Design And Synthesis Of Novel Hydrogen Sulfide Fluorescent Probes And Their Application In Bioimaging

In recent years,with people’s understanding of H₂S continues to deepen,more and more research results show that H₂S is the third endogenous gas signal molecule following NO and CO.Endogenous H₂S has important physiological and pathological effects in regulating the nervous system,protecting cardiovascular,enhancing antioxidation,and enhancing immunity.However,abnormal concentrations of endogenous H₂S are closely related to the occurrence of various diseases,such as Alzheimer’s disease,Down’s syndrome,cardiovascular disease,and cancer.Therefore,development of tools for the visualization of endogenous H₂S will have important physiological and pathological implications for the in-depth study of endogenous H₂S production,transmission mechanisms and metabolism.Fluorescent probes have the advantages of high sensitivity,good selectivity,non-invasive damage to biological samples,real-time detection in real time,etc.They have been widely used in biomolecules detection,disease diagnosis,and environmental monitoring.At present,despite the variety and number of reported H₂S fluorescent probes,there are still problems of low sensitivity,poor selectivity,slow response rate,and unsuitable for live detection.Therefore,aiming at the above problems,this paper carries out the following work:The first part,design and synthesis a novel H₂S fluorescent probe based on NBD-N thiolysis.The nucleophilic substitution of H₂S,based on the PET effect of NBD,condenses the 8-o-,m-,and p-carboxyphenyl BODIPY dyes with NBD via piperazine to obtain fluorescent probes 4o,4m and 4p,respectively.The NBD in the probe is not only a fluorescence quenching group but also a novel H₂S reaction group.The three probes have higher selectivity for H₂S.Among them,the probe 4o with ortho-carboxylic acid attached to NBD is superior to 4m and 4p in terms of reaction rate and fluorescence enhancement factor,and the H₂S fluorescence in tobacco leaves was performed on probe 4o.The second par,design and synthesis a dual-reaction quenching H₂S fluorescent probes with matching reaction speed.Using the strong reducibility and nucleophilic substitution of H₂S,the azide coumarin and NBD were condensed by piperazine to obtain the probe 11b based on the aromatic azide ICT effect and the NBD FRET effect.The double-reactive group in the probe enhances the selectivity of the probe molecule.The double quenching effect makes the fluorescence enhancement factor 3,600 times before and after the probe reaction.At the same time,the introduction of an electron-withdrawing group（fluorine atom）at the ortho position of the azide group increases.The rate of reaction of the azide group matches the rate of thiolysis of NBD-N,thereby increasing the response rate of the entire probe.The fluorescence imaging of endogenous H₂S in live cells and zebrafish was performed on probe11b.The third part,design and synthesis a fast-response dual-reaction long-wavelength H₂S fluorescence probes.Based on the ICT principle of aromatic azide and the PET principle of NBD,using the strong reducing and nucleophilic substitution of H₂S,the azidoxanthene and NBD were condensed by piperazine to obtain the probe 17.The double-reactive group in the probe enhances the selectivity of the probe.The double quenching effect makes the fluorescence enhancement before and after the probe significantly better than that of the single quencher probes 14/16.The positive charge of the nitrogen atom increases the probe response.rate.Probe 17 has a mitochondrial targeting function and was successfully applied to the induction of endogenous H₂S production in HEK 293 cells and mouse imaging studies.