(162d) In Vitro Measurement of Particle Margination in Whole Blood

Fitzgibbon, S., Stanford University
Shaqfeh, E. S. G., Stanford University

In pressure driven flow, the flexibility of red blood cells breaks axial symmetry and causes them to lift away from blood vessel walls, leaving behind a cell free layer near the wall. Platelets migrate into this region, positioning themselves to quickly respond to any injuries encountered in the blood vessel. A lack of platelets near the wall can cause long bleeding times post-injury. Recently, Zhao et. al. have run a large scale simulation of red blood cells and platelets in pressure driven flow. Based on shear induced collisions with red blood cells, they predict rates for platelet and particle margination. Furthermore, they show a qualitative agreement between platelet and sphere margination of comparable sizes. We have built an in vitro fluorescence microscopy experiment to measure their predictions in the lab. Using capillaries similar in size to the simulations, we report the margination of microparticles in pressure driven flow at several different red blood cell concentrations.