| The small molecular biothiols inc luding hydrogen sulfide?H2S?,cysteine?Cys?,homocysteine?Hcy?and glutathione?GSH?are closely related with each other in biological systems.Fuctuations of H2 S may have a significant impact on Cys,Hcy,and GSH metabolism.Therefore,it is necessary to distinguish H2 S with Cys,Hcy,GSH reliably,which is benefic ial for gaining accurate diagnosis of the disease and better understanding influence each other in biological systems in recent ye ars.Fluorescence probe have attracted great attention in molecular recognition due to its high sensitivity,high selectivity,simplic ity and non-destructive visual detection.However traditional fluorescent probes cause fluorescence quenching?ACQ?in high concentration or solid state,which hinders its application seriously.The aggregation-induced fluorescence enhancement?AIE?phenomenon was discovered by Academic ian Tang Benzhong in 2001,which made up for this defect.Generally AIEgens have large Stokes shifts,high quantum yields,wavelengths red-shift in aggregated states.Based on this,several probes with AIE characteristics were synthes ized and characterized by high resolution mass spectrometry?ESI-MS?,1HNMR and IR.Subsequently,the AIE properties and the recognition properties of Cu2+,H2 S,Cys and GSH were studied using UV-Vis absorption spectroscopy and fluorescence emission spectroscopy.Finally,bioimaging studies were carried out.Specifically,it is mainly divided into the following five parts: 1.The properties of AIE,research progress of small molecule biothiol,the research significance and work of this paper was introduced.2.A new method of reducing the detection limit of H2 S in water by fluorescence resonance energy transfer?FRET?and AIE strategies was proposed.One simple fluorescent probe based on the condensation reaction of 5-chlorosalicylaldehyde,1-pyrenecarboxaldehyde with carbohydrazide was synthesized,which exhibited excellent AIE properties.In the presence of Cu2+,the green fluorescence at 525 nm was selectively quenched.1 was a good energy donor that happened energy transfer with the NiR dye to form 1-NiR system,which resulted in fluorescence decrease both NiR and 1 in the presence of Cu2+.On this basis,1-NiR-Cu2+ system was further constructed,and the system could restore the fluorescence of NiR and 1 in the presence of H2 S.As a result,the detection limit of 1 to Cu2+ was 0.132 ?M,and the detection limit of 1-NiR to Cu2+ was 9.12 n M.The detection limit of 1-Cu2+ to H2 S was 2.58 ?M,while the detection limit of 1-NiR-Cu2+ system to H2 S was 0.66 ?M.In conclusion,FRET and AIE strategies can reduce the detection limits of Cu2+ and H2 S,and it provided a new idea for the detection of substances with low intracellular content.3.With different substituent compounds 2-7 based on benzothiazole system were designed and synthesized.2,3,4 and 7 exhibited excellent AEE active compounds.In addition,2,3 and 7 can detect H2 S without interference of Cys and GSH and the detection limits of 2,3 and 7 for H2 S are 0.97 ?M,1.20 ?M and 0.48 ?M respectively.Most importantly,2,3 and 7 gained balance within 20 s towards H2 S,which has rarely been reported at so ultrafast rate so far.Subsequently,sensing mechanism of 2 with H2 S was nucleophilic addition reaction using ESI-MS and 1HNMR.Finally,cell imaging showed that 2 could detect exogenous H2 S.4.Two fluorescent probes based on HBT dyes 8,9 were designed and synthesized.The synthesis of 9 was introduced malononitrile on the basis of 8,and the introduction of malononitrile can not only increase the emission wavelength of 9 but also can be used as a reaction site for Cys,GSH.It is expected that it can distinguish H2 S and Cys,GSH.Therefore,the AIE properties of 8,9 and the recognization of thiols have been studied.8,9 exhibited excellent AIE,which emited strong fluorescence yellow and red in water respectively.8 exhibited ratiometric fluorescence change in the presence of H2 S with a detection limit of 0.46 ?M.Similarly,9 also showed ratiometric fluorescence change in the presence of H2 S with a detection limit of 8.72 ?M without responce to Cys and GSH.However,it is gratifying that the 9-H2 S system can detect Cys,GSH with ratiometric fluorescence change from green to yellow.In addition,the detection limits of Cys and GSH were: 2.5 ?M and 1.02 ?M,respectively.The mechanism investigation indicated that 9 did not respond to Cys,GSH,because the aggregation state of 9 inhibited activity of the cyanovinyl group,while the aggregation form of 9 was destroyed and the activity of the cyanovinyl group is activated resulting response of 9-H2 S to Cys,GSH in the presence of H2 S through p H,DLS.To the best of our knowledge,distinguishing H2 S and Cys,GSH using AIE aggregation and deaggregation and achieving the detection of Cys,GSH with the stimulation of H2 S is reported for the first time.5.Summary and outlook. |
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