Development and characterization of MAO/PLA-nHA nanocomposite coatings on pure zinc for orthopedic applications

Zinc (Zn)-based medical alloys are considered to be a biodegradable material with great potential. Hydroxyapatite (HA) can improve the osteogenic properties of Zn alloys, but its adhesion strength needs improvement. In this study, a micro-arc oxidation (MAO) interlayer and polylactic acid (PLA) composite layers containing different contents of nano-HA (nHA) were successively prepared on the pure Zn surface by MAO and sol–gel impregnation methods. The adhesion results showed that PLA could enhance the adhesion of HA on the Zn surface, where the adhesion of the Zn/MAO/PLA-nHA (7:3) composite coating was close to that of the pure PLA layer. In addition, the degradation rate of the implant could be controlled by varying the content of nHA in the composite coating while significantly improving its bioactivity. Finally, the addition of nHA increased the roughness of the surface of the composite coating, which was favorable for cell adhesion and proliferation. The highest adhesion density of MC3T3-E1 osteoblasts was exhibited on the Zn/MAO/PLA-nHA (7:3) composite coating. The Zn/MAO/PLA-nHA (7:3) composite coatings showed good adhesion, wettability, corrosion resistance, and excellent cytocompatibility. Thus, this study provides a reasonable design guide for the modification of degradable Zn alloy surfaces in bone tissue engineering biomaterials.