Capillary driven microfluidic sequential flow device for point-of-need ELISA: COVID-19 serology testing

Area of Science:

• Biomedical Engineering
• Analytical Chemistry
• Point-of-Care Diagnostics

Background:

• Traditional enzyme-linked immunosorbent assays (ELISA) for SARS-CoV-2 antibody detection are accurate but slow and expensive for widespread use.
• Existing point-of-care tests like lateral flow assays lack the sensitivity required for reliable detection of antibodies in clinical samples.
• There is a critical need for accessible, sensitive, and rapid serology testing for COVID-19 management and immune status assessment.

Purpose of the Study:

• To develop a capillary-driven microfluidic device for sensitive and user-friendly serology assays, specifically for SARS-CoV-2 antibody detection.
• To achieve ELISA-level sensitivity in a simple, point-of-need format suitable for at-home or clinical settings.
• To enable rapid determination of prior infection, immunity, and vaccination status through accessible COVID-19 serology testing.

Main Methods:

• A microfluidic sequential flow device was engineered using transparency film, double-sided adhesive, and paper pumps for capillary-driven reagent delivery.
• Automated sequential washing and reagent addition steps were integrated into the device design, requiring only two simple end-user steps.
• Enzyme labels and colorimetric substrates were employed to generate an amplified, visible signal for enhanced sensitivity and reproducibility.

Main Results:

• The capillary-driven immunoassay (CaDI) system demonstrated the ability to detect SARS-CoV-2 antibodies at concentrations as low as 2.8 ng mL⁻¹ from whole blood.
• The device achieved sensitivity comparable to well-plate ELISA, which detected 1.2 ng mL⁻¹ using the same antibodies.
• Integrated washing steps effectively reduced false positives and improved the overall reproducibility of the assay.

Conclusions:

• The developed capillary-driven microfluidic device offers a significant advancement in point-of-care diagnostic technology for COVID-19 serology.
• The CaDI system provides a simple, equipment-free solution for sensitive antibody detection, bridging the gap between rapid tests and laboratory-based assays.
• This technology has the potential to revolutionize infectious disease monitoring and management by enabling widespread, accessible, and accurate serological testing.