| Abstract
| - Poly(ethylene oxide) (PEO) polymer, in linear and star form, was covalently grafted to siliconsurfaces, and the surfaces were tested for their ability to adsorb proteins. Linear PEG of molecular weight3400, 10 000, and 20 000 g/mol and star PEO molecules were coupled via their terminal hydroxyl groupsactivated by tresyl chloride to aminosilane-treated silicon wafers. The amount of PEO coupled to thesurface was varied by changing the concentration of the tresyl-PEO solution. The dry PEO thickness onthe surface was measured using X-ray photoelectron spectroscopy (XPS) and ellipsometry, from whichthe grafting density was calculated. The PEO surfaces were exposed to solutions of each of threeproteins: cytochrome-c, albumin, and fibronectin. The degree of adsorption of each protein was determinedby XPS and ellipsometry and recorded as a function of PEO grafting density. All three proteins werefound to reach zero adsorption at the highest grafting densities on all three PEG surfaces, which for allthree PEG surfaces was a PEO content of 100 ± 10 ng/cm2. On both star PEO surfaces, albumin andfibronectin decreased to zero adsorption at intermediate values of grafting density, whereas cytochrome-ccontinued to adsorb at all grafting densities, although with a decreasing trend. A physical model of thesurface helped explain these protein adsorption results in terms of the spacing and degree of overlap ofgrafted PEO chains.
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