Multicolor sensor for organophosphorus pesticides determination based on the bi-enzyme catalytic etching of gold nanorods

Abstract

Compared with optical density variations, human eyes are more sensitive to color variations. Herein, we develop a multicolor biosensor for organophosphorus pesticides (OPs) detection based on the enzymatic etching of gold nanorods (AuNRs). In the presence of acetylcholinesterase (AChE) and choline oxidase (CHO), the substrate acetylcholine (ACh) is catalyzed to generate H2O2. The resultant H2O2 etches AuNRs and lead to the etching of AuNRs, accompanying with distinct color changes. OPs inhibit the activity of AChE, which prevent the generation of H2O2 and the etching of AuNRs. Visual semi-quantitative determination of OPs is significantly improved due to multiple colors are presented in this biosensor. LSPR shift (ΔW), after and before inhibition, was utilized to quantitatively measure OPs. Under optimum conditions, the LSPR band shift of AuNRs are linearly dependent on the logarithm of inhibitor concentration over the ranges from 0.01 to 50 μg/L and from 1.0 to 500 μg/L, for dichlorvos and demeton, respectively. LOD are much lower than the maximum residue limits specified in the U.S Department of Agriculture and European Union pesticide regulations. They are also lower than those obtained by previously reported colorimetric methods.