Covalent surface modification of a titanium alloy with a phosphorylcholine‐containing copolymer for reduced thrombogenicity in cardiovascular devices

Our objective was to develop a surface modification strategy for a titanium alloy (TiAl 6 V 4 ) to provide thromboresistance for surfaces in rigorous blood‐contacting cardiovascular applications, such as that found in ventricular assist devices. We hypothesized that this could be accomplished by the covalent attachment of a phospholipid polymer, poly(2‐methacryloyloxyethylphosphorylcholine (MPC)‐ co ‐methacryl acid) (PMA). TiAl 6 V 4 was H 2 O plasma treated by radio frequency glow discharge, silanated with 3‐aminopropyltriethoxysilane (APS), and ammonia plasma treated to increase surface reactivity. The TiAl 6 V 4 surface was then modified with PMA via a condensation reaction between the amino groups on the TiAl 6 V 4 surface and the carboxyl groups on PMA. The surface composition was verified by X‐ray photoelectron spectroscopy, confirming successful modification of the TiAl 6 V 4 surfaces with APS and PMA as evidenced by increased Si and P. Plasma treatments with H 2 O and ammonia were effective at further increasing the surface reactivity of TiAl 6 V 4 as evidenced by increased surface PMA. The adsorption of ovine fibrinogen onto PMA‐modified surfaces was reduced relative to unmodified surfaces, and in vitro ovine blood contact through a rocking test revealed marked reductions in platelet deposition and bulk phase platelet activation relative to unmodified TiAl 6 V 4 and polystyrene controls. The results indicate that the PMA‐modification scheme for TiAl 6 V 4 surfaces offers a potential pathway to improve the thromboresistance of the blood‐contacting surfaces of cardiovascular devices. © 2008 Wiley Periodicals, Inc. J Biomed Mater Res, 2009