Design And Biological Application Of Small Molecule Fluorescent Probe Based On Cleavage Disulfide Bond

Sulfur-containing small molecules,such as cysteine（Cys）,homocysteine（Hcy）,glutathione（GSH）and H₂S,are involved in many important physiological processes in organisms.The abnormal content of this specieses is closely related to cancer.So it is very meaningful to detect the content of Cys,Hcy,GSH and H₂S in cells.Fluorescence detection method is the most potential detection method,and a part of fluorescent dyes have been used as photosensitizers for cancer photodynamic therapy research.Disulfide bonds have been widely studied as GSH cleavage sites.In this paper,naphthimide and tetrastyrene are used as fluorophores and disulfide bonds are used as recognition sites to synthesize compounds Naph-SS-Fc,TPE-SS-C₁₄ and TPE-SS-PEG.Through ultraviolet absorption spectroscopy,fluorescence emission spectroscopy and biological imaging,the identification ability and biological application potential of compounds have been studied.1.A photo-induced electron transfer（PET）probe Naph-SS-Fc with the function of targeting mitochondria was synthesized.In PBS buffer,Naph-SS-Fc has a good fluorescence enhancement response to Cys and Hcy,especially for GSH,and shows a strong fluorescence emission peak at 545 nm.A good linear relationship between the emission of Naph-SS-Fc at 545 nm and the concentration of GSH in 10-100μM was obtained.Moreover,Naph-SS-Fc has low biological toxicity,and it is mainly accumulated in the mitochondria due to the triphenylphosphine group.Furthermore,it can show fluorescence signals of different intensities for different concentrations of GSH in cells.According to the level of its different GSH content,it can successfully distinguish normal cells from cancer cells.2.Tetraphenylethylene and C₁₄ alkyl chain were linked by disulfide bonds to synthesize an aggregation-induced emission hydrophobic compound TPE-SS-C₁₄successfully.TPE-SS-C₁₄ has a good recognition ability for ATP and H₂S.Moreover,TPE-SS-C₁₄ show a weak fluorescence in aqueous solution,however,a strong red emission peak at 630 nm was observed after adding ATP.When interacting with H₂S,the fluorescence emission intensity of TPE-SS-C₁₄ gradually decreased without being interfered by GSH,Cys and Hcy.TPE-SS-C₁₄ has been successfully used for the recognition of ATP and H₂S in cells.Furthermore,TPE-SS-C₁₄ emitted a red light can produce ¹O₂.The phototoxicity of TPE-SS-C₁₄ was studied by MTT method.TPE-SS-PEG has strong phototoxicity to cancer cells.Therefore,TPE-SS-C₁₄has good photodynamic（PDT）application potential.3.Aggregation-induced emission amphiphilic compound TPE-SS-PEG composed of tetraphenylethylene and PEG linked by disulfide bonds was synthesized.The fluorescence emission of TPE-SS-PEG is weaker than that of TPE-SS-C14 in aqueous solution.What’s more,TPE-SS-PEG has a good ability to recognize H₂S and ATP without being interfered by GSH,Cys and Hcy.TPE-SS-PEG has a good biocompatibility and has been successfully used for the recognition of ATP and H₂S in cells.Under the protection of PEG,TPE-SS-PEG significantly improved the production efficiency of ¹O₂.The phototoxicity of TPE-SS-PEG was studied by MTT method.TPE-SS-PEG has strong phototoxicity to cancer cells at a concentration of 5μM.At this time,the activity of cancer cells is reduced to 20%,while the activity of normal cells is still 80%.Therefore,TPE-SS-PEG has good photodynamic（PDT）potential.