Spectroscopic Methods for Label-Free Optical Nanoscopy

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It is becoming increasingly evident that the nanoscale organization and structure of macromolecules play a significant role in determining the function and properties of biological systems. To understand the relationships between biological structure and function at nanometer length scales, there is a need for methods which enable imaging of intact nanoscale biological structure. An ideal technique for these applications is sensitive to nanoscale structure below the resolution limit of conventional optical microscopy (~200nm), achieves label-free contrast, is non-perturbing to biological samples, is quantitative, is capable of molecular specificity, is high-throughput, and finally is simple, enabling widespread utilization. Existing techniques meet some of these criteria, but all have limitations. For example, super-resolution optical microscopy methods achieve molecular-specific nanoscale resolution well below the resolution limit of conventional optical microscopes, however, they rely on fluorescent labels often at high densities that can be toxic and can often require potentially damaging illumination intensities for imaging. As a result, there remains a need for label-free optical techniques to study the nanoscale structural properties of cells. To address this need, the development of instrumentation and algorithms for Partial Wave Spectroscopic (PWS) microscopy will be described. PWS is a spectroscopic, label-free, nanoscale sensitive microscope which, senses rather than resolves structure below the resolution limit of conventional microscopes (~200nm). First, PWS has shown utility as a diagnostic screening tool for cancer due to nanoscale structural alterations that occur in cells as part of the earliest stages of carcinogenesis. Instrumentation and algorithms developed to enable high-throughput cancer screening applications will be described. Further enhancement of data acquisition and analysis speed will then be described through the development of new analysis algorithms, which enable a new application, whole-slide imaging. Next, the development of a combined confocal and PWS microscope is described enabling biological experiments, which investigate nanoscale structure at molecular specific sites. To further enhance the ability to study biological processes in relation to structure the development of a live cell version, the PWS microscope will be described and experiments showing real-time nanoscale structural changes in live-cells will be shown. Finally, a collaborative effort in the development of a new partial rank aggregation algorithm will be discussed and applied to the ecological problem of coral thermotolerance ranking.

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  • 12/01/2017
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