(806a) Measuring Cell Mechanics By Optical Alignment Compression Cytometry

Cell mechanical properties are a useful indicator of cell health. Differences in cell deformability between disease states have been demonstrated in cases such as cancer, malaria, and sickle cell anemia using a variety of bulk and individual-cell measurement techniques. While bulk approaches provide average properties, small cell subpopulations go undetected. Individual cell testing techniques on the other hand, including micropipette aspiration and AFM, are capable of identifying single diseased cells but are time consuming. To increase throughput, we have developed a non-destructive cell deformability testing method, optical alignment compression (OAC) cytometry, that combines an extensional flow geometry with a linear optical trap to induce collisions between cells. To demonstrate this approach, we direct red blood cells (RBCs) using combined hydrodynamic and optical forces toward the geometric stagnation point within a microfluidic platform. Cell deformation occurs at the stagnation point during cell-cell collision due to hydrodynamic drag. We employ the Kelvin-Voigt viscoelastic model to quantify cell response and find expected elastic and viscous parameters for untreated RBCs of 8.62 ± 3.10 µN/m and 1.21 ± 0.69 µN s/m. Measured values of 17.1 ± 7.55 µN/m and 1.15 ± 0.75 µN s/m for glutaraldehyde fixed cells are also consistent with the expected increase in stiffness. To validate our technique, mixed populations were also tested, resulting in measured distributions fully consistent with expectations.