Abstract
In recent years, magnesium (Mg) alloys show a promising application in clinic as degradable biomaterials. Nevertheless, the poor corrosion resistance of Mg alloys is the main obstacle to their clinical application. Here we successfully seal the pores of plasma electrolytic oxidation (PEO) coating on AZ31 with Mg-Al layered double hydroxide (LDH) via hydrothermal treatment. PEO/LDH composite coating possess a two layer structure, an inner layer made up of PEO coating (~5 μm) and an outer layer of Mg-Al LDH (~2 μm). Electrochemical and hydrogen evolution tests suggest preferable corrosion resistance of the PEO/LDH coating. Cytotoxicity, cell adhesion, live/dead staining and proliferation data of rat bone marrow stem cells (rBMSCs) demonstrate that PEO/LDH coating remarkably enhance the cytocompatibility of the substrate, indicating a potential application in orthopedic surgeries. In addition, hemolysis rate (HR) test shows that the HR value of PEO/LDH coating is 1.10 ± 0.47%, fulfilling the request of clinical application. More importantly, the structure of Mg-Al LDH on the top of PEO coating shows excellent drug delivery ability.
Highlights
Many studies have been focused on decreasing number and size of pores on the surface of plasma electrolytic oxidation (PEO) coating to improve its corrosion resistance[20,21,22]
With regard to PEO/layered double hydroxide (LDH) coating, the homogeneous and compacted nanoflake-like structure was formed on the top of PEO coating after hydrothermal treatment, successfully sealing the pores of PEO coating
As AZ31 contains Mg and Al element, Mg2+ and Al3+ ions would release from the substrate during the PEO process, reacted with OH− and formed Mg-Al LDH
Summary
Many studies have been focused on decreasing number and size of pores on the surface of PEO coating to improve its corrosion resistance[20,21,22]. As long as PEO coating contains pores or cracks, its long-term corrosion resistance cannot be guaranteed. Li et al used hydroxyapatite to seal the pores of PEO coating and found that osseointegration and corrosion resistance of Mg alloy are enhanced[23]. To sealed the pores of PEO coating and enhanced its corrosion resistance and biocompatibility[12]. Both hydroxyapatite and poly(L-lactide) are unable to work as a drug delivery platform. Cytocompatibility, hemolysis rate and drug loading ability of PEO/LDH composite coating were evaluated subsequently
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