An Ultrasensitive Upconversion Fluorescence Aptasensor Based on Graphene Oxide Release and Magnetic Separation for Staphylococcus aureus Detection

In this study, we developed an efficient method based on magnetic Fe3O4-modified graphene oxide (MNPs@GO) along with aptamer-functionalized upconversion nanoparticles (UCNPs) for Staphylococcus aureus detection. MNPs@GO are prepared using aptamer-functionalized MNPs and GO by means of pi-pi stacking interaction. In the absence of Staphylococcus aureus, MNPs@GO are formed and are magnetically separated. The upconversion fluorescence (UCF) peak intensity at 547 nm was not affected without GO. In the presence of Staphylococcus aureus, MNPs@GO are cleaved and GO are not magnetically separated. This leads to a decrease in the UCF intensity at 547 nm from aptamer-functionalized UCNP donor to GO acceptor due to fluorescence resonance energy transfer (FRET). The MNPs@GO-UCNP fluorescence biosensor achieved to detect Staphylococcus aureus, with a lower limit of detection (13 CFU/mL). The MNPs@GO-UCNP fluorescence biosensor for determination of Staphylococcus aureus showed satisfactory results in chicken samples.