Minimally Invasive Injection of Magnesium-Doped Bioactive Glass Hydrogels for Immunomodulatory Repair of Bone Defects

Repair of large-scale bone defects has always been a major challenge for orthopedic surgeons. Biomaterials that can be injected and adapted to different shapes of bone defects are hot topics in current research. In this study, bioactive glass (MBG) with a mesoporous structure and magnesium-doped MBG (MBG-Mg) were prepared, encapsulated with methacrylate esterified filipin protein (SilMA), and formed into minimally invasive, injectable, light-cured hydrogels. The results showed that MBG significantly increased the mechanical properties of the hydrogel and decreased the swelling, water absorption, and degradation rates, making the hydrogel more suitable for bone repair. The composite hydrogel possessed good cytocompatibility, and the addition of magnesium endowed the hydrogel with more significant properties for inducing macrophage polarization to the M2 phenotype and regulating osteogenic differentiation of rat bone marrow mesenchymal stem cells. Repair experiments in vivo confirmed that magnesium-doped hydrogels enhanced the bone regeneration properties of hydrogels, and the release of magnesium ions significantly regulated the expression of the macrophage M2 phenotype around bone defects, induced the deposition of bone matrix proteins, and promoted bone formation. In conclusion, the combination of hydrogel and MBG helps to better adapt to the bone defect area, and the biological properties of magnesium-doped MBG make the composite hydrogel one of the most attractive choices for bone regeneration materials.