2.3. Measurement of Transepithelial Electrical Resistance (TEER)

Electrical resistance across the Caco-2 epithelial monolayer was measured using a MILLICELL-ERS^® instrument (Millipore Corporation, Bedford, MA, USA) with “chopstick” electrodes; TEER was calculated as reported previously [17]. In brief, the values obtained from blank inserts were subtracted to give the net resistance, which was multiplied by the membrane area to give the resistance in area-corrected units (Ω·cm²). The change in electrical resistance was represented by percentage baseline resistance, which was calculated as follows: %baseline resistance = ((resistance from each time point) − (resistance from a blank insert))/((baseline resistance) − (resistance from a blank insert)) × 100, where baseline resistance was the resistance at time point 0 [18].