Iridium-Doped Prussian Blue Nanozymes for Photothermal and Photodynamic Therapy

Although photodynamic therapy (PDT) shows great promise in tumor treatment, severe hypoxia in the tumor microenvironment (TME) of most solid tumors dramatically restricts therapeutic use of PDT. It has been reported that Prussian blue (PB) nanoparticles have catalase (CAT)-like activity and can modulate TME to alleviate tumor hypoxia. Nevertheless, the lower catalytic activity of PB is far from satisfactory. In this paper, iridium oxide (IrO2)-coated PB (designated as PBIr NPs) nanoparticles with excellent photothermal conversion efficiency and CAT activity have been synthesized using a simple approach. Further, PBIr@Ce6 NPs were obtained for photothermal therapy (PTT) and enhanced PDT of tumors by loading the photosensitizer Ce6. The results show that the prepared PBIr@Ce6 NPs possess uniform dimensions and good biocompatibility. The photothermal conversion of PBIr NPs was as high as 38.8% under 808 nm near-infrared laser irradiation. Moreover, PBIr NPs integrate the CAT catalytic activity of PB and IrO2, which can effectively catalyze the production of oxygen (O2) from hydrogen peroxide (H2O2), thereby enhancing PDT efficacy. Notably, the antitumor experiments at both the cellular and animal levels demonstrated that combined PTT and enhanced PDT based on PBIr@Ce6 NPs were effective at killing tumor cells. Taken together, this work provides a paradigm for modulating the in situ production of O2 by TME to achieve combined PTT and enhanced PDT treatment of tumors.