Cryogenic 3D printing of porous scaffolds for <i>in situ</i> delivery of 2D black phosphorus nanosheets, doxorubicin hydrochloride and osteogenic peptide for treating tumor resection-induced bone defects.

Tumor resection is widely used to prevent tumor growth. However, the defected tissue at the original tumor site also causes tissue or organ dysfunction which lowers the patient's life quality. Therefore, regenerating the tissue and prevent tumor recurrence are highly important. Herein, according to the concept of "first kill and then regenerate", a versatile scaffold-based tissue engineering strategy based on cryogenic 3D printing of water-in-oil polyester emulsion inks containing multiple functional agents was developed,in order to realize the elimination of tumor cells with recurrence suppression and improved tissue regeneration sequentially. To illustrate our strategy, water/poly(lactic-co-glycolic acid)/dichloromethane emulsions containing β-tricalcium phosphate (β-TCP), 2D black phosphorus (BP) nanosheets, low-dose doxorubicin hydrochloride (DOX) and high-dose osteogenic peptide were cryogenically 3D printed into hierarchically porous and mechanically strong nanocomposite scaffolds,with multiple functions to treat bone tumor resection-induced tissue defects. Prompt tumor ablation and long-term suppression of tumor recurrence could be achieved due to the synergistic effects of photothermotherapy and chemotherapy, and improved bone regeneration was obtained eventually due to the presence of bony environment and sustained peptide release. Notably, BP nanosheets in scaffolds significantly reduced the long-term toxicity phenomenon of released DOX during in vivo bone regeneration. Our study also provides insights for the design of multi-functional tissue engineering scaffolds for treating other tumor resection-induced tissue defects.