Aptamer structure switch fluorescence anisotropy assay for aflatoxin B1 using tetramethylrhodamine-guanine interaction to enhance signal change

Fluorescence anisotropy (FA) assay in homogenous solution is simple, sensitive and reproducible. Here, we reported an aptamer structure switch FA assay for detection of aflatoxin B1 (AFB1), one of the most toxic mycotoxins, by using tetramethylrhodamine (TMR)-labeled aptamer probe and its complementary DNA (cDNA) with tandem G bases extension, to meet the demand in sensitive and selective detection of AFB1. The hybridization of aptamer and cDNA drew TMR close to the repeated guanine (G) bases, and a high FA value was induced due to TMR-G interaction and restricted local rotation of TMR. In the presence of AFB1, aptamer bound to AFB1 instead of the cDNA due to competition. Thus, the TMR-G interaction was eliminated, and FA value of TMR decreased. This assay enabled the detection of AFB1 with detection limit of 125 pmol/L and dynamic range from 125 pmol/L to 31.2 nmol/L (C) 2020 Chinese Chemical Society and Institute of Materia Medica, Chinese Academy of Medical Sciences. Published by Elsevier B.V. All rights reserved.