Effects of micro-arc oxidation/poly(lactic-co-glycolic acid) composite coating on the degradation and biocompatibility of ZK60 magnesium alloy

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The composite coating consisting of a micro-arc oxidation (MAO) ceramic layer and a poly(lactic- co -glycolic acid) (PLGA) layer was designed on ZK60 magnesium alloy for synergistic corrosion protection and bio-integration. The evolution of microstructure, composition, electrochemistry, in vitro degradation, and biocompatibility of the coatings was investigated by varying the lactic acid/glycolic acid (LA/GA) copolymerization ratio, and the composition-structure-property relationship was established. The bilayer structure of the composite coating provides dual protection: the MAO layer provides physical barrier protection by providing ionic buffer and preventing Cl − diffusion. At the same time, the PLGA layer seals the defects in the MAO ceramic layer through viscous flow and reduces the SBF penetration through the hydrophobic effect. Electrochemical analysis shows that the synergistic strategy of combining physical barrier and chemical passivation effects endows optimal corrosion resistance to the MAO/PLGA8515 composite coating with a protection efficiency of 99.66 ± 0.06 %. In addition, the lactic acid derivatives released from the hydrolysis of PLGA polymer stabilize the pH, providing a suitable microenvironment for cell proliferation and adhesion. Meanwhile, the PLGA enables the osteoblasts co-cultured with the composite coating to exhibit elongated filopodia protrusions and spindle-like morphology and higher than 95 % cell viability, showing superior cytocompatibility. • A MAO layer incorporating PA-functionalized GO was grown in situ on magnesium alloy. • Development of a composite coating by utilizing MAO and PLGA. • PLGA could seal the defects and provide hydrophobic protection to reduce corrosion. • The composite coating could control degradability by adjusting the PLGA monomer ratio. • The composite coating achieved superior corrosion resistance and biocompatibility.