Reaction-Based Fluorescence Probes And Their Application For Bioimaging

Compared with the fluorescent probes based on weak interaction between subject and object,reaction-based fluorescent probes exploit chemical reaction of analytes to modulate fluorescence change,so they have certain advantages in selectivity and sensitivity.Nowadays it has been a hot research field of fluorescence sensing,and it has been widely used in real-time monitoring and imaging of small molecules or ions related to biology.This thesis focuses on the messenger molecule biological hydrogen sulfide,mercaptan,reactive oxygen species-hypochlorous acid which can regulate important physiological and pathological functions,combined with specificific chemical reaction and addition,this paper also employs specific chemical reaction by 2-?phenylethynyl?aniline derivatives with Au³⁺,and constructs a highly selective fluorescent probes recognizing Au³⁺,which provides a visualization tool for the study of pharmacological and pathological roles of ions.The related contents are as follows:?1?Based on the 5?6?-carboxyl-rhodamine as the fluorophore and7-nitro-1,2,3-benzoxadiazole?NBD?as the recognition unit,a fluorescent probe 2-1a for the biological gasotransmitter-hydrogen sulfide?H₂S?,and a fluorescent probe 2-1b for the biothiols have been designed and synthesized by exploiting the Spiroring-“Open and Close” mechanism and Photo-induced Electron Transfer mechanism?PET?respectively.In PBS buffer?10 mM,pH=7.4,1 mM CTAB?,probe 2-1a mainly exists in a nonfluorescence spirocyclic form,and releases the ring-opening rhodamine after the thiolysis of NBD amine moiety of the probe by H₂S,with solution color changing from colorless to pink,and fluorescence enhancement of160-fold.Further biological experiments show that the probe can be used to image endogenous H₂S in HeLa cells.In PBS buffer?10 mm,pH 7.4?,the probe 2-1b mainly exists in the ring-open form.Because of the PET from the rhodamine fluorophore to the NBD group,probe itself is nonfluorescent;the NBD amine unit is thiolysised by Cys,and causes turn-on fluorescenceaccompanied with the obvious enhancement.The detection limit is 2.8×10-8mol/L.?2?A mitochondria-targetable fluorescent probe3-1with detection of hypochlorous acid?HOCl?is designed and synthesized,which is based on a naphthalimide as the fluorophore,selenomorpholine as the recognition site and triphenylphosphonium salt as the mitochondria located group.In the PBS buffer solution?20 mM,pH=7.4?,the probe is nonfluorescent.Upon treatment with HOC1,the fluorescence of probe 3-1 would boost because of the hampered PET process induced by the formation of selenoxide.The probe is of high sensitivity,and 1 equivalent of HOCl can cause the fluorescence enhancement of 40-fold,with the detection limit of 4.8nM for HOCl;probe 3-1 exhibits excellent selectivity for HOCl,and other reactive oxygen species can cause negligible fluorescence response.Further studies show that the probe could selectively locate the mitochondria,and realize reversible detection of extra and endogenous HCOl in RAW246.7 cells.?3?A fluorescent probe 4-1 for Au³⁺ of high selectivity is constructed based on a boron dipyrromethene?BODIPY?derivative as a core and 2-?phenylethynyl?aniline as the recognition unit.In the ETOH-PBS buffer solution?20 mM,1:1,v/v,p H=7.4?,the probe is no almost fluorescence due to photoinduced intramolecular electron transfer from the aniline unit to Bodipy moiety,whereas transforming the 2-?phenylethynyl?aniline unit into the 2-phenylindole by Au³⁺ induced intramolecular cyclization reaction gives rise to strong fluorescene emission.Probe 4-1 can recognize Au³⁺ selectively,and other metal cations could not form obvious interference.Further studies point out that probe 4-1 can be used for the detection of Au³⁺ in water samples,serum and Hala cells.