PCR- and label-free SARS-CoV-2 electrochemical immunosensor

Abstract

Cases of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) are still ubiquitously persistent, as new variants have emerged worldwide. Furthermore, severity and infectiousness are still not fully understood. Therefore, an imperative need still exists for more and better viral detection and diagnosis tools. Nanostructured electrochemical biosensors have shown outstanding features for highly sensitive Coronavirus disease 2019 (COVID-19) detection and diagnosis. This work reports on an electrochemical immunosensor based on nanocomposite-decorated screen-printed carbon electrodes (SPCE) for one-step detection of the spike protein by differential pulse voltammetry (DPV) without the need for enzymatic or PCR amplification. The SPCEs were decorated with graphene quantum dots (GQDs) coexisting with gold and platinum nanoparticle nanocomposite (GQDs@AuPt), improving their conductive properties and offering a high surface area and available carboxylic groups for the covalent immobilization of capture recombinant antibodies. As a result, the biosensor demonstrated high sensitivity and specificity in detecting spike protein by DPV in a linear range from 0.05 to 1.5 µg/mL and with a LOD of 60.14 ng/mL (0.78 nM). In addition, its potential application was demonstrated by detecting eleven positive concerning four negative nasopharyngeal swab samples from patients with COVID-19 and healthy individuals previously analyzed by the RT-PCR gold standard.