Electrochemical immunoassay on a microfluidic device with sequential injection and flushing functions

Area of Science:

• Microfluidics
• Electrowetting
• Biosensing

Background:

• Integrated microfluidic devices offer potential for miniaturized and automated biological assays.
• Electrowetting-based valves provide precise control over fluidic transport in microchannels.
• Immunoassays are crucial for detecting biomarkers but often require complex laboratory setups.

Purpose of the Study:

• To develop an integrated microfluidic device with automated injection, flushing, and sensing capabilities.
• To demonstrate the device's utility in performing a simulated sandwich immunoassay.
• To achieve sensitive electrochemical detection of immobilized antigens.

Main Methods:

• Fabrication of a microfluidic device using glass and PDMS substrates with integrated electrowetting valves.
• Utilizing spontaneous solution movement in hydrophilic channels for microfluidic transport.
• Immobilizing human alpha-fetoprotein (AFP) or anti-AFP antibody on electrodes for detection.
• Performing electrochemical detection after incubation with labeled antibodies (e.g., glucose oxidase-labeled).

Main Results:

• Successful demonstration of automated injection and flushing of solutions using electrowetting valves.
• Detection of immobilized antigens (AFP or anti-AFP antibody) with a detection limit of 0.1 ng.
• Obtained sigmoidal calibration curves, indicating a dose-dependent response.
• Electrochemical current correlated with the amount of immobilized antigen.

Conclusions:

• The developed microfluidic system integrates essential functions for automated immunoassays.
• Electrowetting valves enable precise control for sequential reagent delivery and washing.
• The device shows promise as a core component for next-generation microfluidic immunoassays.