A Two-Phase Analysis of Solute Partitioning into the Stratum Corneum

A Multiphase Microscopic Diffusion Model for Stratum Corneum permeability. I. Formulation, Solution, and Illustrative Results for Representative Compounds

“…Binding to keratin protein (or other material associated with the corneocytes, for example, cornified cell envelope proteins and lipid) has, in fact, been well documented for a variety of other solutes, 35,37,43,81 and quantified in terms of an effective partition coefficient correlated with K o/w . 35,70 This phenomenon increases holdup of solute in the corneocyte phase, thereby increasing K cor/w . It concomitantly slows diffusion (i.e., decreases D cor if D cor is taken to describe all (bound and free, not just free) solute) because solute is immobile in its bound state.…”

“…Thus, it is essential to develop procedures for physicochemical parameter estimation, working from experimental data as much as possible, and drawing upon theory to fill in gaps in empirical knowledge. This task is undertaken in a separate analysis 70 of SC/water partition coefficients, and in the companion study to this one, 55 which apples the present model to a large SC permeability database. For the moment we regard all diffusion and partition coefficients to be known in principle, and supply values as needed in the illustrative examples presented later.…”

“…Macroscopically observable affinity of any given solute for the SC is quantified by a partition coefficient K SC/w representing the ratio of superficial solute concentration in the SC (total moles per total volume, accounting for occupancy of both lipid and corneocyte phases by the solute) relative to the concentration in an adjacent aqueous solution (at a prescribed pH) at equilibrium. It is given by the volume average 51,54,70 …”

In Silico Modelling of Transdermal and Systemic Kinetics of Topically Applied Solutes: Model Development and Initial Validation for Transdermal Nicotine

“…where and is the bulk density of keratin (28,29). The diffusion coefficient in the corneocyte ( ) is estimated according to the following equation of hindered diffusion (13):…”

Dermic diffusion and stratum corneum: A state of the art review of mathematical models

“…Several solvents have been used as model for stratum corneum lipids (octanol, hexadecane, olive oil, butadiene and dodecadiene). The most convenient seems to be octanol [30,56,[60][61][62][63][64][65].…”