Multilayer diffusion modeling and Coherent anti-Stokes Raman scattering microscopy for spatially resolved water...

Area of Science:

• Biophysics
• Materials Science
• Dermatology

Background:

• The skin's Stratum Corneum (SC) acts as a primary barrier against external substances.
• Understanding SC's barrier function is crucial for drug delivery and toxicology.
• Previous methods lacked the spatial resolution to fully characterize SC's heterogeneity.

Purpose of the Study:

• To quantitatively measure water diffusion within intact skin tissue with high spatial resolution.
• To investigate the heterogeneity of the Stratum Corneum as a diffusion barrier.
• To develop and validate a combined microscopy and modeling approach for diffusion studies.

Main Methods:

• Utilized Coherent anti-Stokes Raman Scattering (CARS) microscopy for label-free imaging.
• Measured time-dependent, spatially resolved concentration changes of deuterated water (D2O).
• Employed a multilayer diffusion model to extract depth-dependent diffusion coefficients.

Main Results:

• Demonstrated spatial resolution under 1 μm for water diffusion measurements in skin.
• Revealed significant variations in diffusion coefficients across different SC layers, confirming heterogeneity.
• Obtained an average diffusion coefficient of 0.047 ± 0.01 μm²/s, increasing after acetone treatment or tape stripping.

Conclusions:

• The Stratum Corneum exhibits complex, heterogeneous diffusion properties, not a uniform barrier.
• The developed CARS microscopy and diffusion modeling approach is effective for characterizing skin barrier function.
• This technique holds promise for diverse applications in studying substance diffusion in biological tissues.