Figure 1.

Schematic representation of the existing organ/tissue culture models (A–E), exposure methods (F,G), and typical permeation assessment model (H). The simplistic immersion of epithelial tissue in culture medium (pink) (A) is improved by various culture methods accommodating air–liquid interface (ALI) culture conditions (B–E). The latter included the plasma clot (orange) on watch glass (B), agar gel (C), raft made using lens paper/rayon acetate floating on medium (D), and metal grid (E) methods. For epithelial tissue exposure, the chemical substances (green) are placed on the outer surface of the epithelium either via the droplet technique (F) or with a cylinder ring (G). Permeation assays are usually performed in Franz vertical chambers (H), where the permeated substance (yellow) can be measured.