Vascular environment-responsive DNA nanoswitch controls the positive feedback system for spatiotemporal coupling of angiogenesis and osteogenesis.

Vascularization-ossification coupling is pivotal for bone defect repair. Neovascularization guides the migration of osteogenic precursor cells, and osteoblasts in the perivascular area support vascular regeneration through the secretion of cytokines. Delivery systems are being engineered to orchestrate the coupling of vascularization and ossification precisely. However, most delivery systems lack sensitivity to the inherent repair environment, hampering timely bone formation. This study developed a vascular environment-responsive biomaterial: a true bone ceramic/small intestine submucosa (TBC/SIS) scaffold loaded with nanoswitch and Apt19s-functionalized nanoparticles. This scaffold is designed to release the functionalized nanoparticles via an "unfolding-refolding" nanoswitch based on base pairing and protein-nucleic acid recognition. The TBC/SIS scaffold initiates neovascularization, prompting endothelial cells to secrete nucleolin. The nanoswitches detect nucleolin and trigger the release of nanoparticles, thereby creating a responsive vascular environment. Moreover, when modified with aptamer-19s, the nanoparticles can attract mesenchymal stem cells to perivascular areas, facilitating spatial coupling with blood vessels. Encapsulating miR-26a in nanoparticles enhances osteogenic activity and stimulates the secretion of vascular endothelial growth factor. As vascular endothelial cells infiltrate, nanoparticles are continuously released from the scaffold, establishing a positive feedback loop that promotes vascularization-ossification coupling and ultimately enhances bone regeneration. Our findings provide valuable insights for designing intelligent materials that utilize endogenous stimuli to enhance spatiotemporal interactions between vascularization and ossification. Further in-depth studies on the expression of nucleolin in vivo will continue to refine this promising strategy.