Screening of Carbamate and Organophosphate Pesticides in Food Matrices Using an Affordable and Simple Spectrophotometric Acetylcholinesterase Assay

Abstract

Carbamates (CMs) and organophosphates (OPs) are widely used pesticides with known neurotoxicity arising from the inhibition of acetylcholinesterase (AChE). When AChE is active, in vitro, it can hydrolyze certain substrates to colored products while in the presence of an inhibitor this color development is decreased. Based on this principle, an AChE assay for CM and OP compounds was optimized and validated for carbofuran, carbofuran-3-hydroxy and dichlorvos in lettuce and strawberry extracts. The analytical performance of the assay was confirmed by an accredited liquid chromatography tandem mass spectrometry (LC–MS/MS) method. The developed AChE assay achieved low limits of detection (LODs) at the part per billion (ppb) level, depending the analyte inhibitory strength, recovery rates higher than 70% and good repeatability. Moreover, the toxic unit (TU) approach was applied, for extracts containing the validated analytes, and antagonism was noticed in all cases. Overall, the developed method is rapid, simple, cost-effective and may find application as a low-cost pre-screening tool of AChE inhibitors presence. Last but not least, this study can be considered a guide on development, validation and benchmarking of bioassays in food safety, a topic, which is commonly mispresented in the available literature.

Smartphone-based optical assays in the food safety field

“…FoodSmartphone is focused on the development of bioanalytical assays with potential for user friendly smartphone based detection of allergens [ 20 , 21 , 25 , 43 ] and major food contaminants (e.g. marine toxins [ 73 ] and pesticides [ 16 , 74 ]). PhasmaFood aims to achieve on-site food quality testing developing a miniaturized smart sensor based on spectroscopy principles for example ultra-violet (UV) or infrared (IR) spectroscopy [ [75] , [76] , [77] ].…”

Rapid Multi-Residue Detection Methods for Pesticides and Veterinary Drugs

“…Therefore, various colorimetric screening methods have been developed based on this principle. An AChE assay has been optimized and validated for carbofuran, carbofuran-3-hydroxy, and dichlorvos in lettuce and strawberry extracts [ 97 ]. Indoxyl acetate was used as a substrate which can be rapidly hydrolyzed by AChE to produce blue hydrazine.…”

“…Graphene and transition metal carbides have also been used to modify an AChE biosensor for the detection of OP pesticides. The biosensor showed better catalytic performance compared to the biosensors without modification [97]. Furthermore, a robust and novel conjugated polymer and core-shell magnetic nanoparticle containing biosensor was applied to detect pesticides [100].…”

Optical Screening Methods for Pesticide Residue Detection in Food Matrices: Advances and Emerging Analytical Trends

“…ELISAs have been developed for the screening of various pesticide residues in food matrices, for example, OPs [ 37 , 38 ], CMs [ 39 ], neonicotinoids [ 40 ], or fungicides [ 41 ]. In terms of cholinesterase microplate assays, cholinesterases have been employed as recognition elements (both AChE [ 42 ] and butyrylcholinesterase, BChE [ 43 ]) to screen for CM and OP. Considering that, in vitro, cholinesterases hydrolase colorless substrates to colored products, the presence of CMs and OPs can be correlated to a color decrease similarly to competitive ELISAs.…”

“…A great variety of substrates, resulting in different colored products ( Figure 3 b), have been used including acetylthiocholine and butyrylthiocholine halides for AChE and BChE, respectively; indoxyl acetate; α-naphthyl acetate; 2,6-dichloroindophenol acetate; and others [ 44 ]. Importantly, reduced sample and reagent consumption (typically less than 100 μL) as well as low LODs at the μg kg −1 level [ 42 , 45 , 46 ], depending on the matrix, were achieved by cholinesterase microplate assays. However, biochemical assays are still applicable in laboratories as they require certain apparatus and well-trained operators (commonly such assays contain multiple steps).…”