Yu “Winston” Wang

In vivo multiplexed molecular imaging of esophageal cancer via spectral endoscopy of topically applied SERS nanoparticles.

The biological investigation and detection of esophageal cancers could be facilitated with an endoscopic technology to screen for the molecular changes that precede and accompany the onset of cancer. Surface-enhanced Raman scattering (SERS) nanoparticles (NPs) have the potential to improve cancer detection and investigation through the sensitive and multiplexed detection of cell-surface biomarkers. Here, we demonstrate that the topical application and endoscopic imaging of a multiplexed cocktail of receptor-targeted SERS NPs enables the rapid detection of tumors in an orthotopic rat model of esophageal cancer. Antibody-conjugated SERS NPs were topically applied on the lumenal surface of the rat esophagus to target EGFR and HER2, and a miniature spectral endoscope featuring rotational scanning and axial pull-back was employed to comprehensively image the NPs bound on the lumen of the esophagus. Ratiometric analyses of specific vs. nonspecific binding enabled the visualization of tumor locations and the quantification of biomarker expression in agreement with immunohistochemistry and flow cytometry validation data.

Rapid ratiometric biomarker detection with topically applied SERS nanoparticles.

Multiplexed surface-enhanced Raman scattering (SERS) nanoparticles (NPs) offer the potential for rapid molecular phenotyping of tissues, thereby enabling accurate disease detection as well as patient stratification to guide personalized therapies or to monitor treatment outcomes. The clinical success of molecular diagnostics based on SERS NPs would be facilitated by the ability to accurately identify tissue biomarkers under time-constrained staining and detection conditions with a portable device. In vitro, ex vivo and in vivo experiments were performed to optimize the technology and protocols for the rapid detection (0.1-s integration time) of multiple cell-surface biomarkers with a miniature fiber-optic spectral-detection probe following a brief (5 min) topical application of SERS NPs on tissues. Furthermore, we demonstrate that the simultaneous detection and ratiometric quantification of targeted and nontargeted NPs allows for an unambiguous assessment of molecular expression that is insensitive to nonspecific variations in NP concentrations.

Raman-Encoded Molecular Imaging with Topically Applied SERS Nanoparticles for Intraoperative Guidance of Lumpectomy

Intraoperative identification of carcinoma at lumpectomy margins would enable reduced re-excision rates, which are currently as high as 20% to 50%. Although imaging of disease-associated biomarkers can identify malignancies with high specificity, multiplexed imaging of such biomarkers is necessary to detect molecularly heterogeneous carcinomas with high sensitivity. We have developed a Raman-encoded molecular imaging (REMI) technique in which targeted nanoparticles are topically applied on excised tissues to enable rapid visualization of a multiplexed panel of cell surface biomarkers at surgical margin surfaces. A first-ever clinical study was performed in which 57 fresh specimens were imaged with REMI to simultaneously quantify the expression of four biomarkers HER2, ER, EGFR, and CD44. Combined detection of these biomarkers enabled REMI to achieve 89.3% sensitivity and 92.1% specificity for the detection of breast carcinoma. These results highlight the sensitivity and specificity of REMI to detect biomarkers in freshly resected tissue, which has the potential to reduce the rate of re-excision procedures in cancer patients. Cancer Res; 77(16); 4506-16. ©2017 AACR.

Assessing the imaging performance of light sheet microscopies in highly scattering tissues

Light sheet microscopy (LSM) has emerged as an optical-imaging method for high spatiotemporal volumetric imaging of relatively transparent samples. While this capability has allowed the technique to be highly impactful in fields such as developmental biology, applications involving highly scattering thick tissues have been largely unexplored. Herein, we employ Monte Carlo simulations to explore the use of LSM for imaging turbid media. In particular, due to its similarity to dual-axis confocal (DAC) microscopy, we compare LSM performance to point-scanned (PS-DAC) and line-scanned (LS-DAC) dual-axis confocal microscopy techniques that have been previously shown to produce high-quality images at round-trip optical lengths of ~9 - 10 and ~3 - 4 respectively. The results of this study indicate that LSM using widefield collection (WF-LSM) provides comparable performance to LS-DAC in thick tissues, due to the fact that they both utilize an illumination beam focused in one dimension (i.e. a line or sheet). On the other hand, LSM using confocal line detection (CL-LSM) is more analogous to PS-DAC microscopy, in which the illumination beam is focused in two dimensions to a point. The imaging depth of LSM is only slightly inferior to DAC (~2 - 3 and ~6 - 7 optical lengths for WF-LSM and CL-LSM respectively) due to the use of a lower numerical aperture (NA) illumination beam for extended imaging along the illumination axis. Therefore, we conclude that the ability to image deeply is dictated most by the confocality of the microscope technique. In addition, we find that imaging resolution is mostly dependent on the collection NA, and is relatively invariant to imaging depth in a homogeneous scattering medium. Our results indicate that superficial imaging of highly scattering tissues using light sheet microscopy is possible.

