Biomaterials

Biography

Biography: Vanja Kokol

Abstract

Magnesium (Mg) alloys have emerged as innovative orthopaedic implant materials due to their excellent degradability, which eliminates the need for a second surgery for their removal. However, rapid degradation of Mg alloys and subsequent loss of mechanical integrity before the tissue regeneration limits their application. The Mg-4Ag and Mg-5Gd binary alloys` degradation and corrosion properties were studied under in vitro conditions (in a simulated body fluid solution of pH 7.4 at 37°C) by using various analytical techniques and time-frame windows (up to 3 vs. 28 days), and compared with the pure (99.9 wt%) Mg alloy, before and after a biomimetic gelatin (GEL) coating via dopamine. Different kinetics and mechanisms of the alloys` degradation were identified, influencing their corrosion rates` dynamics. The EIS measurements of uncoated alloys, being performed for up to 3 days, revealed that the corrosion of all three alloys are under a kinetic-controlled mechanism, among which only pure Mg and Mg-4Ag show a repassivation ability in this time-frame. However, the corrosion rates of binary alloys were lower, reaching a value of around 0.33 mm/y and a release of 64 mg/L Mg²⁺ ions after 28 days of incubation, that was accompanied by a lower pH change (up to pH 8.3), compared to the pure Mg alloy, getting additionally reduced by GEL coating. The spectroscopic (FTIR, XRD, EDXS) and microscopic (SEM) studies revealed the formation of MgO products, as well as apatite formation on the pure Mg alloy surface, while thick and homogenous layers of differently-shaped and chemically secondary-phased Mg(OH)₂ products were identified on both binary alloys after 28 days. Besides, a protective interface layer between the alloy surface and SBF solution was formed on GEL-coated alloys, which further stimulates the mineralization of calcium phosphate compounds, being patterned by GEL macromolecules conformation. Among the binary alloys tested, the Mg-4Ag alloy seems to be the most appropriate biomaterial regarding the in-vitro degradation process that would lead to a suitable healing process at the implantation site, compared to the others available from the literature.