An Electrochemical Immunosensor Based on Carboxylated Graphene/SPCE for IgG-SARS-CoV-2 Nucleocapsid Determination
Luciana de Souza Freire, Camila Macena Ruzo, Bárbara Batista Salgado, Ariamna María Dip Gandarilla, Yonny Romaguera Barcelay, Ana P. M. Tavares, M. Goreti F. Sales, Isabelle Bezerra Cordeiro, Jaila Dias Borges Lalwani, Robert S. Matos, Henrique Duarte da Fonseca Filho, Spartaco Astolfi‐Filho, Ştefan Ţălu, Pritesh Lalwani, Walter Ricardo Brito
Abstract
The COVID-19 pandemic has emphasized the importance and urgent need for rapid and accurate diagnostic tests for detecting and screening this infection. Our proposal was to develop a biosensor based on an ELISA immunoassay for monitoring antibodies against SARS-CoV-2 in human serum samples. The nucleocapsid protein (N protein) from SARS-CoV-2 was employed as a specific receptor for the detection of SARS-CoV-2 nucleocapsid immunoglobulin G. N protein was immobilized on the surface of a screen-printed carbon electrode (SPCE) modified with carboxylated graphene (CG). The percentage of IgG-SARS-CoV-2 nucleocapsid present was quantified using a secondary antibody labeled with horseradish peroxidase (HRP) (anti-IgG-HRP) catalyzed using 3,3′,5,5′-tetramethylbenzidine (TMB) mediator by chronoamperometry. A linear response was obtained in the range of 1:1000–1:200 v/v in phosphate buffer solution (PBS), and the detection limit calculated was 1:4947 v/v. The chronoamperometric method showed electrical signals directly proportional to antibody concentrations due to antigen-antibody (Ag-Ab) specific and stable binding reaction.