Development and characterization of sandwich-type enzyme-linked aptamer assay for the detection of rongalite in food.

Rongalite is an essentially strong carcinogen, which due to its properties as a bleaching and brightening, is illegally added to the food processing. In this study, a sandwich-type enzyme-linked aptamer assay (ELAA) is developed by using a rongalite-specific aptamer G02 modified fluorescein amidite (FAM) as a capture probe and aptamer C01 modified biotin as a signal element. In the presence of rongalite, the aptamer G02-rongalite-aptamer C01 complex is produced, and the absorbance value can be subsequently measured. The sandwich-type ELAA was shown to detect rongalite with high specificity and affinity, with a KD value of 19.91 ± 1.321 nM. In addition, the standard curve was established, with the limit of quantification (LOQ) for rongalite at 10 ng mL-1. By calculating the slope of the standard curve and the standard deviation of the blank values, the method detection limit (MDL) was 0.572 ng mL-1. Additionally, the accuracy of the sandwich-type ELAA was demonstrated in real food samples. Compared with high-pressure liquid chromatography (HPLC) assay, the sandwich-type ELAA can detect rongalite directly, and it has great advantages in pre-treatment, operation technique and cost. In short, our data suggest that the sandwich-type ELAA may be applicable as a molecular detection technique for rongalite.