Fabrication of two-layered channel system with embedded electrodes to measure resistance across epithelial and endothelial barriers.

This manuscript describes a straightforward fabrication process for embedding Ag/AgCl electrodes within a two-layer poly(dimethylsiloxane) (PDMS) microfluidic chip where an upper and a lower channel are separated by a semiporous membrane. This system allows for the reliable real-time measurement of transendothelial and transepithelial electrical resistance (TEER), an accepted quantification of cell monolayer integrity, across cells cultured on membranes inside the microchannels using impedance spectroscopy. The technique eliminates the need for costly or specialized microelectrode fabrication, enabling commercially available wire electrodes to easily be incorporated into PDMS microsystems for measuring TEER under microfluidic environments. The capability of measuring impedance across a confluent cell monolayer is confirmed using (i) brain-derived endothelial cells (bEND.3), (ii) Madin Darby Canine Kidney Cells (MDCK-2), and mouse myoblast (C2C12) (all from ATCC, Manassas, VA). TEER values as a function of cell type and cell culture time were measured and both agree with previously published values from macroscale culture techniques. This system opens new opportunities for conveniently resolving both transendothelial and transepithelial electrical resistance to monitor cell function in real-time in microfluidic cell cultures.