Single-enzymatic (AChE/ChOx) colorimetric detection of organophosphorus pesticides based on controllable nanoparticles supported by FeCoCu flower-like structure with peroxidase-like activity

Organophosphorus pesticides (OPs) are widely used but easily persist in the environment, which can impact ecological and biological health. In this paper, the nanoparticles supported by FeCoCu flower-like structure (FeCoCu-FN) was successfully synthesized when the molar ratio of Fe:Co:Cu is 0.6:0.4:0.6, which exhibits strong peroxidase-like activity at high V_m (266.7×10⁻⁸ M/s). Combined with 3,3′,5,5′-tetramethylbenzidine (TMB), two types of colorimetric sensors, acetylcholinesterase (AChE) method and choline oxidase (ChOx) method, were firstly proposed in the same reaction system for detection of OPs based on FeCoCu-FN. The comparisons of both the two assays were conducted in details, such as cost, sensitivity, speed and stability. Moreover, the inhibition effects between parathion methyl (PM) and the two enzymes (AChE and ChOx) were predicted and contrasted using the molecular docking method. It can be found that the free binding energy of AChE with PM is smaller than that of ChOx with PM, which indicates that PM is more easily bound to AChE. On the other hand, the inhibition constant of AChE with PM is smaller than that of ChOx with PM, which illustrates the stronger inhibition effect of PM on AChE. The AChE single-enzyme method has higher sensitivity (LOD=0.011 ng/mL), which was consistent with the result of molecular docking. Two analysis methods were used to detect PM in real samples, and the detection results were validated using t-test and F-test. The results showed that there was no significant difference in accuracy and mean between the two methods, and both methods were reliable.