Xian Tong, Qi Li, Yuxin Zhang, Yuncang Li, Chi Yang, Jixing Lin, Cuie Wen, Jisi Zheng, Yusen Dai
Magnesium (Mg) alloys have shown great potential as biodegradable orthopedic-fixation materials owing to their favorable degradability, elastic modulus comparable to that of natural bone, and beneficial biological functionalities. However, their rapid degradation, poor biotribological performance, and insufficient biofunctionality limit their clinical application. To overcome these limitations, this study developed a biodegradable Mg-1Sr-1Zr-3Ho (MSZH) alloy using a combined approach of multi-elemental alloying, ultrasonic vibration, and hot extrusion. The hot-extruded (HE) MSZH alloy demonstrated an ultimate tensile strength of ~293 MPa, tensile yield strength of ~212 MPa, elongation at break of ~11.5%, ultimate compressive strength of ~513 MPa, compressive yield strength of ~194 MPa, and compressive strain of ~17.6%, all of which exceeded those of the HE Mg-1Sr-1Zr (MSZ). The HE MSZH displayed the lowest electrochemical corrosion rate of approximately 0.19 mm/y and degradation rates of 0.42 mm/y via weight loss and 1.20 mm/y via hydrogen evolution after 7 d of immersion in Dulbecco's Modified Eagle Medium+fetal bovine serum among all samples, indicating markedly improved corrosion resistance compared with MSZ. The 25% HE MSZH extract demonstrated exceptional cytocompatibility, angiogenic activity, osteogenic differentiation, and mineralization. Additionally, the HE MSZH exhibited significant antibacterial and anti-inflammatory activities against Staphylococcus aureus in vitro and in vivo. In a rat femoral-defect model, it showed further enhanced angiogenesis, bone-tissue regeneration, integration, and an in vivo degradation rate of 0.93 mm/y while demonstrating favorable biosafety compared with pure Mg.