A water-soluble fluorescence resonance energy transfer (FRET) probe for hypochlorous acid (HOCl), dansyl rhodamine B piperazinoacetohydrazide, was designed, synthesized and characterized. The dansyl moiety in the probe acted as a FRET donor and the rhodamine moiety acted as a FRET acceptor. The two moieties were connected by a HOCl-cleavable active bond, and cleavage of this linker decreased the FRET efficiency and increased the fluorescence intensity of the donor at 501 nm. The water solubility of the probe was improved compared with other probes by introduction of the cationic rhodamine fluorophore. As a result, the probe could be used to detect HOCl in aqueous biosystems with a linear range of 2-10 mol/L and a detection limit of 80 nmol/L (signal- to-noise = 3). The probe was successfully applied to fluorescence imaging of HOCl in HeLa cells.
A novel fluorescent nanoprobe for glutathione S-transferase （GST） has been developed by incorporating 3,4-dinitrobenzamide （a specific substrate of GST） onto CdTe/ZnTe quantum dots. The probe itself displays a low background signal due to the strong quenching effect of the electron-withdrawing unit of 3,4-dinitrobenzamide on the quantum dots. However, GST can efficiently catalyze the nucleophilic substitution of reduced glutathione on the p-nitro group of the nanoprobe, leading to a large fluorescence enhancement. Most notably, this enhancement shows high selectivity and sensitivity towards GST instead of the other biological substances. With this nanoprobe, a simple fluorescence imaging method for intracellular GST has been established, and its applicability has been successfully demonstrated for imaging GST in different living cells, which reveals that A549 cells express GST about 3 times higher than NIH-3T3 and Hela cells.
Jinxin Lu Yanchao Song Wen Shi Xiaohua Li Huimin Ma
