Enhanced biocorrosion resistance of surface modified magnesium alloys using inorganic/organic composite layer for biomedical applications

Abstract

Magnesium (Mg) is a very active element with low surface stability. Thus, the biocorrosion resistance of Mg and its alloys in electrolytic physiological environments is extremely poor, which is the main limitation preventing their use in biomedical applications. In addition, generating an appropriate protective layer to coat the surface of such materials is a challenge due to the low level of surface stability. The aim of this study was to prepare thin Ti-O films on Mg substrates using electron beam physical vapor deposition (EB-PVD) in order to improve the surface stability of Mg. To provide further corrosion resistance and facilitate improved bioactivity and biocompatibility, Ti-O thin films were subsequently coated with PLA as a top layer by dip-coating. The surface properties of the coated layers were characterized by AFM, X-RD, FTIR, SEM, and EDS. Furthermore, the biocorrosion characteristics of samples were measured by electrochemical corrosion and hydrogen evaluation tests in standard simulation body fluid (SBF) at 37.5 °C. Our results showed that incorporation of a composite layer significantly reduced the rate of degradation of Mg alloys, particularly during the initial immersion stages. The rates of hydrogen evolution of Mg bars with and without a Ti-O/PLA composite coating after 18 days was approximately 4.86 and 13.4 ml cm−2, respectively. Together, these results demonstrated that surface treatment of Mg substrates with Ti-O and PLA, together with the associated changes of surface reactivity and chemistry, provide a viable strategy to facilitate cell survival on otherwise non-biocompatible Mg surfaces.