Selection and Application of DNA Aptamers Against Sulfaquinoxaline Assisted by Graphene Oxide–Based SELEX

Single-stranded DNA aptamers that specifically bind to sulfaquinoxaline (SQX) were selected by a graphene oxide–based SEL EX (GO-SELEX) technique assisted by a non-immobilizing TAMRA-labeled oligonucleotide library. After 8 rounds of selection against SQX, two aptamer candidates (i.e., SBA 1 and SBA 2) were obtained. Furthermore, the two full-length aptamers were truncated to obtain the aptamers (i.e. SBA 1-1, SBA 2-1, and SBA 2-2). These candidate aptamers were subjected to binding assays to evaluate their binding affinities and specificities to SQX. Our results show that the dissociation constants K d of the aptamers ranged from 82.54 to 630.41 nM. Using truncated aptamer SBA 2-1 with the highest affinity as the recognition element, a GO-based fluorescent aptasensor was developed for SQX detection with a linear range from 0.05 to 50 ng mL −1 and a limit of detection of 0.11 ng mL −1 with excellent selectivity. Furthermore, the new aptasensor was used to detect SQX in milk samples. Our results showed that the aptasensor demonstrated recoveries ranging from 96.6 to 106.7%, suggesting that the proposed GO-based fluorescent aptasensor holds great potential as promising tool for sensitive detection of SQX in food safety inspection.