Figure 2.

Direct current or quasi-direct current methods for in vivo and in vitro transcellular electrical resistance and impedance measurements. All types of setups include a four-point measurement method based on two current electrodes (red) and two voltage electrodes (blue). (a) Setup for electrical resistance registration of brain surface microvessels. (b) Chopstick and (c) chamber silver/silver chloride (Ag/AgCl) electrode arrangement for the measurement of transcellular resistance across cellular monolayers cultured on different sizes of cell culture inserts. (d) Impedance measurement setup on a hollow-fiber cartridge model. (e) Resistance measurement on a novel lab-on-a-chip model based on electrodes prepared with gold sputter coating (method described in [14]).