Biodegradable metals have garnered considerable interest owing to their capacity for self-degradation following the repair of damaged tissues. This review commences with their historical development and clarifies the essential prerequisites for their successful clinical translation. Subsequently, a detailed review of magnesium-based materials is presented from five critical areas of alloying, fabrication techniques, purification, surface modification, and structural design, systematically addressing their progress in biodegradation rate retardation, mechanical reinforcement, and biocompatibility enhancement. Furthermore, recent breakthroughs in vivo animal experiments and clinical translation of magnesium alloys are summarized. Finally, this review concludes with a critical assessment of the achievements and challenges encountered in the clinical application of these materials, and proposes practical strategies to address current limitations and guide future research perspectives.

Biodegradable magnesium (Mg) and its alloys exhibit excellent biocompatibility and mechanical compatibility, demonstrating tremendous potential for applications in orthopedics. However, the rapid degradation rate has limited their clinical application. Polycaprolactone (PCL) is commonly employed as a polymer coating to impede the rapid degradation of Mg. Unfortunately, its long-term anti-corrosion capability and bioactivity are inadequate. To address these issues, polydopamine (PDA)-modified zeolitic imidazolate framework-8 (PZIF-8) bioactive nanoparticles are fabricated and incorporated into the PCL coating. The PZIF-8 particles, featuring catechol motifs, can enhance the compactness of the PCL coating, reduce its defects, and possess biomineralization ability, thereby effectively improving its anti-corrosive and bioactive properties. Moreover, the active substances released from the degradation of the PZIF-8 particles such as Zn²⁺ and PDA are beneficial for osteogenesis. The corrosion tests indicate that the corrosion current density of PCL-treated sample decreases by more than one order of magnitude and the amount of H₂ released decreases from 0.23 ± 0.12 to 0.08 ± 0.08 ml cm⁻² after doping with the PZIF-8. Furthermore, the improved corrosion resistance and released PDA and Zn²⁺ from the coating can promote osteogenic differentiation by up-regulating the expression of alkaline phosphatase activity, related osteogenic genes, and proteins. In addition, in vivo implantation experiments in rabbit femur defects further offer strong evidence that the doping of PZIF-8 nanoparticles accelerates bone reconstruction of the PCL coating. In summary, this work implies a new strategy to fabricate a PCL-based coating on Mg-based implants by introducing the PZIF-8 particles for orthopedic applications.

To realize economical and effective removal of hazardous 4-nitrophenol from the environment, we developed an easily recyclable ZnO nanowire array decorated with Cu nanoparticles. Its salix argyracea-shaped structure not only provides a platform to achieve stable and good dispersion of Cu nanoparticles, but also offers a great deal of catalytically active sites. The density functional theory calculations reveal that ZnO and Cu have a very beneficial synergistic effect on their catalytic capability. This synergy is ascribed to the electronic localization occurring at ZnO/Cu interface, which helps improve Cu nanoparticle's ability to adsorb electro-negatively 4-nitrophenolate ions and to capture hydrogen radicals, thereby accelerating the hydrogen transfer from metal hydride complex to 4-nitrophenol. Benefiting from these characteristics, it exhibits high efficiency and reusability towards the catalytic reduction of waste 4-nitrophenol to valuable 4-aminophenol with a rate constant of 43.02 × 10⁻³ s⁻¹ and an average conversion of 96.5% in 90 s during 10 cycles. This activity is superior to that of most reported noble- or non-noble-metal powder, bulk, coating, and array catalysts, indicating its competitive advantages in cost and efficiency, as well as enticing application prospects.