Aptasensor for amplified IgE sensing based on fluorescence quenching by graphene oxide.

Water-soluble graphene oxide (GO) with a two-dimensional layered nanostructure was synthesized and used as a quencher to construct a highly sensitive and selective fluorescence resonance energy transfer (FRET) aptasensor for sensing Immunoglobulin E (IgE). The fluorescein isothiocyanate (FITC)-labeled aptamer could be adsorbed stably onto the surface of GO via π → π stacking interaction, which led to the occurrence of FRET from FITC to GO, and the fluorescence of FITC-labeled aptamer was quenched by GO via energy transfer. In the presence of IgE, the fluorescence was recovered due to a higher affinity between the aptamer and IgE compared with interactions between GO and the aptamer, leading to a high signal-to-background ratio. The fluorescence intensity of the aptamer increased in proportion to the amount of IgE in the sample,so that IgE could be detected with a linear range of 60-225 pM and a detection limit of 22 pM. The assay was highly selective because the aptamer was unaffected by the presence of immunoglobulin G (IgG), human serum albumin (HSA) and bovine serum albumin (BSA). The practical application of the proposed aptasensor was successfully carried out for the determination of IgE in human serum samples.