Development of a Diffraction Imaging Flow Cytometer for Study of Biological Cells

Abstract

Visible light interacts with biological cells primarily through elastic scattering. With coherent excitation the scattered light is coherent as well and contains much information about the cells morphology but with the notable difficulty of interpreting the complex diffraction pattern. One option is to develop by experimentation a library of diffraction image patterns with each pattern associated with some cell characteristic and without attempting a physical interpretation. To achieve this goal for rapid analysis of a large cell population, we have designed and built a diffraction imaging flow cytometer with the ability to efficiently acquire high-contrast diffraction images from individual flowing cells. A series of experimental and modeling studies have been carried out to build this instrument including fabrication of square microchannels with optical surfaces, a three fluid focusing chamber, and optical isolation of target particles. Diffraction images were acquired of six cell lines: the Jurkat cells, the Tramp C1 cells, the NALM-6 cells, the U937 cells, the B16F10 mouse melanoma cells, and the MCF-7 cells. From these preliminary image sets both the potential and the problems are apparent. Cell line images are clearly differentiable among the different cell lines in aggregate but the intra cell line variability in certain cell lines, such as the Jurkat and NALM-6 cell, may be too great for discrimination. The experiments of fluidics and chamber construction performed so far clearly indicate that the intra cell line variability can be reduced and therefore demonstrate the significant potential of the new imaging flow cytometer method to discriminate cells from diffraction images.