For different purposes, state-of-the-art antigen detection mechanisms like ELISA are not sufficient in accuracy. Therefore, new approaches have to be developed to get highly sensitive technologies. Graphene's outstanding electrical properties, like ultrahigh charge mobility and sensitivity to dopants, make it to a promising candidate for new electronic devices and their utilization for sensing technologies. Recent progress in nanotechnology has enabled new possibilities and, thus, has allowed the construction of graphene field effect transistors (gFET). In this work, gFET arrays with high yield and good device-to-device characteristic have been fabricated. Siliconoxide (SiO2) and aluminiumoxide (Al2O3) have been used as insulating oxide layers. To utilize the gFET device, a chemical linker was attached by PI-PI stacking interactions. The liker himself binds antibody fragments, so called single chain variable fragments (scFv). In this approach, detection of HER3, a well known breast cancer biomarker, was of interest. Therefore, matching HER3 immunoglobulin G-antigen complexes were used. Conclusions about the concentration of HER3 antigens down to as small as ng/ml were deducible by monitoring the Dirac voltages of the gFET devices.