Credit: © 2007 Wiley

Hydrogen peroxide is an important molecule in cellular oxidation and reduction reactions. However, too much of it can damage DNA and proteins leading to oxidative stress — a common cause of various chronic diseases and an indicator of stale food. Researchers at the National University of Singapore have now shown that quantum dots (QDs) are good peroxide scavengers and can be used as sensitive probes for studying oxidative stress.

Dejian Huang, Ming-Yong Han and colleagues1 coated cadmium selenide QDs with oleic acid — a common fatty acid from animal and vegetable sources — and reacted them with hydrogen peroxide. This quenched the QD fluorescence in a dose-dependent manner. After aging for five days, the oxidized QDs regained their fluorescence — but at a shorter wavelength — and could be requenched by adding more peroxide. When used to quantify the concentration of a representative peroxide compound in food (an indicator of how rancid the food is), the QD assay was twice as sensitive as the conventional test. Although still unclear, it is suggested that the quenching is due to oxidation of selenium atoms on the QD surface.

This new study reveals that although QDs are known to generate reactive molecules when bombarded with light, they can also be used to scavenge them as well.