Design And Synthesis Of Novel Sulphur Dioxide And Thiophenol Fluorescent Probe And Their Application In Foods And Biological Systems

Sulfur dioxide(SO2)and phenylthiophenol(PhSH),as reactive sulfur substances(RSS),have a wide range of uses in the food industry and its related biological research fields.However,illegal use or emissions in food or the environment can lead to excessive levels of SO2 and PhSH.Therefore,it is of great practical importance to establish efficient,sensitive and accurate analytical methods for the accurate identification and quantitative analysis of sulfides.Compared with traditional electrochemical and chromatographic analysis methods,fluorescence spectrometry method has attracted much attention for its advantages of simple operation,in situ real-time detection,high sensitivity,good selectivity,non-invasive and high spatial resolution.In view of this,we developed three new fluorescent probes by rational design with excellent optical properties,large Stokes shift,high biocompatibility and other advantages to achieve accurate,efficient and rapid detection and imaging analysis of SO2 and PhSH in relevant food,environmental and biological samples.Specific research work is as follows:1.In this chapter,a smart fluorescent probe DSF was designed for the rapid detection of PhSH and SO2(SO2+H2O#H2SO3)by selecting a fluorophore with superior optical properties and a double recognition group with chemical specific response to PhSH and bisulfite(HSO3-).To improve the chemical stability of the dye,the structure of the dye was modified by introducing carboxyphenyl groups to prevent the effect of pH fluctuations on the it.The probe has two known response sites,a 2,4-dinitrophenyl ether group(with a strong intramolecular charge transfer(ICT)effect)serves as the recognition site for PhSH and a α,β-unsaturated group(capable of rapid Michael addition reactions)serves as the response site for HSO3-:The former can be sulfated by PhSH,while the latter can undergo a nucleophilic addition reaction with HSO3-thereby destroying the π-system of the fluorophore.The phenomenon differs when DSF has different reaction order with PhSH and HSO3-.When DSF reacts with PhSH first,the color of the solution changes to blue and emits bright red fluorescence.Then adding HSO3-to it,the color of the solution changes from blue to yellow and emitted a bright yellow fluorescence signal.While DSF was added to HSO3-first,the solution color changed to purple with no fluorescence,and then added to PhSH,the color of the solution changes from purple to yellow and emitted a bright yellow fluorescence.It is noteworthy that DSF has high sensitivity and selectivity for the detection of PhSH and HSO3-,the limits of detection(LOD)were as low as 2.27 nM and 22.91 nM,respectivel.More importantly,DSF can detect PhSH and HSO3-in water,real food and biological systems.Therefore,the experimental results suggest that DSF is a reliable novel logical detecting tool for the detection of PhSH and HSO3-in water,real food samples and biological systems.2.The coumarin dyes were modified to synthesize the fluorescent probes CM-PhSH and CM-Ratio-PhSH for the rapid detection of PhSH in food and biological systems,respectively.Although the response mechanisms of the probes were all constructed based on the Michael addition reactions of α,β-unsaturated units,and the structural differences between the two probes are small,the optical signals are completely different.The construction of CM-Ratio-PhSH is mainly based on the synthetic design of CM-PhSH,and the fluorescent probe CM-Ratio-PhSH was synthesized by introducing a nitro at the hydroxyl counterpart of CM-PhSH.Due to the special property of hydroxy-para-nitro group(emission wavelength redshift),CM-Ratio-PhSH probe has a larger emission wavelength than CM-PhSH probe(no obvious fluorescence signal at 480 nm),with a maximum emission wavelength of 552 nm and an orange fluorescence signal.In the spectroscopic exploration of CM-Ratio-PhSH on PhSH,the response of CM-Ratio-PhSH with PhSH was accompanied by the appearance of a new emission peak at 482 nm,and with the increasing concentration of PhSH,the emission spectrum at the long wavelength of 552 nm gradually decreased and the fluorescence intensity of the emission peak at the short wavelength of 482 nm gradually increased,which can achieve the ratio detection of PhSH.In contrast,CM-PhSH fluorescent probe itself showed no obvious fluorescence signal at 480 nm,and the fluorescence intensity of the emission peak at 480 nm gradually increased with the increasing concentration of PhSH.The CM-PhSH and CM-Ratio-PhSH probes showed good linearity in the concentration range of 0-1.0 μM PhSH,and their LOD values were as low as 32.3 nM and 40.2 nM,respectively,and other relevant interferents do not interfere with the response performance of the probes.Ultimately,CM-Ratio-PhSH exhibited favorable detection and imaging capabilities in shiitake mushroom samples and were applied to the detection of PhSH in shrimp models.