Miniaturized capillary isoelectric focusing in plastic microfluidic devices

Area of Science:

• Analytical Chemistry
• Biochemistry
• Microfluidics

Background:

• Conventional capillary isoelectric focusing (CIEF) is a powerful protein separation technique.
• Microfluidic devices offer advantages in miniaturization and reduced sample consumption.
• Adapting CIEF to microfluidic platforms enhances its applicability for complex biological analyses.

Purpose of the Study:

• To demonstrate miniaturized CIEF in plastic microfluidic devices.
• To adapt conventional CIEF for protein separation and interaction studies within microfluidic systems.
• To assess the performance and efficiency of microfluidic CIEF for biological applications.

Main Methods:

• Plastic microfluidic devices with channels (1.2 cm length, 50 µm deep x 120 µm wide) were fabricated.
• Conventional CIEF was adapted for rapid focusing, mobilization, and detection of proteins.
• Protein-protein interactions were studied using specific protein pairs, including IgG with Protein G and anti-6xHis with 6xHis-GFP.

Main Results:

• Rapid protein focusing, mobilization, and detection were achieved within 150 seconds in a 1.2 cm channel.
• High separation efficiency of 1.5 x 10^5 plates (3.2 million plates/meter) was obtained for lysozyme.
• Protein-protein interactions were detected with as little as 50 fmol of protein, demonstrating high sensitivity.

Conclusions:

• Miniaturized CIEF in plastic microfluidic devices is a viable and efficient technique for protein separation.
• The method is highly sensitive for detecting protein-protein interactions, requiring minimal sample amounts.
• This technology is particularly useful for studying interactions where a pI difference exists between complexes and their constituents.