Determination of glutathione and glutathione disulfide in biological samples: An in-depth review

Basal oxidative stress ratio of head and neck squamous cell carcinomas correlates with nodal metastatic spread in patients under therapy

Background

Head and neck squamous cell carcinoma (HNSCC) is a type of cancer that is strongly associated with oxidative damage and oxidative stress. Tobacco and alcohol – sources of massive quantities of reactive oxygen species (ROS) – have been clearly identified as etiologic factors that contribute to these malignancies. Considering the role of glutathione (GSH) in ROS detoxification, we hypothesized that potential biological markers can be found in addition to the parameters of oxidative stress. In line with previous studies that emphasized the accumulation of GSH in tumor cells, in this study, we have reported a lower ratio of oxidized versus reduced GSH in head and neck tumors.

Objective

The aim of the paper was to evaluate the prognostic and clinical significance of the ratio of oxidized versus reduced GSH in patients with head and neck cancers.

Methods

Thirty-six patients with HNSCC were included in this study. The tumoral redox status was determined by measuring the ratio of oxidized/reduced GSH (GSSG/GSH) by capillary electrophoresis. Statistical analysis was performed to assess the correlation between patient, clinical factors and the redox status.

Results

The results showed a low tumoral ratio of GSSG/GSH and a better locoregional control. Moreover, a significant correlation between the tumoral redox status ratio (GSSG/GSH) and nodal stage (N0 versus N1, N2 and N3) was also observed. A higher tumoral redox status ratio was found to be associated with the presence of lymph node metastasis (N1, N2 and N3).

Conclusion

A strong correlation was observed between the oxidative status and locoregional control of the tumors. Moreover, a higher basal tumoral redox status ratio was found to be correlated with the presence of lymph node metastasis.

Sensitive analysis of reduced glutathione in bacteria and HaCaT cells by capillary electrophoresis via online pre-concentration of transient trapping combined with the dynamic pH junction mode

A new method of capillary electrophoresis was developed for the sensitive determination of glutathione in biological samples.

Functionalized Nano-MoS2 with Peroxidase Catalytic and Near-Infrared Photothermal Activities for Safe and Synergetic Wound Antibacterial Applications

We have developed a biocompatible antibacterial system based on polyethylene glycol functionalized molybdenum disulfide nanoflowers (PEG-MoS₂ NFs). The PEG-MoS₂ NFs have high near-infrared (NIR) absorption and peroxidase-like activity, which can efficiently catalyze decomposition of low concentration of H₂O₂ to generate hydroxyl radicals (·OH). The conversion of H₂O₂ into ·OH can avoid the toxicity of high concentration of H₂O₂ and the ·OH has higher antibacterial activity, making resistant bacteria more vulnerable and wounds more easily cured. The PEG-MoS₂ NFs combine the catalysis with NIR photothermal effect, providing a rapid and effective killing outcome in vitro for Gram-negative ampicillin resistant Escherichia coli (Amp^r E. coli) and Gram-positive endospore-forming Bacillus subtilis (B. subtilis) as compared to catalytic treatment or photothermal therapy (PTT) alone. Wound healing results indicate that the synergy antibacterial system could be conveniently used for wound disinfection in vivo. Interestingly, glutathione (GSH) oxidation can be accelerated due to the 808 nm irradiation induced hyperthermia at the presence of PEG-MoS₂ NFs proved by X-ray near-edge absorption spectra and X-ray spectroscopy. The accelerated GSH oxidation can result in bacterial death more easily. A mechanism based on ·OH-enhanced PTT is proposed to explain the antibacterial process.

Mixed results with mixed disulfides

A period of research with Helmut Sies in the 1980s is recalled. Our experiments aimed at an in-depth understanding of metabolic changes due to oxidative challenges under near-physiological conditions, i.e. perfused organs. A major focus were alterations of the glutathione and the NADPH/NADP(+) system by different kinds of oxidants, in particular formation of glutathione mixed disulfides with proteins. To analyze mixed disulfides, a test was adapted which is widely used until today. The observations in perfused rat livers let us believe that glutathione-6-phosphate dehydrogenase (G6PDH), i.a. might be activated by glutathionylation. Although we did not succeed to verify this hypothesis for the special case of G6PDH, the regulation of enzyme/protein activities by glutathionylation today is an accepted posttranslational mechanism in redox biology in general. Our early experimental approaches are discussed in the context of present knowledge.

