Sample pre-concentration by isotachophoresis in microfluidic devices.

Area of Science:

• Analytical Chemistry
• Microfluidics
• Biotechnology

Background:

• Microfluidic devices offer miniaturization advantages but often face limitations in detection sensitivity.
• Isotachophoresis (ITP) and zone electrophoresis (ZE) are powerful separation techniques that can be enhanced when coupled.

Purpose of the Study:

• To develop and validate a microfluidic device coupling isotachophoresis (ITP) with zone electrophoresis (ZE) for improved detection limits.
• To increase the concentration limit of detection in microfluidic systems through enhanced sample stacking.

Main Methods:

• Design of plastic multi-channel microfluidic chips with extended sample injection channels.
• Utilizing discontinuous ITP buffers for sample stacking into a narrow band.
• Subsequent separation of the stacked sample using zone electrophoresis (ZE).
• Analysis of fluorescently labeled reporter molecules and a cell surface protease (ADAM 17).

Main Results:

• Achieved a 400-fold increase in sensitivity compared to chip ZE alone using the ITP-ZE mode.
• Demonstrated sub-picomolar limits of detection for reporter molecules in cell lysate.
• Showcased efficient stacking and separation in buffers of varying ionic strengths, including physiological conditions (≥140 mM salt).
• Applied ITP-ZE to detect ADAM 17 on live cells with detection limits below 10 cells/assay.

Conclusions:

• The coupled ITP-ZE microfluidic system significantly enhances detection sensitivity in microfluidic devices.
• This method is robust across a range of ionic strengths, making it suitable for biological samples.
• ITP-ZE provides a powerful tool for sensitive analysis of biomarkers and cellular components in complex matrices.