Changes of the Properties in the Upper Layers of Human Skin on Treatment with Models of Different Pharmaceutical Formulations—An Ex vivo ESR Imaging Study

Abstract

The noninvasive method of spectral-spatial electron spin resonance imaging (ESRI) was used to obtain a polarity map of human skin. The spin probes TEMPO, TEMPOL, and CAT-1, which are considered to act as drug representatives, were applied as reporter molecules. The polarity in skin layers was described by means of the changes of the hyperfine splitting constant A(iso), which itself is a reflection of interactions at a molecular level, and the effect of polarity on the spatial distribution of spin probes in skin samples was studied. Analyses of ESR tomograms of two-phase systems finalized in a simplified description for the empiric interpretation of values of the isotropic hyperfine coupling constants A(iso) of spin probes in different layers of human skin. The simplified statement provides values for the probability of interactions of water molecules with the NO group of spin probes. This allows conclusions concerning the state of hydration of the spin probes in different layers of the skin and introduces the spatial polarity function as additional and valuable information for existing skin models.