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A Lanthanide Complex-Based Ratiometric Luminescence Probe for Time-Gated Luminescence Detection of Intracellular Thiols

Dai, Zhichao, Tian, Lu, Ye, Zhiqiang, Song, Bo, Zhang, Run, Yuan, Jingli
Analytical chemistry 2013 v.85 no.23 pp. 11658-11664
acetates, electron transfer, europium, luminescence, pH, thiols
A lanthanide complex-based ratiometric luminescence probe, [4′-(2,4-dinitrobenzenesulfonyloxy)-2,2′:6′,2′′-terpyridine-6,6′′-diyl] bis(methylenenitrilo) tetrakis(acetate)-Eu³⁺/Tb³⁺ (NSTTA-Eu³⁺/Tb³⁺), has been designed and synthesized for the specific recognition and time-gated luminescence detection of biothiols in physiological pH aqueous media. The probe itself is almost nonluminescent due to the presence of photoinduced electron transfer (PET) from the terpyridine-Ln³⁺ moiety to the 2,4-dinitrobenzenesulfonyl (DNBS) moiety. In the presence of biothiols, the reaction of NSTTA-Eu³⁺/Tb³⁺ with biothiols results in the cleavage of DNBS to afford the deprotonated (4′-hydroxy-2,2′:6′,2′′-terpyridine-6,6′′-diyl) bis(methylenenitrilo) tetrakis(acetate)-Eu³⁺/Tb³⁺ (HTTA-Eu³⁺/Tb³⁺), which terminates the PET process. After the reaction, the intensity of Eu³⁺ emission at 610 nm is unchanged, while that of Tb³⁺ emission at 540 nm is remarkably increased, which provides a ∼36-fold enhanced intensity ratio of Tb³⁺ emission to Eu³⁺ emission (I₅₄₀/I₆₁₀). This unique luminescence response allows NSTTA-Eu³⁺/Tb³⁺ to be used as a ratiometric probe for the time-gated luminescence detection of biothiols, using the intensity ratio of I₅₄₀/I₆₁₀ as a signal. Thus, based on the probe NSTTA-Eu³⁺/Tb³⁺, a ratiometric time-gated luminescence detection method for biothiols was established and successfully used for the quantitative detection of the total biothiols in several living cell samples.