Enhanced performance of impedimetric immunosensors to detect SARS-CoV-2 with bare gold nanoparticles and graphene acetic acid.

Immunosensors based on electrical impedance spectroscopy allow for label-free, real-time detection of biologically relevant molecules and pathogens, without requiring electro-active materials. Here, we investigate the influence of bare gold nanoparticles (AuNPs), synthesized via laser ablation in solution, on the performance of an impedimetric immunosensor for detecting severe acute respiratory syndrome coronavirus (SARS-CoV-2). Graphene acetic acid (GAA) was used in the active layer for immobilizing anti-SARS-CoV-2 antibodies, owing to its high density of carboxylic groups. Immunosensors incorporating AuNPs exhibited superior performance compared to those relying solely on GAA, achieving a limit of detection (LoD) of 3 x 10 ^-20  g/mL to detect the Spike Receptor Binding Domain (RBD) protein of SARS-CoV-2 and of 2 PFU/mL for inactivated virus. Moreover, these immunosensors presented high selectivity against the H1N1 influenza virus. We anticipate that this platform will be versatile and applicable in the early diagnosis of various diseases and viral infections, thereby facilitating Point-of-Care testing.
Competing Interests: Declaration of competing interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: Osvaldo Novais de Oliveira Jr. reports financial support was provided by Coordination of Higher Education Personnel Improvement (CAPES). Osvaldo Novais de Oliveira Jr. reports financial support was provided by National Council for Scientific and Technological Development (CNPq). Osvaldo Novais de Oliveira Jr. reports financial support was provided by State of Sao Paulo Research Foundation (FAPESP). Rafael Cintra Hensel reports financial support was provided by State of Sao Paulo Research Foundation. Stefano Casalini reports financial support was provided by Nanochemistry for Energy and Health. Stefano Casalini reports financial support was provided by Nexus. Stefano Casalini reports financial support was provided by Complessità Chimica C2. Stefano Casalini reports financial support was provided by Government of Italy Commission for the Selection of Excellence University Departments. If there are other authors, they declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
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