in the baseline, we are examining various scenarios and their corresponding outcomes. In particular, it maintains the ability to distinguish between healthy and tumor tissue with an accuracy of up to 87%, while the ability of existing methods drops near 0%.

Tuned near infrared fluorescent hyaluronic acid conjugates for delivery to pancreatic cancer for intraoperative imaging

The prognosis of pancreatic cancer remains poor. Intraoperative fluorescence imaging of tumors could improve staging and surgical resection, thereby improving prognosis. However, imaging pancreatic cancer with macromolecular delivery systems, is often hampered by nonspecific organ accumulation.

Methods: We describe the rational development of hyaluronic acid (HA) conjugates that vary in molecular weight and are conjugated to near infrared fluorescent (NIRF) dyes that have differences in hydrophilicity, serum protein binding affinity, and clearance mechanism. We systematically investigated the roles of each of these properties on tumor accumulation, relative biodistribution, and the impact of intraoperative imaging of orthotopic, syngeneic pancreatic cancer.

Results: Each HA-NIRF conjugate displayed intrapancreatic tumor enhancement. Regardless of HA molecular weight, Cy7.5 conjugation directed biodistribution to the liver, spleen, and bowels. Conjugation of IRDye800 to 5 and 20 kDa HA resulted in low liver and spleen signal while enhancing the tumor up to 14-fold compared to healthy pancreas, while 100 kDa HA conjugated to IRDye800 resulting in liver and spleen accumulation.

Conclusion: These studies demonstrate that by tuning HA molecular weight and the physicochemical properties of the conjugated moiety, in this case a NIRF probe, peritoneal biodistribution can be substantially altered to achieve optimized delivery to tumors intraoperative abdominal imaging.

Targeted Drug Delivery and Image-Guided Therapy of Heterogeneous Ovarian Cancer Using HER2-Targeted Theranostic Nanoparticles

Cancer heterogeneity and drug resistance limit the efficacy of cancer therapy. To address this issue, we have developed an integrated treatment protocol for effective treatment of heterogeneous ovarian cancer. Methods: An amphiphilic polymer coated magnetic iron oxide nanoparticle was conjugated with near infrared dye labeled HER2 affibody and chemotherapy drug cisplatin. The effects of the theranostic nanoparticle on targeted drug delivery, therapeutic efficacy, non-invasive magnetic resonance image (MRI)-guided therapy, and optical imaging detection of therapy resistant tumors were examined in an orthotopic human ovarian cancer xenograft model with highly heterogeneous levels of HER2 expression. Results: We found that systemic delivery of HER2-targeted magnetic iron oxide nanoparticles carrying cisplatin significantly inhibited the growth of primary tumor and peritoneal and lung metastases in the ovarian cancer xenograft model in nude mice. Differential delivery of theranostic nanoparticles into individual tumors with heterogeneous levels of HER2 expression and various responses to therapy were detectable by MRI. We further found a stronger therapeutic response in metastatic tumors compared to primary tumors, likely due to a higher level of HER2 expression and a larger number of proliferating cells in metastatic tumor cells. Relatively long-time retention of iron oxide nanoparticles in tumor tissues allowed interrogating the relationship between nanoparticle drug delivery and the presence of resistant residual tumors by in vivo molecular imaging and histological analysis of the tumor tissues. Following therapy, most of the remaining tumors were small, primary tumors that had low levels of HER2 expression and nanoparticle drug accumulation, thereby explaining their lack of therapeutic response. However, a few residual tumors had HER2-expressing tumor cells and detectable nanoparticle drug delivery but failed to respond, suggesting additional intrinsic resistant mechanisms. Nanoparticle retention in the small residual tumors, nevertheless, produced optical signals for detection by spectroscopic imaging. Conclusion: The inability to completely excise peritoneal metastatic tumors by debulking surgery as well as resistance to chemotherapy are the major clinical challenges for ovarian cancer treatment. This targeted cancer therapy has the potential for the development of effective treatment for metastatic ovarian cancer.

