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.
Keywords:
biosensor; impedance; cyclic voltammetry; aflatoxin
