Micro/Nano-Structured Metal–Organic/Inorganic Hybrid Coatings on Biodegradable Zn for Osteogenic and Biocompatible Improvement

Biodegradable Zn-based metals have recently gained great attention for orthopedic implant applications, due to their attractive attributes in biodegradability, mechanics, and bio-functionalities. However, Zn-based metals suffer from excessive Zn2+ release leading to bio-incompatibility and insufficient osteogenic properties. Herein, bioactive molecules incorporated zinc phosphate (ZnP) of metal–organic/inorganic hybrid coatings are constructed on Zn surfaces by dip-coating, targeting a decrease in Zn2+ release rate and an improvement in biocompatible and osteogenic properties. The bioactive molecules, cysteine, phenylalanine, and bovine serum albumin, are incorporated into inorganic ZnP using a metal–organic/inorganic coordination strategy. As a result, these hybrid coatings are compact, and present different micro/nanostructured surface morphology. The electrochemical and long-term static immersion results show that the hybrid coatings decrease the corrosion rate of Zn, reduce the Zn2+ ion release rate, and promote hydroxyapatite deposition. In addition, they promote the proliferation and adhesion of preosteoblast MC3T3-E1 and rat bone marrow mesenchymal stem cells, and up-regulate the expression of osteogenesis-related genes. Such appealing properties can be attributed to the characteristic micro/nanostructured surface morphologies and the presence of the bioactive components. These metal–organic/inorganic hybrid coatings provide a novel avenue to modify the surface of Zn-based metals for orthopedic implant applications.