Simple surface modification of a titanium alloy with silanated zwitterionic phosphorylcholine or sulfobetaine modifiers to reduce thrombogenicity

Abstract

Thrombosis and thromboembolism remain problematic for a large number of blood contacting medical devices and limit broader application of some technologies due to this surface bioincompatibility. In this study we focused on the covalent attachment of zwitterionic phosphorylcholine (PC) or sulfobetaine (SB) moieties onto a TiAl 6V 4 surface with a single step modification method to obtain a stable blood compatible interface. Silanated PC or SB modifiers (PCSi or SBSi) which contain an alkoxy silane group and either PC or SB groups were prepared respectively from trimethoxysilane and 2-methacryloyloxyethyl phosphorylcholine (MPC) or N-(3-sulfopropyl)- N-(methacryloxyethyl)- N, N-dimethylammonium betaine (SMDAB) monomers by a hydrosilylation reaction. A cleaned and oxidized TiAl 6V 4 surface was then modified with the PCSi or SBSi modifiers by a simple surface silanization reaction. The surface was assessed with X-ray photoelectron spectroscopy (XPS), attenuated total reflection-Fourier transform infrared spectroscopy (ATR-FTIR) and contact angle goniometry. Platelet deposition and bulk phase activation were evaluated following contact with anticoagulated ovine blood. XPS results verified successful modification of the PCSi or SBSi modifiers onto TiAl 6V 4 based on increases in surface phosphorous or sulfur respectively. Surface contact angles in water decreased with the addition of hydrophilic PC or SB moieties. Both the PCSi and SBSi modified TiAl 6V 4 surfaces showed decreased platelet deposition and bulk phase platelet activation compared to unmodified TiAl 6V 4 and control surfaces. This single step modification with PCSi or SBSi modifiers offers promise for improving the surface hemocompatibility of TiAl 6V 4 and is attractive for its ease of application to geometrically complex metallic blood contacting devices.