A novel method for surface modification to promote cell attachment to hydrophobic substrates.

The ability to study and regulate cell behavior at a biomaterial interface requires strict control over material surface chemistry. Perhaps the greatest challenge to researchers working in this area is preventing the fouling of a given surface due to uncontrolled protein adsorption. This work describes a method for coupling peptides to hydrophobic materials for the purpose of simultaneously preventing nonspecific protein adsorption and controlling cell adhesion. A hexapeptide containing the ubiquitous RGD cell-adhesion motif was coupled to polystyrene (PS) via a polyethylene oxide (PEO) tether in the form of a modified PEO/PPO/PEO triblock copolymer. Triblocks were adsorbed onto PS at a density of 3.3 +/- (5.14 x 10(-4)) mg/m2 (1.4 x 10(5) +/- 2.12 x 10(1) molecules/microm2), which was determined by isotope 125I labeling. The peptide, GRGDSY, was activated at the N terminus with N-Succinimidyl 3-(2-pyridyldithio) propionate and coupled to immobilized triblocks where the terminal hydroxyls had been converted to sulfhydryl groups. Surface peptide density was measured by amino acid analysis and found to be 1.4 x 10(4) +/- 0.47 x 10(4) molecules/microm2. PS modified with PEO/PPO/PEO copolymers alone was found to be inert to cell adhesion both in the presence of serum proteins and when exposed to activated RGD peptide. In contrast, PS conjugated with RGD via endgroup-activated PEO/PPO/PEO copolymers supported cell adhesion and spreading. The surface coupling scheme reported here should prove valuable for studying cell-ligand interactions under simplified and highly controlled conditions.