French research team shows skin penetration of hyaluronic acid by Raman spectroscopy

Carrying out tests monitoring the skin penetration of hyaluronic acids (HA) of different molecular weights, the team from the University of Reims Champagne – Ardenne (URCA) and ingredient supplier Soliance made the discovery using Raman imaging combined with chemometric methods.

The research team states that Raman spectroscopy is a promising approach for probing exogenous molecules in the skin, and that recent studies using this technique have demonstrated the possibility of tracking cosmetic formulations.

In the present study, published in the journal Skin Research and Technology​, the researchers demonstrated the skin permeability of low molecular weight hyaluronic acid and the impermeability of high molecular weight HA.

Study​

To do this, Raman micro-imaging was applied to monitor the skin penetration of different molecular weights of the acid, with the first step being the spectral characterization of these HA.

After, the team determined spectral features of HA by which they can be detected in the skin, and then transverse skin sections were realised and spectral images were recorded.

The results showed a difference of skin permeation of the three HA, with the one with low molecular weight passing through the stratum corneum, in contrast to the impermeability of the one with high molecular weight HA.

“An essential aspect of this work was to determine the most pertinent spectral features to detect various HA in the skin section, by using a statistical test (Mann–Whitney P = 0.05),”​ says the research.

“Raman spectroscopy exhibits several advantages. It enables the detection and the localization of exogenous molecules at a micrometric resolution, in a label-free, non-destructive manner and with a limited sample preparation,”​ it concludes.

Measuring skin penetration​

Topical delivery of molecules into the human skin is one of the main issues in dermatology and cosmetology.

Several techniques have been developed to study molecules penetration into the skin, and, although widely accepted, the conventional methods such as Franz diffusion cells are unable to provide the accurate localization of actives in the skin layers, according to this French study.

This has led to a different approach based on Raman spectroscopy being proposed to follow-up the permeation of actives.

The researchers say it presents a high molecular specificity to distinguish exogenous molecules from skin constituents.