A fluorometric assay for staphylococcal enterotoxin B by making use of platinum coated gold nanorods and of upconversion nanoparticles

An aptamer based fluorometric assay is presented for fast and accurate detection of staphylococcal enterotoxin B (SEB). It is making use of platinum-coated gold nanorods (AuNR@ Pt) and upconversion nanoparticles (UCNPs). The aptamer against SEB is immobilized on AuNR@ Pt while the complementary DNA fragment of SEB aptamer is immobilized on UCNPs. As the concentration of SEB increases, the fluorescence of the satellite assembly (AuNR@ Pt-UCNPs) is gradually restored. Under the optimized conditions, fluorescence (best measured at excitation/ emission wavelengths of 980/ 543 nm) linearly increases in the 2.0-400 pg center dot mL-1 SEB concentration range. The limit of detection is as low as 0.9 pg center dot mL-1 (at an S/ N of 3), significantly lower than existing methods. The method was applied to the determination of SEB in spiked milk samples. The average recoveries ranged from 91.2% to 104.6%, confirming the practicality of this method.