Enhancing commercially available immunoassays through a customized electrokinetic biomolecular preconcentration device†

Immunoassays are widely utilized in various settings, from clinics and emergency rooms to remote and resource-limited environments, such as patients' homes. However, they often present a significant trade-off: while offering simplicity, speed, and cost-effectiveness, they generally lack sensitivity. This study introduces an innovative electrokinetic preconcentration device that employs ion concentration-polarization in micro- and nanofluidic systems to continuously capture and preconcentrate target biomolecules. The system then facilitates their transfer with minimal dilution to standard immunoassays, increasing analyte concentration and enhancing transport kinetics and immunoreaction rates. Designed for cost-effectiveness and ease of use, the device does not require sophisticated equipment such as pumps, making it suitable for point-of-care (POC) commercially available immunoassays. By using this device as a preliminary step for various immunoassays, including enzyme-linked immunosorbent assay (ELISA) and lateral flow assay (LFA), we achieved substantial signal enhancement, improving the limit of detection of these assays by an order of magnitude. The obtained enhancement factor correlated with processed sample volume, operational duration, and assay binding kinetics. Our experimental validations and theoretical analysis lay the groundwork for enhancing commercially available immunoassays without modifying the assays themselves, promising significant advancements in biomedical POC diagnostics.