Facile and Sensitive Epifluorescent Silica Nanoparticles for the Rapid Screening of EHEC

This study was to develop antibodies conjugated fluorescent dye-doped silica nanoparticles (FDS-NPs) aiming to increase signals for the rapid detection of Escherichia coli O157:H7 with glass slide method. The FDS-NPs were produced with microemulsion/sol-gel techniques resulting in spherical in shape with 47 ± 6 nm in diameter. The particles showed high intensity and stable orange color Rubpy luminescent dye. The XRD spectrum showed a broad diffraction peak in the range of 18–30∘ (centered at 22∘) indicating an amorphous structure. Surface modifications for bioconjugation with affinity chromatography purified (IgGs) antibodies were successful. The properties were evident from FTIR spectra at 1631.7 cm−1. Results indicated that nanoparticles could attach onto cells of E. coli O157:H7 coated on a glass slide, and give distinctively bright color under epifluorescence microscope (400x). It was shown that FDS-NPs could detect a very low amount of cells of E. coli O157:H7 (16 CFU in 10 ml) in 60 min. The phosphate buffered saline (PBS) with ionic strength of 1.70 gave zeta potential of good particle dispersion (−40 mV). This work demonstrated that highly sensitive bioconjugated E. coli O157:H7 FDS-NPs were successfully developed with a potential to be used for the rapid detection of E. coli O157:H7 in foods.