Penetration rates into the stratum corneum layer: A novel quantitative indicator for assessing skin barrier function.

BACKGROUND: The stratum corneum (SC), the outermost layer of the skin epidermis, acts as an effective bi-directional barrier, preventing water loss (inside-outside barrier) and entry of foreign substances (outside-inside barrier). Although transepidermal water loss (TEWL) is a widely-used measure of barrier function, it represents only inside-outside protection. Therefore, we aimed to establish a non-invasive method for quantitative evaluation of the outside-inside barrier function and visually present a skin barrier model. MATERIALS AND METHODS: Skin barrier damage was induced by applying a closed patch of 1% sodium dodecyl sulfate to the forearms of eight participants; they were instructed to apply a barrier cream on a designated damaged area twice daily for 5 days. The SC barrier was evaluated by measuring TEWL and fluorescein sodium salt penetration rate before, immediately after, and 5 days after damage. The penetration rate was assessed using tape-stripping (TS) technique and fluorescence microscopy. RESULTS: The rates of fluorescein sodium salt penetration into the lower layers of SC differed significantly based on the degree of skin barrier damage. The correlation between penetration rate and TEWL was weak after two rounds of TS and became stronger after subsequent rounds. Five days after skin barrier damage, the penetration rate of all layers differed significantly between areas with and without the barrier cream application. CONCLUSION: Our findings demonstrated that the penetration rate was dependent on skin barrier conditions. The penetration rate and corresponding fluorescence images are suitable quantitative indicators that can visually represent skin barrier conditions.

Cutaneous Pharmacokinetics of Topically Applied Novel Dermatological Formulations.

Novel formulations are developed for dermatological applications to address a wide range of patient needs and therapeutic challenges. By pushing the limits of pharmaceutical technology, these formulations strive to provide safer, more effective, and patient-friendly solutions for dermatological concerns, ultimately improving the overall quality of dermatological care. The article explores the different types of novel dermatological formulations, including nanocarriers, transdermal patches, microsponges, and microneedles, and the techniques involved in the cutaneous pharmacokinetics of these innovative formulations. Furthermore, the significance of knowing cutaneous pharmacokinetics and the difficulties faced during pharmacokinetic assessment have been emphasized. The article examines all the methods employed for the pharmacokinetic evaluation of novel dermatological formulations. In addition to a concise overview of earlier techniques, discussions on novel methodologies, including tape stripping, in vitro permeation testing, cutaneous microdialysis, confocal Raman microscopy, and matrix-assisted laser desorption/ionization mass spectrometry have been conducted. Emerging technologies like the use of microfluidic devices for skin absorption studies and computational models for predicting drug pharmacokinetics have also been discussed. This article serves as a valuable resource for researchers, scientists, and pharmaceutical professionals determined to enhance the development and understanding of novel dermatological drug products and the complex dynamics of cutaneous pharmacokinetics.

Stratum corneum cytokine levels in mycosis fungoides.

Mycosis fungoides (MF) is characterised by malignant CD4+ T-cell infiltrates in the skin. The functional characteristics of the malignant T cells and their interaction with the tumor immune microenvironment is largely unknown. We performed tape stripping of the stratum corneum (SC), a non-invasive technique, to gain insight into the cytokine secretion patterns in MF skin lesions. In addition, we assessed whether the SC cytokine profile of MF lesions is distinct from that of atopic dermatitis (AD) lesions. We compared nine cytokine levels in 20 patients with MF, 10 patients with AD and 10 healthy controls. In patients with MF and AD, lesional SC levels of IL-8 and MMP9 were significantly higher than in non-lesional SC and in healthy controls. VEGFα was significantly higher in lesional MF and AD skin than in healthy controls. The SC levels of IL-1α were significantly lower in MF and AD lesions than in healthy controls. There was no specific cytokine profile or inflammation pattern that could reliably distinguish MF from AD. In conclusion, in lesional SC of MF patients, pro-inflammatory cytokines can be detected. As a diagnostic method, tape stripping of lesional SC cannot discriminate MF skin from AD skin.

Detection of cutaneous malignant melanoma by tape stripping of pigmented skin lesions - A systematic review.

