| Compared with traditional techniques such as colorimetry,electrochemical analysis and chromatography,fluorescent probe technology has become one of the most popular methods because of its simple preparation,strong adaptability,targeted combination and real-time detection.Among these technologies,near-infrared fluorescence probe has less radiation energy,which can reach deeper tissue level,reduce the interference of bio-spontaneous fluorescence,improve detection sensitivity and selectivity,and less light damage to samples.So it can be better applied in living cell fluorescence imaging or in vivo fluorescence imaging.Ratiometric fluorescence probe can quantitatively detect trace substances by the ratio of two emission wavelengths,and the results will be more accurate.Therefore,the near-infrared ratiometric fluorescent probe combining the two technologies of near-infrared fluorescence and ratio emission shows greater advantages and application prospects.Reactive sulfur species(RSS)is a kind of sulfur-containing reactive molecule in organisms,including H2S and SO2 and their derivatives.Among them,H2S exists mainly in the form of HS"in aqueous solution.Once H2S is at an abnormal level,it may lead to Parkinson's disease,Alzheimer's disease,diabetes,cirrhosis and other diseases.Although H2S has many physiological roles in cell and animal studies,the precise molecular targets of H2S are still unclear,so it is still an important research direction.On the other hand,SO2 is not only an atmospheric pollutant with strong irritating odor,but also plays an important role in the life system.Therefore,quantitative detection of these two reactive sulfur compounds is of great significance to both environmental and biological systems.The standpoint of this paper is the intersection of environmental science,organic chemistry,analytical chemistry and biological science.Taking advantage of the excellent photophysical properties,good biocompatibility and easy regulation of fluorescence mechanism of flavylium derivative,two near infrared ratiometric fluorescence probes were designed and synthesized,which were used for the detection of H2S and SO2,respectively.1?The coumarin 334 was synthesized from 8-hydroxygiulonide,which contains semi-rigid cyclohexyl group and has a higher fluorescence quantum yield.Then it reacted with 4-(diethylamino)salicylaldehyde and 2,4-dihydroxyformaldehyde to obtain two novel near infrared ratiometric fluorescence probes,NIR-H2S and NIR-SO2,respectively.The two compounds were characterized by 1H NMR,13C NMR and MS,and their molecular structures were determined.2?NIR-H2S has been successfully used for the detection of H2S in aqueous and living cells.The experimental results show that with the increase of H2S concentration,the absorbance increases at 437 nm and decreases gradually at 674 nm.Meanwhile the fluorescence intensity of NIR-H2S probe increases gradually at 503 nm,while the fluorescence signal in near infrared region decreases,showing a typical ratio emission mode,accompanied by obvious solution color change(blue-green to yellow).On the other hand,the probe can quickly and selectively recognize H2S(110s)under physiological conditions.The probe has also been successfully used in fluorescence imaging of exogenous and endogenous H2S in living HepG2 cells,indicating its potential application in biological field.3?NIR-SO2,a near infrared ratiometric fluorescence probe designed and synthesized with flavylium derivative as its parent,has also been successfully used for the detection of SO2.Experiments show that the probe NIR-SO2 can selectively recognize SO2 under physiological conditions(<3min),accompanied by obvious color change(blue to light green)and ratio-type fluorescence spectrum change.In addition,the probe NIR-SO2 can also be made into a simple test strip,through different color changes to achieve rapid detection of SO2,which also shows that the probe has good application prospects. |
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