Hyaluronic acid formulation of near infrared fluorophores optimizes surgical imaging in a prostate tumor xenograft

The presence of positive surgical margins confers an increased risk of biochemical relapse and need for salvage therapy in men undergoing radical prostatectomy. Image-guided surgery using near-infrared (NIR) fluorescent contrast agents is a potential method to detect remaining cancerous tissue. The objective of this study was to evaluate three hyaluronic acid (HA) nanoparticle (NP) formulations loaded with NIR fluorophore for their ability to contrast-enhance prostate cancer. HA was modified by conjugation with the hydrophobic ligand, aminopropyl-1-pyrenebutanamide to drive nanoparticle self-assembly. Indocyanine green (ICG) was physicochemically entrapped in the HA-NP, termed NanoICG. Alternatively, Cy7.5 was directly conjugated to amphiphilic HA, termed NanoCy7.5. NanoCy7.5 was synthesized with two HA molecular weights to determine the HA size contribution to delivery to PC3 prostate tumor xenografts. Contrast-enhancement of the tumors and relative biodistribution were assessed by a series of fluorescence imaging, image-guided surgery with spectroscopy, and microscopic techniques. Intravenously administered NanoICG improved tumor signal-to-noise ratio (SNR) at 24 h over ICG by 2.9-fold. NanoCy7.5 with 10 kDa and 100 kDa HA improved tumor SNR by 6.6- and 3.1-fold over Cy7.5 alone, respectively. The PC3 xenograft was clearly identified with the image-guided system providing increased contrast enhancement compared to surrounding tissue for NanoICG and NanoCy7.5 with 10 kDa HA. NIR fluorescence microscopy showed that Cy7.5 in NPs with 10 kDa HA were distributed throughout the tumor, while NanoCy7.5 with 100 kDa HA or NanoICG delivered dye mainly to the edge of the tumor. CD31 staining suggested that PC3 tumors are poorly vascularized. These studies demonstrate the efficacy of a panel of HA-derived NPs in identifying prostate tumors in vivo, and suggest that by tuning the structural properties of these NPs, optimized delivery can be achieved to poorly vascularized tumors.

STATEMENT OF SIGNIFICANCE

We have demonstrated the potential of a panel of near-infrared fluorescent (NIRF) nanoparticles (NPs) for image-guided surgery in a prostate cancer xenograft model. Image-guided surgery and imaging of organs ex vivo showed greater tumor signal and contrast when mice were administered NIRF dyes that were covalently conjugated to (NanoCy7.5_10k-PBA) or physicochemically entrapped in (NanoICG_PBA) hyaluronic acid (HA) NPs, compared to free dyes. These results show the potential to use these NPs as tools to detect the margins of tumors and to differentiate healthy and tumor tissue intraoperatively. Moreover, this project provides insight into selecting optimal formulation strategies for poorly vascularized tumors.

Indocyanine green loaded hyaluronan-derived nanoparticles for fluorescence-enhanced surgical imaging of pancreatic cancer

Pancreatic ductal adenocarcinoma is highly lethal and surgical resection is the only potential curative treatment for the disease. In this study, hyaluronic acid derived nanoparticles with physico-chemically entrapped indocyanine green, termed NanoICG, were utilized for intraoperative near infrared fluorescence detection of pancreatic cancer. NanoICG was not cytotoxic to healthy pancreatic epithelial cells and did not induce chemotaxis or phagocytosis, it accumulated significantly within the pancreas in an orthotopic pancreatic ductal adenocarcinoma model, and demonstrated contrast-enhancement for pancreatic lesions relative to non-diseased portions of the pancreas. Fluorescence microscopy showed higher fluorescence intensity in pancreatic lesions and splenic metastases due to NanoICG compared to ICG alone. The in vivo safety profile of NanoICG, including, biochemical, hematological, and pathological analysis of NanoICG-treated healthy mice, indicates negligible toxicity. These results suggest that NanoICG is a promising contrast agent for intraoperative detection of pancreatic tumors.

