Degradation Characteristics and Biocompatibility of Zinc Alloy in Advanced Biomedical Bone Implants

Biodegradable zinc-based alloys are regarded as a promising avenue of research for the development of bone fixation implants, offering potential solutions to clinical issues, such as stress shielding, secondary surgeries, and biocompatibility. In this study, a Zn-0.8Li-0.4Mg alloy was designed and fabricated and its potential for use as a clinical bone implant was evaluated. The alloy displays an ultimate tensile strength of 450 MPa and an elongation of 18%, thereby satisfying the requisite mechanical specifications for clinical bone implants. The results of the electrochemical and SBF in vitro corrosion tests indicate that the degradation mechanism evolves over time. The initial corrosion product layer is composed of a dense Li-containing corrosion product (LiOH/Li₂CO₃), which subsequently transforms into an Mg-containing corrosion product layer (MgO/Mg(OH)₂) as corrosion progresses. Ultimately, due to the depletion of Li and the erosion by Cl^-, it transitions to a corrosion product layer containing only the Zn and Ca/P layer. The overall degradation mechanism is jointly determined by the degree of local degradation and the corrosion resistance of the product layer. Cytotoxicity tests demonstrate that the Zn-0.8Li-0.4Mg alloy exhibits favorable biocompatibility.