Graphene FET immunosensors for label-free detection of Human Chorionic Gonadotropin Cancer Risk Biomarker

Abstract

We report on chemical vapour deposition (CVD) graphene field effect transistor (GFET) immunosensors for the sensitive detection of Human Chorionic Gonadotropin (hCG), a glycoprotein risk biomarker of pancreatic, prostate, lung and stomach cancers [1-4]. The GFET sensors were fabricated on Si/SiO2 substrate using photolithography with evaporated chromium and sputtered gold contacts. GFET channels were functionalized with a linker molecule, 1-Pyrenebutyric acid Nhydroxysuccinimide (Pyr-NHS) ester, to immobile anti-hCG antibody (Ab) on the surface of graphene. The Pyr-NHS has an aromatic pyrenyl group, which can strongly interact with the graphene surface, via a non-covalent π-π bonding to retain sp2 lattice. Binding reaction of the antibody with varying concentration levels of hCG antigen demonstrated the limit of detection of the GFET sensors to be better than 1 pg/mL [1] using four-probe electrical measurements [5-6]. We also demonstrate that annealing can significantly improve the carrier transport properties of GFETs and shift the Dirac point with reduced p-doping in back-gated measurements. The developed GFET biosensors are generic, selective, fast, low-cost and could find applications in a broad range of point-of-care medical diagnostics in addition to cancer, such as neurodegenerative (Alzheimer’s, Parkinson’s) and cardiovascular disorders. We acknowledge funding from UK’s EPSRC, contract number EP/M006301/1, and the University of Plymouth, GD105227.