Dihydroartemisinin-Loaded ZIF-8 Nanoparticles for Antibacterial and Osteogenic Dual Therapy in Brucella-Infected Bone Defects.

Brucella infection frequently causes multijoint cartilage loss and bone destruction, posing significant challenges for clinical treatment. Conventional two-stage therapy is time-consuming and has a high relapse rate. Dihydroartemisinin (DHA) exhibits significant antibacterial activity against Brucella melitensis 16M in vitro. However, its cytotoxicity to mammalian cells and poor water solubility limit its application. In this study, DHA@ZIF-8/HA nanoparticles were synthesized for targeted delivery to infected macrophages. The nanoparticles consisted of a pH-responsive zeolitic imidazolate framework-8 (ZIF-8) modified with hyaluronic acid (HA) that encapsulated DHA. DHA and Zn2+ were coreleased within the mildly acidic infected macrophage lysosomes. DHA directly killed the intracellular and extracellular B. melitensis 16M, resulting in attenuation of the inflammatory response; meanwhile, osteogenic differentiation was promoted by Zn2+. Furthermore, DHA@ZIF-8/HA was incorporated into a methacrylate gelatin hydrogel to form an injectable composite hydrogel (GelMA/DHA@ZIF-8/HA). GDZH was noncytotoxic to the bone marrow mesenchymal stem cells (BMSCs) and significantly promoted their proliferation and osteogenic differentiation (as evidenced by upregulated alkaline phosphatase activity, mineralized nodule formation, and expression of osteogenic-related proteins) in vitro. In the in vivo rat tail vertebra bone defect model, treatment with GDZH resulted in a 92.9 ± 1.0% reduction in bacterial load compared to the control group 1 week postsurgery, and the bone defect repair was almost completed 8 weeks postsurgery. Histological analysis also confirmed that GDZH effectively reduced inflammatory infiltration and that abundant mature bone was formed. In summary, the GDZH composite hydrogel has a synergistic "antibacterial-anti-inflammatory-osteogenic" characteristic that comprehensively treats complicated Brucella-infected bone defects, providing a multifunctional therapeutic strategy for such refractory infectious bone injuries.