Method for Extracellular Electrochemical Impedance Spectroscopy on Epithelia.

Area of Science:

• Biophysics
• Epithelial Physiology
• Electrophysiology

Background:

• Epithelial tissues are crucial biological barriers.
• Conventional transepithelial resistance (TER) quantifies barrier integrity but lacks detail on electrical properties.
• Advanced electrophysiological methods are needed to fully characterize epithelial electrical behavior.

Purpose of the Study:

• To describe a protocol for galvanostatic electrochemical impedance spectroscopy (EIS) on epithelial tissues.
• To enable measurement of transepithelial capacitance (TEC) and membrane electrical properties.
• To provide a method for quantifying epithelial barrier electrical behavior beyond TER.

Main Methods:

• Utilized galvanostatic EIS with a sinusoidal signal (4 μA amplitude, 2 Hz-50 kHz).
• Employed commercially available cell culture inserts and chambers.
• Detailed apparatus, signal processing, fitting techniques, and error quantification for reproducible measurements.

Main Results:

• Measurements were performed in approximately one minute with low mean absolute error (< 10 Ω).
• Distinct and repeatable values for TER, TEC, and membrane ratio were obtained for different cell types.
• Representative retinal pigment and bronchiolar epithelial samples yielded expected TER ranges and specific TEC and membrane ratio values.

Conclusions:

• Galvanostatic EIS is a rapid and accurate method for characterizing epithelial electrical properties.
• This technique provides more comprehensive data on epithelial barrier function than TER alone.
• The protocol enables detailed analysis of membrane-specific electrical characteristics in epithelial tissues.