Elucidation of penetration enhancement mechanism of Emu oil using FTIR microspectroscopy at EMIRA laboratory of SESAME synchrotron

• Published in: Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy Molecular and biomolecular spectroscopy, 2017-10, Vol.185, p.1-10
• Main Authors: Mansour, Randa S.H., Sallam, Alsayed A., Hamdan, Imad I., Khalil, Enam A., Yousef, Ibraheem
• Format: Article
• Language: English
• Subjects: Chemical mapping; Emu oil; IR microscopy; Keratin structure; Lipid conformation; Penetration enhancement; Stratum corneum
• ISSN: 1386-1425
• DOI: 10.1016/j.saa.2017.05.026

It has been proposed that Emu oil possesses skin permeation-enhancing effect. This study aimed to address its possible penetration enhancement mechanism(s) using IR microscopy, in accordance with LPP theory. The penetration of Emu oil through the layers of human skin was accomplished by monitoring oil-IR characteristic feature at 3006cm−1. The unsaturated components of Emu oil accumulated at about 270μm depth of skin surface. The interaction of Emu oil with lipid and protein constituents of SC was investigated in comparison with a commonly used enhancer, IPM. Inter-sample spectral differences were identified using PCA and linked with possible enhancement mechanisms. Emu oil treatment caused a change in the slope of the right contour of amide I band of the protein spectral range. This was also clear in the second derivative spectra where the emergence of a new shoulder at higher frequency was evident, suggesting disorganization of keratin α-helix structure. This effect could be a result of disruption of some hydrogen bonds in which amide CO and NH groups of keratin are involved. The low intensity of the emerged shoulder is also in agreement with formation of weaker hydrogen bonds. IPM did not affect the protein component. No conclusions regarding the effect of penetration enhancers on the SC lipids were obtained. This was due to the overlap of the endogenous (skin) and exogenous (oil) CH stretching and scissoring frequencies. The SC carbonyl stretching peak disappeared as a result of IPM treatment which may reflect some degree of lipid extraction. A) Penetration of Emu oil through the skin layers. B) Effect of Emu oil on the protein constituent of stratum corneum (red) in comparison to untreated (blue) and isopropylmyristate treated (green) stratum corneum samples. [Display omitted] •The possible penetration enhancement mechanisms of Emu oil are addressed.•The unsaturated components of Emu oil accumulate at about 270μm deep within the skin.•PCA results suggest disorganization of the α-helix structure of keratin by Emu oil.