Photo-controlled biodegradable Zn alloy bone implant.

Abstract

Zinc (Zn)-based biodegradable implants hold great promise for orthopedic applications, yet their clinical translation is hampered by uncontrollable corrosion leading to Zn²⁺ release at potentially toxic levels in the early stage and insufficient osteogenic stimulation later. Herein, a near-infrared (NIR)-responsive hybrid coating composed of indocyanine green-loaded zeolitic imidazolate framework-8 (ICG@ZIF-8) and polycaprolactone (PCL) is engineered on a Zn-Li-Mg alloy to achieve stage-adaptive corrosion regulation. Initially, the PCL barrier effectively slows down corrosion (∼3.84 μm yr^-1) and Zn²⁺ release, ensuring initial biocompatibility. Upon NIR irradiation, photothermal conversion of ICG@ZIF-8 induces localized heating and PCL deformation, on-demand partially restoring corrosion (∼8.53 μm yr^-1) and enabling sustained Zn²⁺ release to leverage its osteogenic effect. In vitro studies demonstrate enhanced osteogenic differentiation and mineralization, mechanistically attributed to the activation of the Wnt/β-catenin/TCF pathway. In vivo, the NIR-triggered platform promotes critical-sized femoral defect regeneration with 26% higher new bone formation. This work provides a smart material strategy for spatiotemporal control of biodegradable Zn implants, offering a promising strategy toward bone repair.