Protein adhesion regulated by the nanoscale surface conformation

Protein adhesion and adsorption behaviors vary in response to variations in surface wettability; however, few reports have examined the dependence of such behaviors on variations in the surface molecular conformations. This study examines the degree to which molecular disorder at the surface of a surface-modified hydrocarbon chain monolayer regulates protein adhesion. Octadecyltrichlorosilane (OTS) molecules were deposited onto silicon wafers at two temperatures, 5 degrees C or 55 degrees C, to prepare two OTS surfaces with different degrees of molecular disorder. Atomic force microscopy (AFM) was used to evaluate the nanoscale adhesion force between proteins and the two types of OTS monolayers during a short contact time (<1 s). Bovine serum albumin (BSA) and human fibrinogen (HF) adhered more strongly to the disordered than to the ordered OTS monolayer. The adhesion strength at longer contact times (30 s-90 min) was evaluated by investigating the resistance of proteins on the OTS monolayer to detachment by washing. The magnitude of the resistance could be predicted from the topologies of the monolayers, as determined by AFM, after the adsorption of proteins and the subsequent washing experiments. After a 90 min adsorption period, BSA displayed a higher resistance to detachment from the disordered OTS monolayer than from the ordered OTS monolayer. HF displayed a higher resistance to detachment from the disordered OTS monolayer for only very short adsorption times of less than 1 min. The results suggest that the proteins altered their adhesion onto monolayers with different OTS conformations and that different adsorption times were required for each protein to present the different degrees of adhesion.