NOVEL NMGO/CMC/ALG HYDROGEL ATTENUATES INFECTED BONE DEFECT THROUGH ANTIBACTERIAL AND OSTEOGENESIS ENHANCEMENT

Therapy for infected bone defect often falls short of expectations, even requiring extended treatment durations. Moreover, misuse of antibiotics results in infections caused by antibiotic-resistant bacteria. To address these challenges, we developed a novel polymeric hydrogel containing nano-magnesium oxide (nMgO) with great potential for repairing infected bone defects. Synthesis and Characterization - nMgO was incorporated into a solution of carboxymethyl chitosan (CMC) and alginate (Alg). The mixture was crosslinked with Ca 2+ ions. The morphology of the freeze-dried hydrogel was examined using scanning electron microscopy (SEM), and Fourier-transform infrared spectroscopy (FTIR) was used to examine the interactions between the metal ions and the macromolecules. In vitro study - MC3T3-E1 preosteoblasts were co-cultured with the nMgO/CMC/Alg hydrogel, then the cell viability was measured by CCK-8 kit, and the osteogenic differentiation of MC3T3-E1 was quantitively evaluated. The nMgO/CMC/Alg hydrogel was in immersed in standard bacteria solution (S.aureus and E.coli). The number of living bacteria was subsequently measured by bacterial colonies counting on coted plates. The bacterial morphology was assessed by biofilm staining, SEM and reactive oxygen species (ROS) assay. In vivo study - The hydrogel was implanted into S.aureus-infected cranial defect of SD rat. The skull specimens were harvested 8 weeks later and scanned using Micro-CT. The specimens were sliced and dyed with hematoxylin and eosin (H&E) staining and Giemsa staining. Additionally, tissue from defect were collected and cultured on LB agar plates. Bacterial colonies were counted after incubation. The nMgO/CMC/Alg hydrogel remained stable due to the coordination between divalent metal ions and side chain COO − groups. The macroporous structure enhanced the cell adhesion and substance exchange. The hydrogel demonstrated excellent biocompatibility and significantly promoted new bone formation, as evidenced by increased alkaline phosphatase activity and upregulated expression of osteogenesis-related genes. Additionally, the hydrogel induced ROS production in bacteria, which effectively suppressed the bacterial growth. The nMgO/CMC/Alg hydrogel exhibits excellent osteoinductive potential and antibacterial properties both in vitro and in vivo, suggesting it's a promising candidate for the treatment of infected bone defects.