Physical characterization of the stratum corneum of an in vitro human skinequivalent produced by tissue engineering and its comparison with normal human skin by ATR-FTIR spectroscopy and thermal analysis (DSC)

An in vitro human skin equivalent may be obtained by culturing human kerati nocytes on a collagen gel containing fibroblasts. The anchored skin equival ent cultured at the air-liquid interface closely resembles human skin and i s acceptable for in vitro percutaneous absorption. However, it is still mor e permeable than human skin. Since intercellular lipids have been recognize d to play an important role in skin permeability, infrared spectroscopy and differential scanning calorimetry were performed on the stratum corneum of bovine or human skin equivalents grown at different days of air-liquid cul ture. The symmetric and asymmetric CH2 stretching vibrations suggested that for all days observed, the intercellular lipids were less organized than t hose in human skin, irrespective of whether bovine or human collagen was us ed. Different culture conditions were also tested and the medium without se rum and no epidermal growth factor at the air-liquid culture showed results significantly more comparable to human skin. Actually, the thermal behavio r of in vitro stratum corneum showed transitions at lower temperatures than human skin. The transition around 80 degrees C, in the form of a lipid-pro tein complex, was absent. These results showed that the structural arrangem ent of intercellular lipids and their thermodynamic properties hold a cruci al role in the barrier function of the stratum corneum. (C) 1999 Elsevier S cience B.V. All rights reserved.