The physical chemistry of the stratum corneum lipids

Abstract

SynopsisThe extracellular matrix of stratum corneum (SC) participates actively in the defensive performance of human skin. Understanding its physicochemical properties is essential for understanding the skin homoeostasis, for the development of efficient therapies for skin disorders and diseases and for ensuring the safety of products designed for topical application. This article summarizes the current knowledge of the composition, self-assembly and molecular organization of the SC lipids, reviews the evidence connecting these parameters and the barrier properties of human skin, and outlines the immediate issues in the field of SC lipid research. R ESUM E: La matrice extracellulaire du stratum corneum (SC) participe activement a la performance d efensive de la peau humaine. Comprendre ses propri et es physico-chimiques est essentielle pour comprendre l'hom eostasie de la peau, pour le d eveloppement de th erapies efficaces pour les troubles et les maladies de la peau, et pour assurer la s ecurit e des produits conc ßus pour une application topique. Cet article r esume les connaissances actuelles sur la composition, l'auto-assemblage, et l'organisation mol eculaire des lipides SC, examine les preuves reliant ces param etres et les propri et es de barri ere de la peau humaine, et d ecrit les probl emes imm ediats dans le domaine de la recherche sur les lipides SC. IntroductionThe field of skin research is replete with opportunities for those intent on working on scientifically interesting topics while making a noticeable, positive difference in people's lives [1]. The range of important problems that the field can help solving is broad. It comprises (i) reducing infant mortality, especially in the developing countries where defective skin barrier is the second major cause of preterm mortality [2][3][4][5][6]; (ii) improving the skin health of some 20-30% of the population in the developed countries which suffer from some sort of skin barrier dysfunction [7,8]; (iii) developing efficient strategies for the dermal and transdermal delivery of drugs and vaccines [9]; (iv) increasing the national and personal security by developing methods to retard or prevent the skin penetration of chemical warfare agents, toxic spills and pesticides [10, 11]; (v) enhancing the safety of topical products (e.g. fragrances, cosmetics, cleansing agents, sunscreens and insect repellents) [12]. Thus, the targets in skin research cover the full spectrum from counter-acting leaky skin and preventing its penetration by chemicals to pushing chemicals through it. One common major problem underlies these diverse topics: our insufficient understanding of the factors that determine skin permeability.Understanding the permeability of human skin to a large extent means understanding the extracellular lipid matrix of the stratum corneum (SC), the topmost skin layer which constitutes the main barrier to transdermal fluxes [13][14][15][16][17][18][19]. As the lipid matrix forms an uninterrupted pathway from the skin surface to the viable skin tissu...

Characterization of human skin equivalents developed at body's core and surface temperatures

“…The composition of the lipid matrix affects the lamellar and lateral organization. The lipid organization has a profound impact on the rate of penetration of therapeutic compounds through the intercellular route when applied topically (Boncheva, ; Bouwstra, Honeywell‐Nguyen, Gooris, & Ponec, ). Compared with NHS, the barrier formation of HSEs is altered, leading to an elevated in vitro diffusion rate and uncertainty in in vitro–in vivo correlations (Regnier, Caron, Reichert, & Schaefer, ; Schmook, Meingassner, & Billich, ; Schreiber et al, ; Thakoersing et al, ).…”

Evidence of hydrocarbon nanodrops in highly ordered stratum corneum model membranes

“…Several models for the organization of SC lipids into the SPP and LPP have been proposed (14)(15)(16)(17)(18). Recently, a model based on neutron diffraction analyses showed that ceramide NS could dictate the length of the unit cell in the SPP, sharing the unit cell space with Chol and FFA.…”

Recent Advances in the Transdermal Delivery of Protein Therapeutics with a Combinatorial System of Chemical Adjuvants and Physical Penetration Enhancements

“…Depending on the plane structure, the arrangement of the lipids has a lateral organization ( x ‐ y plane) and lamellar organization ( x ‐ z or y ‐ z plane). Specifically, the lateral organization is divided into three groups, according to the layout of the head group of the geology: orthorhombic (OR), hexagonal (HEX), and liquid–crystalline (LIQ) phases . The orthorhombic phase has the most densely packed arrangement without both rotational and translational mobility.…”

“…Among them, the orthorhombic phase supports the barrier function structurally. In general, the transition between these phases occurs according to temperature . The transition between OR and HEX (solid–solid) occurs at around 35–40 °C; however, the transition from OR or HEX to LIQ (solid–liquid) occurs at around 70 °C, which can be caused by the topical application of chemical enhancers .…”

“…Coexisting centrosymmetric phases of long (LPP) and short (SPP) periodicity with repeat distances of ≈13 and 6 nm, respectively. (B–D) Reproduced with permission . Copyright 2014, John Wiley and Sons.…”