A novel ADA-coated UCNPs@NB sensing platform combined with nucleic acid amplification for rapid detection of Escherichia coli

In this study, we reported a novel sensing platform based on fluorescence quenching composed of alendronic acid (ADA) coated upconversion nanoparticles (UCNPs) and Nile Blue (NB) combined with polymerase chain reaction (PCR) for rapid, sensitive, and specific detection of Escherichia coli (E. coli). As a fluorescence acceptor, NB has a broad absorption band and can quench upconversion fluorescence intensity at 544 nm and 658 nm based on IFE. PCR is a double-stranded DNA (dsDNA) amplification technique with high specificity. The NB-dsDNA complex can be formed by intercalation of NB between base pairs and groove of dsDNA, leading to upconversion fluorescence recovery. The ADA-coated UCNPs@NB sensing platform achieved to detect E. coli in 1.5 h, with a lower limit of detection (33 CFU mL-1). In addition, the sensitivity of the ADA@UCNPs-NB fluorescence sensor under different PCR cycle numbers was discussed. The results showed that the proposed sensor could effectively shorten the assay time (1.0 h) while maintaining excellent sensitivity. This study demonstrated a rapid and sensitive analytical method for detecting E. coli in chicken, providing a reference for constructing PCR fluorescence sensors.