Keratin coated titanium as an aid to osseointegration: Physicochemical and mechanical properties

Wool-extracted keratin has been shown to promote bone formation in vivo and may therefore be a potential novel bioactive coating material for osseous implants. This study examined the physicochemical and mechanical properties of keratin-coated titanium, to assess its potential for use in bone-implant applications. Keratin was covalently coupled to silane and glutaraldehyde treated titanium by either (a) molecular grafting or (b), solvent casting. The coated titanium surfaces physicochemical properties including contact angle, roughness, degradation, and swelling characteristics, were subsequently characterized using attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR), scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDS), X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD). Mechanical properties including the coating adhesion strength and tensile strength were also examined. ATR-FTIR, XPS, XRD, and SEM-EDS all confirmed the presence of keratin on both coated titanium surfaces. SEM imaging showed that solvent casting produced a thick coating which completely covered the titanium surface, while molecular grafting produced a discontinuous thinner coating. The surface roughness increased similarly using either coating methodology while molecular grafting only, increased surface wettability. Both keratin-modified titanium surfaces were stable in solution over 28 days demonstrating suitability for in vivo applications, while the solvent cast titanium also showed good adhesion and tensile bond strength of the coated keratin. These results show a stable keratin coating on the titanium surface was successfully obtained which has both the physiochemical and mechanical properties required for potential dental and or orthopaedic implant applications.