TZM Mo alloy behaves superb as biodegradable metal for bone-fracture healing intramedullary nail implant

Bone fracture repair, particularly assisted by load-bearing implants, faces tough clinical challenges, necessitating novel biomaterials that are mechanically strong, biocompatible and biodegradable to achieve effective healing. Metallic molybdenum (Mo) has shown promise in this regard, whereas little has been done with considering its alloys that are more advantageous on many aspects over its pure counterpart. Herein, we demonstrate that the TZM Mo alloy (namely Titanium-Zirconium-Molybdenum, also Mo-Ti-Zr) performed superb efficacy in the repair of rat femoral fractures with its intramedullary nails (IMNs) prototype product even as compared with pure Mo. The TZM alloy had superior mechanical strength and more uniform degradation than Mo, meeting the requirements for next-generation biodegradable IMNs. Moreover, the in vitro assays verified the TZM promoted adhesion, migration and proliferation of endothelial cells and bone marrow mesenchymal stem cells and elicited no toxicity. Molecular expression results revealed the TZM may enhance angiogenesis by activating Wnt/β-catenin signaling and facilitated bone formation by up-regulating osteogenic genes via PI3K–Akt, MAPK–ERK, and cAMP–PKA pathways. More important, TZM-based IMNs achieved nearly complete fracture healing at 12 weeks in a rat femoral fracture model. Thus, the TZM Mo alloy holds super potential for clinical translation.