Development of aflatoxin B₁ aptasensor based on wide-range fluorescence detection using graphene oxide quencher

Aflatoxin B₁ (AFB₁) is a carcinogenic substance produced by fungi of genus Aspergillus, especially Aspergillus flavus. Few nanograms of AFB₁ that permeated through the skin is sufficient to cause liver cancer and stunted growth. In this study, a rapid aptamer-based assay for AFB₁ was developed using the fluorescence quenching property of graphene oxide (GO) and a fluorescein amidite (FAM)-modified aptamer specific to AFB₁. The aptamer, modified with the fluorescence dye FAM on its 5'-end, was used as a probe. Once bound by AFB₁, 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 AFB₁, the fluorescence intensity remained unchanged. The aptamer-based AFB₁ assay process was conducted through 3 steps within 40min. The aptamer was incubated with AFB₁ before the addition of GO. The amount of AFB₁ present was measured by the change in fluorescence intensity. The detection system was evaluated with standard solutions of AFB₁ of various concentrations. The results showed that the fluorescence intensity decreased linearly as the concentration of AFB₁ gradually increased. Although the assay was specific to AFB₁, 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.