The effect of the chain length distribution of free fatty acids on the mixing properties of stratum corneum model membranes

Abstract

The stratum corneum (SC) plays a fundamental role in the barrier function of the skin. The SC consists of corneocytes embedded in a lipid matrix. The main lipid classes in the lipid matrix are ceramides (CERs), cholesterol (CHOL) and free fatty acids (FFAs). The aim of this study was to examine the effect of the chain length of FFAs on the thermotropic phase behavior and mixing properties of SC lipids. Fourier transform infrared spectroscopy and Raman imaging spectroscopy were used to study the mixing properties using either protonated or deuterated FFAs. We selected SC model lipid mixtures containing only a single CER, CHOL and either a single FFA or a mixture of FFAs mimicking the FFA SC composition. The single CER consists of a sphingoid base with 18 carbon atoms and an acyl chain with a chain length of 24 carbon atoms. When using lignoceric acid (24 carbon atoms) or a mixture of FFAs, the CER and FFAs participated in mixed crystals, but hydration of the mixtures induced a slight phase separation between CER and FFA. The mixed crystalline structures did not phase separate during storage even up to a time period of 3months. When using palmitic acid (16 carbon atoms), a slight phase separation was observed between FFA and CER. This phase separation was clearly enhanced during hydration and storage. In conclusion, the thermotropic phase behavior and the mixing properties of the SC lipid mixtures were shown to strongly depend on the chain length and chain length distribution of FFAs, while hydration enhanced the phase separation.

Chain Length of Free Fatty Acids Influences the Phase Behavior of Stratum Corneum Model Membranes

“…16 It was shown that the 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 22 observed in Cer24/FFA24-d 47 /Chol mixture suggest a molecular organization allowing unusual motional freedom.…”

“…As reference values (measured the same way as the values presented in Figure 6), the splittings of pure Cer20 was found to be 9.8 cm -1 , 41 whereas that of deuterated solid FFA was 8.5 cm -1 . 16 Therefore Cer24/FFA16-d 31 /Chol mixture appears to be forming extensive phase-separated domains, according to its δCD 2 and δCH 2 splitting values. These values are similar to those previously reported for an equimolar mixture of Cer16/FFA16-d 31 /Chol, 14 where δCD 2 and δCH 2 band splittings were found to be 6 cm -1 , and 9.5 cm -1 respectively, indicating that Cer16 and FFA16 formed phaseseparated crystalline domains with orthorhombic chain packing.…”

Advancements in the maintenance of skin barrier/skin lipid composition and the involvement of metabolic enzymes

“…In a previous study, replacement of the stratum corneum long‐chain fatty acids with short‐chain fatty acids from healthy individuals altered the stratified structure of skin tissues, causing skin barrier dysfunction. In contrast, when FFAs in a lipid mixture that simulates skin lipid production were changed from short‐chain FFAs to long‐chain FFAs, the mixture exhibit a more solid structure and higher stability . During analysis of skin lipid variations in patients with AD, van Smeden et al .…”

In Situ Monitoring of Lipid Phase State Make Target Lipid Mixtures Similar to Intercellular Lipid in the Stratum Corneum

“…NP LM 32, AG LM 32, and AP LM 32 were prepared by drying chloroform/methanol (2:1, v/v), containing CER [NP]/CHOL/PA (1.3:1.0:1.5, mol%), CER [AG]/CHOL/PA (1.9:1.0:4.3, mol%), CER [AP]/CHOL/PA/SCHOS (8.6:6.1:5.4:1.0, mol%), on respective glass plates at 32 °C. These lipids were chosen to have similar carbon chain lengths because it effects the phase separation of LMs . NP LM 80, AG LM 80, and AP LM 80 were obtained by heating NP LM 32, AG LM 32, and AP LM 32 at 80 °C on heat stage for 30 min, then equilibration at room temperature (r. t.) for more than 30 min, respectively.…”