title: Vibrational spectroscopy coupled to classical least square analysis, a new approach for determination of skin moisturizing agents' mechanisms.
abstract: BACKGROUND
  Skin dryness is an omnipresent symptom in various types of skin disorders. Thereby, a large panel of skin care products is developed for therapeutic purposes. However, there is still a lack of non-invasive methods to determine the mechanisms of action of moisturizers at the molecular level.
  
  
  METHODS
  In the present study, confocal Raman spectroscopy coupled to classical least square analyses and ATR-FTIR were used to investigate the effect of different molecules on the stratum corneum (SC) hydration degree and barrier state. First, hygroscopic property was determined by analyzing samples at 90% RH; secondly, the water barrier function was evaluated after the dehydration process (4% RH). The molecules penetration kinetics across SC were also studied for 2 h.
  
  
  RESULTS
  Using the present approach, glycerin and propylene glycol were found to be humectants; lanoline showed occlusive action, lactic acid has both humectant and barrier enhancer properties, and ethylhexyl palmitate and caprylic/capric acid triglyceride seemed to be emollients. These observations are in accordance with literature.
  
  
  CONCLUSIONS
  The present method non-invasively characterizes the mechanism of action of tested molecules. This may improve knowledge of new molecules' structure-activity relationship and help make an effective therapeutic concept dealing with the various skin dysfunctions.
authors.affiliation: Laboratory of Analytical Chemistry, Analytical Chemistry Group of Paris-Sud (GCAPS-EA4041), Faculty of Pharmacy, University Paris Sud, Chatenay-Malabry, France.
authors.forename: R
authors.initials: R
authors.lastname: Vyumvuhore
authors.forename: A
authors.initials: A
authors.lastname: Tfayli
authors.forename: M
authors.initials: M
authors.lastname: Manfait
authors.forename: A
authors.initials: A
authors.lastname: Baillet-Guffroy
mesh_terms: D000328:Adult; D000465:Algorithms; D001834:Body Water / Q000378:metabolism*; D003198:Computer Simulation; D003627:Data Interpretation, Statistical; D003936:Diagnosis, Computer-Assisted / Q000379:methods; D004643:Emollients / Q000494:pharmacology*; D004817:Epidermis / Q000187:drug effects / Q000378:metabolism*; D005260:Female; D006801:Humans; D066298:In Vitro Techniques; D016018:Least-Squares Analysis; D008875:Middle Aged; D015233:Models, Statistical; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D012869:Skin Absorption / Q000187:drug effects / Q000502:physiology*; D017592:Skin Care; D013059:Spectrum Analysis, Raman / Q000379:methods*
chemical_list: D004643:Emollients
keywords: ATR-FTIR; Raman spectroscopy; classical least square analysis; skin moisturizers; stratum corneum barrier function