The Construction And Imaging Application Of Fluorescent Probes For Bioactive Substances

Bioactive substances are involved in a variety of life activities in the human body,and their abnormal concentration or activity is closely related to the occurrence of a series of diseases.Thanks to the advantages of excellent biocompatibility and high spatial and temporal resolution of fluorescent probes,they are used in different industries and domains.Fluorescent probes can visualize the expression of bioactive substances,which can help researchers to explore the relationship between bioactive substances and diseases.In this thesis,three new fluorescent probes were built to detect and image the level of cysteine(Cys),?-glutamyl transpeptidase(GGT)and sulfur dioxide(SO₂).1.A near-infrared fluorescent probe IX with a large Stokes shift was constructed by linking the isophorone derivative with xanthenes.After the reaction between IX and Cys,there was a strong NIR fluorescence emission at 770 nm with a Stokes shift of 180 nm.IX can selectively image the level of Cys in cells.Finally,the fluorescent probe was injected into HCT116 xenograft tumor mice,and found that IX could visualize Cys in tumor mice.On the one hand,the experiments of fluorescence imaging in mice confirmed that the concentration of Cys in tumor is overexpressed.On the other hand,it shows the potential of IX for early diagnosis of tumor.2.As an active enzyme,GGT is closely related to the progression of a series of illness,and can also be used as a biomarkerof tumor.A new fluorescent probe called IX-GSH was built through an addition reaction on the basis of the previous chapter to detect the activity of GGT.After the reaction of IX-GSH with GGT,there was a strong NIR fluorescence emission at 770 nm with a Stokes shift of 180 nm.IX-GSH can detect the activity of GGT under physiological conditions and it has the potential to screen GGT inhibitors.In the experiments of fluorescence imaging in cells,contrary to HCT116 cells,RAW264.7 cells did not produce any fluorescence signal,because the activity of GGT in normal cells is low.Therefore,IX-GSH is expected to be an excellent tool to distinguish between normal cells and cancer cells.In the end,IX-GSH successfully imaged GGT in HCT116 xenograft tumor mice.3.Using 1,1,2-trimethylbenzindole,methyl iodide and p-hydroxybenzaldehyde as raw materials,a ratiometric fluorescent probe BB was synthesized through a simple reaction process to detect SO₂.BB itself produced a strong fluorescence emission at582 nm under the excitation of 516 nm.When BB reacted with SO₂,the fluorescence emssion intensity at 582 nm was decreased.In contrast,a new fluorescence signal appeared at 484 nm under the excitation of 320 nm,and the fluorescence intensity was increased with the increase of the concentration for SO₂.Finally,BB was successfully applied to the fluorescence imaging for the different concentrations of SO₂in human liver cancer cells(Hep G2).