Graphene field-effect transistors for label-free biological sensors

Label-free immunosensors based on aptamer-modified graphene field-effect transistors (G-FETs) were realized. Immunoglobulin E (IgE) aptamers were functionalized on the graphene surface. From atomic force microscopy, functionalized IgE aptamer with approximately 3 nm height was observed. And the drain current of the G-FETs increased after IgE aptamers functionalized on the graphene channel owing to the negatively charged aptamer in the solution, indicating the success of the IgE-aptamer functionalization onto the graphene channel. The aptamer-modified G-FETs electrically detected only IgE molecules, indicating the selectively sensing. From IgE concentration dependence of the drain current variation, the dissociation constant between IgE aptamer and IgE reaction was estimated to be 4.7×10^-8 M, indicating their good affinity. These results indicate that the G-FETs have high potential for the label-free biological sensors.