This study demonstrated the potential application of antibody-conjugated Rubpy dye-doped silica nanoparticles for immunofluorescence microscopic detection ofVibrio choleraeO1. The particle synthesis of 20X of the original ratio was accomplished yielding spherical nanoparticles with an average size of45±3 nm. The nanoparticles were carboxyl functionalized and then conjugated with either monoclonal antibody or polyclonal antibody againstV. choleraeO1. The antibody-conjugated nanoparticles were tested with two target bacteria and three challenge strains. The result showed that monoclonal antibody-conjugated Rubpy dye-doped silica nanoparticles could be effectively used as signal amplification to detectV. choleraeO1 under a fluorescence microscope. Their extremely strong fluorescence signal also enables the detection of a single cell bacterium.
This paper describes an application of Rubpy dye-doped silica nanoparticles (RSNPs) as signal reporter in a dot fluorescence immunoassay strip for rapid screening ofVibrio choleraO1 (VCO1). These nanoparticles have a spherical shape with an average diameter of 45 nm. They appear luminescent orange when excited with a 312 nm UV lamp. Based on the sandwich immunoassay principle, a test strip was made of a nitrocellulose membrane dotted with monoclonal antibodies against VCO1 as analyte capture molecules. After introducing a test sample, followed by polyclonal rabbit anti-VCO1 antibody conjugated RSNPs as detection reporters and one washing step, the presence or absence of the target bacteria could be identified under UV light by naked eyes. A positive sample would signal a bright orange dot on the strip. The proposed assay had a detection limit of4.3×103 cfu/mL and was successfully applied as a rapid screening test for VCO1 in food samples with high sensitivity, specificity, and accuracy.
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