Protein adsorption on poly(ethylene oxide)-grafted silicon surfaces

Poly(ethylene oxide), in linear and star form, was covalently grafted to silicon surfaces in a range of grafting densities and the surfaces tested for their ability to adsorb proteins (cytochrome-c, albumin, fibronectin). The surfaces were analyzed by X-ray photoelectron spectroscopy (XPS) and ellipsometry, where both PEO content and amount of adsorbed protein were determined. All three proteins were found to reach zero adsorption at the highest grafting densities on all three linear PEG surfaces (PEG MW 3400, 10,000, and 20,000 g/mol). On both star PEO surfaces, albumin and fibronectin decreased to zero adsorption at intermediate grafting densities, whereas cytochrome-c continued to adsorb at all grafting densities. It was found that grafting densities of linear PEG in a brush regime were necessary to prevent protein adsorption. On PEO star surfaces, however, it was the decrease in space between grafted molecules to less than the size of the protein that was necessary in preventing the protein from adsorbing to the surface.