2.4. Measurement of TEER
TEER measurement was used to determine barrier integrity. TEER
measurement for each module was conducted by a resistance-based method
illustrated in Fig. 3A. This method was a four-point probe method like
commonly used STX chopstick electrodes.
After co-culturing gut and BBB, the upper and bottom module were
detached from each other. Then, resistance of each module was measured
using Millicell ERS-2 Volt-Ohm meter (Millipore, USA, MERS00002). TEER
of each barrier was determined from the resistance values using equation
(1).
\begin{equation}
TEER=A*\left(R-R_{\text{blank}}\right)\ \ \ \ \ \ (1)\nonumber \\
\end{equation}A is cell culture area (cm2), R is resistance of
module with cell layer (Ω) and Rblank is resistance of
module with no cell (Ω).