Ex-vivo spectroscopic quantification of sunscreen efficacy: proposal of a universal sun protection factor.

The sun protection factor (SPF) describes the protective behavior of sunscreens insufficiently, because this factor takes into account only the UVB spectral range, and strains the volunteers during its determination by invasively invoking an erythema. A new noninvasive method is proposed that is based on the UV spectroscopic measurement of tape strips taken from a sunscreen-treated skin area. The resulting sum transmission spectra of the tape strips reflect the in-vivo distribution of the absorber on the skin and quantify the protective efficacy of the applied sunscreens over the complete UV spectral range.

Evaluation of barrier creams - introduction and comparison of 3 in vivo methods.

Often barrier creams (BC) do not fulfil their protecting behaviour, even when promised by the manufacturers. Therefore, it is of great importance to develop standardized in vivo techniques to prove the potency of BC in humans. In the present study, 3 promising techniques for the analysis of BC were evaluated: laser scanning microscopy, laser doppler flowmetry, and the tape-stripping procedure.

Comparison of stratum corneum penetration and localization of a lipophilic model drug applied in an o/w microemulsion and an amphiphilic cream.

Vehicle dependent effects on the penetration behavior of drugs following topical application are well known from the literature. In this context, many reports concerning the enhancing activities for hydrophilic as well as lipophilic substances by colloidal drug carrier systems, particularly microemulsions, are available. However, there is little knowledge about the localization of the drugs within the skin and the stratum corneum, respectively.

Application of optical non-invasive methods in skin physiology: a comparison of laser scanning microscopy and optical coherent tomography with histological analysis.

Background/purpose: Optical, non-invasive methods, such as fluorescence laser scanning microscopy (LSM) and optical coherent tomography (OCT), have become efficient tools for the characterization of the skin structure in vivo, as well as real-time investigation of distribution and penetration of topically applied substances.

Methods: In the present paper, the results obtained with both non-invasive methods - OCT and LSM - were compared to conventional light microscopy of histological sections. Skin structure and the distribution of topically applied particulate and non-particulate substances on the skin surface and in the epidermis were analyzed.

Investigation of the homogeneity of the distribution of sunscreen formulations on the human skin: characterization and comparison of two different methods.

The efficacy of sun protection, mostly realized by the application of sunscreen formulations, is commonly described by the sun protection factor (SPF). Previous investigations have shown that the efficacy of the sun protection inter alia depends on the homogeneity of the distribution of the topically applied sunscreen formulation on the human skin. Therefore, suitable methods are required to determine the homogeneity of topically applied substances on the skin surface.

Nanoparticles--an efficient carrier for drug delivery into the hair follicles.

The penetration and storage behavior of dye-containing nanoparticles (diameter 320 nm) into the hair follicles was investigated. The results were compared to the findings obtained with the same amount of dye in the non-particle form. In the first part of the experiments, the penetration of the dye into the hair follicles was investigated in vitro on porcine skin, which is an appropriate model for human tissue.

Follicular penetration: development of a method to block the follicles selectively against the penetration of topically applied substances.

Investigations into the penetration pathways of topically applied substances through the skin play an important role in dermatological science. Recently, the hair follicles have increasingly been recognized as an important pathway for percutaneous penetration, although the role of the follicles has still not been clarified in detail. Therefore, the aim of the present study was to develop an in vivo method for the analysis of the follicular rate of penetration processes.

An in vivo model to evaluate the efficacy of barrier creams on the level of skin penetration of chemicals.

The reservoir function and the barrier function are important properties of the skin. The reservoir function is dependent on the barrier function which, however, needs support by protective measures, in particular under working conditions. Barrier creams represent a possibility to protect the skin.

Differential stripping: determination of the amount of topically applied substances penetrated into the hair follicles.

The determination of penetration pathways of topically applied substances into the skin is the subject of several investigations. Recently, follicular penetration has become a major focus of interest. To date, a direct, non-invasive quantification of the amount of topically applied substance penetrated into the follicles had not been possible.