Fluorescence Immunassays for Staphylococcal Enterotoxin A
Staphylococcal food poisonings are one of the main food-borne outbreaks worldwide. Staphylococcal enterotoxins are thermo stable exotoxins that contaminate a wild range of foods, like milk and meat. The most common of the enterotoxins is staphylococcal enterotoxin A (SEA). In the present study fluorescence immunoassays for SEA were developed. Two fluorescent conjugates were prepared, one with SEA and the other with the SEA-specific polyclonal antibody. They were used as fluorescent markers in two different immunoassays: fluorescent linked immunosorbent assay (FLISA), and magnetic nanoparticle (MNP) – based fluorescence immunoassay (FIA). The linear range of the FLISA was from 0.01 pg/mL to 1 μg/mL SEA, whereas the MNP-based FIA had linearity from 0.5 pg/mL to 10 ng/mL SEA, both in buffer solutions. However, the direct FLISA method is time-consuming (more than 2 h), thus the developed MNP-based FIA is preferable (30 min). That is due to the large relative surface area of the MNPs which facilitate the immunoreactions (Ab-SEA). The assay with MNPs was used for SEA detection in milk samples. It was found that the linear range of SEA in milk samples was almost the same.
Keywords - Fluorescent Conjugate, Fluorescence Immunoassay, Magnetic Nanoparticles, Staphylococcal Enterotoxin A.