Surface chemistry modulates fibronectin conformation and directs integrin binding and specificity to control cell adhesion

Integrin-mediated cell adhesion to proteins adsorbed onto synthetic surfaces anchors cells and triggers signals that direct cell function. In the case of fibronectin (Fn), adsorption onto substrates of varying properties alters its conformation/structure and its ability to support cell adhesion. In the present study, self-assembled monolayers (SAMs) of alkanethiols on gold were used as model surfaces to investigate the effects of surface chemistry on Fn adsorption, integrin binding, and cell adhesion. SAMs presenting terminal CH(3), OH, COOH, and NH(2) functionalities modulated adsorbed Fn conformation as determined through differences in the binding affinities of monoclonal antibodies raised against the central cell-binding domain (OH > COOH = NH(2) > CH(3)). Binding of alpha(5)beta(1) integrin to adsorbed Fn was controlled by SAM surface chemistry in a manner consistent with antibody binding (OH > COOH = NH(2) > CH(3)), whereas alpha(V) integrin binding followed the trend: COOH >> OH = NH(2) = CH(3), demonstrating alpha(5)beta(1) integrin specificity for Fn adsorbed onto the NH(2) and OH SAMs. Cell adhesion strength to Fn-coated SAMs correlated with alpha(5)beta(1) integrin binding (OH > COOH = NH(2) > CH(3)), and experiments with function-perturbing antibodies demonstrated that this receptor provides the dominant adhesion mechanism in this cell model. This work establishes an experimental framework to analyze adhesive mechanisms controlling cell-surface interactions and provides a general strategy of surface-directed control of adsorbed protein activity to manipulate cell function in biomaterial and biotechnological applications.