Multimodal Imaging Nanoparticles Derived from Hyaluronic Acid for Integrated Preoperative and Intraoperative Cancer Imaging

Surgical resection remains the most promising treatment strategy for many types of cancer. Residual malignant tissue after surgery, a consequence in part due to positive margins, contributes to high mortality and disease recurrence. In this study, multimodal contrast agents for integrated preoperative magnetic resonance imaging (MRI) and intraoperative fluorescence image-guided surgery (FIGS) are developed. Self-assembled multimodal imaging nanoparticles (SAMINs) were developed as a mixed micelle formulation using amphiphilic HA polymers functionalized with either GdDTPA for T₁ contrast-enhanced MRI or Cy7.5, a near infrared fluorophore. To evaluate the relationship between MR and fluorescence signal from SAMINs, we employed simulated surgical phantoms that are routinely used to evaluate the depth at which near infrared (NIR) imaging agents can be detected by FIGS. Finally, imaging agent efficacy was evaluated in a human breast tumor xenograft model in nude mice, which demonstrated contrast in both fluorescence and magnetic resonance imaging.

Multimodal assessment of SERS nanoparticle biodistribution post ingestion reveals new potential for clinical translation of Raman imaging

Despite extensive research and development, new nano-based diagnostic contrast agents have faced major barriers in gaining regulatory approval due to their potential systemic toxicity and prolonged retention in vital organs. Here we use five independent biodistribution techniques to demonstrate that oral ingestion of one such agent, gold-silica Raman nanoparticles, results in complete clearance with no systemic toxicity in living mice. The oral delivery mimics topical administration to the oral cavity and gastrointestinal (GI) tract as an alternative to intravenous injection. Biodistribution and clearance profiles of orally (OR) vs. intravenously (IV) administered Raman nanoparticles were assayed over the course of 48 h. Mice given either an IV or oral dose of Raman nanoparticles radiolabeled with approximately 100 μCi (3.7MBq) of 64Cu were imaged with dynamic microPET immediately post nanoparticle administration. Static microPET images were also acquired at 2 h, 5 h, 24 h and 48 h. Mice were sacrificed post imaging and various analyses were performed on the excised organs to determine nanoparticle localization. The results from microPET imaging, gamma counting, Raman imaging, ICP-MS, and hyperspectral imaging of tissue sections all correlated to reveal no evidence of systemic distribution of Raman nanoparticles after oral administration and complete clearance from the GI tract within 24 h. Paired with the unique signals and multiplexing potential of Raman nanoparticles, this approach holds great promise for realizing targeted imaging of tumors and dysplastic tissues within the oral cavity and GI-tract. Moreover, these results suggest a viable path for the first translation of high-sensitivity Raman contrast imaging into clinical practice.

Near Infrared Fluorescent Nanoparticles Derived from Hyaluronic Acid Improve Tumor Contrast for Image-Guided Surgery

Tumor tissue that remains undetected at the primary surgical site can cause tumor recurrence, repeat surgery, and treatment strategy alterations that impose a significant patient and healthcare burden. Intraoperative near infrared fluorescence (NIRF) imaging is one potential method to identify remaining tumor by visualization of NIR fluorophores that are preferentially localized to the tumor. This requires development of fluorophores that consistently identify tumor tissue in different patients and tumor types. In this study we examined a panel of NIRF contrast agents consisting of polymeric nanoparticle (NP) formulations derived from hyaluronic acid (HA), with either physically entrapped indocyanine green (ICG) or covalently conjugated Cy7.5. Using orthotopic human breast cancer MDA-MB-231 xenografts in nude mice we identified two lead formulations. One, NanoICG_PBA, with physicochemically entrapped ICG, showed 2.3-fold greater tumor contrast than ICG alone at 24 h (p < 0.01), and another, NanoCy7.5_100-H, with covalently conjugated Cy7.5, showed 74-fold greater tumor contrast than Cy7.5 alone at 24 h (p < 0.0001). These two lead formulations were then tested in immune competent BALB/c mice bearing orthotopic 4T1 breast cancer tumors. NanoICG_PBA showed 2.2-fold greater contrast than ICG alone (p < 0.0001), and NanoCy7.5_100-H showed 14.8-fold greater contrast than Cy7.5 alone (p < 0.0001). Furthermore, both NanoICG_PBA and NanoCy7.5_100-H provided strong tumor enhancement using image-guided surgery in mice bearing 4T1 tumors. These studies demonstrate the efficacy of a panel of HA-derived NPs in delineating tumors in vivo, and identifies promising formulations that can be used for future in vivo tumor removal efficacy studies.

