Magnetically controlled graphene field-effect transistor biosensor for highly sensitive detection of cardiac troponin I

Herein, we have constructed a magnetic graphene field-effect transistor biosensor for highly sensitive detection of cardiac troponin I (CTNI). Graphene film was used as a conductive channel and transferred onto a glass substrate with two indium tin oxide (ITO) electrodes. CTNI aptamer was immobilized onto the graphene film via 1-pyrene-butanoic acid succinimidyl ester (PBASE) to capture CTNI. Magnetic nanobeads modified with CTNI antibody were added to the reaction chamber to form an aptamer/CTNI/antibody/magnetic nanobeads sandwich-type complex. By applying a periodic magnetic field, we found that the magnetic force exerted on the complex leads to an impedance change of the graphene film. The results were rationalized using a model wherein the magnetic force causes the CTNI aptamer strand to bend, thereby resulting in magnetic nanobeads/CTNI aptamer modulation of the double conductive layer of graphene transistors. With periodic sampling integration, different concentrations of CTNI can be detected with high sensitivity. Due to the specific binding property of the aptamer to the antigen, the magnetic graphene field-effect transistor biosensor can be used for the specific detection of different kinds of proteins and can potentially be a detection tool for DNA, specific cells, etc.