Fluorescent Dye-Doped Silica Nanoparticles with Polyclonal Antibodies for the Rapid Detection of Salmonella spp.

This study investigated a novel detection method of Salmonella spp. based on immunofluorescence microscopy using fluorescent dye-doped silica nanoparticles (FDS-NPs). Tetraethyl orthosilicate (TEOS) was used as a precursor. The FDS-NPs produced with microemulsion combined with sol-gel techniques were spherical in shape and 40-70 nm in diameter. The observation of the particles under fluorescence microscope showed high intensity orange color luminescent (Rubpy dye) with high photostability. Surface modifications for bioconjugation with polyclonal antibodies were performed by two methods, amine and carboxyl group modifications. The FDS-NPs were coated with polyclonal antibodies (purified IgGs) against Salmonella spp. Results of bacterial detection by FDSNPs indicated that nanoparticles with amine modified surface could attach onto the cells of the test organisms, Salmonella weltevreden and S. enteritidis, producing a distinctively bright color under fluorescence microscope. However, the nanoparticles with carboxyl group modification alone did not bind well with the test organisms. The FDS-NPs developed here show a high potential for use in the rapid detection of Salmonella and other bio-molecules.