We report on the development of label-free chemical vapour deposition (CVD) graphene field effect transistor (GFET) immunosensors for the sensitive detection of Human Chorionic Gonadotropin (hCG), a glycoprotein risk biomarker of certain cancers. The GFET sensors were fabricated on Si/SiO2 substrate using photolithography with evaporated chromium and sputtered gold contacts. GFET channels were functionalised with a linker molecule to an immobile anti-hCG antibody on the surface of graphene. The binding reaction of the antibody with varying concentration levels of hCG antigen demonstrated the limit of detection of the GFET sensors to be below 1 pg/mL using four-probe electrical measurements. We also show that annealing can significantly improve the carrier transport properties of GFETs and shift the Dirac point (Fermi level) with reduced p-doping in back-gated measurements. The developed GFET biosensors are generic and could find applications in a broad range of medical diagnostics in addition to cancer, such as neurodegenerative (Alzheimer’s and Parkinson’s) and cardiovascular disorders.

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Selectivity and sensitivity are important figures of merit in the design and optimization of electrochemical biosensors. The efficiency of the fabricated immunosensing surface can easily be influenced by several factors, such as detection limit, non-specific binding, and type of sensing platform. Here, we demonstrate the effect of macro-and micro-sized planner working electrodes (4 mm and 400 µm diameter, respectively) on the electrochemical behavior and the performance of the developed biosensor to detect human chorionic gonadotropin (hCG), please say why hCG here briefly. The fabricated screen-printed sensor was constructed by modifying the carbon macro-and micro-electrodes with a linker, 1-pyrenebutyric acid-Nhydroxysuccinimide ester (PANHS) and immobilization of anti-hCG antibodies to detect specifically the hCG protein. The characterization of the developed electrodes was performed by cyclic voltammetry (CV) and square wave voltammetry (SWV). Each immunesensing system has its unique electrochemical behavior which might be attributed to arrangement of particles on the surface. However, the smaller surface area of the micro-electrode is found to show higher sensitivity (1 pg/mL) compared to the macro-electrode sensor with a lower detection limit of 100 pg/mL. The proposed assay represents a promising approach that is highly effective for specific detection of an analyte and can be exploited to target biomarkers for a variety of point-of-care diagnostic applications.

Optical data storage is advancing rapidly as we move forward in the 21st Century.

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