Extruded biodegradable Zn-5Cu alloys with integrated osteoimmunomodulatory, antibacterial, and anti-osteolytic properties for patellar fracture suture repair.

Abstract

Zn-based biodegradable alloys hold promise for fracture suture-line applications, but are often limited by insufficient mechanical performance. In this study, alloying and extrusion were employed to regulate the microstructure of Zn-5Cu alloys, thereby synergistically optimizing their mechanical properties, corrosion behavior, and biological functions. Samples extruded at 200 °C exhibited the most favorable comprehensive mechanical performance, achieving a tensile yield strength of 191.5 MPa, an ultimate tensile strength of 208.3 MPa, and an elongation of 39.2%. After 28 days of immersion in simulated body fluid, the samples extruded at 200 °C showed the slowest degradation rate of 31.8 μm·y^-1. Notably, the extruded Zn-5Cu alloys exhibit better antibacterial performance than that of pure Zn due to the release of Cu²⁺. In vitro biological evaluations confirmed suitable cytocompatibility with negligible cytotoxicity. The extruded Zn-5Cu alloys also exhibited a pronounced ability to induce M2 macrophage polarization, thereby promoting osteogenesis and inhibiting osteoclast differentiation in vitro. In vivo studies confirmed the alloy's osteoimmunomodulatory and anti-osteolytic functions. Collectively, these findings indicate that these extruded Zn-5Cu alloys with suitable degradation rates, enhanced mechanical properties, and integrated antibacterial, immunomodulatory, and osteogenic capabilities represent a promising material for fracture suture lines. STATEMENT OF SIGNIFICANCE: Biodegradable zinc alloys have shown promise for fracture fixation, yet their clinical translation remains hindered by insufficient ductility, uncontrolled degradation, and limited biological functionality. Here, we demonstrate that low-temperature extrusion of a Zn-5Cu alloy uniquely orchestrates immunomodulatory, antibacterial, and anti-osteolytic functions within a single material platform-a triad rarely achieved together. Through microstructure tailoring at 200 °C, our alloy achieves clinically suitable mechanical strength (191.5 MPa) and degradation rate (0.032 mm/y) while harnessing Cu²⁺ release to promote M2 macrophage polarization, enhance osteogenesis, and suppress osteoclast differentiation. For readers, this work establishes a processing‑microstructure‑function paradigm for designing bioactive biodegradable metals that transcend passive fixation toward actively orchestrating bone regeneration.