Biopolymer Hydrogels for Adaptive Remodeling of the Tumor Microenvironment to Improve Cancer Immunotherapy

Abstract Immunotherapy has revolutionized oncology by harnessing intrinsic immune pathways to precisely target and eliminate malignant cells. However, systemic toxicity from off‐target immune activation, inefficient tumor penetration of immunotherapeutic agents, and the immunosuppressive complexity of the tumor microenvironment critically limits therapeutic efficacy. Emerging as transformative solutions, biopolymer‐driven injectable hydrogels integrate spatiotemporally controlled drug release with dynamic tumor microenvironment reprogramming, enabling dual modulation of immunostimulatory signaling and antigen presentation networks. Capitalizing on their inherent biocompatibility, tunable physicochemical properties, and biomimetic extracellular matrix interactions, these hydrogel platforms orchestrate localized immunotherapeutic delivery through mechanisms spanning chemo‐mechanical cue regulation, immune cell trafficking guidance, and metabolic reprogramming. This review focuses on the characterization, delivery modes, and functions of various biopolymer hydrogels, as well as emerging immunotherapeutic applications, and systematically explores the state‐of‐the‐art design of biopolymer‐based hydrogels for synergistic immunomodulatory‐microenvironmental engineering. This analysis provides a roadmap for developing next‐generation hydrogel platforms to overcome spatial‐temporal barriers in cancer immunotherapy and accelerate clinical adoption.