Stx 100c electrode

Experiments were carried out on Caco-2 cell monolayers (CacoReady™, Readycell, Barcelona, Spain) according to Denaro et al. [35 (link)]. Briefly, 8.5 × 10⁴ cells/cm² Caco-2 cells (passage number 45–55) were seeded on polyester permeable supports (6.5 mm, 0.33 cm², and 0.4 µm) in 24-well HTS plates (Corning Incorporated, Corning, NY, USA). DMEM low glucose (1 g/L) with 10% fetal calf serum (FCS), 2 mM glutamine, 1 U/mL penicillin, and 1 U/mL streptomycin was added onto the apical (0.3 mL) and basolateral side (0.9 mL) of each transwell support. After 21 days of culture incubation at 37 °C, 5% CO₂, and 95% relative humidity, the Caco-2 cells were completely differentiated and polarized, resembling the morphological and functional features of mature enterocytes lining the small intestine. Before conducting the experiments, the monolayer integrity was checked by measuring the trans-epithelial electrical resistance (TEER) with a Millicell^® ERS-2 V/ohmmeter (Merck Millipore, Darmstadt, Germany) equipped with an STX 100C electrode (World Precision Instruments, Sarasota, FL, USA). Only Caco-2 monolayers with epithelial resistance ≥800 Ω/cm² were used to carried out the experiments.

HUVECs seeded in Transwell^® inserts (Corning, Cat.: 3392, 0.143 cm ² growth area) coated with 0.2% gelatin solution (Sigma Aldrich, San Luis, MO, USA) were maintained in a 5% CO₂ incubator at 37 °C until they reached confluence. Then, the cells were treated with 10% of pooled sera from each immunized mice group and incubated at 37 °C (5% CO₂). Transendothelial electrical resistance (TEER) was evaluated at 2, 6, and 24 h after treatment using the EVOM2 voltmeter with a STX100c electrode (World Precision Instruments, Sarasota, FL, USA). The TEER values in ohms (Ω) of the negative controls (inserts without cells) were subtracted from the values obtained in each insert with cells. Finally, the values were multiplied by the area of the inserts, resulting in the TEER reported in Ω × cm ².