Schwan equation and transmembrane potential induced by alternating electric field

Area of Science:

• Biophysics
• Cell Biology
• Electrochemistry

Background:

• The transmembrane potential of cells is influenced by alternating electric fields (ac).
• The Schwan Equation models this relationship, but experimental validation in living cells is crucial.
• Understanding membrane breakdown potential is key to electroporation and drug delivery.

Purpose of the Study:

• To measure the critical electric breakdown potential (delta psi crit) of murine myeloma cell membranes using ac fields.
• To validate the applicability of the Schwan Equation for predicting transmembrane potential in living cells across various frequencies and resistivities.
• To determine the internal resistivity of the cell cytoplasm.

Main Methods:

• Utilized a murine myeloma cell line (Tib9) and monitored propidium iodide dye entry to detect membrane perforation.
• Applied ac electric fields of varying frequencies (0.1-300 kHz) and measured the critical field intensity (Ecrit).
• Performed experiments in media with different resistivities (52,600, 7,050, and 2,380 omega cm) and a field duration of 200 ms.

Main Results:

• The critical electric breakdown potential (delta psi crit) remained constant across the studied frequency range for a given medium resistivity.
• Measured delta psi crit values were 0.33, 0.48, and 0.53 V for decreasing external resistivities.
• Determined the internal cytoplasmic resistivity (rho int) to be 910-1,100 omega cm, assuming a membrane capacitance (Cmembr) of 0.90 microF cm-2.

Conclusions:

• The Schwan Equation accurately describes the transmembrane potential generated by oscillating electric fields in living cells.
• Experimental data closely fit the Schwan Equation, supporting its predictive power for cell membrane electroporation.
• This study provides valuable insights into cell membrane electropermeability and the parameters governing electrical breakdown.