Protein resistance of PNIPAAm brushes: application to switchable protein adsorption.

Protein adsorption, as the primary process occurring when a foreign surface comes into contact with a biosystem, was studied on thin polymer brush films consisting of poly(N-isopropylacrylamide) (PNIPAAm) and poly(2-vinylpyridine) (P2VP). These films were prepared by the "grafting to" method. The protein resistance of stimuli responsive PNIPAAm-brushes toward serum albumin was recorded and compared with protein adsorption on P2VP brushes. To achieve a better understanding of protein resistance, PNIPAAm brushes with different molecular weights were investigated below and above the lower critical solution temperature of 32 degrees C. To use these findings for the adjustment and switching of protein adsorption, in a first attempt the adsorption on a mixed brush system consisting of PNIPAAm and P2VP chains was studied. This system showed temperature-dependent adsorption behavior due to the presence of PNIPAAm, representing a smart surface with stimuli-responsive changes in the physicochemical surface properties. With this mixed brush, the adsorbed amount of protein could be controlled, depending on composition and the temperature of the surroundings.