Rapid Quantification of Oxidized and Reduced Forms of Glutathione Using Ortho -phthalaldehyde in Cultured Mammalian Cells In Vitro

Quantification of both oxidized and reduced forms of glutathione (GSSG and GSH, respectively) has been achieved through the use of Ortho-phthalaldehyde (OPA). OPA becomes highly fluorescent once conjugated to GSH but is unable to conjugate GSSG until reduced. Here, we describe a multiparametric assay to quantify both using protein quantification for normalization.

We aim to offer a novel means to quantify thio concentration with a specific focus on the GSH and GSSG concentrations of the various cell lines that can be performed in situ. We consider this a useful protocol for the scientific community. Numerous efforts have been made to detect niche and specific biomarkers of interest of reactive oxygen species.

And several have found great interest in detecting short-lived reactive oxygen species, such as radical detection and small molecules such as hydroxyls and singlet oxygen. One key challenge for several institutions has been the ability to accurately and specifically detect biomarkers of interest without the need of expensive equipment or laborious processes. This protocol allows for multi-parametric analysis, allowing for normalization of data without the need for separate protocols.

And remove several stages found in other assays that are highly time consumptive, present incompatible reagents, or use reagents hazardous to health. The Nanomaterial Safety Group will continue to assess various nanomaterials and polymers for the effect they may have on human health. We consider this protocol an essential part of our toolkit in achieving this goal, as this protocol can potentially be multiplexed to detect additional biomarkers.

To begin, prepare all the required materials for the assay. For GSH standards, add 40 microliters of total glutathione buffer to each well. Next, aspirate the media from each well of a plate containing the cell pellet and wash the cell three times with ice cold PBS.

Prepare the calibration range with 10 microliters of glutathione and double distilled water as blank in triplicates. For desired target quantification, incubate the washed cells with the appropriate mixtures in an orbital shaker at 300 RPM for two minutes. Then add five microliters of 0.01 molar Tris 2-carboxyethyl phosphine solution to each well and incubate again for 10 minutes.

Next, centrifuge the plate at 200 G for five minutes. And transfer 25 microliters from each sample well to a separate, clear 96 well plate for protein quantification. Then add 170 microliters of working ortho-phthaldehyde solution to each well containing 30 microliters of samples.

To shield the plate from light, cover it thoroughly with a foil and incubate it in the orbital shaker for 15 minutes. Finally, read the fluorescence using a plate reader at 340 nanometers excitation and 450 nanometers emission. A-549 cells treated with various nanomaterials showed different glutathione disulfide ratios in this assay.

And the highest value was observed for the cells treated with 125 micrograms per milliliter of silver.