Highly selective and sensitive determination of several antioxidants in human breast milk using high-performance liquid chromatography based on Ag(III) complex chemiluminescence detection

Ascorbic acid (AA), uric acid (UA) and glutathione (GSH) are the most important water-soluble antioxidants. The concentrations of GSH and glutathione disulfide (GSSG) and their molar ratio are the indicators of oxidative stress. Little is known about the contents of UA, GSH and GSSG in human milk; a reliable and sensitive method to monitor the concentrations of the four compounds simultaneously in human milk is of critical importance. A new method for separation and quantification of these water-soluble antioxidants by HPLC coupled with Ag(III) chemiluminescence detector has been developed in this work with better recoveries. The antioxidants contents were determined in different times of lactation utilizing this method. The results show that the levels of AA, UA, GSH and GSH/GSSG of human colostrum are significantly higher than those of mature milk (P<0.05). It is concluded that colostrum contains more water-soluble antioxidants than mature milk.

The leishmanicidal activity of oleuropein is selectively regulated through inflammation- and oxidative stress-related genes

Background

Much research effort has been focused on investigating new compounds derived from low-cost sources, such as natural products, for treating leishmaniasis. Oleuropein derived from numerous plants, particularly from the olive tree, Olea europaea L. (Oleaceae), is a biophenol with many biological activities. Our previous findings showed that oleuropein exhibits leishmanicidal effects against three Leishmania spp. in vitro, and minimizes the parasite burden in L. donovani-infected BALB/c mice. The aim of the present study is to investigate the possible mechanism(s) that mediate this leishmanicidal activity.

Methods

We determined the efficacy of oleuropein in elevating ROS and NO production in L. donovani-infected J774A.1 macrophages and in explanted splenocytes and hepatocytes obtained from L. donovani-infected BALB/c mice. We also assessed the expression of genes that are related to inflammation, T-cell polarization and antioxidant defense, in splenocytes. Finally, we determined the ratios of specific IgG2a/IgG1 antibodies and DTH reactions in L. donovani-infected BALB/c mice treated with oleuropein.

Results

Oleuropein was able to elevate ROS production in both in vitro and in vivo models of visceral leishmaniasis and raised NO production in ex vivo cultures of splenocytes and hepatocytes. The extensive oxidative stress found in oleuropein-treated mice was obviated by the upregulation of the host’s antioxidant enzyme (mGCLC) and the simultaneous downregulation of the corresponding enzyme of the parasite (LdGCLC). Moreover, oleuropein was able to mount a significant Th1 polarization characterized by the expression of immune genes (IL-12β, IL-10, TGF-β1, IFN-γ) and transcription factors (Tbx21 and GATA3). Moreover, this immunomodulatory effect was also correlated with an inhibitory effect on IL-1β gene expression, rather than with the expression of IL-1α, IL-1rn and TNF-α. Furthermore, oleuropein-treated BALB/c mice mounted a delayed-type hypersensitivity (DTH) response and an elevated Leishmania-specific IgG2a/IgG1 ratio that clearly demonstrated an in vivo protective mechanism.

Conclusion

The ability of Oleuropein to promote a Th1 type immune response in L. donovani-infected BALB/c mice points towards the candidacy of this bioactive compound as an immunomodulatory agent that may complement therapeutic approaches to leishmaniasis.

Reversible and Dynamic Fluorescence Imaging of Cellular Redox Self-Regulation Using Fast-Responsive Near-Infrared Ge-Pyronines

Cellular self-regulation of reactive oxygen species (ROS) stress via glutathione (GSH) antioxidant repair plays a crucial role in maintaining redox balance, which affects various physiological and pathological pathways. In this work, we developed a simple yet effective strategy for reversible, dynamic, and real-time fluorescence imaging of ROS stress and GSH repair, based on novel Ge-pyronine dyes (GePs). Unlike the current O-pyronine (OP) dye, the fluorescence of GePs can be quenched in GSH reduction and then greatly restored by ROS (e.g., ClO(-), ONOO(-), and HO(•)) oxidation because of their unique affinity toward thiols. The "on-off" and "off-on" fluorescence switch can complete in 10 and 20 s, respectively, and exhibit excellent reversibility in vitro and in cells. GePs also show excitation in the long wavelength from the deep-red to near-infrared (NIR) (621-662 nm) region, high fluorescence quantum yield (Φ(fl) = 0.32-0.44) in aqueous media, and excellent cell permeability. Our results demonstrated that GePs can be used for real-time monitoring of the reversible and dynamic interconversion between ROS oxidation and GSH reduction in living cells. GePs might be a useful tool for investigating various redox-related physiological and pathological pathways.

