Multifunctional Photothermal Hydrogel in the Second Near-Infrared Window for Localized Tumor Therapy

A copper selenide-embedded gellan gum hydrogel (Cu_2-xSe@GG) is designed as an "all-in-one" antitumor agent. The obtained nanocomposite hydrogel exhibits strong near-infrared light absorption and high photothermal conversion efficiency in both the NIR-I and NIR-II biowindows. The photothermal conversion efficiency achieves 58.8% under the irradiation of 0.75 W/cm² with a 1064 nm laser. Furthermore, the nanocomposite hydrogel has catalase- and peroxidase-mimicking activities, which could alter the tumor microenvironment by reducing hypoxia and/or increasing the production of reactive oxygen species. Moreover, the multifunctional Cu_2-xSe@GG nanocomposite hydrogel can also be used as an immune agonist resiquimod (R848) carrier to promote immune regulation and enhance the therapeutic effect. The single-syringe R848/Cu_2-xSe@GG treatment achieves synergetic photothermal immunotherapy, showing 97.4% of tumor regression rate from an initial large tumor of 300 mm³.