Ex vivo TSM online monitoring of skin dehydration

This study presents a new online skin investigation technique for tracking products-to-skin mechanical effects. Ex vivo abdominal skin explants from plastic surgery and kept alive are used for this study. Considering the skin as a complex fluid made of membrane and fiber structures immersed in liquid, its mechanical response of a bulk thickness shear wave excitation (i.e. stress-strain analysis) involves both a viscous component associated with energy dissipation and an elastic component associated with energy storage. A tight monitoring of these two components from the response of a TSM sensor (based on an AT cut quartz resonator at 5 MHz) in contact to the dermis of the ex vivo explant give us access to the complex dynamic shear moduli (G´ and G") evolution of the skin; The appropriate mechanical model describing the sensor response vs. shear waves/matrix interactions allows investigating the impact of the product (or treatment) to the viscoelastic properties of the skin. The complex study of the TSM response in time domain permits a control a) of the dehydration evolution at 37 °C due to interpenetrated intercellular lipid membranes matrix including the first step of permeation process from dermis to SC; b) the impact on the kinetics of the permeation process by a product applied at the SC surface. This information includes the structure and properties evolution of the collagen and elastic fibers and the proteoglycans located in the skin. A comparison of mechanical results with other techniques in the literature confirms the validity of the model. These preliminary results show that our TSM technique can be an appreciable new way for ex vivo skin investigation for test and optimization of new cosmetic products.