Cell-Type-Tailored Hydrogels for Adoptive Cell Therapy in Cancer.

Hydrogel-enabled adoptive cell therapy (ACT) offers a localized and controllable strategy for improving cellular immunotherapy in solid tumors. Hydrogels can enhance cell retention and persistence, support immune cell function within the tumor microenvironment, and reduce systemic toxicity associated with broadly delivered immune stimulants. However, delivery of living immune cells imposes practical constraints on hydrogel selection, including cytocompatible encapsulation, minimal handling and injection stress, adequate transport of oxygen and soluble cues, and an appropriate balance between local retention and timely cell egress. This review summarizes natural, synthetic, and hybrid hydrogel platforms and compares physical/supramolecular assembly, covalent and enzymatic crosslinking, and photo-crosslinking. Injectable in situ-forming depots and shear-thinning/self-healing gels are highlighted for locoregional administration. Key design and reporting dimensions of hydrogels are linked to immune cell outcomes relevant to ACT. These properties include mechanics and viscoelasticity, porosity and mass transport, degradability and remodeling, bioadhesion and extracellular matrix (ECM) mimicry, and immunogenicity versus immune shielding. Finally, a cell-type-tailored framework is presented for chimeric antigen receptor T (CAR-T), T cell receptor-engineered T (TCR-T), and tumor-infiltrating lymphocyte (TIL) products, natural killer (NK) cells, and dendritic cells (DCs) or macrophage/monocyte-derived effectors. Distinct biological requirements are used to motivate corresponding material architectures and cue presentation strategies. The review also provides quantitative reporting guidance, identifies evidence gaps for γδ T cells, and discusses in vivo validation, combination ACT strategies, and translational handling constraints.