BACKGROUND: Cutaneous malignant melanoma (MM) is potentially aggressive, and numerous clinically suspicious pigmented skin lesions are excised, causing unnecessary mutilation for patients at high healthcare costs, but without histopathological evidence of MM. The high number of excisions may be lowered by using more accurate diagnostics. Tape stripping (TS) of clinically suspicious lesions is a non-invasive diagnostic test of MM that can potentially lower the number needed to biopsy/excise. MATERIALS AND METHODS: The aim is to determine the diagnostic accuracy of TS in detecting MM in clinically suspicious pigmented skin lesions. This systematic review following PRISMA guidelines searched PubMed, Web of Science, and Embase (September 2022) using melanoma combined with tape stripping, adhesive patch(es), pigmented lesion assay, or epidermal genetic information retrieval. RESULTS: Ten studies were included. Sensitivity ranged from 68.8% (95% confidence interval [CI] 51.5, 82.1) to 100% (95% CI 91.0, 100). Specificity ranged from 69.1% (95% CI 63.8, 74.0) to 100% (95% CI 78.5, 100). A pooled analysis of five studies testing the RNA markers LINC00518 and PRAME found a sensitivity of 86.9% (95% CI 81.7, 90.8) and a specificity of 82.4% (95% CI 80.8, 83.9). CONCLUSION: Overall quality of studies was low, and the reliability of sensitivity and specificity is questionable. However, TS may supplement well-established diagnostic methods as pooled analysis of five studies indicates a moderate sensitivity. Future studies are needed to obtain more reliable data as independent studies with no conflict of interest.

Epidermal biomarkers of the skin barrier in atopic and contact dermatitis.

Dysfunction of the skin barrier plays a critical role in the initiation and progression of inflammatory skin diseases, such as atopic dermatitis and contact dermatitis. Epidermal biomarkers can aid in evaluating the functionality of the skin barrier and understanding the mechanisms that underlay its impairment. This narrative review provides an overview of recent studies on epidermal biomarkers associated with the function and integrity of the skin barrier, and their application in research on atopic dermatitis and contact dermatitis. The reviewed studies encompass a wide spectrum of molecular, morphological and biophysical biomarkers, mainly obtained from stratum corneum tape strips and biopsies. Lipids, natural moisturizing factors, and structural proteins are the most frequently reported molecular biomarkers. Additionally, corneocyte surface topography and elasticity show potential as biomarkers for assessing the physical barrier of the skin. In contact dermatitis studies, biomarkers are commonly employed to evaluate skin irritation and differentiate between irritant and allergic contact dermatitis. In atopic dermatitis, biomarkers are primarily utilized to identify differences between atopic and healthy skin, for predictive purposes, and monitoring response to therapies. While this overview identifies potential biomarkers for the skin barrier, their validation as epidermal biomarkers for atopic dermatitis and contact dermatitis has yet to be established.

Tobramycin and antiglaucoma agents as increasing culprits of periorbital allergic contact dermatitis from topical ophthalmic medications: A 24-year study from Turkey.

BACKGROUND: Allergic contact dermatitis (ACD) from topical ophthalmic medications (TOMs) poses an additional disease burden to patients who already suffer from eye problems. OBJECTIVES: To investigate the epidemiological/clinical profile of patients with periorbital ACD from TOMs in Turkey. PATIENTS AND METHODS: This was a retrospective, cross-sectional, single tertiary centre study based on files of 75 patch tested patients with suspected periorbital ACD from TOMs among a total of 2801 consecutively patch tested patients with suspected ACD of any origin between 1996 and 2019. RESULTS: Periorbital ACD was diagnosed in 25 of 75 (33.3%) patients (female:male = 1.8:1; age range: 6-85 years) with suspected ACD from TOMs showing an overall prevalence of 0.9% (25/2801) among the whole patch test population. Atopy was not present. Tobramycin-containing TOMs were the most frequent culprits, followed by antiglaucoma preparations. Their frequency increased, whereas no new cases of neomycin-induced ACD were observed after 2011. Positivities with thimerosal were of unknown clinical relevance, while benzalkonium chloride (BAC) caused ACD in two patients. The diagnosis would be missed in each 20% of patients without performing day (D) 4 and D7 readings and strip-patch testing. Ten culprits were identified only by testing with patients' own TOMs in eight (32%) patients. CONCLUSIONS: Aminoglycosides, particularly tobramycin, were the leading cause of ACD from TOMs. The frequency of ACD from tobramycin and antiglaucoma medications increased after 2011. BAC was a rare but important allergen. Additional D4 and D7 readings, strip-patch testing, and testing with patients' own TOMs seem essential when patch testing with eye medications.

