Surface deformation and shear flow in ligand mediated cell adhesion

TL;DR

This paper develops a multi-scale model to analyze how ligand-coated deformable cells adhere or detach under shear flow, revealing hysteresis, bistability, and conditions favoring adhesion, with implications for cell adhesion dynamics.

Contribution

It introduces a unified multi-scale model combining microscale ligand forces with macroscale fluid dynamics to study cell adhesion under shear flow, highlighting hysteresis and bistability phenomena.

Findings

Hysteretic transition between adhesion and fragmentation regimes.

Adhesion favored in highly ionic fluids and with increased cell deformability.

Identification of a bistable region with abrupt switching at critical shear rates.

Abstract

We present a single, unified, multi-scale model to study the attachment\detachment dynamics of two deforming, near spherical cells, coated with binding ligands and subject to a slow, homogeneous shear flow in a viscous fluid medium. The binding ligands on the surface of the cells experience attractive and repulsive forces in an ionic medium and exhibit finite resistance to rotation via bond tilting. The macroscale drag forces and couples describing the fluid flow inside the small separation gap between the cells, are calculated using a combination of methods in lubrication theory and previously published numerical results. For a select range of material and fluid parameters, a hysteretic transition of the sticking probability curves between the adhesion and fragmentation domain is attributed to a nonlinear relation between the total microscale binding forces and the separation gap between the cells. We show that adhesion is favored in highly ionic fluids, increased deformability of the cells, elastic binders and a higher fluid shear rate (until a critical value). Continuation of the limit points predict a bistable region, indicating an abrupt switching between the adhesion and fragmentation regimes at critical shear rates, and suggesting that adhesion of two deformable surfaces in shearing fluids may play a significant dynamical role in some cell adhesion applications.