A core-shell structured VEGF-SiO₂@ZnO nanorod array for enhancing osteogenesis performance of Zn-based implants

Excessive Zn²⁺ ions are released from Zn-based implants during their degradation, inducing cytotoxicity and thereby affecting early osteogenesis. To address this issue, a core-shell structured nanorod array with ZnO as the core and VEGF-loaded mesoporous SiO₂ as the shell was constructed on a Zn-1Ca substrate using a hybrid process comprising hydrothermal treatment (HT), a sol-gel method and impregnation. ZnO formed via HT could effectively protect the substrate from serious corrosion; mesoporous SiO₂ further increased the anti-corrosion properties of the substrate and served as a carrier for vascular endothelial growth factor (VEGF). The nanorod array exhibited high binding strength with the substrate and improved the behaviors of bone marrow stroma cells (BMSCs) and HUVECs owing to the appropriate release of Zn and Si ions as well as the VEGF. The distinct effects of Zn and Si ions on the osteogenesis of BMSCs and angiogenesis of HUVECs were confirmed, respectively. The positive effect of the nanorod array constructed on the Zn-1Ca implant for new bone formation was also demonstrated in vivo. Overall, this work provides a core-shell structured nanorod array to reduce the degradation of Zn-based implants and accelerate their early biointegration by enhancing angiogenesis and new bone formation.