Acetylcholinesterase Biosensor Based On Graphene Composite For Detection Of Organophosphates

With the continuous improvement of people’s living standard, the problem of pesticide residues in agricultural products has aroused widespread concern and close attention, due to its potential harm to people’s health. In recent years, the biosensors used for the detection of pesticide residues have developed rapidly, the test forms of the biosensor tend to diversity, the response time is shortened, and the degree of automation is greatly improved, which showed wide prospect in pesticide detection. In this paper, acetylcholinesterase (AChE) was immobilized on the working electrode surface through covalent bonding and cross-linking method, using graphene-BMIMPF6composite, graphene-AuNPs and graphene-Fe3O4nanocomposites modified working electrode, the AChE biosensor with good performance, which could be used for rapid and sensitive OPs detection. The main contents of this paper include:1. A highly sensitive organophosphates (OPs) amperometric biosensor was developed by immobilizing acetylcholinesterase (AChE) through covalent bonding to l-butyl-3-methylimidazolium hexafluorophosphate (BMIMPF6)-graphene-chitosan composite. Because of the higher specific surface area of graphene and high ionic conductivity of the BMIMPF6, BMIMPF6-graphene-chitsoan composite material not only provided a biocompatible microenvironment to keep the bioactivity of AChE, but also exhibited a strong synergetic effect on improving the sensing properties of OPs. The inhibition of malathion was proportional to its concentration ranging from0.1nmol/L to1.0nmol/L and1.0nmol/L to10nmol/L, with a detection limit of0.04nmol/L (S/N=3).2. A simple method to immobilize acetylcholinesterase (AChE) on graphene (GR) and nano-Au composite by chitosan film-forming effect. Therefore, a new AChE biosensor was developed. Under the optimal experimental conditions, linear relationship between the rate of decrease in peak current and the concentration of malathion was found in the range of2.0×10-10to1.0×10-9mol/L and4.0×10-9to5.0×10-8mol/L, with a detection limit of2.0×10-11mol/L (S/N=3), and the recovery results were from92.0%～109.0%. 3. A highly sensitive electrochemical biosensor has been developed for the determination of methyl parathion (MPT) and parathion (PT), which was based on acetylcholinesterase (AChE) immobilized onto graphene-Fe3O4nanocomposite film modified glassy carbon electrode. The nanocomposite not only provided a biocompatible microenvironment to keep the bioactivity of AChE, but also exhibited a strong synergetic effect on improving the sensing properties of MPT and PT. A value of0.19mmol/L for the apparent Michaelis-Menten constant (Kmapp) was obtained. The inhibition percentages of methyl parathion and parathion were proportional to their concentrations in the range of2.5±100-9～2.5×10-6g/mL and5.0×10-9～1.0×10-5g/mL, respectively. For methyl parathion, the detection limit was3.0×10-10g/mL and the detection limit for parathion was8.0×10-10g/mL (S/N=3).