Development of fluorescent aptasensing system for ultrasensitive analysis of kanamycin

The analysis of residual kanamycin (KANA) has drawn great attentions based on its potential threat to human health and environment caused by its residual in aquatic and soil system. Herein, an ultrasensitive fluorescent aptasensing system was proposed based on the fluorescence change resulting from the conformation switch of kanamycin-aptamer (KANA-aptamer) with or without kanamycin in the sensing system, in which berberine was employed as the fluorescence reporter and KANA-aptamer as the recognition unit. Free berberine emits weak fluorescence at 535 nm in aqueous solution, and its fluorescence enhanced remarkably after it intercalated to KANA-aptamer. Once kanamycin was introduced into the sensing system, the randomly coiling structure of KANA-aptamer switched to a hairpin form, which made the dissociation of berberine from the KANA-aptamer, thus the fluorescence was quenched. Various experimental conditions including the concentration of berberine, KANA-aptamer, pH, ion strength and equilibrium time were studied in detail. Under the optimal experimental condition, a good correlation was obtained between the fluorescence of the sensing system and the concentration of kanamycin ranged from 5.0 nM to 71.0 nM with LOD at 2.3 nM. The presented fluorescent aptasensor also showed a delightful recovery of 96.50%–101.20% in human serum and milk. The excellent analytical performance of kanamycin shows a promising prospect in the practical application.