Chemistry

Detecting Potential Toxins

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Science  31 Oct 2003:
Vol. 302, Issue 5646, pp. 749
DOI: 10.1126/science.302.5646.749b

Organophosphorus compounds, such as paraoxon, are widely used in pesticides and insecticides, but they are an environmental concern because of their structural similarity to some nerve agents. Hence, there is a need to monitor these compounds in food and groundwater. Constantine et al. have used layer-by-layer assembly techniques to fabricate a biosensor that can detect paraoxon at nanomolar concentrations. The sensor is initially made from alternating layers of chitosan and thioglycolic acid-capped CdSe quantum dots (QDs). The chitosan strongly absorbs onto negatively charged surfaces and tends to forms films, giving the sensor its physical stability. Alternating layers of the enzyme organophosphorus hydrolase and QDs are then added to the film. When exposed to a solution containing paraoxon, the hydrolase cleaves it to form p-nitrophenol, which is readily detected by spectroscopy. The exposure to paraoxon also changes the QD photoluminescent intensity, which is enhanced by their confinement to the layered assembly, thus giving the biosensor two methods for measuring chemical exposure. — MSL

Langmuir 10.1021/la035237y (2003).

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