Monitoring the penetration enhancer dimethyl sulfoxide
The stratum corneum (SC) barrier typically consists of layers of corneocytes embedded in a lipid continuum that regulates barrier function. The lipid domain containing ceramides, cholesterol, and free fatty acids provides the major pathway for most drugs permeating across SC (1). Penetration enhancers diminish the SC barrier function. The classic enhancer is dimethyl sulfoxide (DMSO) (2). Its mechanisms of action remain unclear, although DMSO disrupts lipid organisation and may displace protein-bound water (3). Here we use confocal Raman spectroscopy to probe molecular interactions between a finite (depleting) dose of DMSO and SC, as functions of depth and time, providing novel information about residence time and location of DMSO in human SC in vivo.