Targeted reduction-responsive nanovehicles for photodynamic therapy-primed immunotherapy in melanoma

Melanoma, a common malignant skin tumor, faces challenges with multidrug resistance and high recurrence rates. Combining photodynamic therapy (PDT) and immunotherapy offers a promising personalized treatment approach. However, poor water solubility and significant side effects of photosensitizers and immune checkpoint inhibitors (ICIs) limit their application. Enhancing delivery efficiency while reducing adverse effects is crucial. Herein, we formulate BM@HSSC nanoparticles (NPs), which consist of a reduction-responsive hyaluronic acid (HA) backbone modified with photosensitizer chlorin e6 (Ce6) and loaded with the programmed cell death-ligand 1 (PD-L1) inhibitor BMS-1. This system synergistically integrates PDT, immunogenic cell death (ICD), and immunotherapy for melanoma treatment. BM@HSSC NPs target and accumulate at the tumor site via the CD44 receptor. The disulfide bonds (-S-S-) in the NPs react with high glutathione (GSH) concentrations in tumor cells, rapidly releasing Ce6 and BMS-1. Under 660 nm laser irradiation, BM@HSSC NPs generate cytotoxic reactive oxygen species (ROS), inducing cell apoptosis and triggering ICD via PDT damage-associated molecular patterns (DAMPs) and tumor-associated antigens (TAAs) released from ICD promote dendritic cell (DC) maturation, enhancing antigen presentation and activating cytotoxic T lymphocytes (CTLs). Meanwhile, BMS-1 blocks the programmed cell death-1 (PD-1)/PD-L1 pathway, countering the immunosuppressive tumor microenvironment (iTME) and inhibiting tumor cell immune escape. This strategy amplifies antitumor immune responses by enhancing immunogenicity and synergizing with ICIs, resulting in robust antitumor efficacy.