Therefore, a reliable, low-cost and easy method is needed for in vivo and ex vivo testing of formulations and substances. An overview of different in vivo and in vitro methods to study the penetration and permeation through damaged skin is given by Gattu and Maibach [17] and [44]. These methods can be divided into mechanical,

chemical and biological methods, as well as investigations on clinical diseased skin. The most common method for simulating a disturbed skin barrier is the tape-stripping method [10], [18], [19] and [20]. The horny cell layers are gradually removed with adhesive tape. The tape-stripping method is minimally invasive and can be applied in vivo and ex vivo for humans as well as for animals (e.g., pigs and rats). The efficacy of the tape-stripping method can be influenced by the anatomical site, the application Nutlin-3a molecular weight pressure, the duration of pressure, the removal rate [3] and the type of tape [21]. Furthermore, another difficulty is the inhomogeneous removal of the cell layers due to the elastic network of furrows [22, 23], and the required repetitions to achieve an adequate degree of damage are quite time- and cost-intensive Obeticholic Acid mouse using the validated tape-stripping method by the Simonsen and Fullerton [10]. The objective of the present study was to develop an alternative in vitro skin model to

simulate skin barrier impairment. The following requirements should be fulfilled by this model: simple and quick application, low cost, and good repeatability. Therefore, the stratum corneum was mechanically removed by a sponge with a rough surface, and the permeation of three model drugs, caffeine, sorbic acid and testosterone, which differ in physicochemical properties, such

as octanol-water-coefficient (log P) and molecular weight (MW), was studied and compared with intact and tape-stripped skin. Caffeine and testosterone are marker compounds recommended by the OECD, and sorbic acid is a preservative frequently used in cosmetics. Untreated porcine ears (domestic pig) Bumetanide were obtained from a local slaughterhouse and immediately transferred to the lab under cool conditions. Porcine ears were washed by rinsing with moderately warm water and wiped with paper towels, and the bristles were carefully shortened by trimming. Full-thickness skin was obtained from the outer side of the porcine auricle [24] and stored at −20 °C for up to 3 months. Porcine skin was chosen due to its similarity to human skin in terms of its morphology and permeability [25] and due to its availability. Prior to skin permeation studies, the thawed porcine full-thickness skin was prepared. Untreated skin (intact skin) and skin with an impaired barrier were used to conduct skin uptake studies.