An Aptamer-based Colorimetric Sensor for Streptomycin and Its Application in Food Inspection

An aptamer-based colorimetric biosensor was developed, which could be used to detect residual strepto- mycin from food quickly and cost-effectively. The ssDNA aptamer target for streptomycin was obtained using sys- temic evolution of ligands by exponential enrichment through affinity chromatography. A total of 19 candidates were obtained after 10 rounds of selection and were grouped into 3 families according to their similarity of sequence and structure. Among them, aptamer A15 showed the highest affinity for streptomycin tested by fluorescence intensity analysis with a dissociation constant of 6.07 nmol/L. Aptamer A15 also exhibited a higher streptomycin specificity with the lowest detectable limit of 25 nmol/L according to the value of A620/A520 ratio with AuNP-based colorimetric assay. The method was specific and sensitive for the detection of streptomycin from simply-treated milk and honey at 100 and 125 nmol/L, respectively, and is a promising approach to monitor antibiotics or other small molecules ana- logues in food inspection.