Do glutathione levels decline in aging human brain?

For the past 60 years a major theory of "aging" is that age-related damage is largely caused by excessive uncompensated oxidative stress. The ubiquitous tripeptide glutathione is a major antioxidant defense mechanism against reactive free radicals and has also served as a marker of changes in oxidative stress. Some (albeit conflicting) animal data suggest a loss of glutathione in brain senescence, which might compromise the ability of the aging brain to meet the demands of oxidative stress. Our objective was to establish whether advancing age is associated with glutathione deficiency in human brain. We measured reduced glutathione (GSH) levels in multiple regions of autopsied brain of normal subjects (n=74) aged one day to 99 years. Brain GSH levels during the infancy/teenage years were generally similar to those in the oldest examined adult group (76-99 years). During adulthood (23-99 years) GSH levels remained either stable (occipital cortex) or increased (caudate nucleus, frontal and cerebellar cortices). To the extent that GSH levels represent glutathione antioxidant capacity, our postmortem data suggest that human brain aging is not associated with declining glutathione status. We suggest that aged healthy human brains can maintain antioxidant capacity related to glutathione and that an age-related increase in GSH levels in some brain regions might possibly be a compensatory response to increased oxidative stress. Since our findings, although suggestive, suffer from the generic limitations of all postmortem brain studies, we also suggest the need for "replication" investigations employing the new (1)H MRS imaging procedures in living human brain.

Surface enhanced Raman spectroscopic direct determination of low molecular weight biothiols in umbilical cord whole blood

Biothiols are determined in whole blood samples by Surface Enhanced Raman Spectroscopy (SERS).

Gold nanoparticles-immobilized, hierarchically ordered, porous TiO2 nanotubes for biosensing of glutathione

Glutathione (GSH) is vital for several functions of our human body such as neutralization of free radicals and reactive oxygen compounds, maintaining the active forms of vitamin C and E, regulation of nitric oxide cycle, iron metabolism, etc. It is also an endogenous antioxidant in most of the biological reactions. Given the importance of GSH, a simple strategy is proposed in this work to develop a biosensor for quantitative detection of GSH. This particular biosensor comprises of gold nanoparticles (Au NPs)-immobilized, hierarchically ordered titanium dioxide (TiO₂) porous nanotubes. Hexagonally arranged, honeycomb-like nanoporous tubular TiO₂ electrodes are prepared by using a simple electrochemical anodization process by applying a constant potential of 30 V for 24 hours using ethylene glycol consisting of ammonium fluoride as an electrolytic medium. Structural morphology and crystalline nature of such TiO₂ nanotubes are analyzed using field emission scanning electron microscope (FESEM) and X-ray diffraction (XRD). Interestingly, nanocomposites of TiO₂ with Au NPs is prepared in an effort to alter the intrinsic properties of TiO₂, especially tuning of its band gap. Au NPs are prepared by a well-known Brust and Schiffrin method and are immobilized onto TiO₂ electrodes which act as a perfect electrochemical sensing platform for GSH detection. Structural characterization and analysis of these modified electrodes are performed using FESEM, XRD, and UV-visible spectroscopic studies. GSH binding events on Au NPs-immobilized porous TiO₂ electrodes are monitored by electrochemical techniques, namely, cyclic voltammetry (CV) and chronoamperometry (CA). Several parameters such as sensitivity, selectivity, stability, limit of detection, etc are investigated. In addition, Au NPs dispersed in aqueous medium are also explored for naked-eye detection of GSH using UV-visible spectroscopy in order to compare the performance of the proposed sensor. Our studies clearly indicate that these materials could potentially be used for GSH sensing applications.

