Potentiometric competitive immunoassay for determination of aflatoxin B1 in food by using antibody-labeled gold nanoparticles

The authors report on a competitive potentiometric immunoassay for aflatoxin B-1 (AFB(1)) in food that displays distinctly improved sensitivity. Gold nanoparticles (AuNPs; 16 nm i. d.) were functionalized with polyclonal anti-AFB(1) antibody (pAb), whilst the sensor electrode was prepared by immobilizing AFB(1)-bovine serum albumin conjugate (AFB(1)-BSA) on a glassy carbon electrode. Upon addition of target AFB(1), competitive immunobinding occurs between the analyte and AFB(1)-BSA for the labeled pAb on the AuNPs. The change in the surface charge as a result of the antigen-antibody reaction causes a shift in the electrical potential. With increasing concentrations of analyte (AFB(1)), the quantity of pAb-AuNP captured by the electrode decreases. The shift in the output potential is linearly proportional to the logarithm of AFB(1) concentration in the 0.1 to 5.0 mu g center dot kg(-1) range, with a detection limit (LOD) of 87 ng center dot kg(-1) (87 ppt). An intermediate precision of 10.9 % was accomplished in batch-to-batch identification. The selectivity over AFB(2) with similar chemical structure is acceptable. The method accuracy was evaluated by analyzing naturally contaminated and spiked peanut samples, giving consistent results (with RSD values of < 12 %) between this immunoassay and the commercial ELISA.