Electrochemical Immunoassay for the Detection of SARS-CoV-2 Nucleocapsid Protein in Nasopharyngeal Samples.
Anal Chem
; 94(11): 4712-4719, 2022 03 22.
Article
in English
| MEDLINE | ID: covidwho-1735180
ABSTRACT
Point-of-care (POC) methods currently available for detecting SARS-CoV-2 infections still lack accuracy. Here, we report the development of a highly sensitive electrochemical immunoassay capable of quantitatively detecting the presence of the SARS-CoV-2 virus in patient nasopharyngeal samples using stencil-printed carbon electrodes (SPCEs) functionalized with capture antibodies targeting the SARS-CoV-2 nucleocapsid protein (N protein). Samples are added to the electrode surface, followed by horseradish peroxidase (HRP)-conjugated detection antibodies also targeting the SARS-CoV-2 N protein. The concentration of the virus in samples is quantified using chronoamperometry in the presence of 3,3'5,5'-tetramethylbenzidine. Limits of detection equivalent to less than 50 plaque forming units/mL (PFU/mL) were determined with virus sample volumes of 20 µL. No cross-reactivity was detected with the influenza virus and other coronavirus N proteins. Patient nasopharyngeal samples were tested as part of a proof-of-concept clinical study where samples were also tested using the gold-standard real-time quantitative polymerase chain reaction (RT-qPCR) method. Preliminary results from a data set of 22 samples demonstrated a clinical specificity of 100% (n = 9 negative samples according to RT-qPCR) and a clinical sensitivity of 70% for samples with RT-PCR cycle threshold (Ct) values under 30 (n = 10) and 100% for samples with Ct values under 25 (n = 5), which complies with the World Health Organization (WHO) criteria for POC COVID-19 diagnostic tests. Our functionalized SPCEs were also validated against standard plaque assays, and very good agreement was found between both methods (R2 = 0.9993, n = 6), suggesting that our assay could be used to assess patient infectivity. The assay currently takes 70 min from sampling to results.
Full text:
Available
Collection:
International databases
Database:
MEDLINE
Main subject:
SARS-CoV-2
/
COVID-19
Type of study:
Diagnostic study
/
Prognostic study
/
Randomized controlled trials
Limits:
Humans
Language:
English
Journal:
Anal Chem
Year:
2022
Document Type:
Article
Affiliation country:
Acs.analchem.1c04966
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