Altered Gene Expression of IL-35 and IL-36α in the Skin of Patients with Atopic Dermatitis.

A comprehensive understanding of atopic dermatitis (AD) pathogenesis is desired, especially in the current era of novel biologics and small molecule drugs. In recent years, new cytokines have emerged that may play a significant role in the pathogenesis of AD. Using the tape stripping (TS) method, this study analyzed the gene expression of IL-35 and IL-36α in lesional and nonlesional AD skin compared with healthy skin and their association with the clinical features of AD among the Polish population. Ten AD patients and seven healthy individuals were enrolled. The lesional skin of the AD patients showed significantly higher expression levels of IL-35 compared to healthy skin (p = 0.0001). The expression level of IL-36α was significantly higher in lesional AD skin than in nonlesional AD skin (p = 0.0039) and healthy skin (p = 0.0045). There was a significant negative correlation between AD severity and the expression level of IL-35 in both lesional (R = -0.66, p = 0.048) and nonlesional skin (R = -0.9, p = 0.0016). In summary, both IL-35 and IL-36α appear to play a role in the pathogenesis of AD. Furthermore, it might be speculated that IL-35 and IL-36α may be potential candidates for disease biomarkers. However, further studies are needed to verify these assumptions and comprehensively elucidate their importance in the pathogenesis of AD.

Recent Advances in Characterization of Melanin Pigments in Biological Samples.

The melanin pigments eumelanin (EM) and pheomelanin (PM), which are dark brown to black and yellow to reddish-brown, respectively, are widely found among vertebrates. They are produced in melanocytes in the epidermis, hair follicles, the choroid, the iris, the inner ear, and other tissues. The diversity of colors in animals is mainly caused by the quantity and quality of their melanin, such as by the ratios of EM versus PM. We have developed micro-analytical methods to simultaneously measure EM and PM and used these to study the biochemical and genetic fundamentals of pigmentation. The photoreactivity of melanin has become a major focus of research because of the postulated relevance of EM and PM for the risk of UVA-induced melanoma. Our biochemical methods have found application in many clinical studies on genetic conditions associated with alterations in pigmentation. Recently, besides chemical degradative methods, other methods have been developed for the characterization of melanin, and these are also discussed here.

Development of Essential Oil-Loaded Polymeric Nanocapsules as Skin Delivery Systems: Biophysical Parameters and Dermatokinetics Ex Vivo Evaluation.

Essential oils (EOs) are natural antioxidant alternatives that reduce skin damage. However, EOs are highly volatile; therefore, their nanoencapsulation represents a feasible alternative to increase their stability and favor their residence time on the skin to guarantee their effect. In this study, EOs of Rosmarinus officinalis and Lavandula dentata were nanoencapsulated and evaluated as skin delivery systems with potential antioxidant activity. The EOs were characterized and incorporated into polymeric nanocapsules (NC-EOs) using nanoprecipitation. The antioxidant activity was evaluated using the ferric thiocyanate method. The ex vivo effects on pig skin were evaluated based on biophysical parameters using bioengineering techniques. An ex vivo dermatokinetic evaluation on pig skin was performed using modified Franz cells and the tape-stripping technique. The results showed that the EOs had good antioxidant activity (>65%), which was maintained after nanoencapsulation and purification. The nanoencapsulation of the EOs favored its deposition in the stratum corneum compared to free EOs; the highest deposition rate was obtained for 1,8-cineole, a major component of L. dentata, at 1 h contact time, compared to R. officinalis with a major deposition of the camphor component. In conclusion, NC-EOs can be used as an alternative antioxidant for skin care.

