Development of a fluorescence sensing platform for specific and sensitive detection of pathogenic bacteria in food samples

Pathogenic bacteria cause disease outbreaks and threaten human health, which prompts the research on advanced detection assays. Herein, based on the fluorescence resonance energy transfer (FRET) between upconversion nanoparticles (UCNPs) combined with aptamers and black hole quencher 1 (BHQ-1) ligated with cDNA, a fluorescence sensing platform was developed for specific and sensitive detection of pathogenic bacteria. The desirable distance (less than 10 nm) between UCNPs (donor) and BHQ-1 (acceptor) for FRET was achieved via the base pairing of aptamer and cDNA. Furthermore, the fluorescence emission spectrum of UCNPs and the absorption spectrum of BHQ-1 overlapped well, which enabled the occurrence of FRET and caused fluorescence quenching. Stable stem-loop structures might be the structural basis for the aptamer to specifically recognize target bacteria. In the presence of target bacteria, UCNPs-aptamer preferentially captured the bacteria, which decreased the UCNPs-aptamer-cDNA-BHQ-1 complex and caused fluorescence recovery. Using this sensing platform, we successfully detected one strain of S. aureus, ATCC 29213, with a limit of detection (LOD) of 6 cfu/mL in the linear range of 36–3.6 ⅹ107 cfu/mL and have verified this method in relevant food samples with good recoveries. In the future, the developed assay could also be used to detect other targets by selecting proper aptamers, which further broadens the potential applications of this method.