Combination of an Integrin-Targeting NIR Tracer and an Ultrasensitive Spectroscopic Device for Intraoperative Detection of Head and Neck Tumor Margins and Metastatic Lymph Nodes

Despite major advances in targeted drug therapy and radiation therapy, surgery remains the most effective treatment for most solid tumors. The single most important predictor of patient survival is a complete surgical resection of the primary tumor, draining lymph nodes, and metastatic lesions. Presently, however, 20%–30% of patients with head and neck cancer who undergo surgery still leave the operating room without complete resection because of missed lesions. Thus, major opportunities exist to develop advanced imaging tracers and intraoperative instrumentation that would allow surgeons to visualize microscopic tumors during surgery. The cell adhesion molecule integrin αvβ3 is specifically expressed by tumor neovasculature and invading tumor cells, but not by quiescent vessels or normal cells. Here we report the combined use of an integrin-targeting near-infrared tracer (RGD-IRDye800CW) and a handheld spectroscopic device, an integrated point spectroscopy with wide-field imaging system, for highly sensitive detection of integrin overexpression on infiltrating cancer cells. By using an orthotopic head and neck cancer animal model, we show that this tracer–device combination allows intraoperative detection of not only invasive tumor margins but also metastatic lymph nodes. Correlated histological analysis further reveals that microscopic clusters of 50–100 tumor cells can be detected intraoperatively with high sensitivity and specificity, raising new possibilities in guiding surgical resection of microscopic tumors and metastatic lymph nodes.

Image-guided tumor surgery: will there be a role for fluorescent nanoparticles?

Image-guided surgery (IGS) using fluorescent nanoparticles (NPs) has the potential to substantially impact patient treatment. The use of fluorescence imaging provides surgeons with real-time feedback on the location of diseased tissue using safe, low-cost imaging agents and instrumentation. Fluorescent NPs are likely to play a role as they are capable of taking advantage of the enhanced permeability and retention (EPR) effect and can be modified to avoid clearance, increase circulation time, and specifically target tumors. Clinical trials of IGS using the FDA-approved fluorophores indocyanine green and methylene blue have already shown preliminary successes, and incorporation of fluorescent NPs will likely improve detection by providing higher signal to background ratio and reducing false-positive rates through active targeting. Preclinical development of fluorescent NP formulations is advancing rapidly, with strategies ranging from passive targeting to active targeting of cell surface receptors, creating pH-responsive NPs, and increasing cell uptake through cleavable proteins. This collective effort could lead to clinical trials using fluorescent NPs in the near future. WIREs Nanomed Nanobiotechnol 2016, 8:498-511. doi: 10.1002/wnan.1381 For further resources related to this article, please visit the WIREs website.

Near infrared fluorescent nanoparticles based on hyaluronic acid: Self-assembly, optical properties, and cell interaction

