Syntheses And Bioimaging Applications Of Novel Lanthanide Complex-Based Luminescent Probes

Time-gated(or time-resolved)luminescence bioassay technique using lanthanide complexes as luminescent probes allows effective elimination of the effect of background fluorescence,which enables it to be widely useful in various highly sensitive bioassays.Design and synthesis of lanthanide complex-based luminescence probes that can specifically recognize bioactive species to give luminescence responses are the key essential for the development and application of this technique.In this doctoral dissertation,through suitable structure modifications of the ligands,several new lanthanide complex-based luminescence probes that can specifically respond to HOCl and biothiols have been designed and synthesized.After characterization of the properties,the applicability of the probes for time-gated luminescence bioimaging was explored.By introducing a 2,4-dinitrophenyl-hydrazine moiety to a terpyridine polyacid-Eu3+luminophore,a Eu(Ⅲ)complex-based luminescence probe that can specifically respond to HOCl,NPPTTA-Eu3+,was designed and synthesized.The presence of intramolecular photoinduced electron transfer(PET)makes the probe’s luminescence be quenched,while the reaction of the probe with HOCl allows dinitrophenyl to be cleaved,to enable the luminescence of Eu(Ⅲ)complex to be restored.The luminescence response of the probe to HOCl is rapid and specific,which enabled it to be used for the highly sensitive time-gated luminescence detection of HOCl in aqueous media(detection limit,1.1 nM).Using this probe,the luminescence imagings of endogenous HOClgenerated in living RAW 264.7 cellsand exogenous HOCl up-taken by Daphnia magna were successfully realized.By incorporating a mitochondria-anchoring motif,triphenylphosphonium(TPP),and a p-nitropheny1-thioester moiety to a terpyridine polyacid-Eu3+ complex luminophore,a Eu3+ complex-based mitochondria targetable luminescence probe for HOCl,Mito-NPSTTA-Eu3+,was designed and synthesized.The presence of intramolecular PET makes the probe’s luminescence be quenched,while the reaction of the probe with HOCl allows the cleavage of the dinitrophenyl-thioester,to enable the luminescence of Eu(III)complex to be restored.The mitochondria-targeting feature of the probe was demonstrated by the co-localization imaging experiments of the probe with Mito-Tracker Green in living cells(Pearson’s correlation coefficient ＝0.934).The luminescence response of the probe to HOCl has advantages of highspecificity and sensitivity,wide pH available range and rapid response,which enabled it to be successfully used for the time-gated luminescence imaging of endogenous HOClgenerated in living RAW 264.7 cells.By incorporating a triphenylphosphonium(TPP)moiety and a 2,4-dinitrobenzenesulfonyloxy moiety to a terpyridine polyacid ligand,a mitochondria targetable ratiometric luminescence probe based on the mixed Eu(III) and Tb(Ⅲ)complexes for biothiols,Mito-NSTTA-Eu3+/Tb3+,was designed and synthesized.Upon reaction with biothiols,the Tb(Ⅲ)emission of the probe was switched on,while the Eu(Ⅲ)emission of the probe was unchanged,which allowed Mito-NSTTA-Eu3+/Tb3+ to be used as a ratiometric probe for the time-gated luminescence detection of biothiols.The mitochondria-targeting feature of the probe was demonstrated by the co-localization imaging experiments of the probe with Mito-Tracker Red in living HeLa cells(Pearson’s correlation coefficient = 0.950).Using this probe,the luminescence imaging of endogenous biothiols in living RAW264.7 cells and the quantitative detection of biothiols in several single cells were realized.