A DNA tweezers fluorescence aptasensor based on split aptamer -assisted magnetic nanoparticles for the detection of enrofloxacin in food

A DNA tweezers fluorescence aptasensor based on split aptamer assisted-magnetic nanoparticles (MNPs) and magnetic separation was established for the detection of Enrofloxacin (ENR). The DNA tweezers' fluorescence aptasensor consists of two arms with fluorophores (FAM) and quenchers (BHQ1) connected at both ends. Meanwhile, the high fluorescence signal can be generated with FAM and BHQ1 being spatially separated. Split aptamer 1 (SPA1) of ENR was annealed and incubated with avidin-coated MNPs. ENR and split aptamer 2 (SPA2) were added to form a sandwich structure with two split aptamer strands (MNPS-SPA1/ENR/SPA2). After magnetic separation, the supernatant did not interact with DNA tweezers, which made DNA tweezers a “turn-on” aptasensor to enhance the fluorescence signal. In the absence of ENR, SPA2 was free in the supernatant to dramatically quench the fluorescence which made DNA tweezers a “turn-off” aptasensor. The linear range of ENR detection was 0.01–100 ng/mL with a limit of detection of 0.008 ng/mL. The prepared DNA tweezers fluorescence aptasensors were applied to detect ENR in spiked milk samples, which showed good recoveries between 90.27% and 106.62%. In addition, the present method showed great potential for the target, employing a split aptamer detection platform in practical application.