Development of aflatoxin B aptasensor based on wide-range fluorescence detection using graphene oxide quencher.

Aflatoxin B (AFB) is a carcinogenic substance produced by fungi of genus Aspergillus, especially Aspergillus flavus. Few nanograms of AFB that permeated through the skin is sufficient to cause liver cancer and stunted growth. In this study, a rapid aptamer-based assay for AFB was developed using the fluorescence quenching property of graphene oxide (GO) and a fluorescein amidite (FAM)-modified aptamer specific to AFB. The aptamer, modified with the fluorescence dye FAM on its 5'-end, was used as a probe. Once bound by AFB, a conformational change of the aptamer was caused that led to its interaction with the well-known fluorescence quencher GO, resulting in a decrease of the fluorescence intensity of the system. In the absence of AFB, the fluorescence intensity remained unchanged. The aptamer-based AFB assay process was conducted through 3 steps within 40min. The aptamer was incubated with AFB before the addition of GO. The amount of AFB present was measured by the change in fluorescence intensity. The detection system was evaluated with standard solutions of AFB of various concentrations. The results showed that the fluorescence intensity decreased linearly as the concentration of AFB gradually increased. Although the assay was specific to AFB, there was slight interference by other types of aflatoxin. When the assay was applied to a real sample, the limit of detection was 4.5 ppb, which was within the wide detection range of up to 300ppb with good linearity. Thus, this biosensor is considered to be competitive with the conventional detection methods in the field owing to its wide detection range and assay rapidity.