Mimicking the mechanical properties of cortical bone with an additively manufactured biodegradable Zn-3Mg alloy

Yuzhe Zheng; Chengcong Huang; Yageng Li; Jiaqi Gao; Youwen Yang; Shangyan Zhao; Haodong Che; Yabin Yang; Shenglian Yao; Weishi Li; Jie Zhou; Amir A Zadpoor; Luning Wang

doi:10.1016/j.actbio.2024.05.023

Mimicking the mechanical properties of cortical bone with an additively manufactured biodegradable Zn-3Mg alloy

Acta Biomater. 2024 May 13:S1742-7061(24)00262-9. doi: 10.1016/j.actbio.2024.05.023. Online ahead of print.

Authors

Yuzhe Zheng¹, Chengcong Huang¹, Yageng Li², Jiaqi Gao¹, Youwen Yang³, Shangyan Zhao¹, Haodong Che¹, Yabin Yang⁴, Shenglian Yao¹, Weishi Li⁵, Jie Zhou⁶, Amir A Zadpoor⁶, Luning Wang⁷

Affiliations

¹ Beijing Advanced Innovation Center for Materials Genome Engineering, School of Materials Science and Engineering, University of Science and Technology Beijing, 30 Xueyuan Road, Haidian District, Beijing, 100083, China.
² Beijing Advanced Innovation Center for Materials Genome Engineering, School of Materials Science and Engineering, University of Science and Technology Beijing, 30 Xueyuan Road, Haidian District, Beijing, 100083, China; Institute of Materials Intelligent Technology, Liaoning Academy of Materials, Shenyang, 110004, China. Electronic address: yagengli@ustb.edu.cn.
³ Institute of Additive Manufacturing, Jiangxi University of Science and Technology, Nanchang 330013, China.
⁴ School of Materials Science and Engineering, Sun Yat-Sen University, Guangzhou 510275, China.
⁵ Department of Orthopaedics, Peking University Third Hospital, No. 49 NorthGarden Road, Haidian District, Beijing, 100191, China; Beijing Key Laboratory of Spinal Disease Research, Beijing, 100191, China; Engineering Research Center of Bone and Joint Precision Medicine, Ministry of Education, Beijing, 100191, China.
⁶ Department of Biomechanical Engineering, Delft University of Technology, Delft 2628 CD, the Netherlands.
⁷ Beijing Advanced Innovation Center for Materials Genome Engineering, School of Materials Science and Engineering, University of Science and Technology Beijing, 30 Xueyuan Road, Haidian District, Beijing, 100083, China; Institute of Materials Intelligent Technology, Liaoning Academy of Materials, Shenyang, 110004, China. Electronic address: luning.wang@ustb.edu.cn.

PMID: 38750914
DOI: 10.1016/j.actbio.2024.05.023

Abstract

Additively manufactured (AM) biodegradable zinc (Zn) alloys have recently emerged as promising porous bone-substituting materials, due to their moderate degradation rates, good biocompatibility, geometrically ordered microarchitectures, and bone-mimicking mechanical properties. While AM Zn alloy porous scaffolds mimicking the mechanical properties of trabecular bone have been previously reported, mimicking the mechanical properties of cortical bone remains a formidable challenge. To overcome this challenge, we developed the AM Zn-3Mg alloy. We used laser powder bed fusion to process Zn-3Mg and compared it with pure Zn. The AM Zn-3Mg alloy exhibited significantly refined grains and a unique microstructure with interlaced α-Zn/Mg₂Zn₁₁ phases. The compressive properties of the solid Zn-3Mg specimens greatly exceeded their tensile properties, with a compressive yield strength of up to 601 MPa and an ultimate strain of >60 %. We then designed and fabricated functionally graded porous structures with a solid core and achieved cortical bone-mimicking mechanical properties, including a compressive yield strength of >120 MPa and an elastic modulus of ≈20 GPa. The biodegradation rates of the Zn-3Mg specimens were lower than those of pure Zn and could be adjusted by tuning the AM process parameters. The Zn-3Mg specimens also exhibited improved biocompatibility as compared to pure Zn, including higher metabolic activity and enhanced osteogenic behavior of MC3T3 cells cultured with the extracts from the Zn-3Mg alloy specimens. Altogether, these results marked major progress in developing AM porous biodegradable metallic bone substitutes, which paved the way toward clinical adoption of Zn-based scaffolds for the treatment of load-bearing bony defects. STATEMENT OF SIGNIFICANCE: Our study presents a significant advancement in the realm of biodegradable metallic bone substitutes through the development of an additively manufactured Zn-3Mg alloy. This novel alloy showcases refined grains and a distinctive microstructure, enabling the fabrication of functionally graded porous structures with mechanical properties resembling cortical bone. The achieved compressive yield strength and elastic modulus signify a critical leap toward mimicking the mechanical behavior of load-bearing bone. Moreover, our findings reveal tunable biodegradation rates and enhanced biocompatibility compared to pure Zn, emphasizing the potential clinical utility of Zn-based scaffolds for treating load-bearing bony defects. This breakthrough opens doors for the wider adoption of zinc-based materials in regenerative orthopedics.

Keywords: Biocompatibility; Degradation behavior; Laser powder bed fusion; Mechanical properties; Zinc alloy.