Metabolic Osteoimmune Biodegradable Zn-Mn Alloys: High Strength-Ductility and In Situ Vascular-Osteogenic Coupling.

Abstract

Driven by the demand for sustainable, safe, and cost-effective medical materials, design of biodegradable metals increasingly aims to achieve higher strength and biofunctionality with less alloying. This study proposes a high strengthening-efficiency (high-SE) design strategy and develops novel Zn-0.8Mn-0.1Mg and Zn-0.8Mn-0.1Li alloys. With total alloying additions below 1 wt.%, these alloys achieve yield strength of 369-397 MPa, elongation of 42-57%, and remarkable strengthening efficiency (SE) of 6.4-6.8. These SE values represent the highest level among high strength-ductile Zn alloys (YS > 300 MPa, EL > 40%). Benefiting from the synergistic release of Zn²⁺, Mn²⁺, and Li⁺/Mg²⁺ ions, both the alloys exhibit superior antibacterial activity, cytocompatibility, controlled degradation rates, and in vivo osteogenesis, demonstrating excellent degradation-osteogenesis coupling effect. Notably, Zn-0.8Mn-0.1Mg further enhances osteogenesis by activating the PI3K/Akt/HIF-1α signaling axis, which coordinates cascades of immunomodulation (e.g., IGF2, P2rx5), anti-inflammation (e.g., Nfkbia inhibition), and cellular energy metabolism (e.g., Ndufaf3), resulting in a more pronounced osteogenic effect. This work establishes a new paradigm for high-efficiency alloy design, achieving simultaneous breakthroughs in mechanical and biofunctionality, offering a promising framework for next-generation Zn-based orthopedic implants.