Because avidin and biotin molecules exhibit the most specific and strongest non-covalent interaction, avidin-biotin technology is widely used in ELISA (enzyme-linked immunosorbent assay) kits for the detection of different bio-macromolecules linked to different diseases including cancer and influenza. Combining the outstanding electrical conductivity (200,000 cm2V-1s-1) of graphene with the unique avidin and biotin interaction, we demonstrate a novel graphene field-effect transistor (GFET) biosensor for the quantitative detection of bio-macromolecules. The GFET consists of six pairs of interdigital Cr/Au electrodes supported on Si/SiO2 substrate with an avidin immobilized single layer graphene channel as the sensing platform. By monitoring the real time current change upon the addition of biotin solution in bovine serum albumin (BSA) in the silicone pool preformed onto the GFET, the lowest detectable biotin concentration is estimated to be 90 fg/ml (0.37 pM). The specificity of the GFET is confirmed both by controlled and real sample measurements. From the magnitude of current change upon the addition of different concentrations of biotin solutions, the dissociation constant Kd is estimated to be 1.6 × 10-11 M. Since biotin is capable of conjugating with proteins, nucleotides and other bio-macromolecules without altering their properties, the present GFET sensor with its ultra-high sensitivity (0.37 pM) and specificity can be tailored to the rapid point-of-care detection of different types of desired biomolecules at very low concentration level through biotinylation as well as the exogenous biotin in blood serum.
Keywords: Avidin; Biosensor; Biotin; Clinical diagnosis; Field-effect transistor; Graphene.
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