An immunosensor for ultrasensitive detection of aflatoxin B1 with an enhanced electrochemical performance based on graphene/conducting polymer/gold nanoparticles/the ionic liquid composite film on modified gold electrode with electrodeposition

The paper described an immunosensor for aflatoxin B1 with an enhanced electrochemical performance based on graphene/conducting polymer/gold nanoparticles/the ionic liquid composite film. Graphene oxide, 2,5-di-(2-thienyl)-1-pyrrole-1-(p-benzoic acid) and gold nanoparticles, in this order, were electrodeposited on gold electrode surface. The graphene was characterized and its apparent heterogeneous electron transfer rate constant determined to be 28.55 ± 0.17 cm s−1 which is better than that of a bare gold electrode. An electrochemical immunoassay for aflatoxin B1 was developed by immobilizing the respective antibody on the conducting polymer film, and a solution containing ionic liquid and chitosan was then dropped onto this electrode. The presence of graphene and gold nanoparticles warrant fast electron transfer, and the ionic liquid provides a benign microenvironment for the antibody. The method displays a good sensitivity, detection limit (at S/N = 3) as low as 1 fM, a dynamic range from 3.2 fM to 0.32 pM, and an excellent long-term stability (over 26 weeks). This immunoassay represents a remarkable improvement in terms of sensitivity, repeatability and stability when compared to other method for the determination of aflatoxin B1. It was successfully applied to the determination of aflatoxin B1 in spiked food samples, with recoveries in the range from 96.3% to 101.2%.