Biodegradable magnesium alloy WE43 porous scaffolds fabricated by laser powder bed fusion for orthopedic applications: Process optimization, in vitro and in vivo investigation

Jinge Liu; Bingchun Liu; Shuyuan Min; Bangzhao Yin; Bo Peng; Zishi Yu; Caimei Wang; Xiaolin Ma; Peng Wen; Yun Tian; Yufeng Zheng

doi:10.1016/j.bioactmat.2022.02.020

Biodegradable magnesium alloy WE43 porous scaffolds fabricated by laser powder bed fusion for orthopedic applications: Process optimization, in vitro and in vivo investigation

Bioact Mater. 2022 Feb 24:16:301-319. doi: 10.1016/j.bioactmat.2022.02.020. eCollection 2022 Oct.

Authors

Jinge Liu^{1

2}, Bingchun Liu^{3

4}, Shuyuan Min^{3

4}, Bangzhao Yin^{1

2}, Bo Peng^{1

2}, Zishi Yu^{1

2}, Caimei Wang⁵, Xiaolin Ma⁵, Peng Wen^{1

2}, Yun Tian^{3

4}, Yufeng Zheng⁶

Affiliations

¹ The State Key Laboratory of Tribology, Tsinghua University, Beijing, 100084, China.
² Department of Mechanical Engineering, Tsinghua University, Beijing, 100084, China.
³ Department of Orthopaedics, Peking University Third Hospital, Beijing, 100191, China.
⁴ Engineering Research Center of Bone and Joint Precision Medicine, Ministry of Education, Beijing, 100191, China.
⁵ Beijing AKEC Medical Co., Ltd., Beijing, 102200, China.
⁶ School of Materials Science and Engineering, Peking University, Beijing, 100871, China.

Abstract

Laser powder bed fusion (L-PBF) of magnesium (Mg) alloy porous scaffolds is expected to solve the dual challenges from customized structures and biodegradable functions required for repairing bone defects. However, one of the key technical difficulties lies in the poor L-PBF process performance of Mg, contributed by the high susceptibility to oxidation, vaporization, thermal expansion, and powder attachment etc. This work investigated the influence of L-PBF energy input and scanning strategy on the formation quality of porous scaffolds by using WE43 powder, and characterized the microstructure, mechanical properties, biocompatibility, biodegradation and osteogenic effect of the as-built WE43 porous scaffolds. With the customized energy input and scanning strategy, the relative density of struts reached over 99.5%, and the geometrical error between the designed and the fabricated porosity declined to below 10%. Massive secondary phases including intermetallic precipitates and oxides were observed. The compressive strength (4.37-23.49 MPa) and elastic modulus (154.40-873.02 MPa) were comparable to those of cancellous bone. Good biocompatibility was observed by in vitro cell viability and in vivo implantation. The biodegradation of as-built porous scaffolds promoted the osteogenic effect, but the structural integrity devastated after 12 h by the immersion tests in Hank's solution and after 4 weeks by the implantation in rabbits' femur, indicating an excessively rapid degradation rate.

Keywords: Additive manufacturing; Biodegradable metal; Laser powder bed fusion; Magnesium alloy; Porous scaffold; WE43.