Study On Applications Of Graphene As Long Range Resonance Energy Transfer Acceptor In The Detection Of Prion Protein

Fluorescence resonance energy transfer (FRET) is a nonradiative process whereby an excited state donor (D, usually a fluorophore) transfers energy to a proximal ground state acceptor (A) through long-range dipole-dipole interactions. Recently, FRET has been widely applied for the detetion of biomolecules, organisms, inorganic ions. In traditional FRET, however, both the energy donor and acceptor are dye molecules. The energy transfer in traditional FRET between the molecular dye donor and acceptor can effectively occur in the distance within1-10nm, and the energy transfer rate (k) has (R)-6dependence on the relative distance (R) between the donor and the acceptor in the Forster equation. As Swathi and coworkers theoretically predicted, if a two dimensional (2-D) graphene sheet acts as the acceptor, the rate of energy transfer from dye to the surface of graphene has a R-4dependence (k∝R-4). For the fluorescence energy transfer from donor to graphene, FRET is found to be appreciable up to a distance of30nm. This is the theory of long-rang resonance energy transfer (LrRET). In this contribution, graphene oxide (GO) is introduced to the detetion of prion protein through LrRET between GO and fluorescence donor labeled aptamer.(1) By introducing GO as energy acceptor, a LrRET strategy for the detection of cell prion protein (PrPC) is explored. In the absence of PrP, TAMRA labeled molecule aptamer beacon (MAB) can be adsorbed on the surface of GO, and the fluorescence of TAMRA is quenched by GO following LrRET process. In the presence of PrC, however, the MAB forms a ligand-binding structure, leaving the surface of GO owing to the π-π interaction between the rings of the nucleotide bases and the honeycomb surface of GO. As a result, fluorescence emission from TAMRA gets restored. It was found that a detection limit of0.309mg/mL could be achieved. The strategy is sensitive, simple and specific.(2) A dual-aptamer strategy by LrRET between GO and quantum dots (QDs) for PrPC detection was constructed. Two aptamers (Aptl and Apt2), which can recognize their two corresponding distinct epitopes of PrPC, were coupled to GO and QDs, to make GO-Aptl and QDs-Apt2ready first, which then could be coassociated together through the specific recognitions of two aptamers with their two corresponding distinct epitopes of PrPC, forming a sandwich structure of GO-PrPc-QDs and quenching the fluorescence of QDs. To ensure the formation of the sandwich structure, High resolution transmission electron microscope (HRTEM) imaging was performed, and large compact3-dimensional (3-D) GO-PrPc-QDs complexes were observed clearly. Energy donor-acceptor separation distance ranges from19to27nm.