Isoelectric focusing in a poly(dimethylsiloxane) microfluidic chip.

Area of Science:

• Analytical Chemistry
• Microfluidics
• Biochemistry

Background:

• Poly(dimethylsiloxane) (PDMS) is widely used for microfluidic chip fabrication due to its advantageous properties.
• However, unstable electroosmotic flow (EOF) and cathodic drift in PDMS hinder applications like isoelectric focusing.
• These issues necessitate strategies to improve the stability and reproducibility of microfluidic separations.

Purpose of the Study:

• To investigate the application of methylcellulose (MC) in PDMS microfluidic systems for ampholyte-based isoelectric focusing.
• To reduce electroosmosis and mitigate peak drift during microchip electrophoresis.
• To enhance the performance and reliability of isoelectric focusing in PDMS microchannels.

Main Methods:

• Development of a dynamic methylcellulose (MC) coating for the inner walls of PDMS microfluidic channels.
• Utilizing broad-range ampholytes for isoelectric focusing.
• Employing fluorescent proteins as analytes in microchip channels with varying electric field strengths.

Main Results:

• A significant reduction in electroosmotic flow (EOF) was achieved by applying MC dynamic coatings to PDMS channel walls.
• Higher MC concentrations effectively increased electrode solution viscosity, suppressing pH gradient drift and compression.
• Successful focusing of fluorescent proteins within 3-10 minutes in microchip channels.

Conclusions:

• Methylcellulose (MC) is an effective additive for stabilizing isoelectric focusing in poly(dimethylsiloxane) (PDMS) microfluidic devices.
• The MC coating strategy successfully addresses challenges of EOF and peak drift, enhancing separation performance.
• This approach offers a promising method for reproducible and efficient microscale biochemical separations.