A simple paper-based biosensor for on-site visual detection of organophosphate residues

Abstract

In general, the laboratory method of analyzing pesticides in vegetables is complicated due to the high cost of equipment and chemicals. The process of analyzing pesticide residues generally requires expertise as well as a significant period of time. In this study, a paper-based biosensor was developed for the detection of acetylcholinesterase (AChE) inhibitors, particularly organophosphate pesticides. The paperbased biosensor was constructed based on the Ellman colorimetric assay by immobilizing AChE on cellulose paper with 2% alginate gel, 0.25% glutaraldehyde and the colorimetric reagent 5,5-dithio-bis-(2-nitrobenzoic acid) (DTNB) in phosphate buffer (pH 8.0). As a substrate, acetylthiocholine chloride (ATChCl) was used. The results showed that the developed paperbased biosensor has been stable for 2 weeks with a detection limit of 0.03 mM of chlorpyrifos. The paper-based biosensor was applied to detect organophosphate pesticides in vegetables from the farmers’ market, Ratchaburi Province. It was found that the test results of the paper-based biosensor were similar to the commercial GT-test kit. The paper-based biosensor was 10 times faster than the GT-test kit in terms of testing time and the results were easy to identify due to the color-based indicator. As a result, a paper-based biosensor is rapid, portable and easy to use by the general population.