A direct comparison of methods used to measure oxidized glutathione in biological samples: 2-vinylpyridine and N-ethylmaleimide

The ratio of glutathione disulfide (GSSG) to reduced glutathione (GSH) in biological samples is a frequently used parameter of oxidative stress. As a result, many methods are developed to measure GSSG. The most popular and convenient of these relies on enzymatic cycling following the chemical masking of GSH in the sample using 2-vinylpyridine (2VP). However, 2VP is a slow reactant and its use may result in artificially high GSSG values due to oxidation of the sample over time. Fast-reacting reagents such as N-ethylmaleimide (NEM) may provide more accurate results. We performed a direct comparison of methods using 2VP and NEM. With 2VP, the percentage of total glutathione (GSH+GSSG) in the oxidized form was significantly higher in all tested tissues (kidney, lung and liver) compared to the same procedure performed using NEM. We conclude that NEM, when coupled with a simple solid-phase extraction procedure, is more accurate for the determination of GSSG. We also tested the effects of various handling and storage conditions on GSSG. A detailed description and a discussion of other methods are also included.

Enhancing permanganate chemiluminescence detection for the determination of glutathione and glutathione disulfide in biological matrices

Acidic potassium permanganate chemiluminescence enables direct post-column detection of glutathione, but its application to assess the redox state of a wider range of biological fluids and tissues is limited by its sensitivity. Herein we show that the simple on-line addition of an aqueous formaldehyde solution not only enhances the sensitivity of the procedure by two orders of magnitude, but also provides a remarkable improvement in the selectivity of the reagent towards thiols such as glutathione (compared to phenols and amino acids that do not possess a thiol group). This enhanced mode of detection was applied to the determination of glutathione and its corresponding disulfide species in homogenised striatum samples taken from both wild type mice and the R6/1 transgenic mouse model of Huntington's disease, at both 8 and 12 weeks of age. No significant difference was observed between the GSH/GSSG ratios of wild type mice and R6/1 mice at either age group, suggesting that the early disease progression had not significantly altered the intracellular redox environment.

A simple assay for glutathione in whole blood

A method for detecting glutathione selectively in whole blood deposited on filter paper is described. GSH is fractionated from proteins, hemoglobin and other potentially interfering components and determined using a resorufin-acrylate fluorescent probe. The relative standard deviation is lower than 5% (n = 5). Recoveries of GSH from whole blood are between 94% and 108.6%.

Glutathione

Glutathione is an endogenous peptide with antioxidant and other metabolic functions. The nomenclature, formulae, elemental composition, and appearance and uses of the drug are included. The methods used for the synthesis and biosynthesis of glutathione are described. This profile contains the physical characteristics of the drug including: solubility, X-ray powder diffraction pattern, crystal structure, melting point, and differential scanning calorimetry. The spectral methods that were used for both the identification and analysis of glutathione include ultraviolet spectrum, vibrational spectrum, 1H and 13C nuclear magnetic resonance spectra, and mass spectrum. The profile also includes the compendial methods of analysis and the other methods of analysis that are reported in the literature. These other methods of e-analysis are: potentiometric, voltammetric, amperometric, spectrophotometric, specrtofluorometric, chemiluminescence, chromatographic and immunoassay methods. The stability of and several reviews on drug are also provided. More than 170 references are listed at the end this comprehensive profile on glutathione.

Simultaneous determination of ascorbic acid, aminothiols, and methionine in biological matrices using ion-pairing RP-HPLC coupled with electrochemical detector

A novel highly sensitive ion-pairing reversed-phase high performance liquid-chromatography/electrochemical detection method for simultaneous determination of L -ascorbic acid, aminothiols, and methionine in biological matrices is presented. Reduced forms of the analytes are extracted from sample matrices with 10% m-phosphoric acid solution(aqueous). To determine the total vitamin C, the total aminothiols, and the total methionine, samples are treated with tris(2-carboxyethyl)phosphine solution in 0.05% trifluoroacetic acid solution(aqueous) subsequent to deproteination to reduce the oxidized forms of these compounds. Various analytes are separated on a C18 (250 × 4.6 mm, 5 μm) analytical column using methanol-0.05% trifluoroacetic acid solution(aqueous) (05:95 v/v, containing 0.1 mM 1-octane sulfonic acid as the ion-pairing agent) as the isocratic mobile phase that is pumped at a flow rate of 1.5 ml/min at room temperature. The column eluents are monitored at a voltage of 0.85 V. These analytes are efficiently resolved in less than 20 min using n-acetyl cysteine as the internal standard.

