Catch-and-display immunoassay for digital biomarker detection.

Area of Science:

• Biotechnology
• Nanotechnology
• Analytical Chemistry

Background:

• Digital immunoassays offer high sensitivity for detecting low-abundance biomarkers.
• Widespread adoption is hindered by high costs and complex workflows of existing platforms.
• There is a need for accessible, laboratory-friendly digital immunoassay solutions.

Purpose of the Study:

• To introduce a cost-effective and laboratory-friendly digital immunoassay, the Catch-and-Display Immunoassay (CAD-IA).
• To demonstrate CAD-IA's utility for detecting biomarkers in common research settings.
• To validate CAD-IA's performance using a traumatic brain injury biomarker.

Main Methods:

• Development of a nanomembrane-based Catch-and-Display Immunoassay (CAD-IA) using ultrathin silicon nitride membranes.
• Utilizing pipette-powered filtration to capture fluorescent nanoparticles within membrane pores.
• Quantification of fluorescent immunocomplexes via confocal microscopy for digital signal generation.
• Implementation on the microfluidic device featuring an ultrathin silicon membrane for diagnostics (µSiM-DX) platform.

Main Results:

• CAD-IA demonstrated consistent digital outputs and linear quantification over two orders of magnitude.
• The assay maintained linearity in serum matrices.
• Achieved a limit of detection (LoD) of 0.02 µg mL⁻¹ for S100B with tyramide signal amplification (TSA), suitable for clinical diagnostics.

Conclusions:

• CAD-IA represents a novel, cost-effective, and laboratory-deployable digital immunoassay.
• The technology provides a practical alternative to expensive commercial platforms for biomarker detection.
• This proof-of-concept demonstrates the potential of CAD-IA for widespread use in research laboratories.