| Blood flow dynamics involves length scales across vastly different ranges. For example, adhesion of leukocytes to substrate entails dimensions ranging from nm to mum in length. Understanding the adhesive and rheological behavior of these cells is essential not only for describing microcirculatory flow dynamics, but also for understanding their function and behavior in health and disease. Models of cell adhesion do not combine molecular and full cellular information.; In this study, a multi-scale computational approach for studying the adhesion kinetics and the deformation and movement of a cell on a substrate is presented. The cellular level model consists of a continuum representation of the field equations and a moving boundary tracking capability to allow the cell to change its shape continuously.; At the receptor-ligand level, a bond molecule is mechanically represented by a spring and a reversible kinetics model is used to describe the association and dissociation of bonds. Communication between the macro- and micro-scale models is facilitated interactively with iterations between models until both levels approach compatible solution in each time step.; The computational model is assessed using a cell adhering and deforming along the vessel wall under imposed shear flows. It confirms existing numerical and experimental results. In previous studies, the cell was modeled as solid body or a liquid drop. In the case of adhesion, only a small portion of the contact area was allowed to peel away from the wall.; In this study, modeling the cell as a compound drop, we show that the presence of the nucleus increases the bond lifetime. We also show that increasing cell surface tension decreases the bond lifetime and that vessel diameter affects the cell rolling velocity. Furthermore, we find that the peeling time for a uniform inlet boundary condition is higher than that of a pulsatile one. In addition, increasing cell viscosity for a fixed hydrodynamic force increases linearly the critical bond force, whereas increasing cell surface tension inversely decreases it. Finally, we have shown that a non-zero initial bond force increases the peeling time. The present work shows that cell deformability and hydrodynamic flow affect cell adhesion. |
