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Advanced functional materials: molecular design of aggregation induced free radical photosensitizer and its application in hypoxic tumor therapy

wallpapers News 2020-09-14

fluorescence imaging mediated tumor photodynamic therapy has the advantages of accurate drug tracking high sensitivity low toxicity minimally invasive synergistic has a wide application prospect in the clinical treatment of cancer. The essence of photodynamic therapy (PDT) is to use light to irradiate the tumor tissue produce reactive oxygen species by photophysical photochemical reaction with the photosensitizer retained in the tissue to destroy the tumor structure so as to achieve the purpose of treatment. There are two main pathways for the production of reactive oxygen species: type II singlet by energy transfer type I free radical reactive oxygen species by electron transfer. Traditional organic photosensitizers (porphyrin phthalocyanine etc.) have strong molecular structure rigidity are easy to aggregate in physiological water environment which leads to serious fluorescence quenching greatly reduced efficiency of reactive oxygen species so it is difficult to achieve the integration of diagnosis treatment. The concept of aggregation induced luminescence (AIE) provides a good strategy to solve the problem of fluorescence aggregation quenching (ACQ). More more AIE photosensitizer materials have been developed one after another their reactive oxygen efficiency is comparable to that of clinical photosensitizer drugs. However most of the reported AIE photosensitizers are mainly type II singlet oxygen their severe oxygen dependence is not conducive to the long-term continuous treatment of hypoxic tumors.

researcher Wang Zhiming of Tang benzhong academician team of South China University of technology together with Dr. Zhang Weijie of Hou Jianquan Professor team of the First Affiliated Hospital of Soochow University the research group uses the idea of excited state energy level regulation to regulate the triplet state of aiegens: by introducing "rotor type" electron rich elements into aiegens it can inhibit molecular motion strengthen intramolecular electricity The charge transfer (ICT) effect activates the radiative transition inter gap crossing (ISC) channels to improve the efficiency of luminescence reactive oxygen species simultaneously. Electron rich elements create abundant electron sources for the aggregate microenvironment which effectively leads to the capture of electrons by high-energy triplet states thus realizing the transformation of free radical reactive oxygen species. The previous research results of

show that type I free radical photosensitizer can greatly improve the utilization rate of oxygen in cells effectively overcome the problem of hypoxia because it can produce rich reactive oxygen species in the cell through the disproportionation reaction regulated by superoxide dismutase is accompanied by the recycling of oxygen. In this paper benzothiadiazole naphthothiadiazole with different triplet energy level distribution characteristics are selected as the research units the asymmetric molecular design strategy is used to introduce the rotor type triphenylamine methoxytriphenylamine electron rich body on one side to ensure that the molecule has AIE properties while the positively charged pyridinium salt electron acceptor is introduced on the other side to improve the hydrophilicity of the molecule so as to construct ICT The effect of red light near infrared fluorescence on the molecular system was studied. With the formation of aggregation state the enhancement of ICT effect the molecular luminescence is red shifted enhanced the ISC channel is effectively activated the efficiency of active oxygen generation caused by aggregation is greatly increased. The results of active oxygen species identification showed that benzothiadiazole based photosensitizers were dominated by type II singlet species while naphthalene thiadiazole based photosensitizers all produced type I free radical active oxygen species. Through theoretical simulation it is found that the formation of high activity T2 exciton may be easier to achieve electron capture which may be the main reason for the realization of I-type radical active oxygen. The long-lived relatively stable T1 exciton is more inclined to form II type singlet oxygen by means of energy transfer. In vitro evaluation results showed that free radical photosensitizer had dynamic targeting to mitochondria lysosomes had good cytotoxicity to cells even in hypoxic environment. The results of imaging treatment evaluation showed that the free radical photosensitizer had good imaging photodynamic therapy effect in vivo. Further study on the mechanism of photodynamic therapy reveals that the double synergistic destruction mechanism of free radical reactive oxygen species on mitochondria lysosomes is the main reason for its good photodynamic therapy effect. The researchers of

believe that this work will provide a new idea for the design of high efficiency AIE radical photosensitizer materials.

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