A sensitive method for the analysis of glutathione in porcine hepatocytes

BACKGROUND

Reduced glutathione (γ-glutamylcysteinylglycine), GSH, is essential when protecting cells from oxidative stress and also an indicator of disease risk. Reported concentrations of GSH and its oxidized form, glutathione disulfide (GSSG), varies considerably, primarily due to the instability of GSH and various analytical methods.

METHODS

We designed a sensitive method to analyze GSH and GSSG in porcine hepatocytes using liquid chromatography-tandem mass spectrometry (LC-MS/MS) after stabilization with N-ethylmaleimide (NEM). This method includes stable isotope labeled internal standards and simple synthesis of labeled GSSG which commercial sources rarely offer. GSH and GSSG were analyzed in porcine liver biopsies giving a reference interval based on a large number of samples (26 pigs; 3 parallels).

RESULTS

The LC-MS/MS results revealed excellent linearity for both GSH and GSSG, with interday coefficient of variation (%CV) for GSH-NEM and GSSG <10 %. Accuracy for recovery tests was between 95.6% and 106.7% (n = 3) for GSH and between 92.3% and 107.7% (n = 3) for GSSG. The limits of quantification were 0.1 μM for GSH-NEM and 0.08 μM for GSSG. The mean concentration of GSH was 3.5 (95% CI = 1.5-8.1) mmol/liter and of GSSG 0.0023 (95% CI = 0.0003-0.019) mmol/liter.

CONCLUSION

For the first time GSH and GSSG are analyzed in porcine hepatocytes by LC-MS/MS yielding a reference level of GSH and GSSG. The method is reproducible in any laboratory with LC-MS/MS service and will probably be applicable in all soft tissues and cell suspensions, essentially with no modification.

Resveratrol improves cognition and reduces oxidative stress in rats with vascular dementia

Resveratrol possesses beneficial biological effects, which include anti-oxidant, anti-inflammatory and anti-carcinogenic properties. Recently, resveratrol has been shown to exhibit neuroprotective effects in models of Parkinson's disease, cerebral ischemia and Alzheimer's disease. However, its effects on vascular dementia remain unclear. The present study established a rat model of vascular dementia using permanent bilateral common carotid artery occlusion. At 8–12 weeks after model induction, rats were intragastrically administered 25 mg/kg resveratrol daily. Our results found that resveratrol shortened the escape latency and escape distances in the Morris water maze, and prolonged the time spent percentage and swimming distance percentage in the target quadrant during the probe test, indicating that resveratrol improved learning and memory ability in vascular dementia rats. Further experiments found that resveratrol decreased malonyldialdehyde levels, and increased superoxide dismutase activity and glutathione levels in the hippocampus and cerebral cortex of vascular dementia rats. These results confirmed that the neuroprotective effects of resveratrol on vascular dementia were associated with its anti-oxidant properties.

Simultaneous determination of reduced and oxidized glutathione in tissues by a novel liquid chromatography-mass spectrometry method: application in an inhalation study of Cd nanoparticles

The paper presents the development of an advanced extraction and fast analytical LC MS/MS method for simultaneous analyses of reduced and oxidized glutathione (GSH and GSSG, respectively) in different animal tissues. The simultaneous determination of GSH and GSSG is crucial because the amount and ratio of both GSH and GSSG may be altered in response to oxidative stress, an important mechanism of toxicity. The method uses the derivatization of free thiol groups in GSH. Its performance was demonstrated for less explored tissues (lung, brain, and liver) in mouse. The combined extraction and analytical method has very low variability and good reproducibility, maximum coefficients of variance for within-run and between-run analyses under 8 %, and low limits of quantification; for GSH and GSSG, these were 0.2 nM (0.06 ng/mL) and 10 nM (6 ng/mL), respectively. The performance of the method was further demonstrated in a model experiment addressing changes in GSH and GSSG concentrations in lung of mice exposed to CdO nanoparticles during acute 72 h and chronic 13-week exposures. Inhalation exposure led to increased GSH concentrations in lung. GSSG levels were in general not affected; nonsignificant suppression occurred only after the longer 13-week period of exposure. The developed method for the sensitive detection of both GSH and GSSG in very low tissue mass enables these parameters to be studied in cases where only a little sample is available, i.e. in small organisms or in small amounts of tissue.

