Quantitative comparison of EGFR expression levels of optically trapped individual cells using a capacitance biosensor

Area of Science:

• Biophysics
• Cell Biology
• Nanotechnology

Background:

• Cellular endocytosis is vital for cell functions like nutrient uptake and waste removal.
• Observing endocytosis at the single-cell level is crucial for understanding cellular processes.
• Existing methods lack the precision to measure real-time capacitance changes during single-cell endocytosis.

Purpose of the Study:

• To develop a novel biosensor for real-time, single-cell capacitance measurements during endocytosis.
• To investigate the capacitance responses of single cancer cells versus normal cells during epidermal growth factor (EGF) endocytosis.
• To establish a method for quantifying epidermal growth factor receptor (EGFR) expression levels based on cellular capacitance.

Main Methods:

• Integration of an optical tweezer for precise single-cell manipulation with a capacitance sensor and incubation chamber.
• Optical trapping of single HeLa (cancer) and NIH3T3 (normal) cells.
• Real-time measurement of single-cell capacitance changes during EGF molecule endocytosis.

Main Results:

• Single HeLa cells exhibited a greater increase in capacitance compared to NIH3T3 cells upon EGF exposure.
• Capacitance change directly correlated with the epidermal growth factor receptor (EGFR) expression level in tested cells.
• A derived equation accurately estimated EGFR expression levels in blind-tested cells.

Conclusions:

• The developed biosensor enables non-invasive, real-time monitoring of single-cell interactions with external ligands.
• The system can distinguish cellular responses between cancer and normal cells.
• This technology offers a new tool for quantifying EGFR levels and understanding cell-ligand interactions.