A Potential Biodegradable Mg-Y-Ag Implant with Strengthened Antimicrobial Properties in Orthopedic Applications

In order to design a potential biodegradable implant, which combines with fine mechanical and antimicrobial properties, Mg-4Y-1Ag (mass fraction, %) alloys were produced by permanent mold casting and then hot extrusion. The microstructure, mechanical behavior, anti-corrosion behavior, and antimicrobial properties of the experimental alloys were comprehensively investigated. The results showed that alpha-Mg, Mg24Y5 (epsilon), and AgMg4 phases existed in the Mg-4Y-1Ag. The grain size of Mg-4Y-1Ag was greatly refined through hot-extrusion. The as-extruded Mg-4Y-1Ag alloy exhibit an ultimate tensile strength of 202.7 MPa with a good elongation of 33.6%. The compressive strength of as-extruded Mg-4Y-1Ag was 385 MPa, and the strength remained 183 MPa after immersing in PBS solution for four weeks. The as-extruded alloy had better corrosion resistance than as-cast alloy and as-extruded pure magnesium in PBS solution, for the reason of refined grain and the formation of Y2O3 film on the surface of Mg-4Y-1Ag alloy. Furthermore, the as-extruded Mg-4Y-1Ag alloys were superior to Ti6Al4V (TC4) and as-extruded pure magnesium in antimicrobial property for released Ag+ ion. Obvious inhibition halo was observed in the LB agar plate adding with as-extruded Mg-4Y-1Ag alloys. Also as-extruded Mg-4Y-1Ag alloys showed no cytotoxicity by co-culturing with L929 using the MTT method.