Purpose: We presented a new aptamer biosensor for Fumonisin B1, which was based on fluorescence resonance energy transfer (FRET) between upconversion fluorescent nanoparticles (UCNPs) and gold nanoparticles (Au NPs).
Methods: The quencher (Au NPs) were attached to 5 end of the molecular beacons (MB) and the donor (UCNPs) attaching to 3 end of the MB. In the absence of target DNA (complementary DNA to FB1 aptamer), the energy donor and acceptor were taken into close proximity, leading to the quenching of fluorescence of UCNPs. Due to the combination between FB1 and FB1-specific aptamer, and caused the some complementary DNA dissociating from magnetic nanoparticles (MNPs). In the presence of the complementary DNA, the MB underwent spontaneous conformational change and caused the UCNPs and Au NPs to detach from each other, resulting in the restoration of UCNPs fluorescence.
Results: The fluorescence of UCNPs was restored in a FB1 concentration-dependent manner, which built the foundation of FB1 quantification. The biosensor provided a linear range from 0.01 to 100 ng/ml for FB1 with a detection limit of 0.01 ng/ml in an aqueous buffer. As a practical application, the biosensor was used to monitor FB1 level in naturally contaminated maize samples with the results consistent with that of a classic ELISA method, indicating that the UCNPs-FRET biosensor was competent for directly sensing FB1in foodstuffs samples without optical interference, which benefited from the near infrared (NIR) excitation nature of UCNPs.
Significance: This work opened the opportunity to develop biosensors for mycotoxins using the developed FRET system.