Fluorescein isothiocyanate conjugated dextran 4 kda fd 4

Alaska pollock skin-derived collagen was obtained from Dongyi Tech Co., Ltd (Qingdao, China). Caco-2 cells (HTB-37) were purchased from ATCC (Rockville, MD, USA). All cell culture reagents and supplies were purchased from Thermo Fisher Scientific Co., Ltd. (Shanghai, China). Alcalase, flavourzyme, papain, and trypsin were purchased from Beijing Solarbio Science and Technology Co., Ltd., (Beijing, China). TNF-α, fluorescein isothiocyanate-conjugated dextran 4 kDa (FD-4), and all other reagents used in this study without attribution were obtained from Sigma-Aldrich Chemical Co. (Shanghai, China).

Hank’s balanced salt solution (HBSS), 2-(N-morpholino) ethanesulfonic acid hydrate (MES), N-(2-hydroxyethyl)piperazine-N’-(2-ethanesulfonic acid) (HEPES), 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) (MTT), fluorescein isothiocyanate-conjugated dextran 4 kDa (FD-4), verapamil, [³H]-digoxin, mucin from porcine stomach type III, ML-7 (an MLCK inhibitor), RO-318220 (a PKC inhibitor), genistein (a tyrosine kinase inhibitor), Na⁺/K⁺ ATPase and 4’,6-diamidino-2-phenylindole dihydrochloride (DAPI) were purchased from Sigma-Aldrich (St. Louis, MO, USA). The clear-sol I scintillation cocktail and protease inhibitor cocktail were from Nacalai Tesque (Kyoto, Japan). The P-gp-Glo™ assay and P-gp antibody were obtained from Promega (Madison, WI, USA) and Alexis Biochemicals (San Diego, CA, USA), respectively. Primary antibodies against zonula occludens-1 (ZO-1) and occludin were from Invitrogen (San Diego, CA, USA). Goat anti-mouse IgG H&L Alexa Fluor® 488 and 568 secondary antibodies, FITC-labeled anti-P-gp [UIC2] monoclonal antibody and horseradish peroxidase (HRP)-conjugated secondary antibody were obtained from Abcam (Cambridge, UK). All other chemical reagents were analytical grades.