Transepithelial/endothelial Electrical Resistance (TEER) theory and applications for microfluidic body-on-a-chip devices

Transepithelial/endothelial electrical resistance (TEER) is a valuable method for assaying in vitro barrier tissue integrity, and is becoming an important measurement for body-on-a-chip barrier tissue devices due to its usefulness and non-invasive nature. The measurement concept is relatively straightforward, with TEER measurements performed by applying an AC electrical signal across electrodes placed on both sides of a cellular monolayer and measuring voltage and current to calculate the electrical resistance of the barrier. However, details of the setup, measurement circuit, and applied electrical signal must be properly designed for accurate measurements. Several main factors contribute to errors and variability in the measurement of TEER values, and while many of these factors can be reasonably controlled with little effort in Transwell®-type culture conditions, these factors can become major issues in body-on-a-chip devices without proper design. This minireview outlines several important aspects of TEER measurements, including the basic theory, commercial systems used to perform measurements, major factors that contribute to measurement errors, and the application of TEER measurements to current body-on-a-chip barrier tissue devices, with the aim of providing guidance for the design of novel body-on-a-chip systems.