Capillary flow-driven immunoassay platform for COVID-19 antigen diagnostics

• Published in: Analytica chimica acta Vol. 1277; p. 341634
• Main Authors: Link, Jeremy S., Carrell, Cody S., Jang, Ilhoon, Barstis, Elijah J.O., Call, Zachary D., Bellows, Rae A., O'Donnell-Sloan, John J., Terry, James S., Anderson, Loran B.R., Panraksa, Yosita, Geiss, Brian J., Dandy, David S., Henry, Charles S.
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 09-10-2023
• Subjects: Antibodies; Capillary-driven microfluidics; COVID-19; COVID-19 - diagnosis; COVID-19 Testing; Diagnostic testing; Enzyme-Linked Immunosorbent Assay; Humans; Immunoassay; Immunoassays; Point-of-care; SARS-CoV-2; COVID-19; Diagnostic testing; SARS-CoV-2; Point-of-care; Immunoassays; Capillary-driven microfluidics
• ISSN: 0003-2670; 1873-4324; 1873-4324
• DOI: 10.1016/j.aca.2023.341634

Over the last few years, the SARS-CoV-2 pandemic has made the need for rapid, affordable diagnostics more compelling than ever. While traditional laboratory diagnostics like PCR and well-plate ELISA are sensitive and specific, they can be costly and take hours to complete. Diagnostic tests that can be used at the point-of-care or at home, like lateral flow assays (LFAs) are a simple, rapid alternative, but many commercially available LFAs have been criticized for their lack of sensitivity compared to laboratory methods like well-plate ELISAs. The Capillary-Driven Immunoassay (CaDI) device described in this work uses microfluidic channels and capillary action to passively automate the steps of a traditional well-plate ELISA for visual read out. This work builds on prior capillary-flow devices by further simplifying operation and use of colorimetric detection. Upon adding sample, an enzyme-conjugated secondary antibody, wash steps, and substrate are sequentially delivered to test and control lines on a nitrocellulose strip generating a colorimetric response. The end user can visually detect SARS-CoV-2 antigen in 15–20 min by naked eye, or results can be quantified using a smartphone and software such as ImageJ. An analytical detection limit of 83 PFU/mL for SARS-CoV-2 was determined for virus in buffer, and 222 PFU/mL for virus spiked into nasal swabs using image analysis, similar to the LODs determined by traditional well-plate ELISA. Additionally, a visual detection limit of 100 PFU/mL was determined in contrived nasal swab samples by polling 20 untrained end-users. While the CaDI device was used for detecting clinically relevant levels of SARS-CoV-2 in this study, the CaDI device can be easily adapted to other immunoassay applications by changing the reagents and antibodies.
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•Developed a device that steps of a traditional ELISA from 1 user step.•Device detects SARS-CoV-2 nucleocapsid protein at similar LOD to an ELISA.•Able to visually detect clinically relevant levels of SARS-CoV-2 in 20 min.•Aspects of the device can be adjusted to detect other diseases.