Osteogenic and antibacterial enhancement by alloying design and microstructural modification of additively manufactured biodegradable metals

Additively Manufactured metallic implants face a critical challenge in simultaneously promoting osteogenesis and preventing infection, two competing requirements in complex orthopedic applications such as implant-associated infections. This study presents a novel strategy combining Cu alloying and heat treatment for biodegradable zinc-based implants fabricated by laser powder bed fusion (L-PBF), in order to address infected bone repair. After alloying, the as-built Zn-2Cu implants showed limited enhancement compared to pure Zn due to the microstructure dominated by solid solution. Subsequent heat treatment at 350 °C for 3 h induced CuZn₅ precipitation and accelerated galvanic corrosion, remarkably improving strength and biodegradation. The resulting HT/Zn-2Cu alloy achieved a high yield strength of 203 MPa through synergistic strengthening mechanisms. More significantly, the co-released Zn²⁺ and Cu²⁺ at favorable concentrations demonstrated dual functionalities according to comprehensive in vitro and in vivo tests. It enhanced osteogenic activity via stimulated osteoblast proliferation, differentiation, and upregulation of osteogenesis-related genes, and introduced potent antibacterial effects through biofilm disruption and bacterial growth inhibition, revealed by transcriptomic analysis. Such findings establish a new paradigm for designing biodegradable implants that concurrently address bone regeneration and infection prevention in clinical applications.