Gerhard Sauermann

Rapid in vivo measurement of the topography of human skin by active image triangulation using a digital micromirror device

Background/aims: Topometry is one of the most relevant methods for biophysical research on skin in dermatologic and cosmetic science, because it relates very closely to the perceived quality of skin. Taking silicon replicas of skin sites under investigation and measuring those imprints with mechanical or optical profilometers is still the most frequently used method. Direct measurement of the topography of human skin in vivo by active image triangulation avoids the need to make replicas and seems to be a promising alternative.

Ultraweak photon emission of human skin in vivo: Influence of topically applied antioxidants on human skin

Publisher Summary This chapter discusses the method to detect ultraweak photon emission (UPE) of human skin in vivo. The monitoring of UPE directly on the skin has the advantages of being noninvasive and providing continuous and convenient monitoring. The effect of the topical application of a-tocopherol and B-carotene was also determined in this study. The UPE detection method provides a useful technique in vivo to determine peroxidative events and efficacy of topically applied antioxidants on human skin. To record the emissions from the skin of human volunteers in vivo, the instruments have to be adapted to special applications. It is necessary to replace small sample compartments and to keep the distance between photocathode and skin surface as short as possible. Avoidance of light from external sources is also necessary. The entire detector head has to be installed in rooms without phosphorescent walls, surfaces, and lamps, and it should be freely movable. Irrespective of theoretical considerations as to whether some kind of physical or biochemical phenomena may be occurring, skin as an organ designed for protection against noxious materials in the environment may be useful as an indicator of free-radical metabolism.

[41] Topically applied antioxidants in skin protection

Publisher Summary Reactive oxygen species (ROS) and free radicals can be generated in skin by ultraviolet (UV) irradiation, ultrasonication, toxic or allergic chemical noxes, or even during normal metabolic processes of cells. More than 10 10 ROS are generated per day and per cell under normal physiological conditions, which have to be dealt with by the endogenous antioxidant system. Oxidative stress arises when the balance between antioxidant and prooxidant processes drifts in favor of a prooxidant status. Some of the general events in the early phase of oxidative stress response in skin are depletion of endogenous intra- and intercellular antioxidants, the enhancement of the intracellular hydroperoxide level, and the induction of specific signal transduction pathways. This chapter presents an example of a screening strategy for the successful selection of in vivo functional topical antioxidants using special in vitro, ex vivo, and in vivo methods. The screening protocol used is subdivided into three steps. In the primary step, the efficacy of antioxidants is evaluated in vitro in cultures of primary skin cells, and the biocompatibility of the selected efficient antioxidants is proved in vitro and in vivo. In the second step, the antioxidant efficacy is tested ex vivo in a clinical pilot study using biopsies from in vivo -pretreated skin sites. In the third step, the in vivo efficacy of preselected antioxidants has been confirmed in clinical studies on panels of human volunteers.

Consequences for sun protection factors when solar simulator spectra deviate from the spectrum of the sun

The sun protection factor (SPF) of two products, one with an expected SPF of 4 and another with an expected SPF of 15 were determined, using two solar simulators: Multiport Solar UV Simulator (xenon, Solar Light, Philadelphia, PA, USA), and Supersun 5000 (metal halide, Mutzhas, Munich, Germany). The mean SPFs using the Multiport were: 4.8 for the low SPF product and 19.4 for the high SPF one. The results using the Supersun were lower: 2.6 for the low SPF product and 7.2 for the high SPF one. Relative emission spectra of the two sources were recorded using a fluorescence spectrophotometer in bioluminescence mode. Efficacy spectra were calculated and compared with the corresponding spectrum of natural sunlight. It was evident that the spectral power of the xenon source is too high in the UVB, leading to overestimation of SPFs, whereas the Supersun irradiator emits too much in the UVA, resulting in too low SPFs. Heat effects and photodegradation of UV filters are discussed as further possible reasons for the discrepancies between the experimentally determined SPFs. Our results confirm a recent publication about theoretical SPFs, calculated with emission spectra of a xenon source and spectra of the sun at different elevation angles, where the authors provide evidence that in natural sunlight the contribution of UVA to total UV radiation is twice as high as in a xenon source. This may contribute to an understanding of why sunscreens tested according to the FDA method (xenon sources) often yield higher SPFs than those obtained from European testing procedures.

Quantitative Analysis of the Skin’s Surface by Digital Signal Processing

The human skin’s three dimensional surface is subjected to continuous structural changes. These result from the influences of the seasons, climate, diurnal rhythms, pathological conditions, age, psychic reactions, and cosmetics [1–6].