Immunosensors Based on Graphene Field-Effect Transistors Fabricated Using Antigen-Binding Fragment

To realize the antigen-antibody reaction for specific protein sensing using graphene field-effect transistors (G-FETs), the antigen-binding fragment (Fab), which is a component of conventional antibodies, was functionalized onto the graphene channel surface. Since the height of the Fab is approximately 3 nm, the antigen-antibody reaction is expected to occur inside the electrical double layer in the buffer solution. After functionalization of Fab onto the G-FET, the transfer characteristics shifted in the positive gate-voltage direction, indicating that the Fab was successfully modified onto the graphene surface. Then, the drain current changed after injecting the target proteins, and the dissociation constant was estimated to be 2.3 nM from the concentration dependence. These results indicate that the Fab-modified G-FETs have high potentials as highly sensitive biological sensors fabricated on the basis of the antigen-antibody reaction. (C) 2012 The Japan Society of Applied Physics