Transepithelial Electrical Resistance (TEER) Measurements

Transepithelial electrical resistance (TEER) values from epithelial monocultures and co-cultures on Transwell^® inserts and CHyA-B scaffolds were quantified throughout the cell culture period to monitor epithelial barrier integrity. Fresh medium was added to the apical and basolateral compartments and TEER was measured using an EVOM voltohmmeter (World Precision Instruments, Hitchin, UK), STX-2 chopstick electrodes (World Precision Instruments) for Transwell^® inserts and STX-3 chopstick electrodes (World Precision Instruments) for CHyA-B scaffolds. Transwell^® inserts were filled with 500 μL of fresh co-culture medium in the apical and 1 mL in the basolateral compartment, while 500 μL were added to the apical side of CHyA-B scaffolds and 2 mL to the basolateral compartment. Electrical resistance on cultures was measured on day 3, 5, 8, 10, 12 and 14 of culture. TEER values were calculated by subtracting the resistance of a cell-free scaffold or insert and corrected to the surface area (1.12 cm²) available for cell growth. TEER measurements for fibroblast monocultures on Transwell^® inserts and CHyA-B scaffolds were performed as n = 2 due to the inability of fibroblast to form tight junctions and, therefore, produce relevant TEER values [19].