Biomimetic scaffolds with synergistic BMSC targeting and ROS scavenging for mitochondrial protection and effective bone-defect repair

The reconstruction of large bone defects remains a significant clinical challenge, primarily owing to the insufficient mitochondrial protection and osteogenic activity of conventional implants. Exosomes (EXOs) derived from mesenchymal stem cells have emerged as promising tools for bone repair. This study reports a mitochondria-targeted therapeutic strategy utilizing EXOs derived from bone marrow mesenchymal stem cells (BMSCs). On MitoQ incorporation, these EXOs (EXO-MitoQ, EM) exhibit the targeted scavenging of mitochondrial reactive oxygen species; moreover, on surface decoration with the nucleic acid aptamer Apt 19 S (EM-Apt), they show the enhanced recruitment and precise delivery of BMSCs. The engineered EXOs show robust BMSC-targeting specificity and mitochondrial protective efficacy. To optimize their regenerative microenvironment and biomechanical properties further, these functionalized EXOs are integrated onto a 3D-printed β-tricalcium phosphate scaffold coated with a small intestinal submucosa (SIS) hydrogel, forming a composite system (TCP/SIS@EM-Apt). In a rat calvarial defect model, this TCP/SIS@EM-Apt scaffold increased the BV/TV by 1.9-fold compared to TCP/SIS, due to the combination of multiple multifunctional therapeutic effects (anti-inflammatory, angiogenic, and osteogenic). The mitochondria-targeting strategy proposed in this study presents a promising solution for the reconstruction of large bone defects and offers a synergistic approach for addressing complex regenerative challenges.