About 130 delegates gathered at the Pavillon Dauphine in Paris on November 30th and December 1st 2011 to better understand how formulations interacted with the skin. A theme chosen in tribute to Dr. Alec D. Bangham, the discoverer of liposomes who died in March 2010. According to Claudie Willemin, a member of the Scientific Council of the French Society of Cosmetology (SFC) and organizer of this conference, "the great discovery of Dr. Alec D Bengham resulted in more than 41,000 publications, 6,000 patents applications and has enabled us to have a rational, scientific and thorough approach of formulation".
These two days program was punctuated by sessions led by renowned European researchers, the greatest names in cosmetics and raw material suppliers. New this year: the opportunity given to a young doctor to present the results of his thesis.
The skin and its surface properties
Skin, an organ whose surface is the most important of the human body has many properties, one of them being to ensure the protection of the skin from its external environment. In his introduction, Dr. Marek Haftek, a Research Director at the CNRS, recalled that "intercellular lipids imparted the stratum corneum with sealing properties and also regulated water fluids. The proper functioning of the stratum corneum barrier is essential to our survival". To better understand skin and its surface properties is an important issue for researchers seeking to design products perfectly suited to this complex environment.
For Gustavo S Luengo, from L’Oréal Research and Innovation "the interaction of liquids with the surface of the skin is of paramount importance since many products are applied in this form". Such techniques as atomic force microscopy, measurements of contact angles, lateral diffusion, help determine on plasties optimum wetting conditions. They depend of the nature of deposited molecules and of the chemistry of the ones present on the surface of the skin.
The CERT (Centre d’Études et de Recherche sur le Tégument - Centre of Studies and Research on Integument) in Besançon, for its part, conducted an in vivo study of the effects of sebum and of various liquids (palmitic acid, squalene...) on the wettability of the skin. According to Ahmed Elkhyat a researcher at the University of Franche Comté, "the cleansing of the skin will lead to an increased hydrophobicity of the skin, while the application a moisturizing cream will reduce it." These surface modifications also act, as explained Dr. Cyril Pailler Mattei from the Central School of Lyon, on the tribology of the skin or its mechanical behaviour, "measurements that enable to distinguish the different skin types and why not, one day to objectively define what a beautiful skin should be".
Percutaneous absorption
To have a good understanding of the medium to better treat it is the first step. The following step consists in measuring what crosses the upper layers of the epidermis even reaching in some cases the bloodstream. The in vitro percutaneous absorption is one of the research tools available to address this need. Its evolution is constant. For example, new skin models take into account the presence or absence of pilosebaceous follicles, an area conducive to penetration. In addition, as stated Dr. Marie-Alexandrine Bolzinger from the Faculty of Pharmacy of Lyon "the development of imaging techniques allows significant advances in the non invasive monitoring of actives and ingredients and in the study of actives / lipids, proteins interactions." To date, there is ample evidence that the sizes of molecules, the ionic charges, the hydrophilic/lipophilic nature, the solubility of the active ingredient, the sites of application and the formulations are essential factors to optimize absorption.
Efficient galenic formulations
In terms of formulations, the liposomes discovered in 1964 by Alec D. Bangham are still relevant as being efficient vectors for active ingredients. The initial technology has inspired many products and materials that were able to evolve by integrating in their conception the latest scientific advances. On the marketplace, these "magic bullet " are used to encapsulate perfumes, control the release of actives, protect sensitive materials, adapt to the needs of the skin... Possibilities are huge and some liposomes are formulated to withstand extreme conditions of pH, of electrolyte concentrations in solvents or in polar oils. The vectorization system is usually based on multi-layers of surfactants or of oil-in-water dispersions. But Prof. Markus Antonietti from the Max Planck Institute of Colloids and Interfaces in Potsdam has opened a new field of investigation by presenting a work on double hydrophilic polymers that can store molecules in the double layer of neutralization.
In a very different domain from liposomes but with a significant interest in terms of formulation, Shiseido researchers have managed to formulate a long-lasting, transfer proof and very bright lipstick with optimal hydration. The technology as it was explained by Mrs. Mouna Ghoul, a researcher for Shiseido Europe is based on the incorporation in the formula of a liquid crystal in combination with an oil with a high refractive index, very viscous and not compatible with the pigments and the liquid crystal. Upon application there is a phase separation and the formation of a glossy film on the surface of the lips. This work was granted the Award of Applied Research at the 2010 IFSCC [1] congress.
In conclusion Étienne Soudan, President of the SFC announced the theme for the 2012 session "skin and senescence". A forever topical subject on which current science is progressing rapidly. Quite enough to attract, again, a large audience.