Fluorescent imaging agents that can specifically highlight tumor cells could have a significant impact on image-guided tumor removal. Here, fluorescent nanoparticles (NPs) derived from hyaluronic acid (HA) are investigated. HA is a ligand for the receptor CD44, which is a common biomarker present on many primary tumor cells, cancer-initiating cells, and tumor-associated fibroblasts. In addition, a family of enzymes that degrade HA, called hyaluronidases (HYALs), are also overexpressed with increased activity in many tumors. We report the design and development of a panel of targeted imaging agents using the near-infrared (NIR) dye, Cy7.5, that was directly conjugated to hydrophobically-modified HA. Two different molecular weights of HA, 10kDa and 100kDa, and three different degrees of hydrophobic moiety conjugation (0, 10, and 30mol%) were utilized to develop a panel of NPs with variable size that ranged from 50 to 400nm hydrodynamic diameter (HD) depending HA molecular weight, extent of fluorescence quenching (25-50%), kinetics of cellular uptake, and targeting to CD44+ cells. The kinetics and energy-dependence of cellular uptake in breast and prostate cancer cell lines, MDA-MB 231 and PC-3 cells, respectively, showed increased uptake with longer incubation times (at 4 and 8h compared to 1h), as well as uptake at 37°C but not 4°C, which indicated energy-dependent endocytosis. NP uptake studies in the presence of excess free HA showed that pre-treatment of cells with excess high molecular weight (MW) free HA decreased NP uptake by up to 50%, while no such trend was observed with low MW HA. These data lay the foundation for selection of optimized HA-derived NPs for image-guided surgery.

STATEMENT OF SIGNIFICANCE

Here, hyaluronic acid (HA), a well-studied biomacromolecule, is modified with a near infrared fluorophore and a hydrophobic moiety. The significance of this work, especially for imaging applications, is that the impact of HA molecular weight and the hydrophobic moiety conjugation degree on fluorescence and cell interaction can be predicted. With respect to existing literature, the eventual use of these HA-based NPs is image-guided surgery; thus, we focus on the dye, Cy7.5, for conjugation, which is more NIR than most existing HA literature. Furthermore, HA is a ligand for CD44, which is associated with cancer and tumor microenvironment cells. Systematic studies in this work highlight that HA can be tuned to maximize or minimize CD44 binding.

Intraoperative Spectroscopy with Ultrahigh Sensitivity for Image-Guided Surgery of Malignant Brain Tumors

Intraoperative cancer imaging and fluorescence-guided surgery have attracted considerable interest because fluorescence signals can provide real-time guidance to assist a surgeon in differentiating cancerous and normal tissues. Recent advances have led to the clinical use of a natural fluorophore called protoporphyrin IX (PpIX) for image-guided surgical resection of high-grade brain tumors (glioblastomas). However, traditional fluorescence imaging methods have only limited detection sensitivity and identification accuracy and are unable to detect low-grade or diffuse infiltrating gliomas (DIGs). Here we report a low-cost hand-held spectroscopic device that is capable of ultrasensitive detection of protoporphyrin IX fluorescence in vivo, together with intraoperative spectroscopic data obtained from both animal xenografts and human brain tumor specimens. The results indicate that intraoperative spectroscopy is at least 3 orders of magnitude more sensitive than the current surgical microscopes, allowing ultrasensitive detection of as few as 1000 tumor cells. For detection specificity, intraoperative spectroscopy allows the differentiation of brain tumor cells from normal brain cells with a contrast signal ratio over 100. In vivo animal studies reveal that protoporphyrin IX fluorescence is strongly correlated with both MRI and histological staining, confirming that the fluorescence signals are highly specific to tumor cells. Furthermore, ex vivo spectroscopic studies of excised brain tissues demonstrate that the hand-held spectroscopic device is capable of detecting diffuse tumor margins with low fluorescence contrast that are not detectable with current systems in the operating room. These results open new opportunities for intraoperative detection and fluorescence-guided resection of microscopic and low-grade glioma brain tumors with invasive or diffusive margins.

