Non-fouling biomaterials based on blends of polyethylene oxide copolymers and polyurethane: simultaneous measurement of platelet adhesion and fibrinogen adsorption from flowing whole blood

Measurements of platelet adhesion and fibrinogen adsorption from flowing whole blood to a series of polyethylene oxide (PEO)-based materials were carried out. A unique experimental design was used in which both quantities were measured in the same experiment. The materials consisted of a polyurethane (PU) as a matrix into which various triblock copolymers of general structure PEO-PU-PEO were blended; the PU block was the same in all materials but the PEO blocks ranged in molecular weight from 550 to 5000. Platelets were isolated from fresh human blood and labeled with (51)Cr; purified fibrinogen was labeled with (125)I. A whole blood preparation containing these labeled species was used for the adhesion/adsorption studies. The surfaces were exposed to the flowing blood in a cone and plate device at a wall shear rate of 300 s(-1). It was found that both platelet adhesion and fibrinogen adsorption decreased with increasing copolymer content in the blends and with decreasing PEO block size for a given copolymer content. The block size effect was due probably to higher PEO surface coverage for the lower molecular weight blocks. Fibrinogen adsorption and platelet adhesion were linearly and strongly correlated. The best performing materials showed very low fibrinogen adsorption of the order of 25 ng/cm(2), and correspondingly low platelet densities around 10,000 per cm(2), i.e. fractional platelet coverage in the vicinity of 0.2%.