Simple and Convenient Three-Electrode Layout for Real-Time Electrorotation Measurement Upon Chemical Stimulation

Area of Science:

• Biophysics
• Cell Biology
• Microfluidics

Background:

• Cell membrane capacitance is a critical indicator of cellular state and response.
• Existing methods for measuring membrane capacitance changes often require fluorescent labeling and complex setups.
• A label-free, high-throughput method is needed for real-time monitoring of cellular responses to stimuli.

Purpose of the Study:

• To develop and validate a novel electrorotation (ROT) device for label-free monitoring of cell membrane capacitance.
• To investigate the correlation between cell rotation rate and membrane capacitance under chemical stimulation.
• To demonstrate the device's capability in assessing cellular responses to specific stimuli, such as ionomycin-induced calcium influx.

Main Methods:

• Fabrication of a microwell array with three electrodes integrated into a fluidic channel.
• Utilizing positive dielectrophoresis (p-DEP) for cell trapping and negative dielectrophoresis (n-DEP) for single-cell formation.
• Applying AC voltages with a 120° phase shift for vertical and simultaneous cell rotation.
• Monitoring the electrorotation rate as a function of applied frequency to determine membrane capacitance.

Main Results:

• A novel electrorotation device was successfully developed, enabling simultaneous rotation of cells within microwells.
• A direct correlation between cell rotation rate and membrane capacitance was established.
• The device accurately monitored the increase in membrane capacitance induced by Ca2+ influx from ionomycin.
• The frequency spectrum of cell rotation shifted to lower frequencies with increased membrane capacitance.

Conclusions:

• The developed electrorotation device offers a simple, label-free method for assessing cellular responses to chemical stimuli.
• This technology facilitates statistical analysis of cell responses without the need for fluorescent markers.
• The device shows promise for label-free assessments of white blood cell responses and other cellular studies.