Abstract
The outermost layer of the skin, the stratum corneum (SC), acts as the natural physical barrier. The SC consists of corneocytes embedded in a crystalline lipid matrix consisting of ceramides, free fatty acids and cholesterol.Although phospholipids are frequently present in topical formulations, no detailed information is reported on the interactions between phospholipids and SC lipids. The aim of this study was to examine the interactions between a model phospholipid, dipalmitoylphosphatidylcholine (DPPC) and synthetic ceramide-based mixtures (referred to as SC lipids).(Perdeuterated) DPPC was mixed with SC lipids and the lipid organization and mixing properties were examined. The studies revealed that DPPC participates in the same lattice as SC lipids thereby enhancing a hexagonal packing. Even at a high DPPC level, no phase separated pure DPPC was observed.When a DPPC containing formulation is applied to the skin surface it must partition into the SC lipid matrix prior to any mixing with the SC lipids. To mimic this, DPPC was applied on top of a SC lipid membrane. DPPC applied in a liquid crystalline state was able to mix with the SC lipids and participated in the same lattice as the SC lipids. However, when DPPC was applied in a rippled gel-state very limited partitioning of DPPC into the SC lipid matrix occurred. Thus, when applied to the skin, liquid crystalline DPPC will have very different interactions with SC lipids than DPPC in a (rippled-)gel phase.
Highlights
Several therapeutic and cosmetic formulations for topical skin health applications on the market contain phospholipids, most commonly phosphatidylcholine
X-ray diffraction studies of human SC have shown that the lipids are arranged in Abbreviations: SC, stratum corneum; CER, ceramide; CHOL, cholesterol; FFA, free fatty acid; Fourier transform infrared spectroscopy (FTIR), Fourier transformed infrared spectroscopy; Small-angle x-ray diffraction (SAXD), small angle X-ray diffraction; FA24, lignoceric acid; dipalmitoyl phosphatidyl choline (DPPC), dipalmytoyl phosphatidyl choline; EOS, ester linked omega-hydroxy acyl chain linked to a sphingosine chain; NS, a non-hydroxy acyl chain linked to a sphingosine base; SPP, short periodicity phase; LPP, long periodicity phase
The thermotropic response of the CD2 stretching frequencies of perdeuterated DPPC is provided in Fig. 1: Only a strong shift occurs with a midpoint transition at around 36 °C indicating a rippled-gel to liquid phase transition [17]
Summary
Several therapeutic and cosmetic formulations for topical skin health applications on the market contain phospholipids, most commonly phosphatidylcholine (lecithin). In this work the interaction between dipalmitoyl phosphatidyl choline (DPPC) and two skin barrier lipid models was examined using Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction. As the extra-cellular lipid domains form a continuous structure in the SC, molecules diffusing across the SC always have to pass through the lipid regions For this reason, the SC lipids play an important role in skin barrier function and the arrangement of the lipids in lamellar domains is a key process in the formation of the skin barrier. X-ray diffraction studies of human SC have shown that the lipids are arranged in Abbreviations: SC, stratum corneum; CER, ceramide; CHOL, cholesterol; FFA, free fatty acid; FTIR, Fourier transformed infrared spectroscopy; SAXD, small angle X-ray diffraction; FA24, lignoceric acid; DPPC, dipalmytoyl phosphatidyl choline; EOS, ester linked omega-hydroxy acyl chain linked to a sphingosine chain; NS, a non-hydroxy acyl chain linked to a sphingosine base; SPP, short periodicity phase; LPP, long periodicity phase
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callMore From: Biochimica et Biophysica Acta (BBA) - Biomembranes
Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
