Highly sensitive colorimetric detection of ethyl parathion using gold nanoprobes

• A highly sensitive yet simple method for the effective detection of ethyl parathion using Cys-AuNPs as colorimetric probe.
• Measurement is based on the colour change due to the aggregation of Cys-AuNPs as a consequence of hydrolysis of acetylthiocholine by acetylcholinesterase.
• Spiked samples were also analyzed using this probe and the limit of detection was found to be 0.081 ng mL−1.
• This method can be employed for the on-site monitoring of OPs owing to its low cost, simple instrumentation and rapid nature.

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.

The proposed colorimetric assay describes the detection of ethyl parathion, a widely used organophosphate pesticide using cysteine capped gold nanoparticles (Cys-AuNPs). The enzyme AChE hydrolyses ATCh to TCh which is the key component responsible for the aggregation of Cys-AuNPs and imparting a colour change from red to blue. On the other hand, presence of ethyl parathion inhibits AChE activity thereby leading to the suppression of TCh. Therefore, Cys-AuNPs remain well dispersed and no colour change is observed.Figure optionsDownload as PowerPoint slide