Structural optimization and in vitro corrosion analysis of biodegradable Mg-Nd-Zn-Zr alloy clip

Abstract

Magnesium (Mg) alloy which benefits from biodegradability and mechanical characteristics offers great potential for the development of degradable hemostatic clips. However, the deformation process induces stress concentration, which in turn accelerates the corrosion rate of Mg hemostatic clips. In this study, two types of R-shape clips based on Mg-Nd-Zn-Zr alloy were designed with structural features of no teeth and staggered teeth and simulated using finite element analysis (FEA), and the corrosion behaviors of the Mg clips were investigated by immersion test and electrochemical measurement. Furthermore, the clamping properties of the Mg clips were evaluated by burst pressure test. The simulation results showed that the R-shape clip with staggered teeth caused the minimum stress (1.237 MPa) to blood vessels. After the clamping deformation process, the closed clips remained intact without any signs of cracking. In vitro degradation analysis indicated that the corrosion rate of the closed clip was slightly faster than that of the open clip, and the Mg clip maintained its efficacy in achieving vascular closure even after a 4-week period of immersion, indicating a commendable performance in secure ligation closure. In addition, the burst pressure test results showed that the staggered teeth clip exhibited a higher burst pressure (88.73 ± 2.58 kPa) with less mechanical damage occurring to the ligated vessels compared with the toothless clip, meeting the requirements for clinical application. Therefore, the newly developed R-shape Mg alloy clip, featuring staggered teeth, has demonstrated excellent mechanical stability and shows great promise in the application of biodegradable tissue clips.