One-pot solvothermal synthesis of polyvinyl pyrrolidone and ethylene glycol-modified Cu2SnS3 (PE/CTS) nanomaterials for photothermal immunotherapy

Photothermal therapy (PTT) not only ablates tumor tissues, but also activates antitumor immunity by enhancing immunogenicity, which highly relies on photothermal nanoagents (PTNAs) with excellent photothermal effect. Herein, polyvinyl pyrrolidone (PVP) and ethylene glycol (EG)-modified Cu₂SnS₃ (PE/CTS) nanoparticles (NPs) and nanosheets (NSs) with excellent biocompatibility and stability were synthesized via the one-pot solvothermal method and applied for photothermal immunotherapy. Because of their strong near-infrared (NIR) light absorption and high extinction coefficient, PE/CTS NPs and NSs possessed high photothermal conversion efficiency (PCE) of 39.3 % and 46.8 %, respectively. Furthermore, the superior photothermal effect of PE/CTS NPs over NSs in the NIR-I region was confirmed both in vitro and in vivo, mainly because of the longer blood circulation time, enhanced tumor accumulation, and higher tumor cell uptake level of NPs. As thus, PE/CTS NPs-mediated PTT effectively inhibited growth of 4T1 xenograft tumors in mice. Moreover, it enhanced local/systemic immune responses by inducing the maturation of dendritic cells (DCs) followed by the activation, proliferation, and intratumoral infiltration of T lymphocytes, and it alleviated immunosuppression by promoting the production of M1-phenotype macrophages and the reduction of regulatory T cells (Tregs). Consequently, PE/CTS NPs-mediated PTT notably inhibited the growth of distant tumors. This study highlights the potential of CTS-based nanomaterials for photothermal immunotherapy, broadening the scope of medical applications of ternary metal chalcogenide nanomaterials.