New approach for hair keratin characterization: Use of the confocal Raman spectroscopy to assess the effect of thermal stress on human hair fibre.

Objective: The objective of our research was to investigate the heat-protecting effect of a product ex vivo and in vivo on human hair fibres.

Methods: A preparatory study was carried out in order to determine an optimal threshold of thermal stress. For this, the structure of cross-sections of the hair fibre was observed by optical microscopy.

Combining Raman imaging and MCR-ALS analysis for monitoring retinol permeation in human skin.

Background: Monitoring the transcutaneous permeation of exogenous molecules using conventional techniques generally requires long pre-analytical preparation or labelling of samples. However, Raman spectroscopy is a label-free and non-destructive method which provides spatial distribution of tracked actives in skin. The aim of our study was to prove the interest of Raman imaging coupled with multivariate curve resolution alternating least square (MCR-ALS) analysis in monitoring retinol penetration into frozen and living human skin.

Conformation changes in human hair keratin observed using confocal Raman spectroscopy after active ingredient application.

Objective: In hair care cosmetic products' evaluation, one commonly used method is to evaluate the hair appearance as a gold standard in order to determine the effect of an active ingredient on the final state of the hair via visual appreciation. Although other techniques have been proposed for a direct analysis of the hair fibres, they give only surface or structural information, without any accurate molecular information. A different approach based on confocal Raman spectroscopy has been proposed for tracking in situ the molecular change in the keratin directly in the human hair fibres.

Atopic skin: In vivo Raman identification of global molecular signature, a comparative study with healthy skin.

Atopic dermatitis (AD) is the most common skin inflammatory disease, affecting up to 3% of adults and 20% of children. Skin barrier impairment is thought to be the primary factor in this disease. Currently, there is no method proposed to monitor non-invasively the different molecular disorders involved in the upper layer of AD skin.

Human skin penetration of hyaluronic acid of different molecular weights as probed by Raman spectroscopy.

Background: Topical delivery of molecules into the human skin is one of the main issues in dermatology and cosmetology. Several techniques were developed to study molecules penetration into the human skin. Although widely accepted, the conventional methods such as Franz diffusion cells are unable to provide the accurate localization of actives in the skin layers.