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

Abstract

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.