Confocal Raman spectroscopy: In vivo biochemical changes in the human skin by topical formulations under UV radiation.

A new approach to the study of the effects on human skin of mycosporine-like amino acids (MAAs) and gadusol (Gad) incorporated in polymer gel is proposed in this work. The depth profile and photoprotector effects of Pluronic F127® gels containing each of the natural actives were evaluated by in vivo confocal Raman spectroscopy aiming at the analysis of the biochemical changes on human skin. Hierarchical cluster analysis (HCA) showed that the data corresponding to different depths of the skin, from surface to 4 µm, and from 6 to 16 µm, remained in the same cluster. In vivo Raman spectra, classified into five different layers of epidermis according to their similarities, indicated that the amount of Gad gel increased by about 26% in the outermost layer of the stratum corneum (SC) and that MAAs gel at 2 µm depth was 103.4% higher than in the outermost layer of the SC. Variations in the SC of urocanic acid at 1490-1515 cm(-1) and 1652 cm(-1) and histidine at 1318 cm(-1) were calculated, before and after UV exposure with or without gels. With the application of gels the vibrational modes that correspond to lipids in trans conformation (1063 and 1128 cm(-1)) increased with respect to normal skin, whereas gauche conformation (1085 cm(-1)) disappeared. Our studies suggest that gels protected the skin against the stress of the natural defense mechanism caused by high levels of UV exposure.

Influence of mycosporine-like amino acids and gadusol on the rheology and Raman spectroscopy of polymer gels.

BACKGROUND: The amphiphilic nature of polymers allows them to be widely incorporated as carriers in different pharmaceutical applications since they are able to work as vehicles for hydro- or lipo-soluble actives. OBJECTIVE: The aim of this study was to determine the rheological behavior and vibrational spectral variations of two hydrophilic gels prepared with Poloxamer 407 (PO) or Pluronic F-127 (PL) with the addition of the actives mycosporine-like amino acids and gadusol. METHODS: The structures of these polymers in two different concentrations (20% w/w and 27% w/w) were characterized by rheological studies and Raman spectroscopy. RESULTS: Gels prepared with higher polymer concentration showed larger G' (storage modulus) values. The C-C stretch and the CH2 rocking predominated in the gels containing PL (20% w/w) and this correlated with a less viscous behavior. The mixture of the actives induced higher contributions of Raman peaks related to trans conformation of the C-C bonds located in hydrophilic polymer blocks, whereas the same peaks decreased in the sample containing only gadusol. CONCLUSIONS: Larger tensile strength and elastic component were observed upon increasing polymer concentration, thus evidencing polymer-polymer and/or polymer-polymer-actives interactions. The presence of the actives affected the mechanical properties of the polymer gels. Gadusol particularly seems to alter the conformation of the polymer chains by favoring gauche orientations, in parallel with rising viscoelastic parameters. More stretched arrangements of the polymer are probably induced in the presence of larger concentration of actives, due to specific interactions with their hydrophilic groups.