SYNTHESIS, SURFACE, AND CELL-ADHESION PROPERTIES OF POLYURETHANES CONTAINING COVALENTLY GRAFTED RGD-PEPTIDES

In an attempt to improve endothelial cell adhesion and growth on a pol yurethane copolymer, cell adhesive RGD-containing peptides were grafte d to the polymer backbone. Two peptide grafting reaction schemes, incl uding one-step and two-step approaches, were developed. FTIR and amino acid analysis confirmed that coupling of the peptide to the polyureth ane backbone was achieved by both the one-step and two-step methods. H owever, the two-step approach showed a higher peptide coupling efficie ncy and resulted in better control of the orientation of the grafted p eptide. The two-step reaction scheme was used to prepare Gly-Arg-Gly-A sp-Ser-Tyr (GRGDSY), GL-Arg-Gly-Asp-Val-Tyr (GRGDVY), and Gly-Arg-Gly- Glu-Ser-Tyr (GRGESY) peptide-grafted polyurethanes with two different peptide densities (100 and 250 mu mol/g polymer). Dynamic contact angl e measurements indicated that the surfaces of the peptide-grafted poly urethanes were more hydrophilic than the starting and carboxylated ver sions of the precursor polyurethane. In addition, the surface hydrophi licity of the peptide-grafted polymers increased with increasing bulk peptide density. Electron spectroscopy for chemical analysis suggested that the grafted peptide was present at the polymer-air interface, in vacuo, fdr the peptide-grafted polyurethanes. The surface peptide den sity appeared to correlate with the incorporated peptide density in th e bulk In vitro endothelial cell adhesion experiments showed that, wit hout the presence of serum in culture medium, the GRGDSY- and GRGDVY-g rafted polyurethanes dramatically enhanced cell attachment and spreadi ng compared with the starting, carboxylated, and GRGESY-grafted polyme rs. Increasing the peptide density from 100 to 250 mu mol/g polymer fo r the GRGDSY- and GRGDVY-grafted polyurethanes resulted in an increase in cell attachment. With approximately the same peptide density (100 or 250 mu mol/g polymer), the GRGDVY-grafted polymers supported more a dherent cells than did the GRGDSY-grafted polymers. Similar trends wer e observed in the in vitro endothelial cell growth studies using cultu re medium containing serum and endothelial cell growth supplement. The GRGDSY- and GRGDVY-grafted polyurethanes promoted more cell growth th an did the starting polyurethane. However, the presence of adhesive se rum proteins and growth factor diminished the differences between the cell-adhesive peptide grafted polymers and the GRGESY-grafted polymers . (C) 1994 John Wiley and Sons, Inc.