Poly(Nisopropylacrylamide) (PNIPAAm) brush surfaces were prepared via surface initiated atom transfer radical polymerization (SIATRP) on initiatorimmobilized silicon surfaces.The interactions between the PNIPAAm modified surfaces and plasma proteins in single protein solutions and in human blood plasma were investigated by radiolabeling and immunoblotting methods.The PNIPAAm modified surfaces showed much lower fibrinogen adsorption than the unmodified silicon.In particular

the adsorption of fibrinogen from plasma at either room temperature or body temperature was less than 5 ng/cm2

suggesting that these surfaces may possess good blood compatibility.In the plasma experiments the Vroman effect (high fibrinogen adsorption at short time or low plasma concentration) was not observed on the PNIPAAm modified surfaces

indicating good fibrinogen resistance in the early stages of blood contact.Moreover

the immunoblot data showed that adsorption from plasma of most of the proteins tested (including the contact coagulation factors:factor XII

factor XI

prekallikrein and high molecular weight kininogen) to the PNIPAAm modified surfaces was also significantly reduced.In general

our results suggest that PNIPAAm

used as a traditional thermoresponsive polymer

is resistant to nonspecific protein adsorption and may be a promising candidate for use in blood contact devices.