Controlled release of reagents in capillary-driven microfluidics using reagent integrators.

Area of Science:

• Microfluidics
• Biotechnology
• Analytical Chemistry

Background:

• Accurate reagent integration and release are crucial for point-of-care (POC) microfluidic diagnostic devices.
• Existing methods often face challenges with handling small reagent quantities and ensuring controlled release.

Purpose of the Study:

• To introduce novel microfluidic functional structures, termed reagent integrators (RIs).
• To demonstrate the capability of RIs to integrate and release minute amounts of dried reagents into microliter sample volumes within capillary-driven microfluidic chips.

Main Methods:

• Design and fabrication of RIs with a specific channel geometry (inlet, central reagent channel, two diluter channels).
• Loading of dried reagents (e.g., horseradish peroxidase, fluorescently labeled antibodies) onto RIs using an inkjet spotter.
• Characterization of reagent reconstitution and release dynamics based on hydraulic resistance during microfluidic chip filling.

Main Results:

• RIs successfully integrated and released ng quantities of dried reagents (down to ~100 pg HRP and ~450 pg dAbs).
• Reagent release exhibited a dilution factor dependent on the RI's channel hydraulic resistance.
• Demonstrated successful application in enzyme activity assays and C-reactive protein (CRP) immunoassays using human serum samples.

Conclusions:

• Reagent integrators offer a simple yet effective solution for controlled reagent integration and release in microfluidic devices.
• RIs maintain the simplicity of lateral flow assays while enhancing control over reagent delivery.
• The technology is broadly applicable to various microfluidic-based biological assays, particularly for POC testing.