title: On the Variation of Water Diffusion Coefficient in Stratum Corneum With Water Content.
abstract: Water permeability and transient water sorption data in human and porcine stratum corneum (SC) are analyzed in conjunction with equilibrium water sorption data and a dynamic skin swelling model to develop a quantitative model for water diffusivity in the SC as a function of its water content. The recommended function (model 1) is phenomenological and treats the SC as a uniform, swellable slab. This approach yields satisfactory agreement with experimental data over a wide range of RH and associated equilibrium SC water content, Cw. It is supported by two alternative approaches. Model 2 considers the SC to be a multilaminate membrane consisting of alternating lipid and protein layers. Diffusivity in the protein phase is estimated from water diffusivity in other keratinized tissues, whereas diffusivity in the lipid phase is assumed to be linearly related to the swelling strain on intercellular lipids. Model 3 uses an analysis previously suggested by Stockdale to rationalize transepidermal water loss data in humans over a wide range of relative humidity. All models yield similar results for 0.20 ≤ Cw ≤ 0.78 g/cm(3), the usual range of SC water content in vivo.
authors.affiliation: UC-P&G Simulation Center, University of Cincinnati, Cincinnati, Ohio 45220.
authors.forename: Xin
authors.initials: X
authors.lastname: Li
authors.affiliation: Research and Development Department, The Procter & Gamble Company, Cincinnati, Ohio 45069.
authors.forename: Robert
authors.initials: R
authors.lastname: Johnson
authors.affiliation: James L. Winkle College of Pharmacy, University of Cincinnati, Cincinnati, Ohio 45267. Electronic address: Gerald.Kasting@uc.edu.
authors.forename: Gerald B
authors.initials: GB
authors.lastname: Kasting
mesh_terms: D000818:Animals; D004058:Diffusion; D006801:Humans; D008055:Lipids / Q000737:chemistry; D010539:Permeability; D012867:Skin / Q000378:metabolism*; D013552:Swine; D014867:Water / Q000737:chemistry / Q000378:metabolism*
chemical_list: D008055:Lipids; D014867:Water
keywords: biophysical models; hydration; mathematical model; skin; water sorption