Carbon dot-based bioplatform for dual colorimetric and fluorometric sensing of organophosphate pesticides

Rapid and sensitive monitoring strategy plays a crucial role in food safety and environment protection for the screening of organophosphorous pesticides ( OPs) due to their extensive usage and harmful neurotoxicity on mammals. Herein, a label-free bioplatform was designed for sensitive detection of OPs through dual-mode (fluorometric and colorimetric) channels based on acetylcholinesterase (AChE)-controlled quenching of fluorescence carbon dots (CDs). This sensing strategy involves the reaction of acetylthiocholine with AChE to produce thiocholine which specifically triggered the decomposition of 5,5-dithiobis (2-nitrobenzoic acid) to form yellow-colored 5-thio-2-nitrobenzoic acid (TNBA). Meanwhile, TNBA with positive charge was capable of functioning as a powerful absorber to quench the fluorescence of CDs through dynamic quenching process. With the presence of OPs, the enzyme activity of AChE was blocked, leading to the recovery of fluorescence signal and the decrease of absorbance intensity with color variation. The dual-output assay provided good sensitivity for rapid detection of paraoxon (model analyte) with a detection limit of 0.4 ngmL(-1). Therefore, taking advantage of the excellent optical property of CDs and the specificity of enzyme, the dual-readout platform can potentially be a promising candidate for OPs detection. (C) 2017 Elsevier B.V. All rights reserved.