Synthesis of Arg-Gly-Asp (RGD) sequence conjugated thermo-reversible gel via the PEG spacer arm as an extracellular matrix for a pheochromocytoma cell (PC12) culture.

Adhesion molecules composed of Gly-Arg-Gly-Asp-Ser (GRGDS) peptides and cell recognition ligands were inculcated into thermo-reversible hydrogel composed of N-isopropylacrylamide, with a small amount of succinyl poly(ethylene glycol) (PEG) acrylate (MW 3400) used as a biomimetic extracellular matrix (ECM). The GRGDS-containing p(NiPAAm-co-PEG) copolymer gel was studied in vitro for its ability to promote cell spreading and to increase the viability of cells by introducing PEG spacers. Hydrogel lacking the adhesion molecules proved to be a poor ECM for adhesion, permitting only a 20% spread of the seeded cells after 10 days. When PEG spacer arms, immobilized by a peptide linkage, had been integrated into the hydrogel, conjugation of RGD promoted cell spread by 600% in a 10-day trial. In addition, in a serum-free medium, only GRGDS peptides conjugated with the spacer arm were able to promote cell spread. In terms of the cell viability, GRGDS peptides conjugated with the PEG-carrying copolymer gel specifically mediated cell spread. This result supports the theory that specific recognition is the result of interaction between the integrin families on the fibroblast, and the RGD sequence on the p(NiPAAm-co-PEG) copolymer gel.