Opa1 -Knocked out EMSCs-Derived EV-Mito Empower Functionalized PEEK/LL37 Scaffolds to Combat Drug-Resistant Bone Infection

Treating bone defects becomes particularly challenging when drug-resistant bacteria take hold. Standard antibiotics often fail to clear these infections completely, and the resulting inflammatory environment actively blocks new bone formation. To tackle this problem, we developed a sulfonated-PEEK scaffold called SPMiL that carries two distinct payloads: the human derived antimicrobial peptide LL37 and mitochondria-rich vesicles (EV-Mito). We generated these vesicles from ectomesenchymal stem cells (EMSCs) lacking Opa1, a key regulator of mitochondrial dynamics. Knocking out this gene substantially boosts vesicle production, solving the supply limitations that have hampered previous attempts to use EV-Mito therapeutically. In tests using MRSA-infected rat calvarial defects, SPMiL released LL37 continuously to eliminate the resistant bacteria while simultaneously transferring functional mitochondria into recipient cells. These transplanted organelles promoted osteogenic differentiation and suppressed osteoclast activity through metabolic reprogramming, antioxidant effects, and restoration of mitochondrial membrane potential. This work demonstrates that combining antibacterial defense with mitochondrial transfer offers a viable approach for treating infected bone defects that resist conventional treatment.