PETRA HUBER*, SARAH MEROLA
*Corresponding author
ZHAW Zurich University of Applied Sciences, Life Sciences and Facility Management,
Campus Grüental, Post box, CH-8820 Wädenswil, Switzerland

Abstract

There is increasing interest in cosmetics in quantifying the penetration of active substances into the skin and the efficiency of delivery of active ingredients using in vitro methods. A novel on-line measurement system has been developed to enhance the classic penetration method using Franz diffusion cells and permit direct quantification of UV-detectable substances in the receptor compartment. With this system, the recovery for an aqueous 0.1% caffeine solution was 97.6% +/- 4.4% with UV-Vis spectrophotometry. Applied as infinite dose on a synthetic membrane-based model, Strat-M^®, the kinetic process on a 95% significance level (Pearson’s correlation coefficient exceeds r = 0.9986 showing that the growth curve is highly linear) is most probably of order zero. This measuring technique, which can also be used at the pre-screening stage, offers time and cost-saving benefits over the classic method.

INTRODUCTION

There is increasing interest in quantifying the penetration of active substances into the skin. Toxicologists wish to demonstrate the non-penetration of sunscreens to confirm product safety. Specialists in biopharmaceutical issues are interested in the penetration kinetics of active ingredients in various skin layers, the release of active ingredients from their carriers (“delivery”) and how different carriers such as simple solutions, emulsions or other carriers affect the efficacy of the product (1). In cosmetics both the penetration into the skin and efficiency of delivery of active ingredients are of interest. There is also a commercial need for better human skin equivalents (HSEs) as clinical skin substitutes and as models for permeation and toxicity screening. Testing methods must confirm that the barrier properti ... ...