Assessment of penetration and permeation of caffeine by confocal Raman spectroscopy in vivo and ex vivo by tape stripping.

OBJECTIVE: Tape stripping is an often-used non-invasive destructive method to investigate the skin penetration of a substance. In recent years, however, the suitability of confocal Raman spectroscopy (CRS) as a non-invasive method of non-destructive examination of the skin has become increasingly apparent. In this study, we compared invasion and depletion penetration and permeation kinetics of a 2% caffeine solution with and without 1,2-pentanediol as a penetration enhancer measured with CRS and tape stripping. METHODS: Porcine skin was used for tape stripping and human skin for CRS. 2% caffeine solution was applied to the skin for different incubation times. Human skin was then examined by CRS while caffeine was extracted from porcine skin and quantified via reverse-phase HPLC. Fluxes were also measured and calculated by sum of the total amounts of caffeine penetrated into the skin. RESULTS: Without penetration enhancers, there is hardly any difference between the penetration profiles of the two measurement methods for invasion, but the curves for depletion are different. Furthermore, the calculated flux values for the invasion are almost identical, but for the depletion the tape stripping values are about twice as high as the CRS values. CONCLUSION: The relevance of conducting invasion and depletion studies became clear and was able to show the still existing problems in the comparability of CRS and tape stripping.

OBJECTIF: Le décapage au ruban adhésif est une méthode destructive non invasive fréquemment utilisée pour examiner la pénétration cutanée d'une substance. Cependant, ces dernières années, la pertinence de la spectroscopie raman confocale, une méthode non invasive pour examiner la peau de manière non destructive, a été de plus en plus mise en évidence. Dans cette étude, nous avons comparé les cinétiques d'invasion et de déplétion de la pénétration et de la perméation d'une solution de caféine à 2 % avec et sans 1,2-pentanediol en tant qu'amplificateur de pénétration, mesurées par spectroscopie raman confocale et par décapage au ruban adhésif. MÉTHODES: La peau de porc a été utilisée pour le décapage au ruban adhésif et la peau humaine pour la spectroscopie raman confocale. Une solution de caféine à 2 % a été appliquée sur la peau pendant différents temps d'incubation. La peau humaine a ensuite été examinée par spectroscopie raman confocale tandis que la caféine a été extraite de la peau porcine et quantifiée par HPLC en phase inverse. Les flux ont également été mesurés et calculés par la somme des quantités totales de caféine ayant pénétré dans la peau. RÉSULTATS: Sans amplificateurs de pénétration, il n'y a presque aucune différence entre les profils de pénétration des deux méthodes de mesure pour l'invasion, mais les profils pour la déplétion sont différents. De plus, les valeurs de flux calculées pour l'invasion sont presque identiques, mais pour la déplétion, les valeurs de ruban adhésif sont environ deux fois plus élevées que les valeurs CRS. CONCLUSION: La pertinence de conduire des études d'invasion et de déplétion est devenue claire et a pu montrer les problèmes toujours existants dans la comparabilité du CRS et du décapage au ruban adhésif.

A controlled forearm washing ex vivo method for assessing the impact of personal cleansing products on skin's acid mantle properties and antimicrobial defence against transient bacteria.

