Self-Adjuvanting Gel for Hierarchical Delivery to Tumors and Lymph Nodes in Liver and Colon Tumor Immunotherapy

Exploiting localized, sustained-release drug delivery carriers to enhance the efficiency of tumor immunotherapy has become a major research interest. However, due to the multistep nature of immune activation and the need to target multiple sites─such as simultaneously activating both tumors and lymph nodes─using a single delivery carrier to meet all the complex requirements of immune activation poses significant challenges and limitations. Here, we report a self-adjuvant gel (SAG) for the delivery of the chemotherapeutic agent doxorubicin (DOX) and the immune adjuvant TLR-9 agonist CpG to tumor sites and lymph nodes, enabling sequential, multistep immune activation. This SAG is cross-linked by polyethylenimine grafted with 4-benzimidazole (PEI-4BImi), which has innate immune activation properties, with oxidized dextran. The released PEI-4BImi further assembles <i>in situ</i> with tumor antigens to form nanoparticles of appropriate sizes that can drain to the lymph nodes, promoting antigen presentation and dendritic cell (DC) activation. The SAG exhibits sustained degradation and drug release both <i>in vitro</i> and <i>in vivo</i> over 25 days, efficiently transporting CpG and antigens to the lymph nodes and enhancing DC activation within the lymph nodes. <i>In vivo</i> therapeutic results demonstrated that the SAG could suppress tumor growth, achieving 93% tumor inhibition rates in a subcutaneous liver tumor model and 97% in an orthotopic colon tumor model. Importantly, the immune activation mechanisms, including antigen release and presentation, DC activation, and T-cell priming, were further confirmed through flow cytometry, RNA-seq, and proteomics. Collectively, this SAG presents a potent targeted strategy for cancer immunotherapy.