Impact of sterilization treatments on biodegradability and cytocompatibility of zinc-based implant materials

Biodegradable zinc (Zn) and Zn-based alloys have been recognized as promising biomaterials for biomedical implants. Sterilization is an essential step in handling Zn-based implants before their use in clinical practice and there are various sterilization methods are available. However, how these treatments influence the Zn-based biomaterials remains unknown and is of critical relevance. In this study, three commonly-applied standard sterilization methods, namely gamma irradiation, hydrogen peroxide gas plasma and steam autoclave, were used on pure Zn and Zn 3Cu (wt%) alloy. The treated Zn and Zn Cu alloy were investigated to compare the different influences of sterilizations on surface characteristics, transient and long-term degradation behavior and cytotoxicity of Zn and Zn alloy. Our results indicate that autoclaving brought about apparently a formation of inhomogeneous zinc oxide film whereas the other two methods produced no apparent alterations on the material surfaces. Consequently, the samples after autoclaving showed significantly faster degradation rates and more severe localized corrosion, especially for the Zn Cu alloy, owing to the incomplete covering and unstable zinc oxide layer. Moreover, the autoclave-treated Zn and Zn Cu alloy exhibited apparent cytotoxic effects towards fibroblasts, which may be due to the excessive Zn ion releasing and its local concentration exceeds the cellular tolerance capacity. In contrast, gamma irradiation and hydrogen peroxide gas plasma had no apparent adverse effects on the biodegradability and cytocompatibility of Zn and Zn Cu alloy. Our findings may have significant implications regarding the selection of suitable sterilization methods for Zn-based implant materials among others. • Sterilization influences on degradation and cytotoxicity of Zn & Zn Cu alloy were compared. • Steam autoclaving accelerated their degradation and elicited more severe localized corrosion. • Steam autoclaving posed adverse fibroblasts cytotoxicity for both Zn and Zn Cu alloy. • Gamma irradiation or H 2 O 2 gas plasma showed only marginal effects on these two aspects. • Appropriate sterilization must be cautiously selected for Zn-based implants among others.