# Ceramide Profiling of Porcine Skin and Systematic Investigation of the Impact of Sorbitan Esters (SEs) on the Barrier Function of the Skin

## TL;DR

This study examines how sorbitan esters affect the skin's barrier function and ceramide levels in porcine skin.

## Contribution

The study introduces a novel LC-MS method to quantify ceramides and evaluates the skin tolerability of sorbitan esters.

## Key findings

- SEs 40, 60, 80, and 120 showed no significant changes in skin barrier function based on TEWL measurements.
- SE 60 and cholesterol-treated samples showed the least ceramide depletion, indicating high skin tolerability.
- SE 120 did not significantly alter lipid content, conformation, or SC thickness.

## Abstract

The stratum corneum (SC) lipids provide the main barrier
of the
skin against the environment. Ceramides make up about half of the
lipids by weight and are thus of particular interest. Emulsifiers
are used in a multitude of topical formulations, e.g., to stabilize
emulsions against coalescence. Investigations showed that some emulsifiers
have the potential to impair skin barrier function. Sorbitan esters
(SEs) are frequently used emulsifiers in pharmaceutical and cosmetic
dermal formulations. Further, cholesterol and lecithin were used as
natural alternatives. However, information on their impact on ceramides
is very scarce. Thus, we first analyzed the SEs by LC-MS with regard
to their composition. Then we developed an LC-MS method to identify
and quantify the ceramides in porcine skin and subsequently investigated
the impact of emulsifiers on the ceramide profile. Besides the LC-MS
measurements, the effect of emulsifiers on the skin barrier function
was investigated by trans-epidermal water loss (TEWL) measurements
and confocal Raman spectroscopy (CRS). Throughout the experiments,
water was used as a negative control and sodium lauryl sulfate (SLS)
as a positive control. It was found that SEs are mixtures of mono-,
di-, and triesters, partially with a complex fatty acid distribution.
LC-MS measurements of the total ceramide content of the SC samples
revealed the SE 60 and cholesterol-treated samples to be those showing
the least ceramide depletion, implying a high skin tolerability in
general. The TEWL measurements showed that SEs 40, 60, 80, and 120
showed no significant changes in skin barrier function. The lipid
content, measured by CRS, was mostly decreased except for SE 120.
Conformation, chain order, and SC thickness, also measured by CRS,
showed no significant differences. These detailed investigations lead
to the view that SEs are skin-friendly substances and can be used
for topical applications, e.g., those commonly used to treat skin
diseases.