Research on the degradation behaviors of biomedical Mg-2 wt.% Zn alloy under a biliary environment in vitro and in vivo

Magnesium and its alloys have been initially applied to biliary tract surgery. Currently, few reports on the degradation behavior of magnesium in the bile environment were investigated. Thus, in-depth research on the degradation behavior of Mg and its alloys in bile is beneficial to the further application of Mg in biliary tract surgery. In this study, the degradation behavior of HP-Mg (HPM) and Mg-2 wt.%Zn (MZ2) alloys in human bile and Hanks balanced salt solution (HBSS) was systematically investigated. The MZ2 alloy biliary stent was implanted into the porcine common bile duct to study the degradation behavior of MZ2 alloy in vivo, and to verify the biosafety of MZ2 alloys degradation in the bile duct. It was found that the degradation product layer formed by MZ2 alloys in bile consisted of three layers, including organic matter (fatty acid, etc.), calcium and magnesium phosphate, and Mg(OH)₂/MgO, respectively from the outside to the inside. The multi-layered degradation product layer slowed down the corrosion of the Mg matrix. During the 21 days of stent implantation, the degradation rate of the MZ2 stent was about 0.83 mm/y, there was no blockage and stenosis of the tube diameter, and the bile drainage function was normal.