Immobilization of RGD peptide on the surface of tyrosine-containing polycarbonates

Abstract

This research has focused on chemical immobilization of RGD-containing peptides (RGD, RGDS, GRGDS) on the surface of tyrosine-derived polycarbonates having carboxyl pendant groups, poly(DTE-co¬-20%DT carbonate) through a two-step reaction. The first step involved an activation of carboxyl groups by N-hydroxysuccinimide (NHS) in the presence of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride (EDCI). The second step was a covalent attachment of RGD-containing peptides. The success of peptide immobilization was determined by ninhydrin method and x-ray photoelectron spectroscopy (XPS). Using hexamethylenediamine as a standard, the grafting density of ~ 8.07 x 10⁻⁸, 6.51 x 10⁻⁸ ,and 5.13 x 10⁻⁸ mol/cm² were estimated for immobilization of RGD, RGDS, and GRGDS, respectively. According to XPS analysis of RGD-immobilized poly(DTE-co-20%DT carbonate) surface after labeling with heptafluorobutyryl chloride, 30 and 74% substitution were calculated for immobilization of RGDS and GRGDS, respectively. Results from in vitro cell studies demonstrated that among all studied RGD-containing peptides, GRGDS can best enhance fibroblast (B95) adhesion and proliferation on the polymer surface. Taking 100% of TCPS as a positive control, cell adhesion ratio and proliferation ratio were elevated from 92 and 100% of the virgin polymer to 117 and 129% respectively, after GRGDS immobilization. Evidently, the extra glycine spacer introduces the flexibility to the peptide and thus allows the RGD part to effectively mediate its specific response to the cells.