Comparing High-Resolution Microscopy Techniques for Potential Intraoperative Use in Guiding Low-Grade Glioma Resections

Fluorescence image‐guided surgery (FIGS), with contrast provided by 5‐ALA‐induced PpIX, has been shown to enable a higher extent of resection of high‐grade gliomas. However, conventional FIGS with low‐power microscopy lacks the sensitivity to aid in low‐grade glioma (LGG) resection because PpIX signal is weak and sparse in such tissues. Intraoperative high‐resolution microscopy of PpIX fluorescence has been proposed as a method to guide LGG resection, where sub‐cellular resolution allows for the visualization of sparse and punctate mitochondrial PpIX production in tumor cells. Here, we assess the performance of three potentially portable high‐resolution microscopy techniques that may be used for the intraoperative imaging of human LGG tissue samples with PpIX contrast: high‐resolution fiber‐optic microscopy (HRFM), high‐resolution wide‐field microscopy (WFM), and dual‐axis confocal (DAC) microscopy.

Microscopic investigation of" topically applied nanoparticles for molecular imaging of fresh tissue surfaces

Previous studies have shown that functionalized nanoparticles (NPs) topically applied on fresh tissues are able to rapidly target cell-surface protein biomarkers of cancer. Furthermore, studies have shown that a paired-agent approach, in which an untargeted NP is co-administered with a panel of targeted NPs, controls for the nonspecific behavior of the NPs, enabling quantitative imaging of biomarker expression. However, given the complexities in nonspecific accumulation, diffusion, and chemical binding of targeted NPs in tissues, studies are needed to better understand these processes at the microscopic scale. Here, fresh tissues were stained with a paired-agent approach, frozen, and sectioned to image the depth-dependent accumulation of targeted and untargeted NPs. The ratio of targeted-to-untargeted NP concentrations-a parameter used to distinguish between tumor and benign tissues-was found to diminish with increasing NP diffusion depths due to nonspecific accumulation and poor washout. It was then hypothesized and experimentally demonstrated that larger NPs would exhibit less diffusion below tissue surfaces, enabling higher targeted-to-untargeted NP ratios. In summary, these methods and investigations have enabled the design of NP agents with improved sensitivity and contrast for rapid molecular imaging of fresh tissues.

Multiplexed Optical Imaging of Tumor-Directed Nanoparticles: A Review of Imaging Systems and Approaches

In recent decades, various classes of nanoparticles have been developed for optical imaging of cancers. Many of these nanoparticles are designed to specifically target tumor sites, and specific cancer biomarkers, to facilitate the visualization of tumors. However, one challenge for accurate detection of tumors is that the molecular profiles of most cancers vary greatly between patients as well as spatially and temporally within a single tumor mass. To overcome this challenge, certain nanoparticles and imaging systems have been developed to enable multiplexed imaging of large panels of cancer biomarkers. Multiplexed molecular imaging can potentially enable sensitive tumor detection, precise delineation of tumors during interventional procedures, and the prediction/monitoring of therapy response. In this review, we summarize recent advances in systems that have been developed for the imaging of optical nanoparticles that can be heavily multiplexed, which include surface-enhanced Raman-scattering nanoparticles (SERS NPs) and quantum dots (QDs). In addition to surveying the optical properties of these various types of nanoparticles, and the most-popular multiplexed imaging approaches that have been employed, representative preclinical and clinical imaging studies are also highlighted.

Molecular imaging of topically applied SERS nanoparticles for guiding tumor resection

To quantitatively image a panel of disease biomarkers for guiding tumor resection, we have developed a wide-area raster-scanned imaging device to rapidly image molecularly targeted SERS nanoparticles topically applied on fresh excised tissues.

Rapid Multiplexed Imaging of Cell-Surface Cancer Biomarkers in Fresh Tissues with Targeted SERS Nanoparticles

Our lab is developing miniature Raman imaging systems and topical-staining protocols to rapidly image cell-surface biomarkers in fresh tissues. In particular, this work employs targeted surface-enhanced Raman scattering (SERS) nanoparticles (NPs) to enable the sensitive and multiplexed detection of a large number of cell-surface biomarkers of cancer. The SERS NPs were functionalized with different targeting antibodies, and their biomarker detection capability was investigated via in vitro and ex vivo experiments with cells and tissues. Here, we design SERS NPs to specifically target the cancer biomarker EGFR upon topical application on cells and tissues. In vitro flow cytometry with fluorescent SERS NPs reveals a high ratio of specific versus nonspecific binding for the tumor cell lines A431 (skin cancer), U251 (glioma) and SkBr3 (breast cancer). For tissue imaging, we have developed a fiber-optic-based spectral detection probe, with 785-nm laser illumination, for rapid detection of SERS NPs with sub-millimeter spatial resolution. Based on the spectral detection probe, multiple imaging systems were customized for rapid tissue phenotyping such as a comprehensive rotational scanning endoscope for in vivo imaging of the rat esophagus and a raster-scanning device for intraoperative imaging of breast tissue margins. Ex vivo experiments were performed to develop a strategy for the rapid detection of multiple cell-surface biomarkers following a brief (5-10 min) topical application of SERS NPs on tissues. By developing high-affinity targeted SERS NPs, sensitive spectral-imaging devices, and an optimized topical-delivery protocol, we demonstrate a ratio metric method to rapidly quantify the specific binding of biomarker-targeted NPs on fresh tissues, thereby eliminating the ambiguities that often arise due to nonspecific sources of contrast. These tools will enable multiplexed molecular imaging for the early detection of epithelial cancers, rapid surgical guidance, and monitoring the molecular response to treatments.