Spectral signals of stratum corneum (SC) acquired from confocal Raman spectroscopy (CRS) are employed to track lipid variations and the most sensitive and efficient signals are of high interest. Herein, 1% of sodium lauryl sulfate treated SC was compared to water-treated one to evaluate statistical difference of spectral signals concerning lipid content, SC thickness and lipid molecular structures. Results showed that peak ratio of 1425 to 1490 cm −1 and 1630 to 1710 cm −1 in fingerprint region and Gaussian-function deconvoluted lipid-keratin peak ratio in high wavenumber (HWN) region were both responsive for analyzing lipid content. SC thickness measurement using the full width of half-maximum (FWHM) of 2920 to 2960 cm −1 signal presented good sensitivity. Nevertheless, the shift of peak 2850 cm −1 indicated less sensitivity compared to trans-gauche peak signals and 1300 cm −1 peak position for lipid conformation analysis. Meanwhile, the ratio of peak 2880 and 2850 cm −1 indicating lipid lateral packing structure presented to be less responsive. More strikingly, FWHM of peak 2850 cm −1 appeared to be unable for lipid lateral packing order analysis in our study. In summary, this research can serve as a pilot study for further investigation of direct drug delivery and interaction between topical applied compounds and skin components.
The class of PEGylated emulsifiers finds broad application in the pharmaceutical and cosmetic industry. We target on one of the categories of polyethylene glycol (PEG) alkyl ethers with different lipophilic and hydrophilic chain length and aim to examine their effects on the skin comprehensively. In this study, we employed confocal Raman spectroscopy for skin depth profiling and imaging. A unique probe of heavy water (D 2 O) was incorporated, which can be tracked percutaneously and simultaneously monitor the effects caused by emulsifiers. According to the results, most of the PEGylated emulsifiers caused changes in skin lipid content/organization and induced the alteration in relative water content/hydrogen bonding structure. The results obtained from the depth profiling analysis provided the possibility to estimate the least penetration depth of emulsifiers. Among them, PEG-20 ethers displayed the most penetration ability. Meanwhile, it is interesting to find that the treatment of emulsifiers also affected the spatial distribution of D 2 O whose differences were in line with the molecular skin variations. In particular, the isotopic H/D substitution in the skin was highlighted in detail. This result supports the possibility to use D 2 O as an excellent and costeffective probe to evaluate the skin barrier function.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.