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Hypochloric acid (HOCl) plays important roles in cell signaling and homeostasis, such as anti-inflammation and immune regulation, pathogen response and so on. Accordingly, direct detection of HOCl at the organelle level is important for investigation of the complex contributions of HOCl to human health. In the present study, a water soluble lysosome-targeting fluorescent probe Lyso-1 bearing a hydrazone moiety as a HOCl-responsive site and a morpholine unit as a lysosomal-targeting group has been synthesized and evaluated for its ability to image lysosomal HOCl. The probe Lyso-1 , based on a novel HOCl-promoted hydrazone oxidation strategy, showed a highly selective fluorescent off/on response to HOCl with the various reactive oxygen species in water. With increasing amount of ClO − from 0.5 to 2.5 μM, a linear correlation between the fluorescence intensity (570 nm) of Lyso-1 and [ClO − ] was found, and the regression equation was y = 96.65 + 110.2068[ClO − ] with a linear coefficient R of 0.9920. The detection limit is determined to be 60 nM. Lyso-1 demonstrated a perfect lysosomal targetable ability, and was successfully applied to image of exogenous, endogenous produced lysosomal HOCl in live L929 cells. The success of subcellular imaging indicated that the lysosome-targetable probe Lyso-1 could be used in further applications for the investigation of biological functions and pathological roles of HClO at organelle levels. [ABSTRACT FROM AUTHOR]

A rhodamine spirolactam derivative ( 1 ) bearing a hydrophilic carboxylic acid group is developed as a fluorescent chemodosimeter for bivalent mercury ions (Hg 2+ ) in 100% aqueous solution. It exhibits a highly sensitive “turn-on” fluorescent response toward Hg 2+ with a 42-fold fluorescence intensity enhancement under 1 equiv. of Hg 2+ added. The chemodosimeter can be applied to the quantification of Hg 2+ with a linear range covering from 3.0 × 10 −7 to 1.0 × 10 −5 M and a detection limit of 9.7 × 10 −8 M. Most importantly, the fluorescence changes of the chemodosimeter are remarkably specific for Hg 2+ in the presence of other metal ions, which meet the selective requirements for practical application. Moreover, the experiment results show that the response behavior of 1 towards Hg 2+ is pH independent in neutral condition (pH 5.0–8.0) and the response is fast (response time less than 3 min). Furthermore, the ring-opening mechanism of the rhodamine spirolactam induced by Hg 2+ was supported by NMR, MS, and DFT theoretical calculations. In addition, the proposed chemodosimeter has been used to detect Hg 2+ in water samples and image Hg 2+ in living cells with satisfying results. [ABSTRACT FROM AUTHOR]

A new colorimetric and fluorogenic probe ( RN 3 ) based on rhodamine-B has been successfully designed and synthesized. It displays a selective response to Hg 2+ in the aqueous buffer solution over the other competing metals. Upon addition of Hg 2+ , the solution of RN 3 exhibits a ‘naked eye’ observable color change from colorless to red and an intensive fluorescence with about 105-fold enhancement. The changes in the color and fluorescence are ascribed to the ring-opening of spirolactam in rhodamine fluorophore, which is induced by a binding of the constructed receptor to Hg 2+ with the association and dissociation constants of 0.22 × 10 5 M −1 and 25.2 μM, respectively. The Job's plot experiment determines a 1:1 binding stoichiometry between RN 3 and Hg 2+ . The resultant “turn-on” fluorescence in buffer solution, allows the application of a method to determine Hg 2+ levels in the range of 4.0–15.0 μM, with the limit of detection (LOD) calculated at 60.7 nM (3σ/slope). In addition, the fluorescence ‘turn-off’ and color ‘fading-out’ happen to the mixture of RN 3 -Hg 2+ by further addition of I − or S 2− . The reversible switching cycles of fluorescence intensity upon alternate additions of Hg 2+ and S 2− demonstrate that RN 3 can perform as an INHIBIT logic gate. Furthermore, the potential of RN 3 as a fluorescent probe has been demonstrated for cellular imaging. [ABSTRACT FROM AUTHOR]

A rhodamine–cyanobenzene conjugate, ( E )-4-((2-(3′,6′-bis(diethylamino)-3-oxospiro[isoindoline-1,9′-xanthene]-2-yl)ethylimino)methyl)benzonitrile ( 1 ), which structure has been elucidated by single crystal X-ray diffraction, was synthesized for selective fluorescent “turn-on” and colorimetric recognition of hydrazine at physiological pH 7.4. It was established that 1 detects hydrazine up to 58 nM. The probe is useful for the detection of intracellular hydrazine in the human breast cancer cells MCF-7 using a fluorescence microscope. Spirolactam ring opening of 1 , followed by its hydrolysis, was established as a probable mechanism for the selective sensing of hydrazine. [ABSTRACT FROM AUTHOR]

A rhodamine spirolactam derivative ( 1 ) is developed as a colormetric and fluorescent probe for trivalent aluminum ions (Al 3+ ). It exhibits a highly sensitive “turn-on” fluorescent response toward Al 3+ with a 70-fold fluorescence intensity enhancement under 2 equiv. of Al 3+ added. The probe can be applied to the quantification of Al 3+ with a linear range covering from 5.0 × 10 −7 to 2.0 × 10 −5 M and a detection limit of 4.0 × 10 −8 M. Most importantly, the fluorescence changes of the probe are remarkably specific for Al 3+ in the presence of other metal ions, which meet the selective requirements for practical application. Moreover, the experiment results show that the response behavior of 1 towards Al 3+ is pH independent in neutral condition (pH 6.0–8.0) and the response of the probe is fast (response time less than 3 min). In addition, the proposed probe has been used to detect Al 3+ in water samples and image Al 3+ in living cells with satisfying results. [ABSTRACT FROM AUTHOR]

Abstract: A colorless and non-fluorescent rhodamine derivative, rhodamine B hydrazide (RH), is applied to detect nitric oxide and form fluorescent rhodamine B (RB). The reaction mechanism of RH with NO is proposed in this study. The probe shows good stability over a broad pH range (pH>4). Furthermore, fluorescence intensity of RH displays an excellent linearity to the NO concentration and the detection limit is as low as 20nM. A 1000-fold fluorescence turn-on from a dark background was observed. Moreover, the selectivity study indicated that the fluorescence intensity increasing in the presence of NO was significantly higher than those of other reactive oxygen/nitrogen species. In exogenously generated NO detection study, clear intracellular red fluorescence was observed in the presence of S-nitroso-N-acetyl-D,L-penicillamine (SNAP, a kind of NO releasing agent). In endogenously generated NO detection study, increasing incubation time of RH with lipopolysaccharied (LPS) pre-treated cells could obtain a highly fluorescent cell image. These cell imaging results demonstrated that RH can efficiently penetrate into Raw 264.7 cells and be used for detection of exogenously and endogenously generated nitric oxide. [Copyright &y& Elsevier]