Carbohydrate-coated magnetic and gold nanoparticles for point-of-use food contamination testing

Abstract

With a significant part of the world facing multiple foodborne outbreaks each year, rapid and affordable detection technologies are needed. This paper presents simple equipment-free isolation of bacteria from foods using glycan-coated Magnetic Nanoparticles (gMNP) and their genomic detection using dextrin-capped Gold Nanoparticles (GNPs) in <7h. The synthesized gMNP and GNPs can be stored at room temperature and do not require expensive recognition biomolecules for bacterial identification. Isolation of E. coli directly from leafy green vegetables was achieved in <60 min, and its binding to gMNP was confirmed using Transmission Electron Microscopy (TEM). As-synthesized GNPs were found to be <50 nm in diameter and showed a characteristic wavelength peak at 520 nm in the visible spectrum. A PCR-less GNP biosensor was developed targeting the uidA gene allowing rapid bacterial detection in <30 min and successfully differentiating (p<0.05) E. coli from S. Enteritidis, K. pneumoniae, and E. cloacae. Hybridization between the uidA gene-specific probe and target DNA resulted in the stability of GNPs under an acidic environment, while their aggregation in the absence of target DNA was observed. Successful detection was achieved at the initial bacterial contamination as low as 5.2 X 102 and 6.3 X 102 CFU/mL from artificially contaminated spinach and lettuce samples, respectively.