Metal-organic Complex Embedded Zinc Phosphate Functional Coating On Biodegradable Zinc

Biodegradable Zn shows great potential for the orthopedic implant applications due to its moderate degradation rate and biofunctions.However,non-uniform degradation mode and insufficient osseointegration largely hinder the clinical translation of Zn-based implants.Herein,we constructed Zn-zoledronic acid(ZA)metal organic complex(MOC)embedded zinc phosphate hybrid coating on Zn substrate.This coating aims to fulfill the corrosion controlling and osteogenesis simultaneously.For the deposition of the hybrid coating,zinc phosphate coating was first constructed as base layer on Zn.Then the block-like zinc phosphate was regulated to flower-like structure via ‘dissolve-restructure’ process by 1-Hydroxyethylidene-1,1-Diphosphonic acid(HEDP).During the restructuring of zinc phosphate,MOC was embedded into the hybrid coating by anchoring to the active sites that provided by HEDP.The MOC embedded zinc phosphate micro-flower hybrid coating was eventually fabricated on Zn.Owing to the homogeneity and compactness,this coating significantly inhibited the degradation of Zn substrate,and thus suppressed the release of Zn ions.Additionally,The HEDP and ZA molecules promoted the deposition of active calcium phosphate,such as hydroxyapatite(HA)and octacalcium phosphate(OCP),which improved the bioactivity of the surface.Consequently,the suppressed Zn ions,as well as the osteo-compatible HEDP and ZA molecules,promoted the adhesion,proliferation and alkaline phosphatase(ALP)activity of osteoblasts,showing potential osteogenic function.Meanwhile,the results of macrophage culture and inflammatory factor test showed that the coating did not induce obvious inflammatory reaction.In summary,the MOC embedded zinc phosphate hybrid coating achieved the dual-task of corrosion controlling and osteogenesis,which showed great potential for bone implants application.The strategy provides a novel approach for the surface modification of biodegradable implants.