Construction And Properties Of Semi Cyanine Fluorescent Probe For Detecting SO₃^2- And PH Value In Cells

With the development of modern biology and analytical techniques,fluorescent probes,as important technical tools,have been applied in various fields,for example,fluorescent probes can be used to detect biomolecules in biological systems for biometric imaging.Therefore,the development of fluorescent probes with excellent properties becomes the hotspot in recent years.The absorption and emission spectra of dye molecules with hemicyanine structure are located in the near-infrared region,so this kind of probes have the advantages of great penetrability of biological tissues,little optical damage to biological tissue samples,and little influence from biological spontaneous fluorescence,so fluorescent probes with hemicyanine structure are favored.Based on the excellent properties of the hemicyanine dyes mentioned above,two new types of ratio fluorescent probes based on the hemicyanine structure were synthesized by introducing different modification groups,and finally applied to the detection of SO₃^2-and pH values in living cells respectively.(1)In this paper,four ratio and zero cross-talk fluorescent probes based on hemicyanine quaternary aminated with coumarin for detecting SO₃^2-were synthesized.The spectral measurement,selectivity and stability of the probes to SO₃^2-were studied.The mechanism study shows that 1,4-conjugate addition of the probe to sulfites was happened,which blocks the ICT process of the probe,thus the ratio recognition of the probe towards sulfites was realized.In addition,these probes were investigated for cytotoxicity,mitochondrial targeting and detection of endogenous and exogenous SO₃^2-.The experimental results show that these four fluorescent probes can be successfully used to detect endogenous or exogenous sulfites in living cells.In summary,it was found that the indole quaternary aminated with coumarin can effectively increase the shift of fluorescence emission peak,and the probes with the coumarin derivatives into the conjugate system own a larger emission peak shift and better performance.(2)In this paper,two novel ratio fluorescent probes for detecting pH values were synthesized by introducing bromoethanol into a coumarin conjugated hemicyanine system.Under alkaline environment,the fluorescent intensity of the maximum emission peak of this probe decreased and the fluorescent intensity of the maximum emission peak increases in the acid condition.In addition,the shift between two emission peaks of the two probes are large(159 nm and 169 nm respectively),which can reduce the cross interference of the two emission peaks.The mechanism study shows that in the alkaline environment,the nucleophilic addition of the probe happened,causing the ring-closure,the conjugate system was broken,and the fluorescent intensity decreased,then adjusted to the acidic environment,the proton can induce the ring of carbazol-oxazolidine system open,so that the fluorescence intensity can be restored.In addition,cytotoxicity,mitochondrial targeting and recognition of intracellular acids and bases were also studied.The results show that these two zero cross-talk fluorescent probes can be used to detect and image the change of pH values in cell microenvironment.