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Published April 12, 2022
Two University of Wyoming researchers have developed a COVID-19 antigen test that is more sensitive than those currently on the market. The test can use a hand-held device to be read, making the test appropriate for diagnosis at the point of care within 30 minutes.
“Our test detects the SARS-CoV-2 spike protein, and the time to result for our test is on par with other tests that detect SARS-CoV-2 proteins,” says Karen Wawrousek, an assistant professor in the UW Department of Chemical Engineering. “Our test is more sensitive than those rapid tests because of the design of the assay and the detection method we use.”
Wawrousek is a co-corresponding author of a paper titled “Rapid, Point-of-Care scFv-SERS Assay for Femtogram Level Detection of SARS-CoV-2” that was published in ACS Sensors March 10. The peer-reviewed research journal is devoted to the dissemination of new and original knowledge on all aspects of sensor science that selectively sense chemical or biological species or processes.
Moein Mohammadi, a UW Ph.D. student in chemical engineering, is a co-first author of the paper. The other first author is Delphine Antoine, a postdoctoral researcher at the National University of Ireland (NUI) Galway. Gerard Wall, a senior lecturer and personal professor in the Department of Microbiology at NUI Galway, is the paper’s other co-corresponding author. Patrick Johnson, a UW professor of chemical engineering and head of the Department of Chemical Engineering, was co-collaborator on the project.
An assay, which is a process of analyzing a substance to determine its composition or quality, was developed using single-chain variable fragments (scFvs) to detect the SARS-CoV-2 spike protein. The antibody fragments can be expressed in bacterial cells, which simplifies the workflow compared to the use of whole antibody molecules. The Wall lab isolated the antibody fragments that bind to the receptor binding domain (RBD) of the SARS-CoV-2 spike protein and characterized the RBD-binding scFvs. The scFvs were incorporated into the diagnostic assay, with optimization and characterization of the assay, at UW.
The Wall lab screened scFvs for binding to the RBD in a matter of weeks, allowing the research group to quickly adjust the diagnostic assay if a COVID-19 variant arises that is no longer recognized well in the group’s rapid antigen test, Wawrousek says.
“We sought to develop an assay that would be closer to the sensitivity of PCR-based assays, but without the delays associated with sending a sample to a laboratory for PCR-based analysis,” she says. “The rapid receipt of a reliable diagnosis can allow people to modify their behaviors accordingly to reduce disease spread.”
PCR is polymerase chain reaction.
Mock test samples in saliva and viral transport media, which nasal swabs are stored in for PCR analysis, have been tested in the lab. The samples are placed in glass vials and inserted into hand-held instruments, called Raman spectrometers, for analysis. This type of assay will allow for testing in rural and remote areas, and on-site at airports, among other locations, Johnson has previously said.
The assay is not yet being used as a test for clinical samples and does not have Food and Drug Administration emergency use authorization approval.
“We will work with the Wyoming Public Health Laboratory to test the assay on clinical samples,” Wawrousek says. “The format of the assay is different from the standard lateral flow antigen test, so we are thinking about how to best scale up production.”
Funding for the research came from a COVID Innovations grant from UW paid for with CARES Act funds; a grant Wall received from the Health Research Board of Ireland; and Wawrousek had an active National Institutes of Health Wyoming IDeA Network of Biomedical Research Excellence (INBRE) grant during the research.