Osteogenic and Antibacterial Enhancement by Alloying Design and Microstructural Modification of Additively Manufactured Biodegradable Metals

Abstract

It is a robust and effective way to employ metal ions to enhance bioactive functions of bone implants. Additive manufacturing emerges as a most promising fabrication method to achieve customized metal implants. In this study, laser powder bed fusion (L-PBF) fabricated biodegradable Zn and Zn-2Cu implants were investigated to address the dilemma between osteogenesis promotion and infections prevention for implant-associated infections. For pure Zn, relatively high level of Zn2+ are necessary to promote antibacterial effect, which deteriorates bone regeneration. Alloying with Cu improves antibacterial effect and mechanical performance. However, the rapid cooling of L-PBF results in supersaturated solidification, inhibiting the release of metal ions. A proper heat treatment at 350°C for 3 hours increases the precipitation of CuZn5, and accelerates galvanic reaction, resulting in the co-release of Zn2+ and Cu2+ at favorable concentrations. Comprehensive in vitro and in vivo tests clarify the synergistic effect on the enhancement of osteogenic and antibacterial functions. The osteogenic activity is boosted through promoting osteoblast proliferation and upregulating osteogenesis related gene; the antibacterial outcome is achieved by suppressing bacterial proliferation and disrupting biofilms. The proposed approach achieves dual osteogenic and antibacterial functionalization, highlighting its potential for clinical applications requiring both bone regeneration and infection control.

Note:
Funding declaration: This work was funded by National Natural Science Foundation of China (82151312, 82272493, 52175274, 52471262), Beijing Natural Science Foundation (L222110, L212066), Beijing Science Nova Program (20220484155), Capital Health Development Research Project (2024-2-5051), and Autonomous Innovation Science Foundation of the Fourth Medical Center of PLA General Hospital (2024-4ZX-MS-15).

Conflict of Interests: The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Ethical Approval: All animal procedures were approved by the Animal Ethics Committee of the Beijing Keyu Animal Breeding Center (KY20220120006).

Keywords: laser powder bed fusion, alloying design, microstructural modification, osteogenesis, antibacterial property