Biocompatibility and bone regeneration of PEO/Mg-Al LDH-coated pure Mg: an in vitro and in vivo study

Abstract

Forming a stable anti-corrosion surface layer on magnesium (Mg) and its alloys has become a major challenge in developing a desirable degradable medical implant in bone. In this study, a porous MgO layer was first formed on Mg by plasma electrolytic oxidation (PEO), and then a Mg-Al layered double hydroxide (LDH) layer was prepared to seal the porous structure of the PEO layer (LDH-2h and LDH-12h) via hydrothermal treatment. The bilayer structure composite coating, which can effectively resist the penetration of surrounding media, is similar to plain Chinese tiles. The in vitro results revealed that compared with other coatings, the LDH-12h composite coating can reduce the release of Mg ions and induce a milder change in pH when immersed in phosphate-buffered saline (PBS). In vitro rat bone marrow stem cell (rBMSC) culture suggested that the LDH-12h composite coating is favorable for cell activity, proliferation and could improve the osteogenic activity of rBMSCs. A subcutaneous implantation test revealed that the as-prepared sample showed enhanced corrosion resistance and histocompatibility in vivo, especially in the LDH-12h group. Moreover, LDH-12h had the lowest rate of degradation and the closest combination with the new bone after being inserted into a rat femur for 12 weeks with no major organ dysfunction. In summary, the asprepared PEO/Mg-Al LDH composite coating is able to improve the corrosion resistance and biocompatibility of Mg and to enhance osteogenic activity in vivo, suggesting its promising prospects for orthopedic applications.