The role of independently variable grafting density and layer thickness of polymer nanolayers on peptide adsorption and cell adhesion.

This contribution demonstrates a simple and reproducible method for fabricating surface-tethered polymer brushes that vary in grafting density and layer thickness for peptide adsorption and cell-adhesion studies. Surface-initiated atom transfer radical polymerization was used together with thiol self-assembly to generate these nanothin polymer brush layers of poly((polyethylene glycol) methacrylate). A kinetic study was done to measure the layer thickness growth rate at room temperature from flat gold substrates presenting different polymerization initiator molecule surface densities. The polymer brush layers transition from mushroom to brush regimes with increasing grafting density. A crossover density of 0.038+/-0.005 chains/nm(2) was determined for the PPEGMA polymer brushes. The results described in this paper show that layer properties such as wettability and dry layer thickness depend strongly on initiator surface density. Ultimately, the adsorbed concentration of an RGD-containing synthetic peptide Gly-Arg-Gly-Asp-Ser and the adhesion and spreading of cells were correlated with surface properties, which continues to be a major research theme in biomedical and biomaterials research.