Rare-earth-free magnesium-zinc alloy with controlled biodegradation and biocompatibility for novel biodegradable metallic stent

Abstract

Biodegradable magnesium (Mg) alloy stents offer a transient alternative to permanent metallic implants; however, clinically used WE43 contains rare-earth (RE) elements, raising concerns regarding the long-term biosafety of RE-containing degradation products and their potential tissue accumulation. Here, we investigated two RE-free Mg–Zinc (Zn)-based alloys, MZ01 (Mg–1Zn–0.1Ca) and ZM115 (Mg–1Zn–1.5Mn–0.5Sr), and established a mechanistic cascade linking alloy composition and microstructure to electrochemical analyses revealed alloy-dependent differences in grain structure and interfacial corrosion resistance, with MZ01 exhibiting the highest charge-transfer resistance. In a mouse subcutaneous model, MZ01 showed more uniform degradation, smaller and more rapidly resolving hydrogen gas cavities, and a significantly lower microcrack area fraction at Day 56 than WE43 and ZM115, accompanied by attenuated inflammatory and fibrotic responses. In the rabbit iliac arteries, all stents maintained luminal patency without thrombosis through 56 days, while MZ01 exhibited lower neointimal thickness, lower perivascular apoptosis and late inflammation, and enhanced early endothelialization compared with WE43. Preliminary descriptive porcine coronary implantation further demonstrated the technical feasibility and sustained patency of MZ01 over 56 days. Collectively, these findings define a composition–microstructure–corrosion–cellular response–vascular healing axis and identify MZ01 as a RE-free Mg–Zn alloy with controlled biodegradation and favorable biocompatibility, supporting its further development as a biodegradable cardiovascular scaffold.