Formation of hybrid bioactive coatings on magnesium alloy for biomedical applications

Abstract

A simultaneous improvement of the corrosion resistance and bioactivity of magnesium implants in order to ensure their uniform biodegradation and cells adhesion during the process of the bone tissue formation is one of the current challenges of modern biomedicine [1–4]. This paper presents the results of investigation of self-healing polymer-containing bioresorbable hybrid coatings, allowing to control the corrosion rate of magnesium implant in physiological liquids. To ensure the bioactivity and improve the adhesive strength between the hybrid inhibitor/polymer layer and the metallic substrate, the hydroxyapatite-containing coating was obtained on Mg-Mn-Ce alloy by plasma electrolytic oxidation (PEO). It was established that the heterogeneity of the formed oxide layer, expressed by the presence of pores and microdefects, is suitable for further corrosion properties improving. The following methods of PEO-coating modification were developed to increase the corrosion resistance of a magnesium alloy: CC-1 – PEO-layer, treated in the 6 wt. % solution of polycaprolactone (PCL) in dichloromethane; CC-2 – hybrid coating, formed by impregnation of PEO-layer with 8-hydroxyquinoline (8-HQ) from the alkaline solution (3 g/l), followed by application of PCL (6 wt. %) from the dichloromethane solution; CC-3 – hybrid coating, obtained by a treatment of PEO layer with 8-HQ (15 g/L) and PCL (6 wt. %) from the dichloromethane solution. The accelerated corrosion tests of formed surface layers in 3 wt. %NaCl solution during 24 h allowed to reveal the best protective performance for the samples with CC-3. The corrosion current densities Ic for these samples were by 6 and 2 fold lower, than those for the samples with CC-1 and CC-2, respectively. The inhibitor efficiency (ηi) of CC-3 hybrid coating was 80 %. After 24 h of samples immersion in NaCl, ηi for CC-3 increased up to 84 %. This work was supported by the Grant of Russian Science Foundation (project no. 20-13-00130).