Homogeneous detection of concanavalin A using pyrene-conjugated maltose assembled graphene based on fluorescence resonance energy transfer.

In this work, we proposed a novel biosensor to homogeneously detect concanavalin A (ConA) using pyrene-conjugated maltose assembled graphene based on fluorescence resonance energy transfer (FRET). Maltose-grafted-aminopyrene (Mal-Apy) was synthesized and characterized by mass spectra, UV-vis and fluorescence spectra. The Mal-Apy was further employed for fluorescence switch and ConA recognition. When Mal-Apy was self-assembled on the surface of graphene by means of π-stacking interaction, its fluorescence was adequately quenched because the graphene acted as a "nanoquencher" of the pyrene rings due to FRET. As a result, in the presence of ConA, competitive binding of ConA with glucose destroyed the π-stacking interaction between the pyrene and graphene, thereby causing the fluorescence recovery. This method was demonstrated the selective sensing of ConA, and the linear range is 2.0 × 10⁻² to 1.0 μM with the linear equation y=1.029x + 0.284 (R = 0.996). The limit of detection for ConA was low to 0.8 nM, and the detection of ConA could be performed in 5 min, indicating that this method could be used for fast, sensitive, and selective sensing of ConA. Such data suggests that the graphene FRET platform is a great potential application for protein-carbohydrate studies, and would be widely applied in drug screening, bimolecular recognition and disease diagnosis.