Influence of scandium on mechanical properties, degradation behavior, and cytocompatibility of Zn-3Cu-0.4Li-xSc alloys for implant applications

Abstract

Zinc (Zn)-based alloys have emerged as promising new biodegradable materials owing to their moderate corrosion rates and potential biological functionalities. Nevertheless, as-cast pure Zn and its alloys possess low mechanical strength, poor ductility and low hardness, which hinders their biomedical application. In this study, biodegradable Zn-3Cu-0.4Li (ZCL) and ZCL-xSc (x = 0.20, 0.35 and 0.55 wt.%) alloys were fabricated by casting and further hot-rolled (HR), with the aim of acquiring satisfactory mechanical, corrosion and biocompatibility properties for orthopedic implant applications. Results indicated that the mechanical properties of HR ZCL and ZCL-xSc alloys were significantly improved compared to the as-cast alloys. The HR ZCL-0.20Sc alloy showed the best combination of mechanical properties: yield strength of 277 MPa; ultimate tensile strength of 337 MPa; elongation of 40%; and a microhardness of 113 HV. The nanohardness of HR ZCL–xSc alloys increased from 1.64 to 2.43 GPa with increasing Sc content from 0 to 0.55 wt.%. Degradation rates of HR ZCL-xSc alloys gradually increased with increasing Sc content, with the HR ZCL-0.55Sc alloy showing the lowest corrosion resistance and the highest degradation rate of 50.1 μm/y after immersion in Hanks’ balanced salt solution for 30 d. In vitro cytocompatibility assessment using human osteoblast-like SaOS2 cells showed high cell viabilities after 1 d of exposure to undiluted extracts of HR ZCL and ZCL-xSc alloys, and also after 5 d with 50% diluted extracts. Overall, the HR ZCL-0.20Sc alloy has great potential as a biodegradable bone-implant material, due to excellent mechanical, satisfactory corrosion and good biocompatibility properties.