Ultraviolet transmission microscopy for the imaging of topical sunscreen emulsions.

OBJECTIVE: Microscopy is widely used during the development and testing of topical formulations; however, it often lacks the ability to be chemically specific with regard to what is being imaged. This article describes how moving outside of the visible light region and into different parts of the ultraviolet (UV) spectrum enables differently UV absorbing components in topical emulsions to be directly visualized using optical transmission microscopy. METHODS: Optical transmission microscopy of different sunscreen emulsions was carried out using a custom-built microscope, imaging in the UVB (313 nm), UVA (365 nm) and visible light (546 nm) and with different magnifications. RESULTS: By using light of different wavelengths, direct visualization of different UV absorbing ingredients within the product emulsion using optical transmission microscopy has been performed and the locations of the UV absorbing actives in the formulations imaged. CONCLUSIONS: Microscopy has long been a valuable tool for the skin researcher, providing structural information about the products and how they perform. By moving outside of the spectral region of visible light and into the UV, it has been possible for the first time to directly image different SPF ingredients within topical formulations using optical microscopy.

OBJECTIF: La microscopie est largement utilisée dans le processus de développement et d'analyse des formulations topiques; cependant, elle ne parvient pas souvent à être chimiquement spécifique en ce qui concerne l'objet de l'imagerie. Le présent article décrit comment le déplacement au-delà de la zone de lumière visible et dans différentes parties du spectre ultraviolet (UV) permet aux ingrédients qui absorbent différemment les UV dans les émulsions topiques, d'être directement visualisés grâce à la microscopie à transmission optique. MÉTHODES: La microscopie à transmission optique de différentes émulsions de crème solaire a été réalisée à l'aide d'un microscope sur mesure, de l'imagerie dans les UVB (313 nm), les UVA (365 nm) et la lumière visible (546 nm) et à différents grossissements. RÉSULTATS: En utilisant la lumière de différentes longueurs d'onde, une visualisation directe des différents ingrédients absorbant les UV dans l'émulsion du produit grâce à la microscopie à transmission optique a été réalisée et les emplacements des substances actives absorbant les UV dans les formulations ont fait l'objet d'imagerie. CONCLUSIONS: La microscopie a été depuis longtemps un outil précieux pour les spécialistes de la peau, en fournissant des informations structurelles sur les produits et leurs performances. En se déplaçant au-delà de la région spectrale de la lumière visible, dans les UV, il a été possible pour la première fois d'obtenir directement une imagerie des différents ingrédients du facteur de protection solaire dans des formulations topiques à l'aide de la microscopie optique.

What Are the Options Beyond SPF 50+? A View on Consumer Behavior and the Sensory Features of Sunscreens.

Skin cancer rates have been on the rise for decades and are still growing in spite of the availability of high-performance sunscreens that provide sufficient protection against the damaging effect of UV radiation everywhere on this globe. This paper investigates behaviors and attitudes to sunscreen use that may cause an increased UV exposure risk, for example, not using sunscreen at all. Alongside educational reasons, there is a link to some aspects of applying sunscreens that seem to be disliked universally. Therefore, the sensory features of 73 globally sourced commercial sunscreens were measured using quantitative descriptive sensory analysis. This revealed the ranges of sensory intensity currently available, which were then compared with what consumers really want, and showed that only a few sunscreens currently fulfill the needs of people in the most abundant consumer group - "dry touch seekers." All this contributes to insufficient or no use at all of sunscreens during sun exposure, which could result in significant UV dosages that turn out to be relevant for skin cancer development. A more integral approach to improving sunscreen formulas, along with more targeted communication to connect more effectively with consumers who currently show those avoidance behaviors, is needed.

Past, Present, and Future of Sun Protection Metrics.

Since the beginning of the development of sunscreen products, efforts have been made to measure and quantify the protection performance of such products. Early on an in vivo method was established that allowed statements on the sun protection performance in humans. Later, by establishing defined basic and experimental conditions, the method became internationally standardized delivering the well-known sun protection factor (SPF). The method was widely used and is nowadays regarded as a gold-standard method. Further standardized methods were added shortly thereafter. However, shortcomings such as the confined radiation spectra used by the methods, the invasiveness, the complexity in their application, as well as their time- and cost-intensity promoted the development of alternative methods. The shortcomings were recently followed by another, namely, the large interlaboratory variances of the sun protection metrics SPFISO 24444. This all together shows that there is a justifiable need to explore the potential of alternative methods, to complement the existing methods, to serve as equivalents, or even to replace it in the future. Based on the work of Uhlig and coworkers, the authors propose to test the suitability of the alternative methods and their possible equivalency to the reference methods in a broad-based investigation, taking into account possible interlaboratory variances. A research program - developed by a consortium - is in public planning where stakeholders from research, industry, authorities, and the public can come together to facilitate and further advance standardization of the measurement of the sun protection performance. The authors give an insight into historical, technical--conceptual, and future developments of methods for -determining the protective performance of sun protection products.

Isolation and structure determination of a tetrameric sulfonyl dilithio methandiide in solution based on crystal structure analysis and 6Li/13C NMR spectroscopic data.

Dilithio sulfonyl methandiides are a synthetically and structurally highly interesting group of functionalized geminal dianions. Although very desirable, knowledge of the structure of dilithio methandiides in solution was lacking up to now. Herein, we describe the isolation and determination of the structure of tetrameric dilithio (trimethylsilyl)(phenylsulfonyl) methandiide in solution and in the crystal. The elucidation of the structure of the tetramer is based on crystal structure analysis and 13C/6Li NMR spectroscopic data. A characteristic feature of the structure of the tetramer is the C 2 symmetric C-Li chain, composed of four doubly Li-coordinated dianionic carbon and five Li atoms. Three Li atoms are devoid of a contact to a dianionic C atom. The tetramer, the dianionic C atoms of which undergo fast exchange, is in THF solution in fast equilibrium with a further aggregate, which is stable only at low temperatures.