A composite coating with physical interlocking and chemical bonding on WE43 magnesium alloy for corrosion protection and cytocompatibility enhancement

Abstract Practical application of magnesium (Mg) alloys to bone fixation implants is hampered by the rapid degradation under the physiological conditions. Herein, a composite coating composed of poly(L-lactic acid) (PLLA) / (3-aminopropyl)triethoxysilane (APTES) / hydroxide nanosheets is produced on the Mg alloy by spin coating, immersion, and hydrothermal methods to enhance the corrosion resistance and cytocompatibility. The combination of the inner hydroxide nanosheets and middle APTES layer promotes the formation of strongly adhering and dense PLLA layer on the Mg alloy by increasing the active sites for chemical bonding and flexible physical interlocking. Electrochemical studies reveal decreased corrosion current densities from 1.3 ± 0.4 × 10−4 to 1.8 ± 0.6 × 10−9 A cm−2 and increased pore resistance from 1.15 × 102 to 2.70 × 107 Ω cm2 in the simulated body fluid (SBF). Propagation of corrosion along the horizontal (surface) and vertical (depth) directions after soaking in SBF for 7 days is retarded notably by the composite coating which is capable of mitigating dissolution of the Mg alloy by impeding electrolyte penetration and minimizing coating delamination. Furthermore, the attachment and viability of MC3T3-E1 pre-osteoblasts in vitro demonstrate the obviously enhanced cytocompatibility by the composite coating.