The influence of poly(ethylene oxide) grafting via siloxane tethers on protein adsorption.

Amphiphilic PEO-silanes (a-c) having siloxane tethers of varying lengths with the general formula alpha-(EtO)3Si-(CH2)2-oligodimethylsiloxane(n)-block-poly(ethylene oxide)8-OCH3 [n=0 (a), n=4 (b), and n=13 (c)] were grafted onto silicon wafers and resistance to adsorption of plasma proteins was measured. Distancing the PEO segment from the hydrolyzable triethoxysilane [(EtO)3Si] grafting group by a oligodimethylsiloxane tether represents a new method of grafting PEO chains to surfaces. Properties of surfaces grafted with a-c were compared to surfaces grafted with a traditional PEO-silane containing a propyl spacer [(EtO)3Si-(CH2)3-poly(ethylene oxide)8-OCH3, PEO control]. As the siloxane tether length increased, chain density of PEO-silanes grafted onto oxidized silicon wafers decreased and hydrophobicity of the PEO-silane increased which led to a decrease in surface hydrophilicity. Despite decreased surface hydrophilicity, resistance to the adsorption of bovine serum albumin (BSA) increased in the order: PEO control<a<b approximately c and to human fibrinogen (HF) increased in the order: PEO control<a<b<c.