TAR (in vitro)
The trans epithelial / trans endothelial electrical resistance ( English Transepithelial / Transendothelial Electrical Resistance abbreviated TEER ) is a measurement variable that is common in the investigation of cell cultures and indicates the alternating current resistance of a flat cell culture at a certain measurement frequency. If the frequency is not specified more precisely, it is 12.5 Hz. The measurement is carried out in vitro . A typical measuring arrangement consists of a cell culture that is wetted on both sides by a conductive (nutrient) medium. The two reservoirs of the medium are only electrically connected through the cell culture and otherwise isolated from one another. A TEER meter has two electrodes, each of which is immersed in one of the two reservoirs. During the measurement, an alternating current is passed through the two electrodes and voltage, current and phase shift are determined. The AC resistance can be calculated from this. This metric is known as the TEER value . The typical excitation amplitude is between 10 and 200 mV.
application
The TEER value is used to assess the condition of a cell culture. For example, it can be used to assess the closeness of a cell culture, since even small gaps in the cell culture cause a significant drop in impedance. In this way, the end of the maturation phase of the cell culture can be determined. Likewise, the effects of harmful influences of test substances on the cell culture can be investigated in vitro, which means that animal experiments can be avoided.
Alternative procedures
In the case of multi-layer cell cultures, a complex electrical equivalent circuit is typically designed as a model of the culture and adapted to the observed measured values by varying its parameters. A TEER measurement makes it possible to draw conclusions about the internal parameters and the structure of the cell culture within certain limits. For more complex models and for more meaningful results, however, the TEER value is not sufficient, since it is only determined at one excitation frequency. The impedance spectroscopy complements the TEER measurement, by detecting the AC impedance for a wide frequency range, thus allowing a more detailed modeling of the cell culture.
See also
literature
- ↑ Balaji Srinivasan, Aditya Reddy Kolli, Mandy Brigitte Esch, Hasan Erbil Abaci, Michael L. Shuler, James J. Hickman: TEER measurement techniques for in vitro barrier model systems , doi : 10.1177 / 2211068214561025 , PMC 4652793 (free full text).
- ↑ C. Lotz, L. Kiesewetter, FF Schmid, J. Hansmann, H. Walles, FK Groeber-Becker: Replacing the Draize eye test: Impedance spectroscopy as a 3R method to discriminate between all GHS categories for eye irritation. Sci Rep 8, 2018, 15049, doi : 10.1038 / s41598-018-33118-2 .