A novel borax-specific ssDNA aptamer screened by high-throughput SELEX and its colorimetric assay with aggregation of AuNPs

Abstract

Borax is considered highly toxic and a strong carcinogen, but it is widely used as a toughening and brightening additive in food processing. At present, there is no definitive standard assay for the direct identification of borax in foods in most countries. In this study, borax-specific aptamers with high affinity and specificity were selected using Systematic Evolution of Ligands by Exponential Enrichment (SELEX) with high throughput sequencing. Next, a colorimetric detection method was proved to be feasible by nuclear magnetic resonance (NMR), using a selected aptamer, Bor-A01, with gold nanoparticles (AuNPs) for the direct detection of borax. Due to the matrix effect of real foods, the actual results of most detection methods may have large deviation or error. After optimizing detection conditions and pretreating food samples, the colorimetric detection assay allowed the specific recognition of borax within 1 h, with the visual limit of detection (LOD) range for borax of 0.30−0.50 μg/mL in different food samples. Overall, this colorimetric method based on aptamer-AuNPs with high sensitivity, simple pre-treatment, short operation time, and low cost will be applicable as a novel detection strategy to prohibit the use of borax in foods.