Rare earth-doped upconversion nanoparticles (UCNPs) have promising potential in the field of food safety because of their unique frequency upconverting capability and high detection sensitivity. Here, we report a rapid and sensitive UCNP-based bacterium-sensing strategy using Escherichia coli. Highly fluorescent and water-soluble UCNPs were fabricated and conjugated with antibodies against E. coli for use as fluorescent probes. The E. coli were successively captured by the fluorescent probes. After the captured cell samples were pelleted, the differences in the fluorescence intensities between sample supernatants and the control were observed to increase linearly with E. coli concentration from 42 to 42 × 10(6) colony-forming units (cfu)/mL (R(2) = 0.9802), resulting in a relatively low limit of detection of 10 cfu/mL. Furthermore, the ability of the bioassay to detect E. coli was also confirmed in adulterated meat and milk samples.
Keywords: Escherichia coli; bacteria; fluorescent probe; sensing; upconversion nanoparticles.