Confocal Raman imaging of skin sections containing hair follicles using classical least squares regression and multivariate curve resolution – alternating least squares

Confocal Raman microscopy (CRM) is applied ex vivo for imaging of the spatial distribution of different skin components in skin sections containing hair follicles. For multivariate data analysis, different methods are used in order to spectrally decom¬pose the reference spectra of the skin components (dermis, viable epidermis, stratum corneum and hair). Classical least squares regression (CLS) and multivariate curve resolution – alternating least squares (MCR-ALS) are chosen as suitable methods. In com-parison to other optical methods, the advantage of CRM is molecu¬lar specificity and dispensability of labelling dyes, which is e.g. nec¬essary in fluorescence microscopy. Therefore, a useful future appli¬cation of CRM in combination with multivariate data analysis lies in the analysis of penetration routes of topically applied substances, such as cosmetic formulations or drugs into the skin, which is par¬ticularly interesting in and around hair follicles.