Optical Coherence Elastography for Real-Time Visualization of Skin Penetration, Associated Dehydration, and Barrier Function: Pilot Ex Vivo Studies and the First In Vivo Demonstration in Humans

This study uses a recently proposed phase-sensitive optical coherence elastography (OCE) method to visualize diffusion and associated skin dehydration by reconstructing osmotically induced strains and assessing topical solution penetration in ex vivo human shin, rat dorsal, and porcine perioral skin, as well as in vivo human forearm skin, for the first time. Aqueous glycerol, ethanol, and tartrazine solutions at various concentrations were investigated. Initial penetration kinetics were characterized over the first 150 s by monitoring penetration-associated osmotic-strains. OCE revealed that, during the initial penetration phase, porcine skin is markedly more permeable than human skin, despite its greater mechanical robustness, whereas rat skin exhibits comparable permeability to human skin. OCE imaging further showed that the stratum corneum (SC), a superficial layer only several tens of micrometers thick, provides the primary skin barrier, and that partial SC removal markedly increases permeability. Enhanced skin stabilization enabled preliminary in vivo measurements by suppressing motion artifacts caused by cardiac pulsation and respiration, and the results were consistent with ex vivo findings. These results indicate that, for the hydrophilic/polar substances tested, rat skin is a more representative model of human skin permeability than porcine skin, highlighting the potential of OCE for real-time monitoring of skin penetration and associated dehydration.