BACKGROUND: An important trend in the personal care industry involves the development of advanced personal cleaning products that not only provide skin mildness but support skin's acid mantle properties and skin's natural antimicrobial defence function. OBJECTIVE: The objective of this study was to develop a controlled forearm washing ex vivo method for assessing the impact of personal cleansing products on skin's acid mantle properties and antimicrobial defence against transient bacteria. METHODS: We developed a controlled forearm washing ex vivo method (ex vivo NET method) to compare the impact of two representative personal cleansing products on skin's acid mantle properties and antimicrobial defence against transient bacteria: one was a low-pH skin cleanser, and the other was high-pH soap cleanser. Skin pH was measured at baseline and 4 h after the product application. Concurrently, D-squame tape stripping procedure was followed to sample the stratum corneum surface layers. Then, two selected transient bacteria, Staphylococcus aureus and Escherichia coli, were inoculated onto the D-squame tapes and incubated under controlled conditions, respectively. The residual bacteria counts can provide an objective measure of skin's acid mantle properties against transient bacteria. Results from the ex vivo NET method were compared with the traditional in vivo cup-scrub RET method. RESULTS: The skin pH was significantly lower 4 h after washing the forearm with the low-pH cleanser versus the high-pH soap, consistent with literatures. Interestingly, the skin surface washed by the low-pH cleanser showed significantly higher hostility against representative transient bacteria as demonstrated by the lower counts of S. aureus by 1.09 log and E. coli by 0.6 log versus the high-pH soap based on the ex vivo NET method. Results from the ex vivo NET method were further supported by the traditional in vivo RET method which also showed the skin washed by the low-pH cleanser had significantly lower counts of S. aureus and E. coli versus the high-pH soap. CONCLUSIONS: The skin's acid mantle properties and antimicrobial defence can be directly impacted by the personal cleansing products. The low-pH skin cleanser works better than the high-pH soap for supporting skin's acid mantle properties and antimicrobial defence against transient bacteria. Results from the ex vivo NET method are consistent with the in vivo RET method. It is important that the ex vivo NET method offers many advantages since it is quicker to run with higher throughput and has better safety without the constraint of inoculating harmful microorganisms onto the human subjects.

CONTEXTE: Une tendance importante du secteur des soins personnels est de développer des produits d'hygiène personnelle sophistiqués qui non seulement rendent la peau plus douce, mais favorisent également les propriétés du manteau acide de la peau et la fonction de défense antimicrobienne naturelle de la peau. OBJECTIF: L'objectif de cette étude était de développer une méthode ex vivo de lavage contrôlé des avant-bras pour évaluer l'impact des produits d'hygiène personnelle sur les propriétés du manteau acide de la peau et la défense antimicrobienne contre les bactéries transitoires. MÉTHODES: Nous avons développé une méthode ex vivo de lavage contrôlé des avant-bras (méthode NET ex vivo) pour comparer l'impact de deux produits d'hygiène personnelle représentatifs sur les propriétés du manteau acide de la peau et la défense antimicrobienne contre les bactéries transitoires: d'une part un nettoyant pour la peau à pH faible, d'autre part un savon nettoyant à pH élevé. Le pH de la peau a été mesuré à l'entrée dans l'étude et quatre heures après l'application du produit. Parallèlement, une procédure de stripping par ruban adhésif D-Squame a été suivie pour prélever des couches de surface de la couche cornée. Ensuite, deux bactéries transitoires sélectionnées, S. aureus et E. coli, ont été inoculées sur les rubans adhésifs D-Squame et incubées dans des conditions contrôlées, respectivement. Le nombre de bactéries résiduelles peut fournir une mesure objective des propriétés du manteau acide de la peau contre les bactéries transitoires. Les résultats de la méthode NET ex vivo ont été comparés à la méthode RET in vivo traditionnelle par coupe-grattage. RÉSULTATS: Le pH de la peau était significativement inférieur quatre heures après le lavage des avant-bras avec le nettoyant à pH faible en comparaison avec le savon à pH élevé, conformément à la littérature. Il est intéressant de noter que la surface de la peau lavée au moyen du nettoyant à pH faible présentait une hostilité significativement plus élevée contre les bactéries transitoires représentatives, comme démontré par le nombre inférieur de S. aureus de 1,09 log et d'E. coli de 0,6 log, en comparaison avec le savon à pH élevé, sur base de la méthode NET ex vivo. Les résultats de la méthode NET ex vivo ont été encore par la méthode RET in vivo traditionnelle, laquelle a également démontré que la peau lavée à l'aide du nettoyant à pH faible présentait des nombres significativement plus faibles de S. aureus et d'E. coli que celle lavée à l'aide du savon à pH élevé. CONCLUSIONS: Les propriétés du manteau acide de la peau et la défense antimicrobienne peuvent être directement affectées par les produits d'hygiène personnelle. Le nettoyant de la peau à pH faible fonctionne mieux que le savon à pH élevé pour ce qui est de favoriser les propriétés du manteau acide de la peau et la défense antimicrobienne contre les bactéries transitoires. Les résultats de la méthode NET ex vivo sont cohérents avec la méthode RET in vivo. Il est important de noter que la méthode NET ex vivo offre de nombreux avantages étant donné qu'elle est plus rapide à exécuter avec une capacité plus élevée et offre une meilleure sécurité sans la contrainte d'inoculer des micro-organismes nocifs à des sujets humains.

