Localized hydrogel delivery of photoactivatable mRNA lipid nanoparticles and hyaluronidase for postoperative TNBC immunotherapy.

Triple-negative breast cancer (TNBC) responds poorly to immunotherapy, in part because its hyaluronic acid (HA)-rich and immunosuppressive tumor microenvironment restricts drug penetration and antitumor immune activation. Here, we developed an injectable alginate hydrogel platform (ICG-LNP@ALG-H) for localized co-delivery of hyaluronidase (HAase) and indocyanine green (ICG)-functionalized lipid nanoparticles (LNPs) carrying messenger RNA (mRNA) encoding interleukin-12 (IL-12) and granulocyte-macrophage colony-stimulating factor (GM-CSF). After administration into the postoperative tumor bed, the hydrogel formed an in situ depot that enabled sustained local retention and release. HAase degraded the HA-rich stromal matrix to enhance nanoparticle penetration, while near-infrared (NIR)-activated ICG generated reactive oxygen species through a photodynamic effect, promoting endosomal escape and improving intracellular mRNA delivery and cytokine expression. This platform integrated stromal remodeling, photoactivated intracellular delivery, and local immunostimulation in a single controlled-release system. In a postoperative 4 T1 TNBC recurrence model, ICG-LNP@ALG-H reduced local recurrence and elicited coordinated local and systemic immune responses, as indicated by enhanced intratumoral IL-12 expression and CD8+ T-cell infiltration, together with increased splenic NK-cell frequency, dendritic-cell maturation, and M1-like macrophage polarization. Short-term safety assessments revealed no overt abnormalities under the tested conditions. These results show that localized delivery of matrix-remodeling and immunostimulatory cargoes can address both stromal and intracellular barriers to mRNA therapy, supporting ICG-LNP@ALG-H as a locoregional controlled-release strategy for postoperative immunotherapy of stromal-rich solid tumors.