A self-healing coating containing curcumin for osteoimmunomodulation to ameliorate osseointegration

To enhance corrosion resistance and osseointegration of Mg-based endosseous implants, novel coatings with self-healing and osteoimmunomodulation functions were fabricated on Mg. The coatings exhibited similar three-layered structure, comprising an inner layer of MgO, an interlayer of poly-L-lactide containing curcumin loaded F-encapsulated mesoporous silica nanocontainers (cFMSNs) and an outer layer of dicalcium phosphate dehydrate, while the amounts of cFMSNs contained in the interlayers were different (thus namely 5FMSN, 10FMSN, 20FMSN). Localized-electrochemical impedance spectroscopy, electrochemical and immersion tests were used to investigate self-healing property and corrosion resistance of the coatings, moreover, curcumin release, immunomodulation effects and osseointegration of these coatings were also assayed, together with cFMSNs-free coating (0FMSN). Due to the cFMSNs functioning as corrosion inhibitor, cFMSNs-contained coatings exhibited obvious self-healing property to enhance protection to Mg in vitro and in vivo compared to 0FMSN, and the enhancements were more pronounced with cFMSNs increase. cFMSNs-contained coatings sustainably released curcumin, and the accumulative curcumin concentration of the 20FMSN immersed physiological saline (PS) was 1.51 μM after 10 days of immersion, which was higher than those of the PS immersing 10FMSN (1.02 μM) and 5FMSN (0.31 μM). Owing to the released curcumin, cFMSNs-contained coatings significantly modulated the immune microenvironment towards favoring osteo-differentiation and extracellular matrix mineralization of bone marrow stem cells, consequently exhibited better osseointegration compared to 0FMSN. 20FMSN exhibited higher immunomodulatory efficiency compared to 10FMSN and 5FMSN, and thus achieved the best osseointegration in vivo. Our work paves an alternative way to design coatings on Mg for realizing improved clinical performance.