An amperometric acetylcholinesterase sensor based on Fe_3O_4 nanoparticle/multi-walled carbon nanotube-modified ITO-coated glass plate for the detection of pesticides

摘要

A method is described for the construction of a highly sensitive electrochemical biosensor for the detection of malathion, chlorpyrifos, monocrotophos and endosulfan based on covalent immobilization of acetylcholinesterase (AChE) on iron oxide nanoparticles (Fe_3O_4NPs)-decorated carboxylated multi-walled carbon nanotubes (c-MWCNTs) electrodeposited onto indium tin oxide (ITO)-coated glass plate. Transmission electron microscopic (TEM) and UV analysis of nanocomposite materials demonstrated that Fe_3O_4NPs were well deposited on the outer walls of c-MWCNTs. The modified electrode was characterized by atomic force microscopy (AFM), cyclic voltammetry (CV), Fourier transform infrared (FTIR) spectroscopy and electrochemical impedance spectroscopy (EIS). The resulting biosensor exhibited a linear response for acetylthiocholine in a concentration range of 0.1-700 μmol L~(-1) with a remarkable sensitivity of 0.402 mA/μmol L~(-1). Under optimum conditions, the inhibition rates of pesticides were proportional to their concentrations in the range of 0.1-70 nmol L~(-1), 0.1-50 nmol L~(-1), 0.1-70 nmol L~(-1) and 0.1-100 nmol L~(-1) for malathion, chlorpyrifos, monocrotophos and endosulfan, respectively. The detection limit of the biosensor for all pesticides was 0.1 nmol L~(-1) at a signal-to-noise ratio of 3. The biosensor showed good reproducibility, no interference by metal ions and long-term stability. The measurement results obtained by the present biosensor were in good agreement with those obtained by the standard gas chromatography-mass spectrometry method. The biosensor was employed for the determination of pesticides in environmental and food samples.