Magnetically-Enhanced Electrochemical ELISA for the Detection of Sars-Cov-2 Nucleoprotein

Abstract

Here we report on the development of a novel, magnetically-enhanced electrochemical (MagEC) bioassay targeting SARS-CoV-2 nucleoprotein. The sensing strategy is similar to microbead-based enzyme linked immunosorbent assays (ELISA) with optical detection. The target analyte is captured using a magnetic microbead functionalized with an antibody specific to SARS-CoV-2 nucleoprotein. Once SARS-CoV-2 nucleoprotein has been captured a detection construct, consisting of polystyrene microbeads functionalized with horseradish peroxidase (HRP) and antibodies specific to SARS-CoV-2 nucleoprotein are attached to form the full microbead construct.Once the full microbead constructs are assembled, they are injected into an electrochemical cell containing an assay solution where they are magnetically enriched at the electrode surface. This magnetic localization brings all of the reactants close to their point of detection at the electrode surface and also creates a positive feedback loop, drastically enhancing signal. The electrochemical assay was optimized using model constructs to emulate the fully assembled bead constructs and identify the optimal electrode configuration. Using the model constructs, we found a 60-fold decrease in limit of detection using the MagEC ELISA compared to optical detection with model bead constructs. We compared performance of a bare gold electrode to several geometries of gold microelectrode arrays. We obtained preliminary results for the detection of SARS-CoV-2 nucleoprotein. Additionally, the assay was expanded to incorporate a fluidic manifold to enhance signal, enhance throughput and enable operation in microgravity environments.