  The study proposes a new efficient wireless biosensor based on magnetoelastic
waves for the detection of antibodies in human plasma, aiming at the
serological diagnosis of COVID-19. The biosensor was functionalized with the N
antigen - nucleocapsid phosphoprotein of the SARS-CoV-2 virus. Validation
analyses, by sodium dodecyl-sulfate polyacrylamide gel electrophoresis
(SDS-PAGE), Western blotting, atomic force microscopy (AFM), scanning electron
microscopy (SEM), micro-Raman spectroscopy, confirmed the selectivity and
effective surface functionalization of the biosensor. The research successfully
obtained, expressed and purified the recombinant antigen, while plasma samples
from COVID-19 positive and negative patients were used to test the performance
of the biosensor. A comparison of performance with the ELISA method revealed
equivalent diagnostic power. These results indicate the robustness of the
biosensor in reliably differentiating between positive and negative samples,
highlighting its potential as an efficient and low-cost tool for the
serological diagnosis of COVID-19. In addition to being fast to execute and
having the potential for automation in large-scale diagnostic studies, the
biosensor fills a significant gap in existing SARS-CoV-2 detection approaches.
