Determination of membrane capacitance and cytoplasm conductivity by simultaneous electrorotation

Area of Science:

• Biophysics
• Cellular Electrophysiology
• Biosensing

Background:

• Accurate determination of cellular electrical properties is crucial for understanding cell function and disease.
• Previous methods for measuring cell electrophysiology were often time-consuming and limited in throughput.

Purpose of the Study:

• To develop and validate a simultaneous electrorotation (ROT) system for high-throughput analysis of hematopoietic cell electrical properties.
• To determine membrane capacitance and cytoplasm conductivity of various hematopoietic cell lines.
• To explore the potential of ROT for discriminating between different cell types based on their electrical characteristics.

Main Methods:

• Fabrication of a three-dimensional interdigitated array (3D-IDA) electrode system for generating rotating electric fields.
• Simultaneous application of AC signals to microband electrodes to induce cell rotation.
• Acquisition and analysis of rotation rates (ROT spectra) from multiple cells within minutes.
• Fitting experimental ROT spectra to theoretical models to extract membrane capacitance and cytoplasm conductivity.

Main Results:

• The simultaneous ROT system successfully rotated multiple hematopoietic cells (K562, Jurkat, THP-1) without cell-to-cell or substrate contact.
• Measured membrane capacitances and cytoplasm conductivities for K562, Jurkat, and THP-1 cells agreed with previously reported values.
• First-time determination of membrane capacitance (8.89 ± 0.25 mF m⁻²) and cytoplasm conductivity (0.28 ± 0.03 S m⁻¹) for WEHI-231 cells.
• Demonstrated the ability to discriminate between cell types based on differences in their ROT rates, correlating with distinct electrical properties.

Conclusions:

• The developed simultaneous ROT system offers a rapid, efficient, and statistically robust method for characterizing hematopoietic cell electrical properties.
• This technology provides a valuable tool for cell analysis, potentially aiding in diagnostics and research.
• The ability to differentiate cell types based on electrical properties opens avenues for advanced cell sorting and analysis applications.