Thermodynamic 2D Silicene for Sequential and Multistage Bone Regeneration.

Bone healing is a multistage process involving the recruitment of cells, revascularization, and osteogenic differentiation, all of which are modulated in the temporal sequence to maximize cascade bone regeneration. However, insufficient osteoblast cells, poor blood supply, and limited bone induction at the site of critical-sized bone defect broadly impede bone repair. 2D SiO 2 -silicene@2,2'-,azobis(2-[2-imidazolin-2-yl] propane) (SNSs@AIPH) with inherent thermodynamic property and osteoinductive activity is therefore designed and engineered for sequentially efficient bone repair. By means of controllable NIR-II irradiation, the integrated SNSs@AIPH stimulates the generation of appropriate intracellular reactive oxygen species, which accelerates early bone marrow mesenchymal stem cells (BMSCs) proliferation and angiogenesis remarkably. Importantly, as silicon-based 2D nanoparticles, the engineered SNSs@AIPH with high biocompatibility features distinct bioactivity to significantly promote BMSCs osteogenesis differentiation by activating TGFβ and BMP pathways. In a rat cranial defect model, SNSs@AIPH-NIR-II leads to a comparable increase of BMSCs proliferation and local vascularization at an early stage, followed by significant osteogenic differentiation, synergically resulting in a highly effective bone repair. Collectively, the fascinating characteristics and exceptional bone repair efficiency of NIR-II-mediated SNSs@AIPH allow it to be a promising bionic-oriented strategy for bone regeneration, broadening a new perspective in the application of cell-instructive biomaterials in bone tissue engineering.