Amperometric detection of triazophos pesticide using acetylcholinesterase biosensor based on multiwall carbon nanotube–chitosan matrix

A simple method for immobilization of acetylcholinesterase (AChE) on multiwall carbon nanotubes (MWNTs)–chitosan (MC) composite was proposed and thus a sensitive, fast and stable amperometric sensor for quantitative determination of organophosphorous insecticide was developed. Atomic force microscopy showed that this matrix possessed homogeneously netlike structure, which prevented enzyme from leaving out of the electrode. MWNTs promoted electron transfer reactions at a lower potential and catalyzed the electro-oxidation of thiocholine, thus increasing detection sensitivity. Based on the inhibition of organophosphorous insecticide to the enzymatic activity of AChE, using triazophos as a model compound, the conditions for detection of the insecticide were explored. Under optimal conditions, the inhibition of triazophos was proportional to its concentration in two ranges, from 0.03 to 7.8 μM and 7.8 to 32 μM with a detection limit of 0.01 μM. A 95% reactivation of the inhibited AChE could be regenerated for using pralidoxime iodide within 8 min. The constructed biosensor processing prominent characteristics and performance such as good precision and reproducibility, acceptable stability and accuracy, fast response and low detection limit has potential application in the characterization of enzyme inhibitors and detection of toxic compounds against to enzyme.