  The generation of physiologically relevant in-vitro models of biological
barriers can play a key role in understanding human diseases and in the
development of more predictive methods for assessing toxicity and drug or
nutrient absorption. Here, we present an advanced cell culture system able to
mimic the dynamic environment of biological barriers while monitoring cell
behaviour through real-time impedance measurements and imaging. It consists of
a fluidic device with an apical and a basal flow compartment separated by a
semi-permeable membrane. The main features of the device are the integration of
a transepithelial electrical impedance (TEEI) meter and transparent windows for
optical monitoring within a dual flow system. Caco-2 cells were cultured in the
TEEI bioreactor under both flow and static conditions. Although no differences
in the expression of peripheral actin and occludin were visible, the cells in
dynamic conditions developed higher impedance values at low frequencies,
indicative of a higher paracellular electrical impedance and thus suggesting
accelerated barrier and tight junction formation with respect to the static
cultures. TEEI measurements at high frequency also enabled monitoring the
evolution of transcellular impedance during culture. The cells subject to flow
showed a typical RC behaviour, while the controls showed minimal capacitive
behaviour, again highlighting the differences between flow and static
conditions.