Augmented microscopy: real-time overlay of bright-field and near-infrared fluorescence images

Intraoperative applications of near-infrared (NIR) fluorescent contrast agents can be aided by instrumentation capable of merging the view of surgical field with that of NIR fluorescence. We demonstrate augmented microscopy, an intraoperative imaging technique in which bright-field (real) and electronically processed NIR fluorescence (synthetic) images are merged within the optical path of a stereomicroscope. Under luminance of 100,000 lx, representing typical illumination of the surgical field, the augmented microscope detects 189 nM concentration of indocyanine green and produces a composite of the real and synthetic images within the eyepiece of the microscope at 20 fps. Augmentation described here can be implemented as an add-on module to visualize NIR contrast agents, laser beams, or various types of electronic data within the surgical microscopes commonly used in neurosurgical, cerebrovascular, otolaryngological, and ophthalmic procedures.

Big data for health

This paper provides an overview of recent developments in big data in the context of biomedical and health informatics. It outlines the key characteristics of big data and how medical and health informatics, translational bioinformatics, sensor informatics, and imaging informatics will benefit from an integrated approach of piecing together different aspects of personalized information from a diverse range of data sources, both structured and unstructured, covering genomics, proteomics, metabolomics, as well as imaging, clinical diagnosis, and long-term continuous physiological sensing of an individual. It is expected that recent advances in big data will expand our knowledge for testing new hypotheses about disease management from diagnosis to prevention to personalized treatment. The rise of big data, however, also raises challenges in terms of privacy, security, data ownership, data stewardship, and governance. This paper discusses some of the existing activities and future opportunities related to big data for health, outlining some of the key underlying issues that need to be tackled.

Detection of plaque structure and composition using OCT combined with two-photon luminescence (TPL) imaging

BACKGROUND AND OBJECTIVES

Atherosclerosis and plaque rupture leads to myocardial infarction and stroke. A novel hybrid optical coherence tomography (OCT) and two-photon luminescence (TPL) fiber-based imaging system was developed to characterize tissue constituents in the context of plaque morphology.

STUDY DESIGN/MATERIALS AND METHODS

Ex vivo coronary arteries (34 regions of interest) from three human hearts with atherosclerotic plaques were examined by OCT-TPL imaging. Histological sections (4 μm in thickness) were stained with Oil Red O for lipid, Von Kossa for calcium, and Verhoeff-Masson Tri-Elastic for collagen/elastin fibers and compared with imaging results.

RESULTS

Biochemical components in plaques including lipid, oxidized-LDL, and calcium, as well as a non-tissue component (metal) are distinguished by multi-channel TPL images with statistical significance (P < 0.001). TPL imaging provides complementary optical contrast to OCT (two-photon absorption/emission vs scattering). Merged OCT-TPL images demonstrate the distribution of lipid deposits in registration with detailed plaque surface profile.

CONCLUSIONS

Results suggest that multi-channel TPL imaging can effectively identify lipid sub-types and different plaque components. Furthermore, fiber-based hybrid OCT-TPL imaging simultaneously detects plaque structure and composition, improving the efficacy of vulnerable plaque detection and characterization.

Indocyanine green-loaded nanoparticles for image-guided tumor surgery

Detecting positive tumor margins and local malignant masses during surgery is critical for long-term patient survival. The use of image-guided surgery for tumor removal, particularly with near-infrared fluorescent imaging, is a potential method to facilitate removing all neoplastic tissue at the surgical site. In this study we demonstrate a series of hyaluronic acid (HLA)-derived nanoparticles that entrap the near-infrared dye indocyanine green, termed NanoICG, for improved delivery of the dye to tumors. Self-assembly of the nanoparticles was driven by conjugation of one of three hydrophobic moieties: aminopropyl-1-pyrenebutanamide (PBA), aminopropyl-5β-cholanamide (5βCA), or octadecylamine (ODA). Nanoparticle self-assembly, dye loading, and optical properties were characterized. NanoICG exhibited quenched fluorescence that could be activated by disassembly in a mixed solvent. NanoICG was found to be nontoxic at physiologically relevant concentrations and exposure was not found to inhibit cell growth. Using an MDA-MB-231 tumor xenograft model in mice, strong fluorescence enhancement in tumors was observed with NanoICG using a fluorescence image-guided surgery system and a whole-animal imaging system. Tumor contrast with NanoICG was significantly higher than with ICG alone.