Indocyanine green-equipped upconversion nanoparticles/CeO2 trigger mutually reinforced dual photodynamic therapy

Although photodynamic-based tumor therapy has attracted considerable attention, the antitumor effect is limited due to the low reactive oxygen species (ROS) generation of photosensitizers. Therefore, it is an urgent need for improving ROS production and promoting therapeutic outcome of tumor. We developed a nanoplatform of indocyanine green (ICG)-equipped upconversion nanoparticles (UCNPs)/CeO2 modified with NH2-PEG1000-cRGDfK (UICCIP). This nanoplatform has two pathways of ROS production for mutually enhanced dual photodynamic therapy (PDT) of tumors. The ultraviolet (UV) emission of UCNPs could trigger CeO2 to produce ROS for PDT under 808 nm laser irradiation, and ICG can also produce singlet oxygen (1O2) at the meantime. Importantly, ICG can enhance the luminescence of UCNPs through energy transfer, thus promoting the PDT effect of CeO2. For another, CeO2 could catalyze endogenous H2O2 to provide O2 then overcome the hypoxic environment of tumor to enhance the PDT effect. By highlighting the full use of the various components of the nanoplatform and establishing interrelationships, ROS production can be increased significantly, resulting in efficient PDT of tumor. It is believed that UICCIP will become a potential ROS producer, which will broaden the thought of exploring new antitumor nanoplatforms.