Syntheses And Properties Of Biothiols Fluorescent Probe Based On 1,3-indandione

Cysteine（Cys）,homocysteine（Hcy）and glutathione（GSH）are abundant small molecule biothiols in living organisms.Each of the three biothiol molecules contains a sulfydryl（-SH）and an amino group（-NH₂）.Hence,they have relatively similar molecular structures and chemical properties,and are closely related to cell redox homeostasis in biological systems and a variety of diseases.Nevertheless,most of the reported fluorescent probes for biothiols possess longer response time.Consequently,it is of great clinical and medical value to construct a simple,sensitive and rapid detection of biothiols fluorescent probes.In this thesis,three kinds of fluorescent probes P11,P21 and P31 based on ICT effect were designed and synthesized for biothiols.Both probes P11 and P21 used trianiline-4-boric acid as starting material to undergo Suzuki coupling reaction with4-bromobenzaldehyde and 5-bromothiophene-2-carbaldehyde,respectively.The aldehyde compounds obtained from Suzuki coupling reactions were further condensed with 1,3-indandione to obtain probes P11 and P21.Probe P31 was prepared by the condensation reaction of 9-ethyl-9H-carbazole-3-carboxaldehyde with 1,3-indandione.The structures of probes P11,P21 and P31 were characterized by ¹H NMR,¹³C NMR and high resolution mass spectrometry（HR-MS）.Each of probes P11,P21 and P31 possesses the advantages of longer emission wavelength,larger Stokes shift,rapid response,reliability in a wide range of p H,excellent selectivity,and can recognize biothiols by"naked eye".Probe P11 can rapidly respond to Cys,GSH,and Hcy within 90 s,with detection limits as low as33.9μM,29.0μM,and 34.3μM,respectively(λ_ex=475 nm,λ_em=690 nm).Probe P21can quickly recognize Cys,GSH and Hcy within 30 s,with detection limits of 10.1μM,7.6μM and 4.3μM,respectively(λ_ex=535 nm,λ_em=755 nm).Probe P31 can promptly recognize Cys,GSH and Hcy within 10 s,with detection limits of 23.5μM,16.2μM and 22.9μM,respectively(λ_ex=470 nm,λ_em=600 nm).Simultaneously,the longer emission wavelength and larger Stokes shift of probes provide possibilities for in vivo bioimaging applications.The sensing mechanism of the three biothiols probes can be attributed to the fact that the ICT process of the probes were blocked by Michael addition reaction of the electron-deficient C=C double bonds and the sulfydryls of biothiols,resulting in the fluorescence quenching of the probes.The recognition mechanisms of probes toward biothiols were convincingly demonstrated by spectral analysis,HR-MS titration analysis and density functional theory（DFT）calculations.More importantly,probes P11 and P21 have been successfully applied to fluorescence imaging of endogenous and exogenous biothiols in mice in vivo,three probes provided effective methods for the diagnosis of biothiols-related diseases.