Intracellular protein determination using droplet-based immunoassays.

Area of Science:

• Biotechnology and Biomedical Engineering
• Analytical Chemistry
• Molecular Biology

Background:

• Accurate quantification of intracellular proteins is crucial for understanding cellular function and disease mechanisms.
• Existing methods like Western blotting are often time-consuming, labor-intensive, and require significant cell numbers.
• There is a need for integrated, sensitive, and rapid analytical platforms for intracellular protein analysis.

Purpose of the Study:

• To develop and implement a sensitive, on-chip immunoassay for intracellular protein analysis using microdroplet technology.
• To integrate cell lysis, protein detection, and quantification into a single, automated workflow.
• To compare the performance of the developed microdroplet immunoassay with traditional Western blot methods.

Main Methods:

• Cells in suspension were introduced into a microfluidic device for in situ electrical lysis.
• Cell lysate was encapsulated with antibody-functionalized beads into water-in-oil microdroplets for on-chip storage.
• Intracellular protein binding to beads was monitored via fluorescence, with quantification against standard additions.

Main Results:

• The microdroplet immunoassay successfully measured intracellular proteins (HRas-mCitrine and actin-EGFP) over 5 orders of magnitude (~50 pM to 1 microM).
• The method demonstrated high sensitivity and required a significantly smaller number of cells compared to Western blotting.
• The developed semiautomated system was faster than conventional Western blot analyses.

Conclusions:

• The implemented microdroplet immunoassay provides a sensitive, rapid, and efficient platform for intracellular protein analysis.
• This technology offers a valuable alternative to traditional methods, particularly when dealing with limited cell samples.
• The integrated workflow streamlines the analytical process, enabling faster insights into cellular protein expression.