Fe3O4@polydopamine and Exo III-assisted homogeneous biorecognition reaction for convenient and ultrasensitive detection of kanamycin antibiotic

Herein we report a Fe3O4@polydopamine (PDA) nanocomposite and exonuclease III (Exo III)-assisted homogeneous fluorescence biosensing method for ultrasensitive detection of kanamycin (Kana) antibiotic. To construct the method, a hairpin DNA containing the Kana-aptamer sequence (HP) was first designed for highly specific biorecognition of target analytes. Due to the aptamer biorecognition-induced structure change of HP and the high-effectively catalyzed reaction of Exo III, a large amount of fluorophore labels were released from the designed fluorescence DNA probe. During the homogeneous reaction process, the Exo III-assisted dual recycling greatly amplified the fluorescence signal output. Meanwhile, the excessive probes were easily adsorbed and separated by the Fe3O4@PDA nanocomposite, which well decreased the background signal and thus increased signal-to-noise ratio. These strategies result in the excellent analytical performance of the method including a very low detection limit of 0.023 pg mL-1 and a very wide linear range of six orders of magnitude. In addition, this method has convenient operation, excellent selectivity, repeatability and satisfactory reliability, and does not involve the design and utilization of too complicated DNA sequences. Thus it exhibits a promising prospect for practical applications.