First-order transition between adhesion states in a system mimicking cell-tissue interaction

We establish a model of cell-tissue interaction consisting of vesicles carrying lipopolymers (to mimic the glycocalix) and mobile specific ligands of the blood platelet integrin α_IIbβ₃ covering the substrate. We find the phase diagram with a first-order transition between a gravity-controlled weak state of the vesicle-substrate adhesion and a strong-adhesion state governed by receptor-ligand interaction. Adhesion energy ε_adh is measured as a function of ligand and repeller concentration by interferometric contour analysis on the basis of a new refined model of soft shell adhesion (accounting for the membrane bending and stretching at the adhesion rim of the ellipsoidal vesicle). At ligand densities comparable to integrin density, ε_adh decreases sharply. Increasing the repeller content weakens the adhesion strength.