Microsecond-Scale Stimulated Raman Spectroscopic Imaging: Technical Innovations and Biomedical Applications

Chien-Sheng Liao, Purdue University

Abstract

Raman spectroscopy provides a label-free approach to identify molecules based on their intrinsic molecular vibrations in cells or tissues. However, due to the weak Raman scattering process, this tool is mainly limited to single point detection or chemical mapping of fixed samples. Recently coherent Raman microscopy has been reported to increase the imaging speed of one single vibrational band to video rate. To further resolve overlapping vibrational bands contributed by target molecules and background components, there has been a great effort in developing coherent Raman spectroscopic platforms. The most advanced coherent Raman spectral acquisition has reached ~3 ms per spectrum. But under this acquisition speed, in vivo and real-time imaging of cells or tissues is still challenging. A platform that can acquire spectroscopic images in real-time and provide detailed understanding of the spatio-temporal dynamics of molecules in living cells or tissues will enable marker-based diagnosis, design of disease-specific drugs and discovery of hidden signature of cancer cells. My thesis work aims to overcome the abovementioned difficulties by developing microsecond-scale stimulated Raman spectroscopic platforms. The technical advances in microsecond-scale vibrational spectral acquisition present a promising direction for label-free real-time assessment of cancerous tissue and high throughput single cell analysis. Based on these high-speed spectroscopic platforms, we further developed a handheld imaging system that allows in situ and in vivo histopathological assessment. Collectively, these efforts hold the potential of pushing Raman spectroscopy, which is mainly used for point measurement or chemical imaging of fixed specimens, towards compositional/functional mapping of intracellular compartments or spectral profiling of flowing cells in a high throughput manner.

Degree

Ph.D.

Advisors

Cheng, Purdue University.

Subject Area

Biomedical engineering|Optics

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