Electrochemical Biosensors For The Detection Of Pesticide

With the development of people's living condition and the improvement of people's health consciousness, there are more concerns about pesticides used to control pests on food crops are dangerous to people who consume those food. Therefore, rapid determination and reliable quantification of trace level of pesticide have become increasingly important for public security and health protection. Traditional analytical methods, such as gas chromatography, gas chromatography-mass spectrometry, liquid chromatography or liquid chromatography-mass spectroscopy have been widely used. These methods are sensitive and reliable for the determination of pesticide residue, however, they are expensive, time-consuming, require complicated pretreatment steps and extensive labor resources, and are not applicable for on-site determination. Electrochemical biosensors offer a simple and inexpensive approach for rapid and onsite biomonitoring of pesticide residue exposure through the change of enzymatic activities. They have been widely used in biosensors because of their rapidity, simplicity, low cost, high sensitivity. Over the past few years, enzyme-based biosensors have emerged as a promising alternative to detect pesticides. This work mainly covered the following areas.1. Preparation of acetylcholinesterase / graphene oxide-chitosan modified glassy carbon electrode and its application in pesticide detection. First, graphene oxide (GO)- chitosan (CHIT) composite film was dropped on glass carbon electrode (GCE), then acetylcholinesterase (AChE) was dropped on GO-CHIT/GCE. Atomic force microscopy (AFM) was used to observe the surface topography. AFM results showed that AChE was well immobilized on GO-CHIT/GCE. Under the optimal experimental condition, the inhibition of carbaryl on the activity of AChE was proportional to carbaryl concentration in the ranges from 0.005 to 0.4μM and from 1.0 to 5.0μM. The detection limit was calculated to be about 4.0 nM. The biosensor provided a new promising tool for pesticide analysis.2. Preparation of acetylcholinesterase / Nafion / Prussian Blue modified glassy carbon electrode and its application in pesticide detection. Prussian blue (PB) was electrodeposited on GCE, then Nafion was drop on PB/GCE, at last AChE was drop on Nafion/PB/GCE. The determination of carbaryl pesticide is based on the inhibition of AChE/ Nafion/ PB/ GCE response by pesticide. The properties and performance of the sensor have been measured by electrochemistry and AFM in detail. AFM results showed that AChE assembled uniformly on Nafion / PB/GCE and formed porous films. The electrochemistry results showed that the response of AChE/ Nafion / PB/ GCE for the carbaryl pesticide depended strongly on the amount of AChE adsorbed on electrode, the deposited time of PB, the amount of Nafion and pH of the supporting electrolyte solution. The AChE/Nafion/PB/GCE constructed in optimal conditions showed a good linear relationship between the peak current and the concentration of pesticide in the range of 0.01-0.5μmol/L & 2.0-10.0μmol/L for carbaryl and 0.02-1μmol/L & 2.0-8.0μmol/L for trichlorfon, respectively. The detection limit was 5.0 nmol/L for carbaryl and 10.0 nmol/L for trichlorfon, respectively. And the modified electrode was applied in the detection of analogous practical samples. It was found that the resulted sensor had the high detection sensitivity, good reproducibility and anti-interference.3. Preparation of acetylcholinesterase / Prussian Blue-Chitosan modified glassy carbon electrode and its application in pesticide detection. PB-CHIT hybrid film was electrodeposited on GCE, subsequently AChE was drop on CHIT-PB/GCE. The PB-CHIT hybrid film exhibited a good biocompatibility with AChE and effectively immobilized AChE on it. AFM was used to observe the surface topography. Nanosized PB-CHIT uniformly distributed. The deposited time of PB-CHIT, concentration of CHIT, the concentration of AChE, pH of the supporting electrolyte solution was discussed. Under the optimal experimental condition, the inhibition of carbaryl on the activity of AChE was proportional to carbaryl concentration in the ranges from 0.01 to 0.4μM and from 1.0 to 5.0μM. The detection limit was calculated to be about 3.0 nM. The biosensor provided a new promising tool for pesticide analysis.