Parametric control of collision rates and capture rates in geometrically enhanced differential immunocapture (GEDI) microfluidic devices for rare cell capture

The enrichment and isolation of rare cells from complex samples, such as circulating tumor cells (CTCs) from whole blood, is an important engineering problem with widespread clinical applications. One approach uses a microfluidic obstacle array with an antibody surface functionalization to both guide cells into contact with the capture surface and to facilitate adhesion; geometrically enhanced differential immunocapture is a design strategy in which the array is designed to promote target cell-obstacle contact and minimize other interactions (Gleghorn et al. 2010; Kirby et al. 2012). We present a simulation that uses capture experiments in a simple Hele-Shaw geometry (Santana et al. 2012) to inform a target-cell-specific capture model that can predict capture probability in immunocapture microdevices of any arbitrary complex geometry. We show that capture performance is strongly dependent on the array geometry, and that it is possible to select an obstacle array geometry that maximizes capture efficiency (by creating combinations of frequent target cell-obstacle collisions and shear stress low enough to support capture), while simultaneously enhancing purity by minimizing non-specific adhesion of both smaller contaminant cells (with infrequent cell-obstacle collisions) and larger contaminant cells (by focusing those collisions into regions of high shear stress).