Highly sensitive colorimetric detection of ethyl parathion using gold nanoprobes

This study reports a simple, rapid and sensitive method using cysteine capped gold nanoparticles as key material for the detection of highly toxic and widely used organophosphate, ethyl parathion. The detection is based on the aggregation of cysteine capped gold nanoparticles leading to a visible colour change from red to blue as a consequence of the generation of thiocholine (TCh). The hydrolytic reaction of acetylthiocholine (ATCh) by the enzyme acetylcholinesterase (AChE) affects the production of thiocholine (TCh). Presence of ethyl parathion leads to suppression of TCh resulting in no colour change whereas its absence leads to a visible colour change from red to blue. The changes in the absorbance of the gold nanoparticle probe solution can be used as a method to determine the amount of pesticide in a given sample. The developed biosensor is rapid and has a limit of detection of 0.081 ng mL(-1). This simple and facile methodology makes the method highly suitable for the detection of pesticides in general and organophosphates, in particular. (C) 2015 Elsevier B.V. All rights reserved.