Confocal Raman Microspectroscopy in the Assessment of Skin Barrier Function and Drug Penetration

Confocal Raman microspectroscopy (CRM) is a powerful tool for in vitro, ex vivo or in vivo non-invasive and label-free investigation of the skin penetration of substances (active substances, formulation ingredients, contaminants), provided they have a Raman signature that can be isolated from the skin spectral background. CRM enables mechanistic investigations as well as the determination of relative intensities or concentrations of both endogenous and exogenous substances in skin. Most studies consist of time-resolved monitoring of permeant absorption within the stratum corneum and simultaneous investigation of the modification of endogenous skin components resulting from interactions between the permeants and skin lipids or proteins. Tracking penetration enhancers in skin by CRM yield novel insight into interactions between the enhancers and endogenous skin components.