Synergistic Chemoimmunotherapy Augmentation via Sequential Nanocomposite Hydrogel‐Mediated Reprogramming of Cancer‐Associated Fibroblasts in Osteosarcoma

In osteosarcoma, immunotherapy often faces hurdles posed by cancer-associated fibroblasts (CAFs) that secrete dense extracellular matrix components and cytokines. Directly removing CAFs may prove ineffective and even promote tumor metastasis. To address this challenge, a sequential nanocomposite hydrogel that reshapes CAF behavior is developed, enhancing tumor-infiltrating T-cells in osteosarcoma. The approach utilizes an injectable blend of carboxymethyl chitosan and tetrabasic polyethylene glycol, forming a hydrogel for controlled release of a potent CAF suppressor (Nox4 inhibitor, Nox4i) and liposomal Doxorubicin (L-Dox) to induce immunogenic cell death (ICD) upon in situ administration. Nox4i effectively counters CAF activation, overcoming T-cell exclusion mechanisms, followed by programmed L-Dox release for ICD induction in stroma-rich osteosarcoma models. Combining the co-delivery gel with αPD-1 checkpoint inhibitor further enhances its effectiveness in an orthotopic osteosarcoma model. Immunophenotyping data underscore a significant boost in tumor T-cell infiltration and favorable anti-tumor immunity at the whole-animal level.