Platelet adhesion onto segmented polyurethane surfaces modified by carboxybetaine

Polyurethanes are widely used as blood-contacting biomaterials due to their good biocompatibility and mechanical properties. Nevertheless, their blood compatibility is still not adequate for more demanding applications. Surface modification is an effective way to improve the hemocompatibility for biomaterials. The purpose of present study was to synthesize a novel nonthrombogenic biomaterial by modifying the surface of polyurethane with Zwitterions of carboxybetaine monomer. The films of polyurethane were grafted with two kinds of carboxybetaine by a three-step procedure. In the first step, the film surfaces were treated with hexamethylene diisocyanate (HDI) in toluene at 50degreesC in the presence of di-n-butyl tin dilaurate (DBTDL) as a catalyst. The extent of the reaction was measured by ATR-FT-IR spectra; a maximum number of free NCO group was obtained after a reaction time of 90 min. In the second step, the hydroxyl group of N,N-dimethylethylethanolamine (DMEA) or 4-dimethylamino-1-butanol (DMBA) was allowed to react in toluene with isocyanate groups bound on surface. In the third step, carboxybetaines were formed in the surface through the ring-opening reaction between tertiary amine of DMEA or DMBA and beta-propiolactone (PL). It was characterized by ATR-FT-IR and XPS that the grafted surfaces were composed of carboxybetaine. The results of the contact angle measurements showed that they were strongly hydrophilic. Platelet adhesion tests showed that films grafted carboxybetaine have good blood compatibility, as featured by the low platelet adhesion.