Sandwich‐Structured Implants to Obstruct Multipath Energy Supply and Trigger Self‐Enhanced Hypoxia‐Initiated Chemotherapy Against Postsurgical Tumor Recurrence and Metastasis

As a currently common strategy to treat cancer, surgical resection may cause tumor recurrence and metastasis due to residual postoperative tumors. Herein, an implantable sandwich‐structured dual‐drug depot is developed to trigger a self‐intensified starvation therapy and hypoxia‐induced chemotherapy sequentially. The two outer layers are 3D‐printed using a calcium‐crosslinked mixture ink containing soy protein isolate, polyvinyl alcohol, sodium alginate, and combretastatin A4 phosphate (CA4P). The inner layer is one patch of poly (lactic‐co‐glycolic acid)‐based electrospun fibers loaded with tirapazamine (TPZ). The preferentially released CA4P destroys the preexisting blood vessels and prevents neovascularization, which obstructs the external energy supply to cancer cells but aggravates hypoxic condition. The subsequently released TPZ is bioreduced to cytotoxic benzotriazinyl under hypoxia, further damaging DNA, generating reactive oxygen species, disrupting mitochondria, and downregulating hypoxia‐inducible factor 1α, vascular endothelial growth factor, and matrix metalloproteinase 9. Together these processes induce apoptosis, block the intracellular energy supply, counteract the disadvantage of CA4P in favoring intratumor angiogenesis, and suppress tumor metastasis. The in vivo and in vitro results and the transcriptome analysis demonstrate that the postsurgical adjuvant treatment with the dual‐drug‐loaded sandwich‐like implants efficiently inhibits tumor recurrence and metastasis, showing great potential for clinical translation.