Inhibitive determination of organophosphate pesticides using acetylcholinesterase and silver nanoparticle as colorimetric probe

Abstract

Accurate and real-time detection of pesticides is needed to ensure food safety and ecosystem protection. A biosensor was developed to determine organophosphate pesticides using acetylcholinesterase (AChE) and silver nanoparticle (AgNP) immobilized on the alginate-chitosan film matrix. The sensing principle is based on organophosphate pesticides (OP) inhibiting AChE activity. AChE hydrolyzes acetylthiocoline (ATCh) to thiocholine (TCh) and acetic acid (AA). The -SH group on TCh induces AgNP aggregation, resulting in fading of the film's brownish-yellow color. The presence of OP in the sample inhibited AChE activity, leading to a decrease in TCh and color fading. The biosensor response is determined by measuring the Red Green Blue (RGB) value of the film. The biosensor offers rapid detection directly in-situ and real time without the use of sophisticated instruments, with optimal measurement conditions of pH 7, incubation time of 1 minute, and concentrations of AgNP, ATCh, and tris-HCl buffer of 10 μg/mL, 50, and 7 mM, respectively. Biosensors have excellent sensitivity, reproducibility, and selectivity. Measurement of OP levels in nine vegetable samples revealed that the proposed colorimetric probe's results agreed well with the GC result as the reference method. Therefore, this method can be applied in monitoring food and environment OP levels.