Biosensor based on cysteine monolayer and monoclonal antibody for specific detection of aflatoxin b1 in rice

Abstract

An electrochemical immunosensor for detection of aflatoxin B1 (AFB1 ) in food samples was developed. The sensor is composed by cysteine monolayer immobilized on gold electrode surface with subsequent bind to monoclonal antibody (MAb-Cys-modified electrode). The AFB1 detection was evaluated by cyclic voltammetry and impedance spectroscopy in the frequency range of 100 mHz-100 kHz. Samples of rice were spiked with AFB1 to evaluate the sensitivity of the sensor. Impedance spectra could be fitted to a Randles equivalent circuit containing a constant phase element. Atomic force microscope (AFM) images showed MAb-AFB1 complex immobilized across the electrode surface. The electron transfer resistance (Rct ) increase was attributed to a decrease in the charge permeability of the MAb-AFB1 -Au surface to a redox probe K4 [Fe(CN)6 ]4- /K3 [Fe(CN)6 ]3- . The surface coverage exhibited a linear relationship as function of toxin concentration and is found to be 0.75 at 30 μg mL-1 . The obtained sensor is a promising candidate for detection of AFB1 in rice with sensitivity and specificity.