Detection of Acetylcholinesterase Inhibitor Pesticides Based on Copper-Glutamic Acid Polymer Nanozyme

Copper-glutamic acid polymer nanoparticles (Cu-Glu CPNs) were prepared by one-step precipitation method from copper nitrate and glutamic acid in aqueous solution at room temperature and atmospheric pressure for detection of acetylcholinesterase (AChE) inhibitor pesticides. AChE catalyzed the hydrolysis of acetylcholine (ACh) to choline (Ch), which was oxidized by choline oxidase (ChOx) to produce hydrogen peroxide (H2O2). H2O2 was further catalyzed by Cu-Glu CPNs with peroxidase-like activity to oxidize the colorless 3,3′,5,5′-tetramethylbenzidine (TMB) to a blue oxidation product, showing a distinct absorption peak at 650 nm. When organophosphorus pesticides (OPs) or carbamate pesticides (CPs) and other AChE inhibitor pesticides were present, they indirectly inhibited the oxidation of TMB, resulting in a decrease in absorbance at 650 nm. The decrease was related to the pesticide concentration, thus achieving colorimetric detection of pesticides. Under the optimal conditions, the limits of detection (LOD) for OPs pesticide malathion (Mal) and CPs pesticide carbaryl (Car) were 2.14 ng/mL and 1.29 ng/mL, respectively. This method was applied to detection of Mal and Car in apples, cucumbers, tomatoes and oranges with recovery rates ranging from 91.6% to 105.7% and 87.1% to 118.6%, respectively, indicating its potential for practical application in agricultural product testing.