In vivo non-invasive determination of the water concentration and water bonding properties in the human stratum corneum using confocal Raman microspectroscopy (mini-review)

Water plays an important role for normal functioning of the skin. The stratum corneum (SC) – the outermost layer of the epidermis – maintains the skin barrier function and regulates the water balance in the organism. Water is non-homogeneously distributed in the SC and its correct determination is important in dermatology and cosmetology. Confocal Raman microspectroscopy (CRM) is the most suitable non-invasive method to determine depth profiles of the water concentration, water with different mobility and hydrogen bonding states of water molecules in human skin in vivo, i.e. to study the SC hydration and moisturising. An in vivo application of CRM on normal human skin for investigation of the water concentration and water bonding properties in the SC is reviewed in this paper. Investigations performed on volunteers of two age groups reveal changes, which show that the SC of older skin binds water more efficiently compared to younger skin.