A NOVEL METHOD FOR SURFACE MODIFICATION TO PROMOTE CELL ATTACHMENT TOHYDROPHOBIC SUBSTRATES

The ability to study and regulate cell behavior at a biomaterial inter face requires strict control over material surface chemistry. Perhaps the greatest challenge to researchers working in this area is preventi ng the fouling of a given surface due to uncontrolled protein adsorpti on. This work describes a method for coupling peptides to hydrophobic materials for the purpose of simultaneously preventing nonspecific pro tein adsorption and controlling cell adhesion. A hexapeptide containin g the ubiquitous RGD cell-adhesion motif was coupled to polystyrene (P S) via a polyethylene oxide (PEO) tether in the form of a modified PEO /PPO/PEO triblock copolymer. Triblocks were adsorbed onto PS at a dens ity of 3.3 +/- (5.14 x 10(-4)) mg/m(2) (1.4 x 10(5) +/- 2.12 x 10(1) m olecules/mu m(2)), which was determined by isotope I-125 labeling. The peptide, GRGDSY, was activated at the N terminus with N-Succinimidyl 3-(2-pyridyldithio) propionate and coupled to immobilized triblocks wh ere the terminal hydroxyls had been converted to sulfhydryl groups. Su rface peptide density was measured by amino acid analysis and found to be 1.4 x 10(4) +/- 0.47 x 10(4) molecules/mu m(2). PS modified with P EO/PPO/PEO copolymers alone was found to be inert to cell adhesion bot h in the presence of serum proteins and when exposed to activated RGD peptide. In contrast, PS conjugated with RGD via end-group-activated P EO/PPO/PEO copolymers supported cell adhesion and spreading. The surfa ce coupling scheme reported here should prove valuable for studying ce ll-ligand interactions under simplified and highly controlled conditio ns. (C) 1998 John Wiley & Sons, Inc.