Development of a bio-electrochemical assay for AFB1 detection in olive oil

A novel biosensor assay format for aflatoxin based on acetylcholinesterase (AChE) inhibition by aflatoxin B-1 (AFB(1)) is proposed. The AChE was present in solution and an amperometric choline oxidase biosensor was used for monitoring its residual activity. To create the biosensor, the choline oxidase was immobilized by cross-linking onto screen-printed electrodes modified with Prussian Blue (PB) and these were used to detect the H2O2 at low potential (-0.05 V versus a screen-printed internal silver pseudoreference electrode). For the development of the AFB(1) assay, several parameters such as AChE and substrate concentration, the methanol effect, and pH were evaluated and optimized. The linear working range was assessed to be 10-60 ppb. Concentrations as low as 2 ppb, which correspond to the legal limit of AFB1 in food for humans, were detected after a pre-concentration step. The suitability of the method was evaluated using commercial olive on samples. A recovery equal to 78 +/- 9% for 10 ppb of AFB(1) in olive oil samples was obtained. (C) 2008 Elsevier B.V. All rights reserved.