Selection, characterization and application of aptamers targeted to Aflatoxin B2

Aflatoxins are naturally occurring mycotoxins that can contaminate foodstuffs and consequently affect human health. In this study, the systematic evolution of ligands by exponential enrichment (SELEX) technology was used to effectively screen DNA aptamers that recognize Aflatoxin B2 (AFB2) with high affinity and specificity. AFB2 was first combined with magnetic nanoparticles, which served as carriers, and then incubated with a library of single-stranded DNA (ssDNA). The entire selection process included incubation, separation, elution, PCR amplification and single chain preparation. The selection conditions were optimized. After 10 rounds of selection, 30 aptamer sequences were obtained and enriched. Homological analysis in combination with structural analysis as well as the affinity and specificity experiments revealed that aptamer sequence 17 showed the best affinity and specificity toward AFB2. The dissociation constants value for aptamer sequence 17 was 9.83 nM. And the specificity experiment results showed the binding between AFB2 aptamer with five other toxins was very week (did not exceed 18% compared to AFB2). The selected AFB2 aptamer was used to construct a fluorescent biosensor. The assay showed a wide linear range, with the AFB2 concentration ranging from 100 ng/L to 1800 ng/L and a detection limit of 50 ng/L. Additionally, the spiked recovery experiment of AFB2 in peanut oil sample exhibited a recovery ratio between 94.0% and 101.6% which showed good accuracy of the proposed aptamer-based bioassay.