Millicell ers 2 voltmeter

Trans-epithelial electrical resistance (TEER) is a valuable measure used to assess the fusion and integrity of a cellular monolayer. For this study, Caco-2 cells were seeded at a density of 1.5 × 10⁴ cells per well in transwell plates with polyester membranes (0.33 cm², 0.4 μm pore size) obtained from Corning, MA, USA. The cells were closely monitored until the TEER values reached a level greater than 300 Ω·cm², indicating the establishment of a tight and intact monolayer; this value was reached after the fifteenth day of sowing. This TEER value signifies the successful formation of cell-to-cell junctions, which are crucial for maintaining the integrity of the epithelial barrier.
Subsequently, the cells were exposed to different treatments. Specifically, they were treated with LE alone at 2.5 mg/mL, lipopolysaccharide (LPS) alone at a concentration of 10 µg/mL, or co-administered with LE at 2.5 mg/mL. These treatments were applied for 24 h. After the treatment period, TEER was measured using a Millicell^® ERS-2 voltmeter from Merck Millipore, Darmstadt, Germany. Before the measurement, the cells were washed twice with phosphate-buffered saline (PBS) to ensure the accuracy of the TEER readings. TEER values were then calculated using the formula: TEER (Ω·cm²) = (Cell resistance − Cell-free resistance) × 0.33 cm².

HNEpCs were seeded on transwell inserts (0.4-μm polyester membrane, diameter 24 mm) in 6-well plates (Corning, MA, United States) at a density of 1 × 10⁵ cells per transwell. The cultural medium was replaced every day. When the cells grew to complete confluence, trans epithelial electrical resistance (TEER) was measured by Millicell^® ERS-2 voltmeter (Merck Millipore, Darmstadt, Germany). A tight monolayer was considered to be formed only if the resistance is greater than 300 Ω cm². The cells were pretreated with 12.5, 25, and 50 μg/mL MFXD-LP for 24 h and then treated with 100 μg/mL PAE, in the presence or absence of 12.5, 25, and 50 μg/mL MFXD for another 4 h. Subsequently, the TEER in the different wells was measured and normalized to the average measured value before adding PAE and after 4 h.
FITC-FD4 was used to assess the paracellular permeability. Briefly, FITC-FD4 (100 μg/mL) was added to the upper chambers and incubated for 2 h to assess paracellular permeability. During that, 200 μL of the samples were collected from the bottom chamber at 30, 60, and 120 min and evaluated using a fluorescence microplate reader (BioTek, Santa Clara, CA, United States).

1‐2 × 10⁵ primary cultured RPE cells from wild type and DKO mice were seeded on 24‐well cell culture inserts to form monolayers (Millipore). The inserts contain a 0.4‐μm pore size polycarbonate membrane pre‐coated with collagen type I. The medium was replaced every 48 hours. TEER and TEP were determined using a Millicell ERS‐2 Voltmeter (MERS00002, EMD Millipore) at 1‐4 weeks.