Transient adhesion mediated by ligand-receptor interaction on surfaces of variable nanotopography

Abstract

Surface microtopography and nanotopography have been shown to influence cell adhesion and function, including proliferation and differentiation, leading both to fundamental questions and practical applications in the field of biomaterials and nanomedicine. However, the mechanisms of how cells sense topography remain obscure. In this study, we measured directly the effect of nanotopography on the kinetics of association and dissociation of ligand–receptor bonds, which are critically involved in the first steps of cell adhesion. We designed models of biological functionalised surfaces with controlled roughness varying from 2 to 400 nm of root mean square, and controlled ligand density. Tests of transient adhesion of receptor–coated microspheres on these surfaces were performed, using a laminar flow chamber assay. We probed Intercellular Adhesion Molecule ICAM–1–anti–ICAM–1 bond adhesion kinetics in the single molecule limit on smooth and rough substrates. Frequency of adhesion did not exhibit any noticeable dependence on roughness parameter, except at high bead velocity. Detachment rate was also independent of roughness. Finally, leucocyte transient adhesion tests were performed on similar substrates, using variable activating incubating media. Here also, no strong effect of roughness was observed in these conditions. Results are rationalised in terms of the role of local geometry on the access of ligands to receptors.