Photo-Enhanced Singlet Oxygen Generation of Prussian Blue-Based Nanocatalyst for Augmented Photodynamic Therapy

Therapeutic effects of photodynamic therapy (PDT) remain largely limited because of tumor hypoxia. Herein, we report safe and versatile nanocatalysts (NCs) for endogenous oxygen generation and imaging-guided enhanced PDT. The NCs (named as PSP) are prepared by coating Prussian blue (PB) with mesoporous silica to load photosensitizer (zinc phthalocyanine, ZnPc), followed by the modification of polyethylene glycol chains. The inner PB not only acts like a catalase for hydrogen peroxide decomposition but also serves as a photothermal agent to increase the local temperature and then speed up the oxygen supply under near-infrared irradiation. The loaded ZnPc can immediately transform the formed oxygen to generate cytotoxic singlet oxygen upon the same laser irradiation due to the overlapped absorption between PB and ZnPc. Results indicate that the PSP-ZnPc (PSPZP) NCs could realize the photothermally controlled improvement of hypoxic condition in cancer cells and tumor tissues, therefore demonstrating enhanced cancer therapy by the incorporation of PDT and photothermal therapy.