Development of hybrid hierarchical coatings on Mg3Zn0.4Ca alloy for orthopaedic implants

A hybrid hierarchical coating (HHC) biodegradable system, consisting of a ceramic (PEO) and a biodegradable microporous polymeric (PLA or PCL) layers, was developed on Mg3Zn0.4Ca alloy and evaluated under quasi-in vivo conditions. The polymer top-coat was produced using the Breath Figures approach by dip-coating the PEO treated ceramic surface onto a PLA/PCL polymer solution and withdraw under high relative humidity. According to our findings, when the polymer coating is applied directly onto the PEO layer using high humidity a negligible corrosion protection was observed. However, this issue was overcome by first applying a thin sealing polymer layer before the microporous polymer layer prepared by dip-coating in the absence of moisture. The HHC system improves the corrosion resistance by 10–12 times compared to the stand-alone PEO coating and, due to its inherent porosity, should be amenable for further functionalization with pharmaceutical agents.