Trans-epithelial/endothelial electrical resistance (TEER): Current state of integrated TEER measurements in organ-on-a-chip devices.

Trans-epithelial/endothelial electrical resistance (TEER) is a non-invasive and quick method of assessing the integrity of barrier tissues. Traditional TEER measurement methods such as chopstick electrode-based and chamber-based measurement work well with static, Transwell-based models; however, the same methods do not directly apply to human on a chip or organ-on-a-chip (OOC) platforms. With the wide variety of organ-on-a-chip devices, innovative designs to accurately measure TEER, without disturbing cells, are customized for various devices. Wire electrode integration, integrating a two-probe or four-probe technique, flexible printed circuit boards or multi-electrode glass substrate-based methods are some of the TEER measurement setups being utilized in conjunction with OOC systems. The variability in measurement setups associated with OOCs make standardization challenging; however, the field is working towards establishing guidelines on acceptable TEER values of different OOC constructs.