Aptamer–Target–Gold Nanoparticle Conjugates for the Quantification of Fumonisin B1

Fumonisin B1 (FB1), a mycotoxin classified as group 2B hazard, is of high importance due to its abundance and occurrence in varied crops. Conventional methods for detection are sensitive and selective; however, they also convey disadvantages such as long assay times, expensive equipment and instrumentation, complex procedures, sample pretreatment and unfeasibility for on-site analysis. Therefore, there is a need for quick, simple and affordable quantification methods. On that note, aptamers (ssDNA) are a good alternative for designing specific and sensitive biosensing techniques. In this work, the assessment of the performance of two aptamers (40 and 96 nt) on the colorimetric quantification of FB1 was determined by conducting an aptamer–target incubation step, followed by the addition of gold nanoparticles (AuNPs) and NaCl. Although MgCl2 and Tris-HCl were, respectively, essential for aptamer 96 and 40 nt, the latter was not specific for FB1. Alternatively, the formation of Aptamer (96 nt)–FB1–AuNP conjugates in MgCl2 exhibited stabilization to NaCl-induced aggregation at increasing FB1 concentrations. The application of asymmetric flow field-flow fractionation (AF4) allowed their size separation and characterization by a multidetection system (UV-VIS, MALS and DLS online), with a reduction in the limit of detection from 0.002 µg/mL to 56 fg/mL

Mathematical characterization of ink diffusion and imbibition processes in chromatography paper as a potential biosensing platform

Materials used for biosensor development normally include silicon, glass, and synthetic polymers, however, paper is a practical and cheap option for the reduction of manufacturing costs with a wide range of applications. Paper-based biosensors have been widely produced, yet poorly characterized on the interaction of different type of molecules with its intricate microstructure. In this work, five ink solutions were prepared as model samples to examine their diffusion and imbibition behavior on grade 3MM chromatography paper. Different mathematical models, previously reported for porous matrices, were fitted and results revealed that upward wicking (r2 ≥ 0.90) equations described the experimental data during the initial stage (< 5 s) and yielded similar permeability values to those calculated from the matrix structural properties. The diffusion coefficient was determined up to attaining equilibrium using the diffusion equation in a cylinder element (r2 ≥ 0.90). This study enabled the characterization of the performance from 3MM chromatography paper, by using ink as a surrogate model of small molecules (e.g. mycotoxins) or small colloidal particles