Selection of DNA aptamers for detecting metronidazole and ibuprofen: two common additives in soft drinks

Abstract

To enhance the effects of functional some soft drinks, drugs, especially metronidazole (MNZ) and ibuprofen (IBF), are often illegally added. This poses a serious threat to the health of consumers. Therefore, developing simple and rapid detection methods for these additives is crucial. In the study, DNA aptamers of metronidazole and ibuprofen were selected using the library-immobilized method. The best aptamer for metronidazole named MNZ-1 has a dissociation constant (Kd) values of 4.9 µM and the aptamer for ibuprofen named IBF-1 shows a Kd of 9.3 µM, as determined by the thioflavin T (ThT) fluorescence assay. The Kd values measured using isothermal titration calorimetry (ITC) were 17.0 µM and 66.7 µM for these two aptamers, respectively. Selectivity experiments indicate that MNZ-1 demonstrates very weak binding to structurally similar drugs, whereas IBF-1 exhibits binding capability to some structurally similar compounds comparable to ibuprofen, enabling simultaneous detection of these types of drugs. Neither MNZ-1 nor IBF-1 bind to other common drugs. Using ThT, a label-free fluorescent detection method was developed for metronidazole and ibuprofen in soft drinks, showing limit of detection of (LOD) 0.6 µM and 4.7 µM, respectively. Owing to their small size and well-defined secondary structures, these aptamers are expected to be utilized in analytical applications for food and environmental monitoring.