On-Chip Analysis of Protein Secretion from Single Cells Using Microbead Biosensors

Area of Science:

• Immunology
• Biotechnology
• Microfluidics

Background:

• Understanding single immune cell effector functions, like cytokine secretion, is crucial for immune system insights, diagnostics, and therapeutics.
• Current methods may lack the precision to analyze cytokine secretion at the single-cell level.
• Heterogeneity in cellular function is vital for applications in cancer research and drug discovery.

Purpose of the Study:

• To develop and validate a microfluidic device for high-throughput, single-cell cytokine secretion analysis.
• To quantitate cytokine secretion from individual immune cells, specifically monocytes.
• To investigate the impact of disrupted paracrine signaling on cytokine secretion.

Main Methods:

• A microfluidic device with 1008 microchambers (∼500 pL each) was designed to pair single cells with antibody-functionalized microbeads.
• Hydrodynamic traps and integrated microvalves were used to isolate cell/bead pairs and prevent cross-contamination.
• A fluorescence sandwich immunoassay was implemented on microbeads for cytokine detection, achieving a 9 pg/mL limit of detection.

Main Results:

• The device successfully detected interleukin-8 (IL-8) secreted by single human monocytes in response to lipopolysaccharide (LPS).
• A limit of detection of 9 pg/mL for IL-8 was achieved using the fluorescence immunoassay.
• A significant reduction in IL-8-secreting monocytes was observed when paracrine signaling was disrupted.

Conclusions:

• The developed microfluidic platform enables precise quantification of single-cell cytokine secretion.
• This technology offers a valuable tool for studying cellular function heterogeneity in various biological contexts.
• Potential applications include cancer research, antibody discovery, and rare cell screening.