Synthesis And Application Studies Of SO₂/GSH Fluorescent Probes Based On Coumarin

Natural coumarin,an important heterocyclic compound,is widely found in many higher plants.Coumarin derivatives have many advantages,such as a large stokes shift,high fluorescence quantum yield,strong molar absorption coefficient and good light stability.These coumarin derivatives have great application values in the field of analysis,dyes,spices and medicine.Sulfur-containing compounds including sulfur dioxide and three thiols such as cysteine?Cys?,homocysteine?Hcy?and reduced glutathione?GSH?,have an irreplaceable role for maintaining the balance of the life system which regulate the physiological processes.Among them,SO₂ can be hydrolyzed to SO₃^2-and HSO₃^-?3:1,M/M?in physiological environment?pH 7.4?.Abnormal concentration levels of SO₃^2-/HSO₃^-and thiols are connected with many diseases,such as cancer,Alzheimer's disease,atherosclerosis and more.Therefore,the development of easy and reliable means of detection is particularly important.Small molecule fluorescent probes have the advantages of simple operation,high sensitivity,good selectivity,and real-time detection which arouse widespread concern of researchers.Based on this,this text designed and synthesized three coumarin-based small-molecule fluorescent probes.The spectroscopic properties and recognition properties of GSH/SO₃^2-/HSO₃^-were studied by UV-Vis spectrophotometer and fluorescence spectrophotometer.It has high clinical and bioscience values.This work divided into the following five parts mainly:The first part introduces the research and application of coumarin derivatives and the design ideas of this thesis.The second part synthesized and constructed coumarin-chloral?probe2-1?based on 3-N,N-diethylaminophenol,and carried out characterization experiments,which showed that probe 2-1 could be used to detect SO₃^2-/HSO₃^-with high selectivity.A 33-fold fluorescence increased when added SO₃^2-/HSO₃^-,which because of the fast-attack aldehyde group of the SO₃^2-/HSO₃^-to probe by nucleophilic addition.Also,the detection limit was as low as 8.8×10^-9 M.Cell imaging experiments showed that the probe had good cell membrane permeability,enabling visual detection of SO₃^2-/HSO₃^-intracellular.In the third part,probe 3-1 was synthesized on the basis of probe 2-1which added indole iodide to expand the conjugation of the system.We envisioned that 3-1 had more excellent properties such as probe's emission wavelength was in the near-infrared region.The structural characterization and UV-Vis/fluorescence spectra of probe 3-1 were studied.The results showed that probe 3-1 was only responsive to SO₃^2-/HSO₃^-in fluorescence.The fluorescence was significantly enhanced?approximately 46-fold?in the pure aqueous phase at 487 nm when a nucleophilic addition reaction occured with SO₃^2-/HSO₃^-.What's more,probe had a very low detection limit(1.1×10^-10 M),good cell membrane permeability,and could be successfully used for imaging studies of SO₃^2-/HSO₃^-in living cells.But,the response time was longer.Also,Cys,GSH,and HS^-could interfere the detection for SO₃^2-/HSO₃^-when the presence of them simultaneously.In the fourth part,probe 4-1 was prepared by the introduction of malononitrile on the basis of the probe 2-1,and the UV-Vis/fluorescence spectra were performed in DMSO-PBS buffer?pH 7.4,1:1,v/v?,indicating that the system responded rapidly for green fluorescence only when added GSH,but undisturbed by Cys,Hcy and other amino acids.Cell imaging experiments showed that the probe can specifically detect endogenous/exogenous GSH in living cells.The fifth part is summary and outlook.