Chromogenic sensing of biological thiols using squarylium dye (original) (raw)
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Tetrahedron Letters, 2011
Two fluorescence probes for the detection of cysteine (Cys), glutathione (GSH) and other biothiols, such as homocysteine (Hcy) and cysteinyl-glycine (Cys-Gly), were developed. These molecular probes are coumarin-based derivatives containing a chalcone-like moiety that reacts with biothiols through a Michael addition reaction, leading to strong fluorescence enhancements. The reactivity of the tested biothiols toward both probes (ChC1 and ChC2) follows the order Cys > GSH > Hcy > Cys-Gly, ChC1 being less reactive than ChC2. Possible interference with other amino acids was assessed. ChC1 and ChC2 display a highly selective fluorescence enhancement with thiols, allowing these probes to be used for fluorimetric thiol determination in SH-SY5Y cells.
Fluorescence-based detection of thiols in vitro and in vivo using dithiol probes
Analytical Biochemistry, 2006
Thiols play a central role in maintaining biological homeostasis. Their levels can change dramatically in response to oxidative stress associated with toxic insults, bacterial infection, and disease. Therefore, a reagent that can monitor thiol levels both in vitro and in vivo would be useful for assays and as a biomarker. Such a reagent should (i) be selective for thiols, (ii) be able to penetrate cell walls, and (iii) have a low reduction potential so as not to create oxidative stress in a cell. We have developed such a fluorescent reagent (DSSA) based on a dithiol linker: (i) the use of a dithiol linker makes it selective for thiols; (ii) the use of fluorophores that populate neutral states at physiological pH improves cell wall penetration; and (iii) because of the reagent's low reduction potential (À0.60 V), it will not stress cells oxidatively. For example, 5 lM of reagent is responsive to changes in glutathione levels in the physiologically relevant range of 1 to 10 mM, yet this would oxidize less than 1% of cellular glutathione. In Escherichia coli, decreased thiol levels were detected in cells deficient in glutathione synthesis. In zebrafish embryos, the DSSA reagent permitted detection of unusually high thiol levels in the zebrafish chorion.
Thiol Reactive Probes and Chemosensors
2012
Thiols are important molecules in the environment and in biological processes. Cysteine (Cys), homocysteine (Hcy), glutathione (GSH) and hydrogen sulfide (H 2 S) play critical roles in a variety of physiological and pathological processes. The selective detection of thiols using reaction-based probes and sensors is very important in basic research and in disease diagnosis. This review focuses on the design of fluorescent and colorimetric probes and sensors for thiol detection. Thiol detection methods include probes and labeling agents based on nucleophilic addition and substitution, Michael addition, disulfide bond or Se-N bond cleavage, metal-sulfur interactions and more. Probes for H 2 S are based on nucleophilic cyclization, reduction and metal sulfide formation. Thiol probe and chemosensor design strategies and mechanism of action are discussed in this review.
Sensors and Actuators B: Chemical, 2014
NBD-chloride is widely used as an efficient probe for selective labelling of thiols in proteins due to formation sulfur-substituted NBD under physiological conditions. Selective conjugation involving thiolate group is favoured over amines of proteins because, amino-substituted NBD can be formed only under more basic and elevated temperature conditions. Sulfur-substituted NBDs generally display weak fluorescence properties compared to amino-substituted derivatives. However, a sulfur-substituted NBD can be converted to corresponding amino-substituted derivative via S-N Smiles rearrangement. Theoretical calculations predicted off-fluorescence state for either the probe or the sulfur-substituted NBD formed upon addition of cysteine. On-fluorescence state was predicted for corresponding amino-substituted NBD derivative. Based on UV-vis and fluorescence spectroscopic studies, most efficient rearrangement was observed for cysteine. The rearrangement was relatively slower for homocysteine and not feasible for glutathione. Detection of cysteine and homocysteine by the probe resulted in 1599-and 760-fold off-on fluorescence enhancements, respectively. Sensing of cysteine by the probe provided a detection limit of 2.0 × 10 −8 M. The sensing of intracellular cysteine by the probe was also demonstrated by live cell imaging.
Organic & Biomolecular Chemistry, 2013
A new and simple chemodosimetric probe L 1 is utilized for the selective detection of biothiols in the presence of other relevant amino acids under physiological conditions (pH = 7.4). This eventually led to a turn-off luminescence response due to an effective photoinduced electron transfer based signaling mechanism. A comparison of the results of the fluorescence kinetic analysis and 1 H NMR studies of the reaction between thiol and L 1 or the analogous compound L 2 revealed the role of intramolecular hydrogen bonding in activating the imine functionality towards nucleophilic addition. Such an example is not common in contemporary literature. Conventional MTT assay studies revealed that this probe (L 1) has low cytotoxicity. Results of the cell imaging studies revealed that this probe was cell membrane permeable and could detect the intracellular distribution of biothiols within living HeLa cells. Furthermore, our studies with human blood plasma demonstrated the possibility of using this reagent for the quantitative optical detection of total biothiols in biological fluid. Such an example for the detection of biothiols in real biological samples is rare in the contemporary literature. These results clearly demonstrate the possibility of using this reagent in medicinal biology and diagnostic applications. † Electronic supplementary information (ESI) available: Characterization data for L 1 and L 2 , hydrolytic stability test, determination of detection limit, scanning of L 1 and L 2 with different amino acids. See
Chemical communications (Cambridge, England), 2018
Two 'turn on' TCF-based fluorescence probes were developed for the detection of biological thiols (TCF-GSH and TCFCl-GSH). TCF-GSH was shown to have a high sensitivity towards glutathione (GSH) with a 0.28 μM limit of detection. Unfortunately, at higher GSH concentrations the fluorescence intensity of TCF-GSH decreased and toxicity was observed for TCF-GSH in live cells. However, TCFCl-GSH was shown to be able to detect GSH at biologically relevant concentrations with a 0.45 μM limit of detection. No toxicity was found for TCFCl-GSH and a clear 'turn on' with good photostability was observed for the exogenous addition of GSH, Cys and HCys. Furthermore, TCFCl-GSH was used to evaluate the effects of drug treatment on the levels of GSH in live cells.