Daphne Meza

Trends in fluorescence image-guided surgery for gliomas.

Mounting evidence suggests that a more extensive surgical resection is associated with an improved life expectancy for both low-grade and high-grade glioma patients. However, radiographically complete resections are not often achieved in many cases because of the lack of sensitivity and specificity of current neurosurgical guidance techniques at the margins of diffuse infiltrative gliomas. Intraoperative fluorescence imaging offers the potential to improve the extent of resection and to investigate the possible benefits of resecting beyond the radiographic margins. Here, we provide a review of wide-field and high-resolution fluorescence-imaging strategies that are being developed for neurosurgical guidance, with a focus on emerging imaging technologies and clinically viable contrast agents. The strengths and weaknesses of these approaches will be discussed, as well as issues that are being addressed to translate these technologies into the standard of care.

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.

Comprehensive spectral endoscopy of topically applied SERS nanoparticles in the rat esophagus

The early detection and biological investigation of esophageal cancer would benefit from the development of advanced imaging techniques 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 the investigation of cancer progression through the sensitive and multiplexed phenotyping of cell-surface biomarkers. Here, a miniature endoscope featuring rotational scanning and axial pull back has been developed for 2D spectral imaging of SERS NPs topically applied on the lumenal surface of the rat esophagus. Raman signals from low-pM concentrations of SERS NP mixtures are demultiplexed in real time to accurately calculate the concentration and ratio of the NPs. Ex vivo and in vivo experiments demonstrate the feasibility of topical application and imaging of multiplexed SERS NPs along the entire length of the rat esophagus.

Sheet-scanned dual-axis confocal microscopy using Richardson–Lucy deconvolution

We have previously developed a line-scanned dual-axis confocal (LS-DAC) microscope with subcellular resolution suitable for high-frame-rate diagnostic imaging at shallow depths. Due to the loss of confocality along one dimension, the contrast (signal-to-background ratio) of a LS-DAC microscope is deteriorated compared to a point-scanned DAC microscope. However, by using a sCMOS camera for detection, a short oblique light-sheet is imaged at each scanned position. Therefore, by scanning the light sheet in only one dimension, a thin 3D volume is imaged. Both sequential two-dimensional deconvolution and three-dimensional deconvolution are performed on the thin image volume to improve the resolution and contrast of one en face confocal image section at the center of the volume, a technique we call sheet-scanned dual-axis confocal (SS-DAC) microscopy.

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.

Platelets modulate endothelial cell response to dynamic shear stress through PECAM-1

INTRODUCTION Both vascular endothelial cells and platelets are sensitive to blood flow induced shear stress. We have recently reported that platelet-endothelial cell interaction could greatly affect platelet activation under flow. In the present study, we aimed to investigate how platelet-endothelial cell interaction affected endothelial cell inflammatory responses under flow. MATERIALS AND METHODS Human coronary artery endothelial cells were exposed to normal or low pulsatile shear stress with or without the presence of platelets. Following shear exposure, endothelial cell ICAM-1 expression was measured using ELISA, Western blot and PCR; cell surface PECAM-1 expression/phosphorylation was measured using ELISA. Platelet adhesion to endothelial cells was quantified using immunofluorescence microscopy. To determine the role of PECAM-1 in platelet-endothelial cell interaction, endothelial cell PECAM-1 expression was suppressed using siRNA. RESULTS Pathological low shear stress induced a significant increase in endothelial cell ICAM-1 expression, at both protein and mRNA levels. Platelet adhesion to endothelial cells increased significantly under low shear stress, co-localizing with PECAM-1 at endothelial cell junctions. The presence of platelets inhibited low shear stress-induced ICAM-1 upregulation. When endothelial cell PECAM-1 expression was suppressed, platelet adhesion to endothelial cells under low shear stress decreased significantly; endothelial cell ICAM-1 expression was not affected by shear stress, with or without platelets. CONCLUSIONS These results suggested that PECAM-1 could mediate platelet adhesion to endothelial cells under shear stress. Platelets binding to endothelial cells interfered with endothelial cell mechanotransduction through PECAM-1, affecting endothelial cell inflammatory responses towards pathological shear flow.

A comprehensive fluid-structure interaction model of the left coronary artery

A fluid structure interaction model of a left anterior descending (LAD) coronary artery was developed, incorporating transient blood flow, cyclic bending motion of the artery, and myocardial contraction. The 3D geometry was constructed based on a patients computed tomography angiography data. To simulate disease conditions, a plaque was placed within the LAD to create a 70% stenosis. The bending motion of the blood vessel was prescribed based on the LAD spatial information. The pressure induced by myocardial contraction was applied to the outside of the blood vessel wall. The fluid domain was solved using the Navier-Stokes equations. The arterial wall was defined as a nonlinear elastic, anisotropic, and incompressible material, and the mechanical behavior was described using the modified hyper-elastic Mooney-Rivlin model. The fluid (blood) and solid (vascular wall) domains were fully coupled. The simulation results demonstrated that besides vessel bending/stretching motion, myocardial contraction had a significant effect on local hemodynamics and vascular all stress/strain distribution. It not only transiently increased blood flow velocity and fluid wall shear stress, but also changed shear stress patterns. The presence of the plaque significantly reduced vascular wall tensile strain. Compared to the coronary artery models developed previously, the current model had improved physiological relevance.

Development and optimization of a line-scanned dual-axis confocal (LS-DAC) microscope for high-speed pathology

We have developed a line-scanned dual-axis confocal (LS-DAC) microscope with subcellular resolution suitable for real time diagnostic imaging at shallow depths. This design serves as a benchtop prototype for a handheld version of the LS-DAC intended for rapid point-of-care pathology. We have assessed the performance trade-offs between the LS-DAC and a point-scanned dual-axis confocal (PS-DAC) microscope via diffraction-theory analysis, Monte-Carlo simulations, and characterization experiments with phantoms and fresh tissues. In addition, we are exploring the use of a sCMOS detector array and rapid 3D deconvolution to improve the sensitivity and resolution of our LS-DAC microscope.