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Human Stratum Corneum (human + stratum_corneum)
Selected AbstractsIn vitro evaluation of sun protection factors of sunscreen agents using a novel UV spectrophotometric techniqueINTERNATIONAL JOURNAL OF COSMETIC SCIENCE, Issue 4 2008M. D. Bleasel Synopsis A method for the in vitro determination of low- and high-value sun protection factors (SPF) of sunscreens using artificial substrates and a novel pseudo double beam (PDB) mode of operation of a standard double beam UV spectrophotometer is described. The method allows transmittance to be calculated from detector responses of reference and sample beams measured at different gain levels and facilitates the accurate quantification of low levels of electromagnetic radiation transmitted through highly absorbing samples. The spectrophotometer was modified to hold quartz diffusing plates on which a substrate [TransporeÔ adhesive tape or human stratum corneum obtained from a skin surface biopsy (SSB)] and the sunscreens to be tested were applied. The PDB mode of operation increased the effective linear range of the detector response of the spectrophotometer by a factor of approximately 20000-fold, enabling the in vitro SPF determination technique to be applied to both high and low SPF value sunscreens. Eight commercial sunscreens with known SPF values ranging from 4 to 77, previously determined by in vivo methods, were tested in vitro using both test substrates and correlations between the in vivo and in vitro values were determined. SPF values determined using the in vitro method correlated well with the known in vivo results (TransporeÔ tape, R2 = 0.611; SSB, R2 = 0.7928). The in vitro SPF obtained for one of the tested products differed substantially from the cited in vivo SPF value. Independent in vitro and in vivo re-evaluation of the SPF of this product matched the value predicted by the present method much more closely than the originally cited in vivo value. All determined SPFs were ordered correctly in comparison to in vivo ranking and the technique appeared to correctly identify a sunscreen that had a labelled SPF value that was significantly higher than its true SPF. Résumé Une méthode destinée à déterminer in vitro les facteurs de protection solaire (SPF) d'écrans solaires de faible et haut indice est décrite. Elle met en ,uvre des substrats artificiels et un nouveau mode opératoire reposant sur l'utilisation du pseudo double faisceau (PDB) d'un spectrophotomètre UV double faisceau standard. La méthode permet le calcul de la transmittence à partir des réponses du détecteur de référence et la mesure en simple faisceau à différents niveaux de gain facilitant ainsi la quantification précise des faibles niveaux de radiation électromagnétique (EMR) transmis à travers des échantillons hautement absorbants. Le spectrophotomètre a été modifié de façon à fixer des plaques diffusantes en quartz sur lesquelles un substrat (ruban adhésif Transport TM ou du stratum corneum humain obtenu à partir de biopsie de surface de peau (SSB) et les écrans solaires testés ont été appliqués. Le mode opératoire PTB augmente la gamme linéaire effective de la réponse du détecteur du spectrophotomètre d'un facteur approximatif 20.000 permettant, à cette technique de détermination des SPF in vitro, d'être appliquée à la fois sur les écrans solaires de haut et bas SPF. Huit écrans solaires commerciaux de SPF connus allant de 4 à 77, préalablement déterminés par des méthodes in vivo, ont été testés in vitro en utilisant les deux substrats, et les corrélations entre les valeurs in vivo et in vitro ont été déterminées. Les valeurs SPF déterminées en utilisant la méthode in vitro est bien corrélée avec les résultats in vivo connus (ruban transport, R2 = 0.611; SSB, R2 = .7928). Le SPF in vitro pour l'un des produits testés diffère fortement des valeurs SPF citées in vivo. Une réévaluation indépendante des SPF in vitro et in vivo de ce produit ajuste la valeur prédite par la présente méthode de façon beaucoup plus proche que la valeur originale citée in vivo. Tous les SPF ainsi déterminés sont ordonnés correctement en comparaison au classement in vivo et la technique semble identifier correctement un écran solaire qui possède un SPF libellé significativement plus haut que son vrai SPF. [source] Polymers effect on estradiol partition coefficient between powdered human stratum corneum and waterJOURNAL OF PHARMACEUTICAL SCIENCES, Issue 12 2002Ronald C. Wester Abstract Macromolecules have gained interest as drug entities unto themselves and as transport facilitators to alter initial phases of percutaneous absorption. Two macromolecular polymers (MW 2081 and 2565) were designed to hold cosmetics and drugs to the skin surface by altering initial chemical and skin partitioning. The effect of these polymers on the partition coefficient (PC) of estradiol with powdered human stratum corneum (PHSC) and water was determined. There was no statistically significant effect on the PC when the concentration of estradiol was increased 100-fold (0.028,2.8 ,g/mL), when the incubation time was increased from 0 to 24 h, or when PHSC was delipidized. The addition of a liphophilic polymer