Formation of 2D ligand-receptor bonds under shear

Formation and dissociation of specific molecular links between opposing surfaces are omnipresent events of the living world. They very often take place in highly dynamic conditions like in blood stream where wall shear rates are believed to vary from 150 to 1600 s$^{-1}$. Thus, a better understanding of shear effects on 2D ligand-receptor bonds formation is a key step towards improving our conception of biological molecular recognition. Using streptavidin-biotin as a model receptor-ligand pair, we have probed the establishment of specific bonds between the surface of a B-lymphocytes and grafted micrometric particles under controlled shear stress. The results showed that shear stress had a determining effect on cell-particle interactions, introducing a ligand surface density condition for the binding and very likely cell mechanical compliance leading to increased binding at high shear. This view will be discussed in the light of other results that we have obtained using a purely colloidal experimental model, made of particles grafted either with streptavidin or biotin and brought into contact under controlled shear stress.