Use of a laminar flow chamber to study the rate of bond formation and dissociation between surface-bound adhesion molecules: Effect of applied force and distance between surfaces

Abstract

It has recently been shown that much information on the behaviour of surface-bound adhesion molecules could be obtained by monitoring the motion of receptor-coated particles along ligand-derivatized surfaces in the presence of a hydrodynamic force of a few pN. This procedure is expected to allow direct monitoring of the formation and dissociation of individual bonds. We present experimental results on the interaction between streptavidin-coated spheres (1.4 µm diameter) and control or biotinylated mica surfaces in a laminar flow chamber. Moving spheres are found to display numerous arrests whose frequency is markedly increased (5–13-fold) in the presence of biotin groups. For a given shear rate, the binding frequency is strongly dependent on the sphere–surface separation. Indeed, this frequency displayed a 14-fold decrease when the velocity increased from 7 to 15 µm s^-1 for a wall shear rate of 20 s^-1. Furthermore, the lifetime of observed arrests was of the order of several seconds, i.e. 5–50-fold higher than previously determined on models such as selectin–ligand, CD2–CD48 or cadherin–cadherin. Finally, this lifetime did not decrease when the wall shear rate was increased from ca. 10 to 40 s^-1.