Beyond lateral flow: vertical flow immunoassays as thermodynamically assisted rapid diagnostics

Area of Science:

• Biomedical Engineering
• Analytical Chemistry
• Diagnostics

Background:

• Lateral flow immunoassays (LFAs) are widely used in point-of-care diagnostics but face limitations like poor analyte capture, high non-specific background, and the hook effect.
• These limitations stem from LFAs' single-pass capillary architecture, which restricts reaction kinetics and washing efficiency.

Purpose of the Study:

• To review the physical-chemical principles behind vertical flow immunoassays (VFAs) and their advantages over LFAs.
• To explore VFA applications in clinical diagnostics, food safety, and environmental monitoring.
• To identify engineering barriers hindering VFA commercialization and propose pathways for deployment.

Main Methods:

• Comparison of VFA stacked-membrane design with LFA single-pass architecture.
• Analysis of VFA performance metrics including washing efficiency, multiplexing capabilities, and limit of detection.
• Survey of VFA integration with advanced detection techniques like SERS and electrochemical methods.

Main Results:

• VFAs demonstrate superior thermodynamic washing (99.94% specific retention, 45% non-specific removal) and eliminate the hook effect.
• Head-to-head comparisons show up to 80-fold improvement in limit of detection for VFAs over LFAs.
• Coupling VFAs with advanced technologies extends sensitivity to sub-picogram-per-milliliter levels.

Conclusions:

• VFAs offer significant performance advantages over LFAs for sensitive biomarker detection.
• Engineering and commercialization challenges need to be addressed for widespread VFA adoption.
• VFAs hold promise for impactful applications in diagnostics and safety testing.