Part III: Mechanical Effects of Environment on Cell Behavior
As a simple theoretical model of a cell adhering to a biological interface, we consider a rigid sphere moving in a viscous shear ﬂow near a wall. Adhesion forces arise through intermolecular bonds between receptors on the cell and their ligands on the wall, which form ﬂexible tethers that can stretch and tilt as the base of the cell moves past the wall; binding kinetics is assumed to follow a standard model for slip bonds. Typically, under physiological conditions, the time scale for the advection of bonds from the front to the back of a rolling sphere (as viewed in the frame of reference of the sphere) is comparable to the bonds’ characteristic lifetime. This advection mechanism may lead to an accumulation of consummated bonds at the trailing edge of the sphere.