Preparation and application of aptamer-functionalized sorbent for the analysis of ultra-trace aflatoxin M1 and analogues in milk

A novel, efficient and specific aptamer-functionalized sorbent was successfully synthesized and applied in the analysis of ultra-trace aflatoxin M1 (AFM1) and its analogues in milk. By using a gold nanoparticle-based colorimetric analysis tool, we could determine that the AFM1-aptamer (M1-aptamer) recognized and bound AFM1 to generate an aptamer-target complex. After analysis and verification, the M1-aptamer on the surface of the carboxyl microspheres were completely modified via EDC/NHs amide formation. The effects of extraction pH, extraction buffer, concentration of Mg 2+ and elution solvents were investigated by single-factor experiments to determine the most suitable analysis conditions. Using these conditions, the extraction performance of the M1-aptamer-functionalized sorbent could be studied and an analytical method for AFM1 and its analogues in milk could be established. The results of adsorption equilibrium as well as adsorption selectivity experiments indicated that the M1-aptamer offered a specific adsorption site to selectively adsorb aflatoxins exhibiting a dihydrofuran oxaphthalene scaffold. The adsorption capacity of the aptamer-functionalized sorbent was 233.1 μg/g. A studied method for the determination AFM1 in milk with low matrix effect demonstrated a good linear correlation in the range of 0 to 2.0 μg/L (R 2  = 0.9982) and high detection sensitivity (detection limits of 7 ng/kg in milk and 21 ng/kg in milk power). Furthermore, excellent spiked recovery and good repeatability were obtained. The method delivered specific, accurate and reproducible results for enriching and detecting ultra-trace AFM1 and its analogues in milk.