Realtime Transepithelial/Endothelial Electrical Resistance Measurements in Multiple Transwell Culture Inserts

Abstract

Epithelial and endothelial cells line the surface of the body. Adjacent cells of both epithelial and endothelial cells are connected to each other via intercellular junction called tight junction that regulates the diffusion of molecules and ions between the apical and basolateral side of the body. Quantification of this barrier is important to evaluate the suitability of in vitro cellular barrier models for drug toxicity or transport studies. Transepithelial/endothelial electrical resistance (TEER), a quantitative technique to access electrical resistance of the cellular monolayer during culture has become one of the most popular quantitative techniques to evaluate the integrity of tight junction. The major advantage of the TEER technique over traditional permeability measurements is that it is quick, label-free, and non-invasive. As such, the TEER technique has been widely used to evaluate in vitro models such as the blood-brain barrier, the intestine epithelial barrier, the alveolar epithelial barrier, and the blood-retina barrier.However, the reported normalized TEER values of a specific cell type in transwell inserts are inconsistent between different research groups. A major cause of data variation is the manual technique that is used for measuring TEER. Typically, a “chopstick” like electrode pair is immersed inside a cell cultured semi-porous transwell insert membrane to measure TEER. Due to the variation in the alignment of the electrodes every time a TEER value is measured, the actual values vary significantly between measurements. A second problem with the conventional manual measurement process is time gap between each measurement (typically 12h or 24h) since a more frequent measurement requires frequent opening and closing of cell culture incubator door that can disturb the cells and introduce potential contamination.Thus, to enable consistency in TEER measurement, and allow automated real-time data acquisition in multiple samples, we built an add-on device (used atop EVOM®, a commercially available TEER instrument) consisting of a 3D printed electrode holder, a temperature sensor, and a custom designed data logger. The 3D printed electrode holder allowed data variation to be minimized by allowing perfect alignment of electrodes during measurement. The real-time data acquisition and in-situ temperature measurement allowed detection and correction of data offset during medium replacement process. The concept and device demonstration presented here should enable research labs to minimize data variations allowing them to produce consistent TEER results without having to spend extra time manually measuring multiple samples.