Polyethylene oxide-containing block copolymers as surface modification additives in polyurethanes for protein and cell resistanc

Polyurethanes (PU) have long been used for biomedical applications because of their excellent mechanical properties. These materials are, however, insufficiently biocompatible for long-term use in the human body. Polyethylene oxide (PEO) has gained recognition as a biocompatible material since it appears to interact minimally with proteins and cells. As a result, there have been many attempts to prepare and utilize PEO surfaces in biomedical applications.;The present work involves surface modification of conventional polyurethanes by blending with novel PEO-containing triblock copolymers PEO-PU-PEO, the PU middle segment having a structure similar to the PU matrix. It is hypothesized that the PEO-PU PEO component will migrate spontaneously to the material/air interface since it is surface active, and even more so to the material/water interface due to the hydrophilic nature of PEO, resulting in surface enrichment of the PEO copolymers. The presence of PEO should provide the interface with protein- and cell-repellent properties. At the same time, the similarity of the PU middle block and the PU matrix should allow strong interactions between the matrix and the copolymer, helping to anchor the block copolymers at the interface.;Protein interactions with the various surfaces were studied in buffer (single proteins, binary systems) and plasma using radiolabelling and immunoblotting methods. The resistance of the blend materials to protein adsorption was found to increase with increasing surface density of the copolymers. All three of the 20% blends showed strong resistance to both fibrinogen (MW 340,000) and lysozyme (MW 14,400) regardless of PEO molecular weight.;Studies of adsorption from human plasma again showed the strong protein resistance of the blend materials. Trends with respect to material properties were similar to those found in the simpler protein systems. In particular there appeared to be little or no selectivity with respect to resistance to different proteins.;It may be concluded that by the simple process of blending with PEO-PU-PEO triblock copolymers, it is possible to transform a PU surface from one having high protein adsorption and platelet adhesion to one which is strongly protein and platelet repellent. (Abstract shortened by UMI.).