Type-I-Organic-Photosensitizer-Functionalized Upconversion Nanoparticles for Enhanced Photodynamic Therapy

Photodynamic therapy (PDT) has achieved great progress in cancer treatment because it generates reactive oxygen species (ROS) in a noninvasive manner. Nonetheless, the majority of light-sensitive photosensitizers (PSs) are only sensitive to UV or visible light, suffering limitations such as phototoxicity (UV) and low tissue penetration capabilities (UV-visible). What is more, another impact factor, namely the hypoxic environment within a tumor always inhibits the production of ROS for treatment efficacy. To overcome these problems, herein, one new type-I PS containing selenium (Se6) is designed. Benefiting from the dual heavy atom effects of selenium and bromine, Se6 can produce short-lived hydroxyl (center dot OH) and long-lived superoxide anion (O2 center dot-) under both normoxic and hypoxic conditions, which is superior to commonly used oxygen-dependent type-II PSs, such as chlorine e6, zinc phthalocyanine. Combining Se6 and upconversion nanoparticles with the ability to upconvert near-infrared (NIR) light to UV-visible light can greatly overcome the tissue penetration depth, phototoxicity, and oxygen-dependent limitation of the PDT process, which demonstrates a significant performance in vivo to achieve better therapy efficiency. Combining the upconversion nanoparticles with type-I photosensitizer can greatly overcome the tissue penetration depth, phototoxicity, and oxygen-dependent limitation of the photodynamic therapy process in tumors with a hypoxic environment to achieve better therapy efficiency, which shows a high potential for cancer therapy. image