Abstract
E. coli is considered to be one of the most dangerous foodborne pathogens and precise detection of E. coli in food is required to ensure the quality and safety of food. In this work, carbon quantum dots (CQDs) were prepared from grapefruit peel as a carbon source by microwave heating method. A fluorescent resonance energy transfer (FRET)-based fluorescent biosensor was constructed by combining CQDs with silver nanoparticles (Ag NPs) for rapid detection of E. coli (BL21). The prepared CQDs showed good dispersion under transmission electron microscopy (TEM), with a spherical shape and an average particle size of 7.4 nm. The CQDs showed bright green fluorescence under UV light irradiation, which was strongly fluorescent (> 1.0 × 103 a.u.) and there was no change in fluorescence intensity over 150 days. Its fluorescence transduction is based on the spectral overlap between the donor (CQDs) emission and the acceptor (nanoparticles) absorbance. The fluorescence of CQDs attached to the aptamer is burst in the presence of Ag NPs. Upon addition of a specific E. coli (BL21) solution, an aptamer-target complex is formed and the preferential interaction of the aptamer with the specific bacteria leads to the release of CQDs and Ag NPs. After a period of incubation, the bacteria are centrifuged, resulting in the precipitation of E. coli aptamer couples and Ag NPs, and therefore the recovery of CQDs fluorescence. This method allows specific detection of E. coli (BL21) in a wide range of pathogenic bacteria. The final results show that the sensor has a linear range of 2×103 ∼ 2×108 CFU·mL−1 and a low detection limit of 77 CFU·mL−1 for E. coli.
Published Version
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