Hydrophobic interactions in donor-disulphide-acceptor (DSSA) probes looking beyond fluorescence resonance energy transfer theory

Donor-linker-acceptor (DSSA) is a concept in fluorescence chemistry with acceptor being a fluorescent compound (FRET) or quencher. The DSSA probes used to measure thiol levels in vitro and in vivo. The reduction potential of these dyes are in the range of -0.60 V, much lower than the best thiol reductant reported in literature, the DTT (-0.33 V). DSSA disulphide having an unusually low reduction potential compared to the typical thiol reductants is a puzzle. Secondly, DSSA probes have a cyclized rhodamine ring as acceptor which does not have any spectral overlap with fluorescein, but quenches its absorbance and fluorescence. To understand the structural features of DSSA probes, we have synthesized DSSANa and DSSAOr. The calculated reduction potential of these dyes suggest that DSSA probes have an alternate mechanism from the FRET based quenching, namely hydrophobic interaction or dye to dye quenching. The standard reduction potential change with increasing complexity and steric hindrance of the molecule is small, suggesting that ultra- low Eo' has no contribution from the disulphide linker and is based on structural interactions between fluorescein and cyclized rhodamine. Our results help to understand the DSSA probe quenching mechanism and provide ways to design fluorescent probes.

A review of recent advances in chemiluminescence detection using nano-colloidal manganese(IV)

The application of 'soluble' (colloidal) manganese(IV) for chemiluminescence detection is reviewed, focussing on papers published since the last comprehensive review of the subject in 2008. Advances in this reagent system include: the on-line formation of manganese(IV); new insight into the light-producing pathway and selectivity of the reagent; its application to assess total antioxidants in plant derived samples and oxidative stress in biological fluids and tissues; and the replacement of the formaldehyde enhancer with ethanol.

Application of vitamin E to antagonize SWCNTs-induced exacerbation of allergic asthma

The aggravating effects of zero-dimensional, particle-shaped nanomaterials on allergic asthma have been previously investigated, but similar possible effects of one-dimensional shaped nanomaterials have not been reported. More importantly, there are no available means to counteract the adverse nanomaterial effects to allow for their safe use. In this study, an ovalbumin (OVA)-sensitized rat asthma model was established to investigate whether single walled carbon nanotubes (SWCNTs) aggravate allergic asthma. The results showed that SWCNTs in rats exacerbated OVA-induced allergic asthma and that this exacerbation was counteracted by concurrent administration vitamin E. A mechanism involving the elimination of reactive oxygen species, downregulation of Th2 responses, reduced Ig production, and the relief of allergic asthma symptoms was proposed to explain the antagonistic effects of vitamin E. This work could provide a universal strategy to effectively protect people with allergic asthma from SWCNTs or similar nanomaterial-induced aggravating effects.

Analytical methods involving separation techniques for determination of low-molecular-weight biothiols in human plasma and blood

Low-molecular-weight biothiols such as homocysteine, cysteine, and glutathione are metabolites of the sulfur cycle and play important roles in biological processes such as the antioxidant defense network, methionine cycle, and protein synthesis. Thiol concentrations in human plasma and blood are related to diseases such as cardiovascular disease, neurodegenerative disease, and cancer. The concentrations of homocysteine, cysteine, and glutathione in plasma samples from healthy human subjects are approximately in the range of 5-15, 200-300, and 1-5 μM, respectively. Glutathione concentration in the whole blood is in the millimolar range. Measurement of biothiol levels in plasma and blood is thought to be important for understanding the physiological roles and biomarkers for certain diseases. This review summarizes the relationship of biothiols with certain disease as well as pre-analytical treatment and analytical methods for determination of biothiols in human plasma and blood by using high-performance liquid chromatography and capillary electrophoresis coupled with ultraviolet, fluorescence, or chemiluminescence detection; or mass spectrometry.

