3D printed Zn-Cu alloy bone scaffolds via nanoparticle incorporation: Microstructural evolution and enhanced mechanical-antimicrobial-osteogenic properties

• A high-speed centrifugal stirring method was developed to uniformly disperse and attach nano-Cu particles onto Zn powder, preserving powder integrity and enabling elemental homogeneity. • LPBF facilitated in-situ precipitation of semi-coherent ε-CuZn 5 phases within ultra-refined equiaxed grains. This microstructure yielded significantly improved mechanical properties. • The scaffold demonstrated an optimized corrosion rate within the ideal range for bone healing, ensuring both stability and biofunctionality. • The scaffold demonstrated controlled Zn 2+ / Cu 2+ co-release kinetics, significantly enhancing in vitro osteogenic differentiation and exhibiting potent broad-spectrum antibacterial activity. • The in vivo experiments confirmed that the scaffold exhibits enhanced osteogenic properties. Zinc-based scaffolds demonstrate great potential in repairing infected bone defects but struggle to balance mechanical stability, degradability, and anti-infection properties. This study overcomes a key limitation of traditional Zn-Cu alloys—unpredictable ion release from uneven microstructures—by using laser powder bed fusion with incorporated Cu nanoparticles. High-speed centrifugal stirring ensured uniform nano-Cu dispersion, promoting in-situ precipitation of semi-coherent ε-CuZn 5 phases within ultra-fine equiaxed grains (∼2 μm). This microstructural control significantly improved mechanical properties: the Zn-2nano Cu alloy showed a 113 % higher yield strength (133.52 MPa) and 79 % higher ultimate tensile strength (186.49 MPa) than pure Zn. Its corrosion rate was optimized for bone healing at 0.21 mm/year. The scaffold demonstrated strong broad-spectrum antibacterial activity, with over 50 % improved efficacy against E. coli and S. aureus . Osteogenic differentiation was enhanced, indicated by a 23 % rise in ALP activity and over 45 % upregulation of key osteogenic genes. In vivo , the scaffold was biosafe and boosted new bone formation in rabbit femoral defects, increasing bone volume fraction by 22 % and trabecular number by 64 %. This work demonstrates that integrated 3D printing of material composition and porous structure is an effective strategy for developing functional bone scaffolds, advancing Zn-based materials toward clinical use.