J. Lademann

Influence of nonhomogeneous distribution of topically applied UV filters on sun protection factors

The aim of the present study is the development of a method to determine quantitatively in vivo the influence of homogeneity of the distribution of sunscreen containing UV filters on the sun protection factor (SPF). The SPF of a sunscreen applied either topically or inside an optical cell (pure or in a solvent) fixed above the skin is determined in vivo. In both cases, in vivo measurements using the erythema formation are carried out. Identical optical parameters of the skin are realized in both experiments. In addition, both in vitro (using tape stripping) and in vivo microscopic measurements are performed to analyze the homogeneity of distribution of the topically applied substances. An SPF of 8 is measured in the experiment applying the UV filters topically, whereas this value increases by a factor of 10 if the same amount of filter substances is distributed homogeneously in solution inside the optical cell. Tape strips removed from skin treated with the sunscreen reflect the inhomogeneous distribution of the topically applied substances on the skin. The direct correlation of homogeneity of distribution with the SPF opens up the possibility to increase the SPF by optimizing the formulation.

Determination of penetration profiles of topically applied substances by means of tape stripping and optical spectroscopy: UV filter substance in sunscreens

Penetration profiles of topically applied drugs and cosmetic products provide important information on their efficacy. The application of tape stripping in combination with UV/VIS spectroscopy is checked to determine the local position of topically applied substances inside the stratum corneum, the penetration profile. The amount of corneocytes removed with each tape strip is quantified via the particle-dependent absorption, the pseudoabsorption, in the visible spectral range. The concentration of a typical UV filter substance, 4-methylbenzylidene camphor, is determined by optical spectroscopy using the tape strips removed originally. In this case, a time-dependent increase in the absorbance must be taken into account. Laser scanning microscopic investigations confirm that the nonhomogeneous distribution of the filter substance, on the strips, can explain this spectroscopic behavior. When reaching a homogeneous distribution, the UV spectroscopic signal reflects the correct concentration. These spectroscopic values are compared with high performance liquid chromatography (HPLC) data. The values obtained with both methods for the concentrations of 4-methylbenzylidene camphor are in good agreement. The data obtained are used to illustrate the determination of a penetration profile of a UV filter substance. The results demonstrate that the described protocol is well suited to characterize, in a simple manner, topically applied substances that have a characteristic UV/VIS absorption band.

Comparison of Transepidermal Water Loss and Spectroscopic Absorbance to Quantify Changes of the Stratum corneum after Tape Stripping

The objective and quantitative application of tape stripping in pharmaceutics and dermatopharmacokinetics requires the determination of the exact position of each removed tape strip inside the stratum corneum (SC) and/or the determination of the relative SC thickness. In this study, transepidermal water loss (TEWL) and the optical spectroscopic data of the corneocytes were measured simultaneously during the complete removal of the SC by tape stripping. The spectroscopic data quantitatively reflect the amount of corneocytes removed by the individual tape strips, whereas TEWL and 1/TEWL are not sensitive enough to measure the relatively small changes in the SC thickness realized by the removal of the individual strips. The relative SC thickness can be determined directly by the spectroscopic data, while the 1/TEWL values require a second independent method. The results demonstrate the importance of tape stripping characterizing the behaviour of topically applied substances.

Reservoir Function of the Stratum corneum: Development of an in vivo Method to Quantitatively Determine the Stratum corneum Reservoir for Topically Applied Substances

Investigations on the stratum corneum (SC) reservoir for topically applied substances are of importance in dermatologic science in order to assess the pharmacokinetics of these substances. In the present study, an in vivo method was developed to determine the SC reservoir quantitatively and to investigate the temporal behavior of this reservoir. Therefore, increasing amounts of an oil-in-water emulsion (o/w emulsion) containing 4% of a chemical UV filter were topically applied onto the flexor forearms of 5 healthy volunteers. The saturation of the SC reservoir was determined utilizing the tape stripping technique 1 and 6 h after application. The capacity of the SC reservoir for the o/w emulsion was found to be approximately 2.7 mg/cm2. Furthermore, a correlation of the capacity of the SC with transepidermal water loss was observed. Extending the time between the topical application and SC removal did not affect the distribution or the recovery rate of the UV filter in the SC. The results indicate that the reservoir of the SC is limited. This is reflected by the saturation level, which depends on the individual volunteer and, presumably, the topically applied substances and formulations used. The results show that the method developed is suited to quantitatively determine in vivo the SC reservoir for topically applied substances.

