The effect of urea and taurine as hydrophilic penetration enhancers on stratum corneum lipid models

Abstract

To optimize transdermal application of drugs, the barrier function of the skin, especially the stratum corneum (SC), needs to be reduced reversibly. For this purpose, penetration enhancers like urea or taurine are applied. Until now, it is unclear if this penetration enhancement is caused by an interaction with the SC lipid matrix or related to effects within the corneocytes. Therefore, the effects of both hydrophilic enhancers on SC models with different dimensionality, ranging from monolayers to multilayers, have been investigated in this study. Many sophisticated methods were applied to ascertain the mode of action of both substances on a molecular scale. The experiments reveal that there is no specific interaction when 10% urea or 5% taurine solutions are added to the SC model systems. No additional water uptake in the head group region and no decrease of the lipid chain packing density have been observed. Consequently, we suppose that the penetration enhancing effect of both substances might be based on the introduction of large amounts of water into the corneocytes, caused by the enormous water binding capacity of urea and a resulting osmotic pressure in case of taurine.

Topical urea in skincare: A review

“…The mechanism by which urea increases the permeability of the SC is not completely understood but is thought to derive from the capacity to increase the amount of water absorbed by corneocytes, a direct consequence of a high water‐binding capacity (Mueller et al, ). At higher doses, urea's keratolytic action might also play a role in drug penetration enhancement (Trommer & Neubert, ).…”

Recent developments in the application of X-ray and neutron reflectivity to soft-matter systems

“…Their new model is particularly geared towards exploitation by XRR or NR: a reduction in thickness provides the opportunity to study the effects of drugs and/or hydrophilic penetration enhancers on the structure of SC in full detail. Indeed the same author has studied the effect of urea and taurine as hydrophilic penetration enhancers on stratum corneum lipid models [48] using -among other techniques -simultaneous infrared (attenuated total reflection, ATR) and neutron reflectivity.…”

Topical anesthetic and pain relief using penetration enhancer and transcriptional transactivator peptide multi-decorated nanostructured lipid carriers

“…However, there still exist obstacles to the clinical application of topical anesthetics. The stratum corneum (SC), the most out-layer of the skin epidermis, is the main permeability barrier to the transport of drugs through the skin (Mueller et al, 2016;M€ unch et al, 2017). Many strategies have been developed to overcome the stratum corneum (SC) barrier, including chemosmosis enhancers, nanostructures, and functionalized nanostructures (Pham et al, 2016;Gul et al, 2018).…”