Abstract
We have evaluated four surface modification techniques for polymeric materials used in the blood contacting artificial organs. Proposed approaches to design nonthrombogenic polymer surfaces include 1) phase separated microdomain surfaces, 2) hydrophilic surfaces, 3) bioactive molecule incorporated surfaces, 4) biomembranelike surfaces. We have developed several in situ surface modification techniques according to these approaches to improve the blood compatibility of blood contacting surfaces of medical devices, including 1) HEMA-styrene block copolymer coating (HEMA/st), 2) poly ethylene glycol grafting (EG), 3) human thrombomodulin immobilization (hTM), 4) 2-methacryloyl oxyethyl phosphorylcholin (MPC) copolymer coating onto segmented polyurethane (PU) surfaces. These surface-modified PUs were evaluated using an epifluorescent video microscope combined with a parallel plate flow cell (EVM system) for assessing in vitro platelet adhesion and complement activation. All surfaces showed significantly lower platelet adhesion than nontreated PU, and showed the ranking of the amount of adhered platelet as follows: PU>EG>hTM>MPCs>HEMA/st. As for complement activation, hTM showed the least C3a production, which attributed to its inherent inhibitory effects on complement activation. Ever known characteristics of each material were confirmed in this experiment. Thus, this EVM system has been proven to be an excellent in vitro analytical method for relative evaluations of nonthrombogenicity of biomaterials.
