Investigation of interaction between immobilized SARS-CoV-2 nucleoprotein and monoclonal antibodies by cyclic voltammetry based electrochemical immunosensor

The affinity of newly designed monoclonal antibodies towards viral proteins is an important factor during the development of bioanalytical systems, where monoclonal antibodies are applied as a biological recognition part, and during the design of antibody-based medications dedicated to the treatment of viral infections. The affinity of antibodies could be estimated by the assessment of antigen-antibody complex formation, which can be determined by immuno-analytical systems. In this work, we report the assessment of the interaction between immobilized severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) nucleoprotein (rN) and newly designed monoclonal antibody (mAb) clone 4B3 (mAb-4B3), which was performed by an electrochemical immunosensor. The electrochemical immunosensor was based on commercially available screen-printed carbon electrodes, which were consecutively modified by: (i) electrodeposited gold nanostructures; (ii) with L-Cysteine-based self-assembled monolayer; and (iii) covalently immobilized recombinant rN protein. Cyclic voltammetry in the presence of redox probe based on K₃[Fe(CN)₆]/K₄[Fe(CN)₆] system was applied to enhance electrochemical signal and to assess the interaction between immobilized recombinant rN SARS-CoV-2 virus protein and dissolved mAb-4B3 antibody. A limit of detection and quantification for designed immunosensor were determined as 0.55 pM and an LOQ of 1.64 pM, respectively.