Abstract
Ceramides are principal components of intercellular lipids and play important roles for skin moisturization and barrier function. However, it is difficult to dissolve ceramides in aqueous formulations such as cosmetic lotion because of their high hydrophobicity and crystallinity. For this reason, various encapsulation technologies for incorporating ceramides into lotion have been reported. Since the outer surface of these capsules is hydrophilic, their affinity for skin was not fully considered. Therefore, we focused on hexosome to develop a new ceramide-containing capsule with consideration of affinity for skin. Hexosome is a capsule with a hydrophobic surface, formed by nano-dispersion of reversed hexagonal liquid crystals (H2). Because of this structural characteristic, hexosome can be expected to efficiently penetrate to the skin (stratum corneum). However, hexosome is a hydrophobic capsule that aggregates immediately in lotion. To solve this problem, studies using poloxamer as a key ingredient (dispersant) have been reported, but no other dispersants have been well studied. Additionally, petroleum-derived materials such as poloxamer tend to be not preferred by consumers, due to the recent global trend of favoring plant-derived materials for cosmetics. Therefore, we have developed a new ceramide-containing hexosome (Cer-Hexosome) stabilized by a plant-based dispersant. First, the structure of the developed Cer-Hexosome was confirmed with small-angle X-ray scattering (SAXS) and cryo-transmission electron microscopy (Cryo-TEM). Next, the skin permeation amount of ceramide was quantified by LC/MS, and it was confirmed that the ceramide permeation effect of hexosome was 1.5 times that of liposome. Then, in a one-month continuous use test, it was confirmed that Cer-Hexosome significantly improved the barrier function of the skin. Finally, the effect on intercellular lipids of the human stratum corneum was analyzed by wide-angle X-ray diffraction (WAXD), and it was confirmed that Cer-Hexosome enhances the orthorhombic structure.
