ABSTRACT
I. LIPID ORGANIZATION IN STRATUM CORNEUM A. Introduction The natural function of the skin is the protection of the body against the loss of endogenous substances such as water and against undesired influences from the environment caused by exogenous substances. The main barrier for diffusion through the skin is the outermost layer of the skin, the stratum corneum (SC) [1]. The SC consists of keratin-filled dead cells, the corneocytes, which are entirely surrounded by crystalline lamellar lipid regions. Furthermore, the cell boundary, the cornified envelope, is a very densely cross-linked protein structure, which prevents easy absorption of drugs into the cells. This has been illustrated by confocal studies, in which it was demonstrated that the penetration pathway of dyes is mainly through the intercellular regions in the SC [2,3]. For these reasons the lipid regions are considered to be of great importance for the skin barrier function [4,5]. In the past 20 years, many studies have been carried out to increase knowledge of the barrier function of the skin. These studies have mainly been focused on the lipid composition and organization in the SC and the changes involved in this lipid organization as a consequence of topical application of drugs in various formulations and patches. This chapter will mainly focus on the structure in the SC and the changes in this structure as a consequence of water, surfactants, and liposomes.
