Aptamer based fluorometric sulfamethazine assay based on the use of graphene oxide quantum dots

The authors have developed a homogeneous “off-on” fluorometric method for the determination of the antibiotic sulfamethazine (SMZ). Aptamer against SMZ was labeled with graphene oxide quantum dots upon which the Graphene oxide quenched the blue fluorescence of the GOQDs. On addition of SMZ, the aptamers will bind SMZ and this will cause the release of GOQDs. As a result, fluorescence will be regenerated. Fluorescence, best measured at excitation/emission wavelengths of 365/455 nm, increases linearly in the 8 pg·mL −1 to 60 ng·mL −1 SMZ concentration range, with a 5 pg·mL −1 detection limit. The method is reliable and was successfully applied to the determination of SMZ in spiked milk samples, with recoveries ranging from 89 to 96% depending on analyte concentration. Graphene oxide quantum dots (GOQDs) were covalently bound to the aptamer (apt) against sulfamethazine (SMZ) and adsorbed on the surface of graphene oxide (GO). This results in quenching of the fluorescence of GOQDs. On addition of SMZ, fluorescence is restored due to the release of GOQD@apt from GO.