Role of endothelial cell-substrate contact area and fibronectin-receptor affinity in cell adhesion to HEMA/EMA copolymers

The objective of this study was to examine the effect of substrate hydrophobicity on cell-substrate contact area and the affinity between adsorbed fibronectin (Fn) and its receptor. Homo- and copolymer films of hydrophobic ethyl methacrylate (EMA) and hydrophilic hydroxyethyl methacrylate (HEMA) were spun-cast onto glass slides. Bovine aortic endothelial cells (BAEC) were plated for 2 h in serum-free medium onto polymers preadsorbed with Fn. Cells were fixed, labeled, and examined by total internal reflection fluorescence microscopy (TIRFM) to determine the topography of the basal surface as a function of distance from the substrate. Phase contrast microscopy was used to examine the total projected area of adherent cells. The cumulative contact area was greatest on cells attached to surfaces prepared from 0% HEMA and lowest on surfaces with the highest HEMA content. An equilibrium adhesion model used these data together with the critical force for detachment and the Fn density (Burmeister et al., J Biomed Mater Res 1996;30:13-22) to determine the affinity between Fn and its receptor and the bond strength. The affinity and force per bond decreased with increasing HEMA content. These results indicate that differences in the strength of endothelial cell adhesion to polymers are influenced by the conformation of the adsorbed adhesion proteins.