High-Throughput Cell Elastic Modulus Cytometry using Single Diode Laser Bar Optical Stretchers

Abstract

Cellular elastic properties can be measured by trapping and deforming them using optical stretchers. Dual optical traps were recently shown to be an efficient experimental method to identify cell types and detect disease states from the measured elastic modulus.However, the low throughput associated with such dual optical traps has significantly limited its utility and application due to the need to sequentially isolate and probe individual cells. We have implemented a pseudo steady-state high-throughput optical stretcher that uses single inexpensive diode laser bar to impart anisotropic forces and stretch osmotically swollen bovine erythrocytes in a continuous microfluidic flow at a rate of ∼ 1 cell/second. This measurement rate is a factor of 10-100 higher than previous demonstrations of optical stretching. We also implemented a numerical model, dynamic ray tracing, to simulate the deformation of elastic capsules induced by the single diode laser bar optical stretcher in flow conditions. Finally, we demonstrated how the numerical model is used to determine the elastic modulus of individual cells from experimental measurements of the steady-state deformation. This new optical approach has the potential to be readily integrated with other cytometric technologies, and with the capability of measuring cell populations, thus enabling true mechanical-property based cytometry.