had no effect on the PC; however, the hydrophilic polymer showed a significant polymer concentration-dependent increase (p,<,0.01) in log PC for estradiol concentrations. Thus, a macromolecular chemical has the potential to alter the partitioning of chemical into the outer layers of skin, the first step in percutaneous absorption. © 2002 Wiley-Liss, Inc. and the American Pharmaceutical Association J Pharm Sci 91:2642,2645, 2002 [source] Keratin-lipid structural organization in the corneous layer of snake,BIOPOLYMERS, Issue 12 2009Alberto Ripamonti Abstract The shed epidermis (molt) of snakes comprises four distinct layers. The upper two layers, here considered as ,-layer, contain essentially ,-keratin. The following layer, known as mesos-layer, is similar to the human stratum corneum, and is formed by thin cells surrounded by intercellular lipids. The latter layer mainly contains ,-keratin. In this study, the molecular assemblies of proteins and lipids contained in these layers have been analyzed in the scale of two species of snakes, the elapid Tiger snake (TS, Notechis scutatus) and the viperid Gabon viper (GV, Bitis gabonica). Scanning X-ray micro-diffraction, FTIR and Raman spectroscopies, thermal analysis, and scanning electron microscopy experiments confirm the presence of the three layers in the GV skin scale. Conversely, in the TS molt a typical ,-keratin layer appears to be absent. In the latter, experimental data suggest the presence of two domains similar to those found in the lipid intercellular matrix of stratum corneum. X-ray diffraction data also allow to determine the relative orientation of keratins and lipids. The keratin fibrils are randomly oriented inside the layers parallel to the surface of scales while the lipids are organized in lamellar structures having aliphatic chains normal to the scale surface. The high ordered lipid organization in the mature mesos layer probably increases its effectiveness in limiting water-loss. © 2009 Wiley Periodicals, Inc. Biopolymers 91: 1172,1181, 2009. This article was originally published online as an accepted preprint. The "Published Online" date corresponds to the preprint version. You can request a copy of the preprint by emailing the Biopolymers editorial office at biopolymers@wiley.com [source] Noninvasive characterization of human stratum corneum of undiseased skin of patients with atopic dermatitis and psoriasis as studied by Fourier transform Raman spectroscopyBIOPOLYMERS, Issue 3 2001Johannes Wohlrab Abstract Etiopathogenetic regulatory disorders of epidermal metabolism and the subsequent changes in the molecular pattern of the stratum corneum play an important role in the clinical differentiation of particular dermatoses (e.g., psoriasis, atopic dermatitis). In this study we present in vitro Fourier transform Raman spectra of the stratum corneum from healthy skin, as well as from clinically undiseased skin of the right heel of atopic and psoriatic volunteers. Differences in the averaged spectra were detected, particularly in the spectral ranges of 1112,1142 (lipid band), 1185,1220, and 1394,1429 cm,1. By using the first derivative of the averaged spectra and/or a statistical evaluation of the spectroscopic data it was possible to distinguish the skin types examined. © 2001 John Wiley & Sons, Inc. Biopolymers (Biospectroscopy) 62: 141,146, 2001 [source] Emollient molecule effects on the drying stresses in human stratum corneumBRITISH JOURNAL OF DERMATOLOGY, Issue 4 2010K. Levi Summary Background Emollient molecules are widely used in skin care formulations to improve skin sensory properties and to alleviate dry skin but little is understood regarding their effects on skin biomechanical properties. Objectives To investigate the effects of emollient molecules on drying stresses in human stratum corneum (SC) and how these stresses are related to SC components and moisture content. Methods The substrate curvature method was used to measure the drying stresses in isolated SC following exposure to selected emollient molecules. While SC stresses measured using this method have the same biaxial in vivo stress state and moisture exchange with the environment, a limitation of the method is that moisture cannot be replenished by the underlying skin layers. This provides an opportunity to study the direct effects of emollient treatments on the moisture content and the components of the SC. Attenuated total reflectance Fourier transform infrared spectroscopy was used to determine the effects of emollient molecules on SC lipid extraction and conformation. Results Emollient molecules resulted in a complex SC drying stress profile where stresses increased rapidly to peak values and then gradually decreased to significantly lower values compared with the control. The partially occlusive treatments also penetrated into the SC where they caused extraction and changes in lipid conformation. These effects together with their effects on SC moisture content are used to rationalize the drying stress profiles. Conclusions Emollient molecules have dramatic effects on SC drying stresses that are related to their effects on intercellular lipids and SC moisture content. [source] | |||||||||||||