Application of FT-IR Microspectroscopy in the Investigation of the Stratum Corneum Barrier Function

Abstract

FT-IR microspectroscopy is acombination of FT-IR spectroscopy and optical microscopy in whichthe samples are magnified by the optical microscope, while infrared spectroscopy provides information on molecular chemistry. This combination has proven to be a highly beneficial technique with wide potential of applications principally in the biological and biomedical research areas in which samples of high complexity and intrinsic heterogeneity are investigated. Recently, IR microspectroscopy has been introduced as a powerful tool for investigation of whole skin and stratum corneum (SC) composition and heterogeneity; it also represents a method to study the effect of penetration enhancement approaches on the biochemical properties of the SC, giving important information related to the mechanism through which penetration enhancers modulate the barrier function of the SC. Visualization of the percutaneous permeation of exogenous agents is also feasible by this technique. The biochemical composition of the SC has important implications for understanding its barrier function hence, the impact of some penetration enhancers on the biochemical composition and structural alterations of the SC, mainly lipids and proteins, is illustrated in this study. Specific regions of the IR spectrum of the SC are sensitive to lipid chain conformational order and packing, and protein secondary structure thus; very useful information can be obtained concerning alteration of the structural properties of the endogenous skin components and the mechanisms of penetration enhancement. Large number of IR spectra for each investigated sample were obtained by IR mapping technique and principal component analysis, in the form of score and loadings plots, was performed to analyze the results. Changes in the structure of the SC was also observed using other techniques like differential scanning calorimetry and permeation studies.