GFAP Antibody Detection Using Interdigital Coplanar Waveguide Immunosensor

Glioma is the most common primary brain tumor with its early detection remaining a challenge. Autoantibodies against glial fibrillary acidic protein (GFAP) have shown the highest differential expression compared with the other glioma expressed autoantibodies. In this paper, an immunosensor to detect GFAP antibody levels is developed using an interdigital coplanar waveguide (ID-CPW). The ID-CPW is fabricated on an SiO2/Si substrate with the CPW and inter-digital electrode conducting layers made using Cr/Au. The sensor is functionalized, and protein extracted from astrocytes is immobilized on the surface. Sensitivity and dynamic range are ascertained using varying the concentrations of a commercial, polyclonal antibody to GFAP. The electrical detection of antigen-antibody binding is performed in both dry and wet environments across the 1-25-GHz range. Our results show that the proposed sensor can detect antibodies to GFAP to a minimum concentration of 2.9 pg/ml with a turnaround time in less than 3 h. Our electrical measurements indicate an improved sensitivity compared with the state-of-the-art optical detection methods. The immunosensor, developed to detect antibody against GFAP, is the first to show the applicability in the detection of glioma using the GFAP autoantibodies.