A facile novel fluorocarbon copolymer solution coating process for improving platelet compatibility of titanium.

Titanium (Ti) and its alloys possess mechanical properties that are desirable in many biomedical applications compared to other metals. Furthermore, the native metal oxide layer that prevents further oxidation is also known to be biocompatible. However, clinical findings have shown that titanium and its alloys are prone to adverse bioreactions such as platelet adhesion and activation which could lead to thrombogenic complications. It has been found that surfaces modified with fluorocarbons could reduce the degree of both platelet adhesion and activation. Nevertheless, direct fluorocarbon deposition onto titanium substrates would require significant technical efforts. Instead, this research utilized a facile coating process with novel copolymers containing 2,2,2-trifluoroethyl methacrylate (TFEMA) and vinylphosphonic acid (VPA) to modify the titanium surface, giving the surface lower surface energy and higher hydrophobicity, significantly reducing the thrombus formation while exhibiting good cytocompatibility. The anchorage group, phosphonic acid provided by VPA, can be covalently bound to the oxide surface of titanium metal. Via free radical polymerization, VPA and TFEMA formed copolymers with different hydrophobicity were then used to modify titanium substrates, on which a series of surface characterization, in vitro platelet adhesion tests, and cytotoxicity assays were performed. Nuclear magnetic resonance (NMR) and X-ray photoelectron spectroscopy (XPS) confirmed the synthesis of the copolymers and the modification of Ti substrates. The platelet adhesion tests showed significantly reduced amount of adherent platelets on certain copolymer-modified Ti substrates with low degrees of activation. The in vitro cytotoxicity assays further highlighted that the modifications conducted on Ti does not induce cytotoxicity.