Comparison of the Performances of Two Aptamers on a Colorimetric Assay for the Quantification of Fumonisin B1

Fumonisin B1 (FB1), a mycotoxin commonly produced by Fusarium verticillioides and classified as a group 2B hazard, has been identified in various food products; hence, sensitive and rapid analytical detection methods are needed. Since the first reported aptamer (96 nt ssDNA) for the highly specific molecular recognition of FB1, only 30 aptamer-based biosensors have been published. A critical point, yet commonly overlooked during the design of aptasensors, is the selection of the binding buffer. In this work, a colorimetric assay was designed by incubating a folded aptamer with FB1 and the subsequent addition of gold nanoparticles (AuNPs). The changes in the aggregation profile of AuNPs by a 40 nt aptamer and a 96 nt aptamer were tested after the addition of FB1 under different buffer conditions, where the incubation with Tris-HCl and MgCl2 exhibited the most favorable performances. The assay with the longest aptamer was specific to FB1 and comparable to other aptasensors with a limit of detection (LOD) of 3 ng/mL (A650/520 ratio). Additionally, the application of asymmetric-flow field-flow fractionation (AF4) with multidetection allowed for the analysis of the peak area (λ) and multi-angle light scattering (MALS) with LODs of up to the fg/mL level.