Development and evaluation of a quality control system based on transdermal electrical resistance for skin barrier...

In vitro skin permeation experiments are highly relevant for pharmaceutical, cosmetic, agricultural developments, and regulatory evaluation. A key requirement is the skin barrier integrity, that is accompanied by an intact stratum corneum (SC) which implements high skin quality. A variety of integrity tests are currently available, for example, measurement of transepidermal water loss, monitoring the permeation of tritiated water and the measurement of transdermal electrical resistance (TER).

We aimed for a non-destructive examination of barrier integrity as quality control system, based on TER. Therefore, the in-house developed instrument SkinTER measures electrical resistance on excised human skin samples in a non-invasive and easy-to-use pattern. In this proof of concept study, we compared three human in vitro skin models with focus on their TER and permeation properties. The skin integrity was impaired to mimic conditions of skin during age, lifestyle (eg, shaving) or diseases (eg, obesity, psoriasis, and atopic dermatitis). The OECD permeation marker caffeine was correlated to the corresponding TER value.

A correlation between both was obtained by having a Pearson coefficient of -0.830. Hereby, a minimum TER value for intact skin samples of ~1.77 kΩ*cm² was suggested. Intact samples are significantly different (α = ≤0.05) to their impaired counterparts in flux and TER values.

The new SkinTER instrument gives a quick and non-invasive feedback on skin quality before a permeation experiment.