Design,synthesis And Application Of Lysosome-targeting Sulfur Dioxide/Viscosity Fluorescent Probes

SO₂,mainly generated from sulfur-containing amino acids（eg.L-cysteine and glutathione）through biosynthetic pathways,participates in many physiological processes in term of bisulfite/sulfite(HSO₃^-/SO₃^2-,3:1,M/M,in neutral liquids).SO₂derivatives also play significant roles in our life,especially in foods and beverages preservation.However,the abnormal SO₂ exposure could affect the amount and activity of lysosomal enzymes in organisms,which will lead to some diseases even cancer.On the other hand,lysosomes maintain a high viscosity environment（47-190 c P）to ensure their normal functions of breaking down cellular waste.In fact,the viscosity change has been regarded as an important benchmark of lysosomal functionality.Consequently,it is of great significance to develop lysosome-targeted high-sensitivity organic small molecule fluorescent probes to monitor various biological small molecules in lysosomes.In this paper,we have synthesized three novel fluorescent probes for the detection of HSO₃^-/viscosity.Based on a series of basic characterizations,the sensing mechnisims of probes to HSO₃^-/viscosity were verified.The biological imaging studies and the experiments for quantitative detection HSO₃^-in real samples were successfully conducted.The main contents of this paper are as follows:（1）Probe 1 is a ratiometric fluorescent probe,synthesized by the condensation reaction between quinolone derivatives and ethyl cyanoacetate.It exhibites high selectivity towards HSO₃^-in 4-（2-hydroxyerhyl）piperazine-1-erhanesulfonic acid（50m M,p H=5）buffer solution with the detection limit of 0.24μM.In addition,1 has been successfully utilized to monitor endogenous and exogenous HSO₃^-in live C6 glioma cells,and quantitatively detect HSO₃^-in water samples.（2）A based-hemicyanidin fluorescent probe 2 has been used for the dual detection of bisulfite and viscosity.In the mixture solution of HEPES/DMSO,it shows high selectivity and sensitivity to HSO₃^-with the detection limit of 0.78μM.Probe 2 can also monitor viscosity with high selectivity.Moreover,probe 2 has been successfully utilized to image lysosomal HSO₃^-and visosity in living C6 glioma cells.The test paper experiment was successfully applied for detecting HSO₃^-by using the colorimetric method.（3）Probe 3 was obtained by the condensation reaction of quinolone derivatives and 2-dicyanomethylene-3-cyano-4,5,5-trimethyl-2,5-dihydrofuran（TCF）,which can detect HSO₃^-based on Michael addition reaction in an almost pure HEPES buffer solution,the detection was caculated to be 0.37μM.In addition,probe 3 can also monitor viscosity based on twisted intramolecular charge transfer（TICT）Importantly,3 has been successfully utilized to monitor HSO₃^-and viscosity in lysosomes of C6 glioma cell and in zebrafish,and can be applied for quantitative detection of HSO₃^-in real water samples.