Contents Vol. 26, 2013

N. Ahmad, Madison, Wisc. P. Altmeyer, Bochum C. Antoniou, Athens H. Bachelez, Paris J.M. Baron, Aachen E. Benfeldt, Roskilde E. Berardesca, Rome D.R. Bickers, New York, N.Y. I. Bogdan Allemann, Zürich K. De Paepe, Brussels P. Elsner, Jena A. Farkas, Szeged A. Giannetti, Modena M.W. Greaves, London R.H. Guy, Bath J. Hadgraft , London E.M. Jackson, Bonney Lake, Wash. J. Kresken, Viersen J. Krutmann, Düsseldorf R. Neubert, Halle D.R. Roop, Aurora, Colo. T. Ruzicka, Munich M. Schäfer-Korting, Berlin S. Seidenari, Modena J. Wohlrab, Halle Journal of Pharmacological and Biophysical Research

Contents Vol. 24, 2011

N. Ahmad, Madison, Wisc. P. Altmeyer, Bochum C. Antoniou, Athens H. Bachelez, Paris J.M. Baron, Aachen E. Benfeldt, Roskilde E. Berardesca, Rome D.R. Bickers, New York, N.Y. I. Bogdan Allemann, Zürich K. De Paepe, Brussels P. Elsner, Jena A. Farkas, Szeged A. Giannetti, Modena M.W. Greaves, London R.H. Guy, Bath J. Hadgraft , London E.M. Jackson, Bonney Lake, Wash. Y. Kawakubo, Chiba H.-C. Korting, Munich J. Krutmann, Düsseldorf R. Neubert, Halle D.R. Roop, Aurora, Colo. T. Ruzicka, Munich M. Schäfer-Korting, Berlin S. Seidenari, Modena J. Wohlrab, Halle S. Yamamoto, Hiroshima Journal of Pharmacological and Biophysical Research

Contents Vol. 21, 2008

N. Ahmad, Madison, Wisc. P. Altmeyer, Bochum C. Antoniou, Athens H. Bachelez, Paris J.M. Baron, Aachen E. Benfeldt, Copenhagen E. Berardesca, Rome D.R. Bickers, New York, N.Y. J.E. Birnbaum, East Hanover, N.J. K. de Paepe, Brussels P. Elsner, Jena A. Farkas, Szeged A. Giannetti, Modena M.W. Greaves, Kuala Lumpur R. Guy, Bath J. Hadgraft , Chatham Maritime B.M. Henz, Berlin E.M. Jackson, Sumner, Wash. Y. Kawakubo, Saitama H.-C. Korting, Munich J. Krutmann, Düsseldorf R. Neubert, Halle D. Roop, Houston, Tex. T. Ruzicka, Munich M. Schäfer-Korting, Berlin S. Seidenari, Modena B. Shroot, San Antonio, Tex. J. Wohlrab, Halle S. Yamamoto, Hiroshima Journal of Pharmacological and Biophysical Research

Laser spectroscopic investigation of radical formation during laser-tissue interaction

Laser spectroscopic measurements are an effective method for the on-line investigation of formation processes of harmful substances during laser treatment of tissue in medicine. Specific radicals like CO, CO2, CN, OH, CN, CH2, C2, NH, SH, CS produced during laser application for cutting and evaporation of tissue characterize the kind of laser tissue interaction. The molecule fragments in the ground or excited states have been detected in dependence on the applied medical laser system by spontaneous or laser induced fluorescence. The chemical reaction processes in the laser tissue interaction zone can be changed significantly by the surrounding gas atmosphere. An increasing oxygen content in the surrounding atmosphere reduces the amount of harmful substances in the laser plume. The laser spectroscopic investigation inside the reaction zone reflects clearly the interplay of complete and incomplete oxidation in dependence on different gas atmospheres in the reaction zone. The application of pure oxygen and oxygen enriched gases is limited in laser medicine because of safety regulating. Therefore water was used as an oxygen donor. The water was added into the laser tissue interaction zone using a water aerosol spray. The oxygen was released during the laser treatment with the result of the water dissociation under the high temperature conditions. The production of toxic and carcinogenic substances was reduced significantly by this method. The cutting efficiency in the case of water spray application is unchanged in comparison to the treatment without water spray but the quality can be improved, as histological investigations demonstrate.