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Biosensor for measuring stress in cells

Reactive oxygen compounds, including the well-known "free radicals", have an oxidation effect that causes damage to cells. However, at low levels, they also regulate key life processes. Scientists at the German Cancer Research Centre (DKFZ) have developed a highly sensitive biological measuring system for determining the oxidation state of living cells in real time.

It is the first system that enables researchers to directly observe oxidation state variations accompanying biological processes. The biosensor can also be used for studying the oxidation effect of food constituents and pharmaceutical substances. The results have recently been published in Nature Methods by a group of researchers led by Dr. Tobias Dick.
Cancer, nervous system disorders such as Parkinson’s disease, cardiovascular disorders and old age have one thing in common: scientists have observed oxidative changes in important biomolecules, both in affected tissue and in ageing cells. These changes are caused by reactive oxygen molecules, including the notorious "free radicals" that are formed as a by-product of cellular respiration and that attack cellular proteins, nucleic and fatty acids.
Today, reactive oxygen molecules are no longer widely regarded as baddies, since it has become clear that they are also involved in regulating major life processes such as growth and cell death. The right balance between oxidation and the reverse reaction, reduction, makes the difference between health and disease. "Oxidative stress" arises when this balance shifts towards oxidation-promoting processes.

Difference in fluorescence reveals degree of oxidation

So far, it has been virtually impossible for scientists to measure the level of oxidation and, thus, the stress status of living cells. This will now be feasible thanks to a highly sensitive biomarker presented in the journal Nature Methods by Dr. Tobias Dick and his colleagues from the German Cancer Research Centre and their colleagues from the University of Heidelberg.
The biosensor specifically measures the oxidation state of glutathione. This is an important protection molecule that captures a large portion of reactive oxygen molecules within a cell by oxidation. If much of a cell’s glutathione is present in an oxidized state, it is an important indicator of the cell’s overall oxidation level. The investigators equipped test cells with a fluorescent protein that reacts to changes in oxidation level by emitting light signals. Since the fluorescent protein on its own is not sensitive enough, it was coupled with an enzyme called glutaredoxin. This enzyme "measures" the oxidation state of glutathione and transmits the value to the fluorescent protein.
Human cancer cells with biosensors show different fluorescence before (left) and after (right) the development of
Human cancer cells with biosensors show different fluorescence before (left) and after (right) the development of "oxidative stress" (scale: 20 µm). (Photo: DKFZ)
The stress biosensor developed by Dick and his colleagues measures the slightest changes in the oxidation state of glutathione without destroying the cell. Even more relevant, however, is its precise time resolution, as Tobias Dick explains: "In order to measure short-term variations of the oxidation state, the systems needs to react instantly and dynamically. This is guaranteed with our biosensor, which works down to the scale of seconds." The measuring system allows researchers to determine the short-term variations that occur when reactive oxygen compounds are released as signalling molecules. However, the biosensor is equally suitable for use in pharmaceutical research, for example, to determine the effect of new substances or plant food constituents on oxidative processes and, thus, on the stress status of cells.

Source: DKFZ - 13th May 2008
Literature: Marcus Gutscher, Anne-Laure Pauleau, Laurent Marty, Thorsten Brach, Guido H. Wabnitz, Yvonne Samstag, Andreas J. Meyer and Tobias P. Dick: Real-time imaging of the intracellular glutathione redox potential. Nature Methods 2008, DOI: 10.1038/nmeth.1212
Website address: https://www.gesundheitsindustrie-bw.de/en/article/press-release/biosensor-for-measuring-stress-in-cells