Rapid method for glutathione quantitation using high-performance liquid chromatography with coulometric electrochemical detection

A rapid, sensitive, and direct method (without derivatization) was developed for the detection of reduced glutathione (GSH) in cultured hepatocytes (HepG2 cells) using high-performance liquid chromatography with electrochemical detection (HPLC-ECD). The method was validated according to the guidelines of the U.S. Food and Drug Administration in terms of linearity, lower limit of quantitation (LOQ), lower limit of detection (LOD), precision, accuracy, recovery, and stabilities of GSH standards and quality control samples. The total analysis time was 5 min, and the retention time of GSH was 1.78 min. Separation was carried out isocratically using 50 mM sodium phosphate (pH 3.0) as a mobile phase with a fused-core column. The detector response was linear between 0.01 and 80 μmol/L, and the regression coefficient (R(2)) was >0.99. The LOD for GSH was 15 fmol, and the intra- and interday recoveries ranged between 100.7 and 104.6%. This method also enabled the rapid detection (in 4 min) of other compounds involved in GSH metabolism such as uric acid, ascorbic acid, and glutathione disulfite. The optimized and validated HPLC-ECD method was successfully applied for the determination of GSH levels in HepG2 cells treated with buthionine sulfoximine (BSO), an inhibitor, and α-lipoic acid (α-LA), an inducer of GSH synthesis. As expected, the amount of GSH concentration-dependently decreased with BSO and increased with α-LA treatments in HepG2 cells. This method could also be useful for the quantitation of GSH, uric acid, ascorbic acid, and glutathione disulfide in other biological matrices such as tissue homogenates and blood.

Design of two and three input molecular logic gates using non-Watson–Crick base pairing-based molecular beacons

A single, resettable, and sensitive molecular beacon has been developed to operate two-input, three-input, and set–reset logic gates.

Glutathione redox dynamics and expression of glutathione-related genes in the developing embryo

Embryonic development involves dramatic changes in cell proliferation and differentiation that must be highly coordinated and tightly regulated. Cellular redox balance is critical for cell fate decisions, but it is susceptible to disruption by endogenous and exogenous sources of oxidative stress. The most abundant endogenous nonprotein antioxidant defense molecule is the tripeptide glutathione (γ-glutamylcysteinylglycine, GSH), but the ontogeny of GSH concentration and redox state during early life stages is poorly understood. Here, we describe the GSH redox dynamics during embryonic and early larval development (0-5 days postfertilization) in the zebrafish (Danio rerio), a model vertebrate embryo. We measured reduced and oxidized glutathione using HPLC and calculated the whole embryo total glutathione (GSHT) concentrations and redox potentials (Eh) over 0-120 h of zebrafish development (including mature oocytes, fertilization, midblastula transition, gastrulation, somitogenesis, pharyngula, prehatch embryos, and hatched eleutheroembryos). GSHT concentration doubled between 12h postfertilization (hpf) and hatching. The GSH Eh increased, becoming more oxidizing during the first 12h, and then oscillated around -190 mV through organogenesis, followed by a rapid change, associated with hatching, to a more negative (more reducing) Eh (-220 mV). After hatching, Eh stabilized and remained steady through 120 hpf. The dynamic changes in GSH redox status and concentration defined discrete windows of development: primary organogenesis, organ differentiation, and larval growth. We identified the set of zebrafish genes involved in the synthesis, utilization, and recycling of GSH, including several novel paralogs, and measured how expression of these genes changes during development. Ontogenic changes in the expression of GSH-related genes support the hypothesis that GSH redox state is tightly regulated early in development. This study provides a foundation for understanding the redox regulation of developmental signaling and investigating the effects of oxidative stress during embryogenesis.

Coupling gold nanoparticles to silica nanoparticles through disulfide bonds for glutathione detection

Advances in the controlled assembly of nanoscale building blocks have resulted in functional devices which can find applications in electronics, biomedical imaging, drug delivery etc. In this study, novel covalent nanohybrid materials based upon [Ru(bpy)3](2+)-doped silica nanoparticles (SiNPs) and gold nanoparticles (AuNPs), which could be conditioned as OFF-ON probes for glutathione (GSH) detection, were designed and assembled in sequence, with the disulfide bonds as the bridging elements. The structural and optical properties of the nanohybrid architectures were characterized using transmission electron microscopy, UV-vis spectroscopy and fluorescence spectroscopy, respectively. Zeta potential measurements, x-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy were employed to monitor the reaction processes of the SiNPs-S-S-COOH and SiNPs-S-S-AuNPs synthesis. It was found that the covalent nanohybrid architectures were fluorescently dark (OFF state), indicating that SiNPs were effectively quenched by AuNPs. The fluorescence of the OFF-ON probe was resumed (ON state) when the bridge of the disulfide bond was cleaved by reducing reagents such as GSH. This work provides a new platform and strategy for GSH detection using covalent nanohybrid materials.