Considering the multiple biological barriers before the entry of photosensitizers (PSs) into cytoplasm, it is of paramount importance to track PSs to elucidate their behaviors and distributions to guide the photodynamic therapy (PDT). Also, the developed PSs suffer from strong oxygen dependency. However, reports on such ideal theranostic platforms are rare. Herein, we developed a theranostic platform (CMTP-2) based on the coumarin-based D-π-A system, which, for the first time, can reveal the holistic intracellular delivery pathway and near-infrared (NIR)-activated mitophagy to guide synergistic type-I PDT and photothermal therapy. The dynamic endo-lysosomal escape of CMTP-2 was monitored, as well as its changeable distributions in endosomes, lysosomes, and mitochondria, demonstrating the preferential accumulation in mitochondria at the end. Upon NIR-I irradiation, CMTP-2 generated toxic radicals and heat, triggering the execution of mitophagy and apoptosis. In vivo experiments on mice indicated that CMTP-2 under 808 nm irradiation realized complete cancer ablation, showing great potential for advancements in synergistic phototherapy.
The most common working mechanism of photodynamic therapy is based on high-toxicity singlet oxygen, which is called Type II photodynamic therapy. But it is highly dependent on oxygen consumption. Recently, Type I photodynamic therapy has been found to have better hypoxia tolerance to ease this restriction. However, few strategies are available on the design of Type I photosensitizers. We herein report an unexpected strategy to alleviate the limitation of traditional photodynamic therapy by biotinylation of three photosensitizers (two fluorescein-based photosensitizers and the commercially available Protoporphyrin). The three biotiylated photosensitizers named as compound 1 , 2 and 3 , exhibit impressive ability in generating both superoxide anion radicals and singlet oxygen. Moreover, compound 1 can be activated upon low-power white light irradiation with stronger ability of anion radicals generation than the other two. The excellent combinational Type I / Type II photodynamic therapy performance has been demonstrated with the photosensitizers 1 . This work presents a universal protocol to provide tumor-targeting ability and enhance or trigger the generation of anion radicals by biotinylation of Type II photosensitizers against tumor hypoxia.
Zhijia Sheng,Chao Zhao,Xiaoyan Huang,Jing Wang,Yi Liu
Hypoxia is a common feature of solid tumors and is considered to be the fatal flaw of conventional photodynamic therapy (PDT), which severely reduces the overall therapeutic efficacy. Here, we developed a series of halogenated photosensitizers to address this issue. The results showed that the introduction of heavy atoms enhanced the spin-coupling effect of the photosensitizers and effectively improved the type I PDT (non-oxygen-dependent) efficiency. The preferred iodine-substituted photosensitizer NRh–I was used as the basic architecture, and further nitrosyl modification was performed to obtain the NO small-molecule prodrug, which was finally encapsulated with DSPE-mPEG 5k to obtain a biocompatible NO nanophotocontrolled prodrug. By using the enhanced permeability and retention effect (EPR), the prodrug system can precisely target the lesion site, release a high concentration of NO by photocontrol, kill the tumor cells, and at the same time, cascade with ROS released with the same “time-space” precision to generate higher cytotoxicity, ONOO − , which generates a stronger targeted synergistic therapeutic effect. This “butterfly effect” strategy maximizes the effect of PDT and broadens the idea of translational medicine.
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