Cell Stiffness Governs Its Adhesion Dynamics on Substrate Under Shear Flow

We develop an efficient numerical method to study adhesion dynamics of a single cell on a substrate under shear flow. This method is based on the coupling ofLattice Boltzmann fluid and coarse-grained cell models through immersed boundary method, and a probabilisticmodel is adopted to capture dynamics of ligand-receptor binding for adhesion. With such a model at hand, a phase diagram of the adhesion dynamics in terms of adhesion strength Ad and stiffness of cell Ca is established. Four types of motion, including free motion, stable rolling, stop-and-go, and firm adhesion, are found through our numerical simulations, depending on the adhesion strength Ad and stiffness of cell Ca. In addition, demargination behavior of the cell occurs when reducing the adhesion strength Ad in the regime of soft cells (high Ca). Such a demargination behavior is induced by the deformability of cell, resulting in a wall-induced lift force in the shear flow. Lastly, a scaling relation of a number of ligand-receptor bonds is obtained under the synergistic effect of Ad and Ca. The present effort provides a robust and efficient way to understand the adhesion dynamics of cells on substrate in shear flow. The obtained results are useful in understanding the biological adhesion process and developing adhesion-based microfluidic technologies.