Journal
BIOSENSORS-BASEL
Volume 12, Issue 5, Pages -Publisher
MDPI
DOI: 10.3390/bios12050265
Keywords
SARS-CoV-2; nucleocapsid protein; electrochemical impedance spectroscopy; immunosensor; saliva; antigen tests
Funding
- Ministry of Science and Technology, Taiwan [MOST111-2327-B-005-002, MOST 110-2321-B-005-010]
- Innovation and Development Center of Sustainable Agriculture from The Featured Areas Research Center Program within the Higher Education Sprout Project by the Ministry of Education, Taiwan
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This study developed an EIS-based immunosensor for the detection of SARS-CoV-2 nucleocapsid protein in saliva. The immunosensor showed high sensitivity, low limit of detection, and good reproducibility. It also exhibited minimal cross-reactivity with other viral antigens.
The timely detecting of SARS-CoV-2 coronavirus antigens for infection validation is an urgent request for COVID-19 pandemic control. This study constructed label-free electrochemical impedance spectroscopy (EIS)-based immunosensors based on gold nanostructured screen-printed carbon electrodes (AuNS/SPCEs) to detect the SARS-CoV-2 nucleocapsid protein (N-protein) in saliva. Using short-chain 3-mercaptopropionic acid (MPA) as a linker to covalently bond streptavidin (SA) and bovine serum albumin (BSA) for controlling the oriented immobilization of the biotinylated anti-N-protein antibody (BioAb) can offer a greater sensitivity, a lower limit of detection (LOD), and better reproducibility of immunosensors (defined as BioAb/SA-BSA/MPA/AuNS/SPCEs) than the antibody randomly immobilized immunosensors and the long-chain 11-mercaptoundecanoic acid (MUA)-modified immunosensors (BioAb/SA-BSA/MUA/AuNS/SPCEs). The BioAb/SA-BSA/MPA/AuNS/SPCE-based immunosensors presented good linearity from 0.01 ng/mL to 100 ng/mL and a low LOD of 6 pg/mL in a phosphate buffer solution (PBS) and PBS-diluted saliva. Moreover, the immunosensor exhibited little cross-activity with other viral antigens such as MERS-CoV N-protein, influenza A N-protein, influenza B N-protein, and SARS-CoV-2 spike protein, indicating the high specificity of the immunosensors. The disposable label-free EIS-based immunosensors have promising potential in facilitating the rapid and sensitive tests of saliva-based COVID-19 diagnostics.
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