Nonfouling biomaterials based on polyethylene oxide-containing amphiphilic triblock copolymers as surface modifying additives: Adsorption of proteins from human plasma to copolymer/polyurethane blends
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Three polyethylene oxide-polyurethane-polyethylene oxide (PEO-PU-PEO) block copolymers of variable PEO block size (MW 550, 2000, and 5000) were used to modify the surface of a conventional segmented polyurethane (PU) with the objective of inhibiting interactions with proteins. The surface-active copolymers were blended with the PU by solution methods. Protein adsorption from human plasma to the modified materials was investigated using radiolabeling and immunoblotting methods. From the radiolabeling experiments, it was found that fibrinogen adsorption from plasma to all of the modified surfaces was much lower than to the unmodified PU matrix. For blends of low copolymer content, resistance to adsorption was greatest on the copolymer 1 (PEO550)-modified materials, and increased with increasing copolymer content for all three blend types. At high copolymer content inhibition of adsorption was very strong and independent of PEO block size. The immunoblotting experiments showed that on materials of high copolymer content (20 wt %), the proteins investigated (fibrinogen, albumin, complement C3, and apolipoprotein A-I) were undetectable. At low copolymer content (< or = 5 wt %), the blends of copolymer 1, with the shortest PEO block, exhibited greater protein resistance than those of copolymers 2 and 3 (PEO blocks of MW 2000 and 5000, respectively), and resistance decreased with decreasing protein size. Evidence of complement activation was seen for the blends of low copolymer content. Adsorption of C3 and complement activation decreased with increasing content of the copolymers. It was concluded that surface density of PEO is more important than chain length for protein resistance in contact with plasma.