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A multiphase microscopic diffusion model for stratum corneum permeability. I. Formulation, solution, and illustrative
Tsuo-Feng Wang1, Gerald B Kasting, Johannes M Nitsche
1Department of Chemical and Biological Engineering, University at Buffalo, State University of New York, Buffalo, 14260-4200, USA.
Journal of Pharmaceutical Sciences
|February 1, 2006
Summary
This study presents a microscopic transport model of the stratum corneum (SC), revealing that corneocyte transport significantly influences skin permeability for various molecules, challenging the intercellular pathway dominance.
Area of Science:
- Biophysics
- Dermatology
- Materials Science
Background:
- The stratum corneum (SC) acts as a primary barrier to transdermal transport.
- Understanding SC transport mechanisms is crucial for drug delivery and skincare formulation.
- Current models often oversimplify the complex SC lipid and corneocyte interactions.
Purpose of the Study:
- To develop a detailed 2D microscopic transport model of the stratum corneum.
- To investigate the influence of corneocyte hydration and lipid matrix anisotropy on permeability.
- To quantify the relative contributions of intercellular and transcellular pathways.
Main Methods:
- Developed a two-dimensional microscopic transport model of the SC.
- Incorporated varying corneocyte hydration and permeability within an anisotropic lipid matrix.
- Calculated dimensionless permeability as a function of lipid and corneocyte phase parameters.
- Modeled transport for water, ethanol, nicotinamide, and testosterone.
Main Results:
- Skin permeability is governed by dimensionless parameters R and sigma, reflecting lipid and corneocyte transport ratios.
- SC lipid transport is highly anisotropic, with lateral diffusion significantly exceeding transcellular hopping.
- Corneocyte-phase transport plays a major role for all modeled permeants, including water and ethanol.
- Model calculations align with experimental permeability and partition data.
Conclusions:
- Corneocyte transport is a critical determinant of stratum corneum permeability.
- The SC transport pathway is not primarily intercellular, contrary to common belief.
- The developed model provides a more accurate representation of SC barrier function.
- Findings have implications for optimizing topical drug delivery and formulation design.