Highly Sensitive Electrochemical Immunosensor Platforms\nfor Dual Detection of SARS-CoV‑2 Antigen and Antibody based\non Gold Nanoparticle Functionalized Graphene Oxide Nanocomposites

Abstract

In this work, we report a facile\nsynthesis of graphene oxide–gold\n(GO–Au) nanocomposites by electrodeposition. The fabricated\nelectrochemical immunosensors are utilized for the dual detection\nof severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) antigen\nand SARS-CoV-2 antibody. The GO–Au nanocomposites has been\ncharacterized by UV–vis spectroscopy, X-ray diffraction (XRD),\ntransmission electron microscopy (TEM), cyclic voltammetry (CV), differential\npulse voltammetry (DPV), and electrochemical impedance spectroscopy\n(EIS) for its biosensing properties. The linear detection range of\nthe SARS-CoV-2 antigen immunosensor is 10.0 ag mL^–1 to 50.0 ng mL^–1, whereas that for the antibody\nimmunosensor ranges from 1.0 fg mL^–1 to 1.0 ng mL^–1. The calculated limit of detection (LOD) of the SARS-CoV-2\nantigen immunosensor is 3.99 ag mL^–1, and that for\nSARS-CoV-2 antibody immunosensor is 1.0 fg mL^–1 with\nhigh sensitivity. The validation of the immunosensor has also been\ncarried out on patient serum and patient swab samples from COVID-19\npatients. The results suggest successful utilization of the immunosensors\nwith a very low detection limit enabling its use in clinical samples.\nFurther work is needed for the standardization of the results and\ntranslation in screen-printed electrodes for use in portable commercial\napplications.