Characterization of Water Self-Diffusion in Human Stratum Corneum

Area of Science:

• Biophysics
• Dermatology
• Materials Science

Background:

• The stratum corneum (SC) is the skin's outermost protective layer.
• It comprises corneocytes embedded in a lipid matrix, acting as a barrier.
• SC hydration influences its structure and permeability to water and chemicals.

Purpose of the Study:

• To investigate how hydration and SC structure affect water self-diffusion.
• To understand the role of corneocyte orientation and lipid matrix.

Main Methods:

• Utilized pulsed-gradient stimulated echo nuclear magnetic resonance (NMR) spectroscopy.
• Measured proton (¹H) self-diffusion of water within human SC.
• Varied hydration levels, temperature (20°C–40°C), and lipid extraction.

Main Results:

• Water self-diffusion parallel to corneocytes was independent of lipid extraction.
• Temperature effects aligned with water diffusion activation energy in wool.
• Perpendicular diffusion was less hydration-dependent and generally slower than parallel diffusion, except at low hydration.

Conclusions:

• Water diffusion within SC is anisotropic, influenced by corneocyte structure.
• A free-volume diffusion model effectively describes parallel diffusion.
• Findings provide insights into SC barrier function and hydration dynamics.