Determination of glutathione and glutathione reductase with a silver sulfide membrane electrode

Hassan, Saad S. M.; Rechnitz, G. A.

doi:10.1021/ac00249a013

Cited by 95 publications

(54 citation statements)

References 32 publications

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“…It was interesting to note that the intracellular concentration of free glutathione was 1-10 mM, while the extracellular concentration was less than 10 lM. [19] The intracellular glutathione would be benign to the long-term stability of GSH-CdTe QDs, whereas the fluorescence of QDs capped by other thiols would be sensitive to such an excess of intracellular glutathione. This report described the synthesis of GSH-CdTe QDs with an excellent QY.…”

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confidence: 99%

Synthesis and Cell‐Imaging Applications of Glutathione‐Capped CdTe Quantum Dots

2007

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Quantum dots (QDs) are of great interest to biological applications such as fluorescent biosensors and biolabels. Our study describes a synthesis of glutathione-capped CdTe QDs in aqueous solution that is cost-efficient and convenient compared to the conventional organometallic approaches. The fluorescence of the as-prepared glutathione-capped CdTe QDs was tunable from 500 to 650 nm. Without any postpreparation treatment, the glutathione-capped CdTe QDs achieved quantum yields (QYs) as high as 45 %, comparable to, or even better than, QDs derived from organometallic routes. With an overall size as small as 4 nm, they could gain access to cellular targets and stain fine features such as the cell nucleolus. These QDs were successfully conjugated with biotin for immunostaining and with F3 peptide for delivery to live cells, demonstrating their potentially broad application as biolabels.Fluorescent semiconductor nanoparticles or QDs have been extensively investigated in the past decade, and have been widely used as biolabels in imaging and biodetection.[1] Fluorescence imaging can greatly benefit from the use of QDs, which show brighter fluorescence, less photobleaching, and multiple colors with a single excitation. For biolabeling applications, QDs are commonly capped with trioctylphosphine oxide (TOPO) through organometallic synthesis, followed by phospholipid, [2] silica, [3] or polymer [4] coating to impart watersolubility and biocompatibility. With the multilayer coating, the final size of the QD biolabels would typically be 12-20 nm, which might be too bulky to gain access to cells for in vitro and in vivo imaging. In addition, the large dimensions would dramatically lower the labeling efficiency on specific target sites within the cells. Compared to conventionally used organic dyes, the size of QDs presented a major drawback as it limited the range of applications in biolabeling. To overcome this obstacle, water-soluble QDs with only one layer of capping ligand on the surface have been developed by ligand exchange with thiols [5] or phosphine [6] on TOPO-capped QDs.Both the ligand-addition and ligand-exchange methods were complicated, and even the high-quality QDs derived from organometallic methods have exhibited reductions in QY from 65-85 % in the organic phase to 35-50 % in aqueous solution.[7]Alternatively, thiol-capped QDs could be prepared directly in aqueous solution with thiols as stabilizers, but low QYs of 1-10 % were typically obtained.[8] Although their QYs could be significantly improved by a variety of after-treatments, such as photochemical etching, [8] size-selective precipitation, [9] and long-term illumination, [10] these QDs have a tendency to agglomerate during such treatments. Glutathione is a thiol-containing oligopeptide found in most organisms, and it plays an important role in the detoxification of heavy metals in plant cells. The physiological mechanism of detoxification involves the binding of heavy-metal nanoclusters by glutathione and the formation of a phytochelatin shell, cat...

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Synthesis and Cell‐Imaging Applications of Glutathione‐Capped CdTe Quantum Dots

2007

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“…Cellular GSH levels must be maintained, since they are constantly fluctuating due to degradation and consumption in various biological processes [2]. The intracellular concentration of GSH (1 -10 mm) is substantially higher than the extracellular concentration (e.g., 2-20 mm in plasma) [3]. Extracellular GSH concentrations are relatively low, because GSH is readily oxidized to glutathione disulfide (GSSG) by direct interaction with free radicals or, more often, when GSH acts as a cofactor for antioxidant enzymes such as GSH peroxidases [4].…”

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Nonenzymatic, Self‐Elimination Degradation Mechanism of Glutathione

Deshmukh

Kutscher

Stein

et al. 2009

Chemistry & Biodiversity

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In the present in vitro studies, evidence is provided showing that glutathione (GSH) can undergo spontaneous, nonenzymatic auto-degradation. The initial cleavage of the Glu-Cys bond involves nucleophilic attack of the N-terminal amino group of GSH at the gamma-carbonyl side chain, followed by an unusual cleavage of the Cys-Gly amide bond that is complete within 3-5 weeks in the physiological pH range. These observations may be useful for the development of novel biodegradable polymers and releasable prodrugs for sustained and targeted drug delivery applications.

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“…The experiments were repeated three times for each point. The initial slope method described by Hassan et al [19][20][21][22] was used in all measurements. The EMF was continuously monitored every 3 s (defined as an interval time).…”

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confidence: 99%