Degradable Zn-5Ce alloys with high strength, suitable degradability, good cytocompatibility, and osteogenic differentiation fabricated via hot-rolling, hot-extrusion, and high-pressure torsion for potential load-bearing bone-implant application

Zinc (Zn)-based alloys are considered the next-generation biodegradable material for promising bone-implant devices due to their good degradability, formability, and functionality. Nevertheless, the as-cast Zn alloys showed a low strength-toughness, making it challenging to meet the mechanical properties requirements for high-load-bearing bone implants due to their hexagonal close-packed structure, coarse grain size, and less sliding system. Herein, we have developed biodegradable Zn-5Ce alloys by cerium (Ce) alloying followed by hot-rolling, hot-extrusion, and high-pressure torsion (HPT), respectively, for potential bone-implant application. Mechanical testing revealed that the HPT sample exhibited the best mechanical performance matching among the Zn-5Ce samples with a high ultimate tensile strength of-345 MPa, yield strength of-230 MPa, a moderate elongation of-11.4%, and macro-hardness of-96.6 HB. Electrochemical corrosion and static immersion testing revealed that the HPT sample showed the highest electrochemical corrosion rate of-416 mu m/y and degradation rate of-43.8 mu m/y in Hanks' solution among the Zn-5Ce samples, which is suitable for degradation rate requirements for bone-implant application. Bio-tribological testing revealed that the HPT sample showed high bio-tribological properties matching in Hanks' solution with the lowest friction coefficients of-0.530 and moderate wear loss of-2.2 mg. Cytocompatibility and osteogenic differentiation assessment revealed that the diluted extract of the HPT sample showed the highest cytocompatibility towards 3T3 and MG-63 cells and osteogenic differentiation performance towards 3T3 cells among the most diluted extracts. Accordingly, the HPT Zn-5Ce sample is ex-pected to be used for high-load-bearing degradable bone-implant devices, including bone fixation and guided bone regeneration systems.