Acetylcholinesterase entrapment onto carboxyl-modified single-walled carbon nanotubes and poly (3,4-ethylenedioxythiophene) nanocomposite, film electrosynthesis characterization, and sensor application for dichlorvos detection in apple juice

Abstract

Abstract Carboxylic acid functionalized single-walled carbon nanotubes and poly (3,4-ethylenedioxythiophene), C-SWCNT:PEDOT, were homogenously electrodeposited onto working electrodes (WE) in order to develop an acetylcholinesterase (AChE)-based biosensor. RAMAN, FTIR, SEM, EDX and electrochemical methods provided evidence for the enzyme immobilization and the conducting composite formation. The SWCNT dissolved in poly (sodium 4-styrenesulphonate) (PSS), and 3,4-ethylenedioxythiophene (EDOT) dissolved in polyethyleneglicol (PEG) were used for composite electrodeposition to provide a homogenous layer and a compatible environment around the AChE. The composite C-SWCNT:PEDOT has proved to be highly efficient for retaining the activity and stability of AChE and also for promoting the electron transfer reaction to the gold electrode. Under optimized experimental conditions, the inhibition of dichlorvos (DVSO) on AChE showed a proportional inhibition current signal with increasing concentrations of DVSO in the range 1\xa0ppb to 600\xa0ppb. The correlation coefficient obtained with spectrophotometer enzyme assay method versus a biosensor was 0.989. It showed high accuracy, precision. The detection limits were 5.54\xa0ppb using the CA method and 0.447\xa0ppb using differential pulse voltammetry (DPV). Both values are below the permitted limit for DVSO in fruit and vegetables. The sensor showed stability and could be used as a disposable amperometric sensor with potential application for monitoring organophosphorus pesticides.