Fig. 1

a–c Quality control steps for the cultivation of Caco-2 cells on filter inserts. Increase in TEER over the cultivation period (a). Caco-2 cells were seeded onto filter inserts applying Protocol #2 and TEER was measured as detailed in Supplementary Protocol #3 (Additional file 1). The data points represent mean ± SD from three inserts from the respective plate. Representative image of a Caco-2 cell monolayer grown on a filter insert for 21 days (b). Depicted is a maximum projection of the top view and the optical cross sections obtained by CLSM. Cell nuclei are shown in blue (DAPI) and the tight junction protein ZO-1 in red (Alexa Fluor 594 conjugated anti ZO-1 antibody). Staining was carried out as described in Protocol #6. Dextran Blue permeability of a filter insert without cells and a filter insert with a fully differentiated cell monolayer (c). Filter inserts were incubated with Dextran Blue as described in Supplementary Protocol #4 (Additional file 1) over a period of 6 h and sampling every hour. The data points represent mean ± SD from three to four independent experiments