Acetylcholine esterase enzyme doped multiwalled carbon nanotubes for the detection of organophosphorus pesticide using cyclic voltammetry.

Use of immobilized acetylcholine esterase (AChE) for detecting organophosphorus pesticides in water sources and body fluids can bring down the detection costs dramatically. In the present study, AChE was directly doped on multiwalled carbon nanotube (MWCNT) surface modified with carboxylic groups through amide bond and used for organophosphorus pesticide detection. Amide bond formation between MWCNTs and the enzyme molecules avoid use of any intermediate membranes, cross-linkers or binding materials. This strategy overcomes the hindrance to electron transfer posed by membranes or cross-linkers and increases the sensitivity of detection. MWCNTs carrying carboxyl groups were deposited on glassy carbon electrode and were subsequently immobilized with AChE. The activity of AChE was monitored by cyclic voltammetry after immobilization. Scanning electron microscopy and atomic force microscopy were used to characterize the electrode surface. FT-IR spectra were taken to characterize enzyme-MWCNT complex. Under optimized parameters, the electrode showed linear range between 10 and 50 nM, which is promising for detection of trace amounts of the pesticide. The lower and higher detection limits of the sensor are 0.1 nM and 500 nM respectively. The stability and reusability of the electrode were determined. Finally, successful detection of organophosphorus compounds in real samples established it as reliable for sensor applications.