This proposal describes a rapid, non-invasive method for characterizing the states of differentiated stem cells. The technique is morphological in nature and is called cellular optical wavefront sensing (COWS). Cytometry is a set of techniques designed for counting, imaging, measuring specific cellular parameters and phenotypes. Modern cytometers can rapidly identify and sort individual cells within large populations of heterogeneous cells via fluorescence activation. However, the tagging of cells with fluorescent antibodies is invasive to the cells, rendering them unusable for further clinical uses. Forward and side light scattering of cells are non-invasive detection methods also employed in conventional cytometers to determine cell size and granularity, but the information derived from these modalities is insufficient to identify cell states accurately. In the COWS technique, single stem cells in a flow stream traverse a sub-aperture region of a collimated laser beam whose wavefront is perturbed in response to the physical structure of each single cell. A magnified image of the cell is relayed to a Shack-Hartmann wavefront sensor, which measures the local tilts of the perturbed wavefront. The Zernike coefficients of the aberrated cellular wavefronts are calculated. These Zernike coefficients provide distinct signatures by which the cells are classified into particular types.
Keywords: Stem Cells, Wavefront Sensing, Cytometry, Non-Invasive Screening
