Toward one-step point-of-care immunodiagnostics using capillary-driven microfluidics and PDMS substrates

Area of Science:

• Biomedical Engineering
• Analytical Chemistry
• Diagnostics

Background:

• Microfluidics offers significant advantages for point-of-care diagnostics, including sample preservation, enhanced sensitivity, and faster reaction times.
• A key challenge in microfluidic diagnostics is the integration of reagents and user-friendliness for rapid assays.

Purpose of the Study:

• To develop and validate a novel one-step microfluidic immunoassay for point-of-care diagnostics.
• To integrate essential reagents and microfluidic elements for a capillary-driven, sandwich immunoassay.

Main Methods:

• Integration of microfluidic components including a sample collector, delay valves, flow resistors, and a reaction chamber sealed with a patterned polydimethylsiloxane (PDMS) substrate.
• Optimization of inkjet deposition of detection antibodies (dAbs) and patterning of capture antibodies (cAbs) and analytes on PDMS.
• Detection of C-reactive protein (CRP) in human serum using capillary forces and fluorescence microscopy.

Main Results:

• The developed one-step microfluidic chip successfully detected CRP in 5 microL of human serum.
• Detection limits for CRP were achieved at 10 ng/mL in under 3 minutes and below 1 ng/mL within 14 minutes.
• Storage of patterned PDMS with desiccant maintained over 51% of capture antibody activity for up to 6 months.

Conclusions:

• This integrated microfluidic device enables a simple, one-step fluorescence immunoassay for point-of-care applications.
• The capillary-driven microfluidic system demonstrates potential for rapid and sensitive detection of biomarkers like CRP.
• The findings may promote the use of microfluidics and PDMS substrates in fluorescence immunoassays for diagnostics.