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.