MEASURING CELL REFRACTIVE INDEX BY CONFOCAL REFLECTANCE AND HP MICROSCOPY

Massachusetts Institute Of Technology, Cambridge MA

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Abstract

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Quantitative phase measurements have achieved uniquely stable and high resolution measurements of phase and it becomes the appealing feature that they can be interfaced with an existing optical microscope for biomedical research. This label-free quantitative phase measurement allows us to study live cell without perturbation. However the technique offers only a total phase that is the line integral of the refractive index and the light beam's path through a cell. This work demonstrates a combining confocal reflectance and quantitative phase microscopy can be used to better estimate an average refractive index of living cell. Using the confocal reflectance to obtain the cell contour and the Hilbert phase microscopy to obtain the phase shift induced by the cell, the average refractive index of cell which presents protein contents (dry-mass) can be determined without postulating or constraining the cell to a known geometry. This approach can provide novel biological assays of label-free living cells in situ.