Injectable Self-Polymerizing Hydrogel as Bone Filler for Bone Defect Treatment

Poly(methylemethacrylate) (PMMA) bone cement treats bone defects that have a sol-gel behavior that allows injection application. However, it raises concerns such as leakage, toxicity, infection, and incompatible porous structure. Here, we report an injectable gel catalyzed by silver nanoparticles (AgNPs), allowing highly efficient and biocompatible in situ polymerization to fill up the defects and eliminate infection. This gel consists of gelatin methacryloyl (GelMA) and methacrylated chitosan (ChiMA), providing a similarity to the extracellular matrix for improved cell growth, where mussel-inspired polydopamine (PDA), reduced nano silver can be a catalyst for free radical polymerization due to its high electron activity. We further found the high surface/volume ratio of micro hydroxyapatite (HA) immobilized AgNPs for enhanced catalytic ability. The Ag-PDA-HA in GelMA/ChiMA produces gelation in a tunable time. After two months, the filling gel could completely eliminate S.aureus and raise bone volume fraction to 49.9% in infected skull models, which is approximately 30% more than contrast groups. The gel has not only increased the volume but also induced the maturation of the newly regenerated bone from H&E staining. Overall, this innovative bone filler has fast polymerization, anti-infection, and proven bone regeneration acceleration.