Dynamic analyte introduction and focusing in plastic microfluidic devices for proteomic analysis

Area of Science:

• Analytical Chemistry
• Biochemistry
• Microfluidics

Background:

• Traditional isoelectric focusing (IEF) uses a full channel for sample loading, limiting preparative capabilities.
• Microfluidics-based electrokinetic separations often have lower sample loading capacities.
• Enhancing sample loading is crucial for increasing analyte concentrations in IEF.

Purpose of the Study:

• To develop and demonstrate a dynamic sample introduction approach for IEF in plastic microfluidic devices.
• To increase the sample loading capacity and analyte concentrations in microfluidic IEF.
• To investigate the control of electrokinetic injection parameters for optimized sample loading.

Main Methods:

• Proteins and peptides were injected dynamically into a microchannel containing a pre-established pH gradient using electrokinetic principles.
• The microfluidic device facilitated continuous migration of analytes into the channel for focusing and separation.
• Electrokinetic conditions, including injection time and electric field strength, were controlled to manage sample introduction.

Main Results:

• The dynamic sample introduction method significantly enhanced sample loading, achieving 10-100 fold increases compared to conventional IEF.
• Analyte focusing and separation were achieved within the microchannel under the established pH gradient.
• Sample loading differences were influenced by electrokinetic injection bias and individual analyte electrophoretic mobility.

Conclusions:

• Dynamic electrokinetic injection is an effective strategy for substantially increasing sample loading in microfluidic IEF.
• This method offers improved preparative capabilities for microfluidic separation techniques.
• The approach allows for direct control over sample loading through electrokinetic parameters.