Graphene, a two-dimensional nanomaterial, has gained immense interest in biosensing applications due to its large surface-to-volume ratio, and excellent electrical properties. Herein, a compact and user-friendly graphene field effect transistor (GraFET) based ultrasensitive biosensor has been developed for detecting Japanese Encephalitis Virus (JEV) and Avian Influenza Virus (AIV). The novel sensing platform comprised of carboxy functionalized graphene on Si/SiO 2 substrate for covalent immobilization of monoclonal antibodies of JEV and AIV. The bioconjugation and fabrication process of GraFET was characterized by various biophysical techniques such as Ultraviolet-Visible (UV-Vis), Raman, Fourier-Transform Infrared (FT-IR) spectroscopy, optical microscopy, Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM). The change in the resistance due to antigenantibody interaction was monitored in real time to evaluate the electrical response of the sensors. The sensors were tested in the range of 1 fM to 1 μM for both JEV and AIV antigens, and showed a limit of detection (LOD) upto 1 fM and 10 fM for JEV and AIV respectively under optimised conditions. Along with ease of fabrication, the GraFET devices were highly sensitive, specific, reproducible, and capable of detecting ultralow levels of JEV and AIV antigen. Moreover, these devices can be easily integrated into miniaturized FET-based real-time sensors for the rapid, cost-effective, and early Point of Care (PoC) diagnosis of JEV and AIV. The development of Point of Care (PoC) disease detection kits providing ultra-sensitive, selective, and rapid advances in recent times. In this article, we have focused on graphene-based biosensors for the detection of two different viruses by detecting their respective viral antigen i.e. Japanese encephalitis virus (JEV) and Avian Influenza Virus (AIV). JEV belongs to the family Flaviviridae genus Flavivirus 1 and exists in a zoonotic cycle between the vector i.e. Culex mosquitos, while humans are the dead end host due to low and short-lived viremia of JEV 2-5. Most infections of JEV are asymptomatic, however, the case-fatality rate among those with encephalitis can be as high as 30%, or more in children. It causes clinical symptoms in humans, including a non-specific febrile illness, meningitis, encephalitis and meningo-encephalitis. Pigs play an important role and serve as an amplifier and have a natural infection rate of 98-100% 6. As JEV is incurable and the vaccination is not full-proof, an early diagnosis is critical in preventing an epidemic outbreak, especially since the initial symptoms are usually mistaken for dengue or malaria. The conventional diagnostic methods for JEV 7 such as Enzyme-Linked Immunosorbent Assays (ELISA) 8 ,
