An Atomistic Model Of The Human Stratum Corneum: Permeation Through The Long Periodicity Phase. Effect of a pro-penetrant.

The stratum corneum (SC) layer of the human skin is the outermost and primary barrier against chemical topical exposure. The ability of a chemical to pass the SC is a key point for risk assessment and development of cosmetic ingredients. From neutron diffraction data, the SC peaks comprise a short periodicity phase (SPP) with a repeat distance of 6 nm, and a long periodicity phase (LPP) with a repeat distance of 13 nm. The LPP captures long-scale dynamics and can be represented as a sandwich model by Bouwstra.

Here we present a simulation model of the LPP with a mixture of three ceramides (Ceramides 1, 2, and 3), cholesterol, and lignoceric acid and we investigate whether the use of solute-penetration enhancers (known as pro-penetrant) (ex. dipropylene glycol -DPG-) significantly alter the barrier properties of these skin models. In our model, we find that DPG increases the hydrogen-bonding profile and, by consequence, reduces the lipid diffusivity in the lateral direction (D_L) by one order of magnitude. Using multi-microsecond constant-velocity steered molecular dynamics of several solutes (hydrophilic and hydrophobic, …) we expect to be able to construct a chemical profile model of the human stratum corneum of broad applicability in Cosmetics.