Surface and Biological Effects of Peptide Orientation Evaluated Using Gold-Coated Polyurethanes

Abstract

Cell adhesion and growth are central issues in the otherwise promising method of endothelialization of materials for improving blood compatibility. To improve cell adhesion to biomaterial surfaces, surface modification with cell adhesion peptides is often used. In particular, arginine-glycine-aspartic acid (RGD), long recognized as a peptide sequence that plays and important role in cell adhesion, has been covalently attached to surfaces to enhance cell adhesion. In this work, the effect of the orientation of the cell adhesion peptide immobilized on the surface was studied through using gold surfaces, which can be readily modified with thiols and sulfur-containing groups. Peptide orientation was controlled by the placement of the cysteine (C) at either the C- or N-terminus, Two cell adhesion peptides, the non-specific RGD and more endothelial cell specific REDV (arginine-glutamic acid-aspartic acid-valine), were studied for their effect on the surface chemical and biological properties, including effects on the interactions with the endothelial cell line ECV304. Vitronectin adsorption to the modified surfaces was specifically examined as a possible reason for differences noted. The results suggest that peptide orientation plays an important role in the interactions of cells and proteins to the modified surfaces. Peptides with the cysteine at the N-terminus showed increased adhesion of endothelial cells from the ECV304 line, with the greatest adhesion noted consistently on the CREDV-modified surfaces. Differences in surface chemistry as evaluated by x-ray photoelectron spectroscopy were also found higher levels of bonded peptide when the thiol-containing cysteine was in the N-terminal position. These results suggest that the secondary structure of the peptide can be used to enhance or to limit its reaction with the surface. Furthermore, while cell adhesion was noted during culture in the absence of serum, significant increases in the numbers of adherent cells were noted on all surfaces when the cells were grown in the presence of serum. Immunoblotting and culture with antibodies demonstrated that this increase in the adhesion of the cells is likely mediated primarily by the cell adhesion peptide vitronectin.