Hierarchically Structured Zn‐ZnO@HA/PCL Biocompatible Coating: Enabling Controlled Degradation and Mechanical Stability of Magnesium Alloy Bone Implants
Chao Zhang, Jiaying Wang, Xuhui Liu, Yilong Dai, Hongshuai Cao, Huijuan Wang, Kaiwei Tang, Feng Peng, Chang Chen, Fugang QiABSTRACT
Biodegradable magnesium alloys are limited in orthopedic applications due to their rapid corrosion and poor interfacial stability. In this work, a composite coating is constructed via magnetic filtered cathodic vacuum arc (MFCVA) deposition of a Zn interlayer, followed by hydrothermal in situ generation of ZnO to induce hydroxyapatite (HA) formation, and subsequent polycaprolactone (PCL) modification. This design enables structural integration and interfacial regulation while effectively overcoming the intrinsic brittleness of conventional HA coatings. Electrochemical results demonstrate that the coating reduces the corrosion current density ( i corr ) from 2.58 × 10 −6 to 2.54 × 10 −10 A cm −2 (∼4 orders of magnitude) and the polarization resistance ( R p ) increases to 1.50 × 10 12 Ω cm 2 . Meanwhile, the carrier concentration ( N D ) decreases from 10 22 to 10 12 cm −3 , indicating that interfacial charge transfer is significantly suppressed. In terms of mechanical performance, the adhesion strength (critical load, LC) increases to 13.43 N, the stress ( σ ) decreases to 0.46 GPa, the elastic recovery rate ( R ) decreases to 0.27, and the plasticity index (PI) increases to 0.77, enabling a transition from brittle fracture to elastoplastic cooperative deformation. In addition, the coating exhibits excellent antibacterial activity and promotes cell proliferation and mineralization. This study provides a new strategy for resolving the trade‐off between functional enhancement and structural brittleness in biodegradable magnesium‐based implants.