A new approach to graft bioactive polymer on titanium implants: Improvement of MG 63 cell differentiation onto this coating

Integration of titanium implants into bone is only passive and the resulting fixation is mainly mechanical in nature, with anchorage failure. Our objective, to increase the biointegration of the implant and the bone tissue, could be obtained by grafting a bioactive ionic polymer to the surface of the titanium by a covalent bond. In this paper, we report the grafting of an ionic polymer model poly(sodium styrene sulfonate) (polyNaSS), in a two-step reaction procedure. Treatment of the titanium surface by a mixture of sulfuric acid and hydrogen peroxide allows the formation of titanium hydroxide and titanium peroxide. In the second reaction step, heating of a metal implant, placed in a concentrated solution of sodium styrene sulfonate monomer (NaSS), induces the decomposition of titanium peroxides with the formation of radicals capable of initiating the polymerization of NaSS. Various parameters, such as temperature of polymerization and time of polymerization, were studied in order to optimize the yield of polyNaSS grafting. Colorimetry, Fourier-transformed infrared spectra recorded in an attenuated total reflection, X-ray photoelectron spectroscopy techniques and contact angle measurements were applied to characterize the surfaces. MG63 osteoblastic cell response was studied on polished, oxidized and grafted titanium samples. Cell adhesion, alkaline phosphatase activity and calcium nodules formation were significantly enhanced on grafted titanium samples compared to unmodified surfaces.