Selection of acrylamide-specific aptamers by a quartz crystal microbalance combined SELEX method and their application in rapid and specific detection of acrylamide

Abstract

Acrylamide (AA) is a small molecule with neurotoxicity, potential carcinogen, and genotoxicity. Aptamers, known as “chemical antibodies”, are single-stranded DNA or RNA specific binding to their targets. Herein, aptamers specific to AA were first selected by a quartz crystal microbalance (QCM) combined with systematic evolution of ligands by exponential enrichment (SELEX) method. The selection started with a single-stranded DNA (ssDNA) library of 1015 molecules randomized at central 45 nt. In each round, the binding affinity of ssDNA pool to AA was in real-time characterized by monitoring the change of frequency (Δf) before and after incubation with AA. After 14 rounds of positive selection and 4 rounds of counter selection, AA aptamer candidates were enriched, of which two aptamer candidates (A5 and C14) were selected and characterized by QCM and dot blot assay. The dissociation constants of A5 and C14 were 17.2 nmol L−1 and 115.2 nmol L−1, respectively. Both A5 and C14 didn’t show affinity to acrylamide analogues, including acrylic acid, methacrylic acid, and methacrylamide. To enable rapid and specific detection of AA with the selected aptamers, a label-free colorimetric aptasensor was developed. The detection linear range of the aptasensor was from 0.5 to 10 μmol L−1 with a detection limit of 0.390 μmol L−1.