Das Projekt "Quality of skin as a barrier to ultra-fine particles (NANODERM)" wird vom Umweltbundesamt gefördert und von Universität Leipzig, Fakultät für Physik und Geowissenschaften durchgeführt. Objective: Today' s population is increasingly exposed to ultrafine particles (less than 20 nm; e.g. Aerosil, TiO2) contained in body care and household products. Tape stripping studies and recent ion microscopy pilot studies revealed that such particles in, liposomal formulations penetrate the horny layer with large concentrations at the stratum granulosum and the possible risk of further penetration into vital tissue, especially for skin with an impaired barrier function. Here, apart from electron microscopy, high-resolution ion-microscopy techniques will be employed on skin cross-sections from biopsies (pig, human), which yield elemental maps of both the epidermis and dermis with ppm sensitivity for Ti or higher sensitivity with radiotracers (labelled TiO2) on pig skin. Pathways for percutaneous uptake and clearance will be studied. If such particles penetrate into the dermis, in-situ studies of tissue and in-vitro studies of particle-cell interactions follows.
Das Projekt "Quantitative Analyse der biochemischen Effekte von phenolischen Verbindungen an biologischen Membransystemen" wird vom Umweltbundesamt gefördert und von Eidgenössische Anstalt für Wasserversorgung, Abwasserreinigung und Gewässerschutz durchgeführt. The goal of this project is to set up Quantitative Structure Activity Relationships (QSAR) to describe and to predict the toxicity of phenolic compounds on a mechanistic level. Highly substituted phenols, namely chlorinated and nitrated phenols, are toxic because they uncouple the ATP-synthesis from the electron transport. In addition to dissipating the chemiosmotic proton gradient, some phenols may also exhibit inhibitory activity on the electron transport chain (or other targets) and cause narcosis. In using time-resolved spectroscopy, it is possible to distinguish and quantify these different modes of action in a simple cyclic photosynthetic system, chromatophores of Rb Sphaeroides - an experimental set-up that has been well established during the study of photosynthesis. One common feature of the mode of toxic action of these compounds as well as many other hydrophobic ionizable compounds is the target site being the membrane or embedded into the membrane. Therefore, it is important to know which species and how much of each species are taken up into biological membranes. This issue is investigated in the second part of this study which focuses on distribution experiments of substituted phenols between water and different model membranes, typically liposoms made up of bilayer forming lipids. The understanding of the sorption behavior together with the mechanism-based toxicity data will help to establish meaningful QSAR-equations.