Hierarchical ZnO Nanotube/Graphene Oxide Nanostructures Endow Pure Zn Implant with Synergistic Bactericidal Activity and Osteogenicity

Zinc (Zn) material has recently become a rising biodegradable metal in orthopedic applications owing to its critical physiological functions and degradation characteristics. However, the unsatisfactory cytocompatibility due to the locally high concentration of Zn ions liberated during degradation accompanied with a lack of antibacterial property and osteogenesis severely obstruct the clinical adoption of pure Zn implants. To address these challenges, we construct hierarchical ZnO nanotube/graphene oxide (GO) nanostructures (GO-An-Zn) on the pure Zn substrates via anodic oxidation followed by silk fibroin/GO self-assembly in the present study. The resultant surface displays superior bacteria-killing performances against both Gram-negative and Gram-positive bacteria. Moreover, osteoblasts on the dexamethasone (Dex)-laden hierarchical microstructured/nanostructured Zn (GO-Dex-An-Zn) show the enhanced cell compatibility and osteogenicity, outperforming these on pure Zn substrates. It is mainly attributed to the synergistic delivery of Zn ions and Dex from bulk materials during degradation, forming a favorable microenvironment for cell survival and bone tissue remodeling. Accordingly, such work provides a novel solution to simultaneously improve the bactericidal activity and osteogenic potential of Zn-based biomaterials, bode well for their orthopedic use.