Design and Fabrication of Biosensor Based on Immobilized AchE on Modified Electrode by Graphene-multiwall Carbon Nanotubs/Beta Cyclodexterin-chitosan

Organophosphorus (OP) forms an important class of toxic compounds. They inhibit acetyl cholinesterase (AChE, EC 3.1.1.7) that results in respiratory and myocardial malfunctions. Pesticides could be accumulated in vegetables and fruits, so detection of them is very important. The goals of this study are decreasing detection time and detection limit of methyl parathion biosensor. In this research the methyl parathion biosensor based on modified glassy carbon (GC) electrode-immobilized AChE is constructed. β-cyclodexterin (β- CD)/chitosan-multiwall carbon nanotube (CS-MCNT) composite, first by polymer wrapping method and then by layer-by-layer selfassembly technique, was prepared. Then different combination of β-CD, CS-MCNT and graphene was deposited on GC electrode. AChE solution (4 mg ml-1) was deposited on the modified GC electrode and dried in air at room temperature. The electrochemical measurement is based on AChE inhibition by methyl parathion (MPT) in the presence of acetyl choline iodide (ACTI) as substrate with cyclic voltammetry method. The results show that using graphene contributes to considerable increasing in current up to 27 μA. These measurements were done in phosphate buffer (pH = 7.5) and at 25 °C. The optimum pH and temperature were 7.5 and 55 °C receptively. Detection limit for MPT was obtained 5nM.