Ceramide Analysis in Combination With Genetic Testing May Provide a Precise Diagnosis for Self-Healing Collodion Babies.

Self-healing collodion baby (SHCB), also called "self-improving collodion baby", is a rare mild variant of autosomal recessive congenital ichthyosis and is defined as a collodion baby who shows the nearly complete resolution of scaling within the first 3 months to 1 year of life. However, during the neonatal period, it is not easy to distinguish SHCB from other inflammatory forms of autosomal recessive congenital ichthyosis, such as congenital ichthyosiform erythroderma. Here, we report a case study of two Japanese SHCB patients with compound heterozygous mutations, c.235G>T (p.(Glu79∗))/ c.1189C>T (p.(Arg397Cys)) and c.1295A>G (p.(Tyr432Cys))/ c.1138delG (p.(Asp380Thrfs∗3)), in CYP4F22, which encodes cytochrome P450, family 4, subfamily F, polypeptide 22 (CYP4F22). Immunohistochemically, inflammation with the strong expression of IL-17C, IL-36γ, and TNF-α was seen in the skin at birth. CYP4F22 is an ultra-long-chain FA ω-hydroxylase responsible for ω-O-acylceramide (acylceramide) production. Among the epidermal ceramides, acylceramide is a key lipid in maintaining the epidermal permeability barrier function. We found that the levels of ceramides with ω-hydroxy FAs including acylceramides and the levels of protein-bound ceramides were much lower in stratum corneum samples obtained by tape stripping from SHCB patients than in those from their unaffected parents and individuals without SHCB. Additionally, our cell-based enzyme assay revealed that two mutants, p.(Glu79∗) and p.(Arg397Cys), had no enzyme activity. Our findings suggest that genetic testing coupled with noninvasive ceramide analyses using tape-stripped stratum corneum samples might be useful for the early and precise diagnosis of congenital ichthyoses, including SHCB.

Investigator Impact on Reproducibility of Drug Bioavailability in Stratum Corneum Sampling by Tape Stripping.

PURPOSE: Skin sampling by tape stripping measures the local bioavailability of topical drug products in the stratum corneum (SC). The goal of the current study was to evaluate the impact of different investigators in studies that utilize a tape stripping protocol designed to minimize investigator variability. METHODS: Two open-label clinical studies compared two lidocaine patches and a diclofenac patch and solution in twelve healthy volunteers. The mass of drug was determined in SC samples collected on tape strips at three time points following product removal in duplicate by two investigators. Investigator results were compared with each other and with results for the diclofenac solution measured by another laboratory using a similar protocol. RESULTS: For drug mass, the geometric mean ratio comparing two investigators is within the acceptable bioequivalence interval for most measurement times and drug products. Drug uptake into the SC from the diclofenac solution was not statistically different from that determined in another laboratory. The average flux from the SC over the clearance intervals for the four drug products correspond well with flux measurements from in vitro permeation tests. CONCLUSIONS: Results from different investigators are reproducible within the limitations of measurement variability, which can be managed by increasing volunteer numbers.

In-Vivo Tape Stripping Study with Caffeine for Comparisons on Body Sites, Age and Washing.

PURPOSE: Assessing the percutaneous absorption of cosmetic ingredients using in-vitro human skin reveals certain limitations, such as restricted anatomical sites and repeated exposure, and to overcome these issues, in-vivo studies are required. The aim of the study is to develop a robust non-invasive in-vivo protocol that should be applicable to a wide range of application. METHODS: A robust tape stripping protocol was therefore designed according to recent recommendations, and the impact of two different washing procedures on caffeine distribution in tape strips was investigated to optimise the protocol. The optimised protocol was then used to study the effect of age and anatomical area on the percutaneous absorption of caffeine, including facial areas which are not readily available for in-vitro studies. RESULTS: With tape stripping, a difference between the percutaneous absorption on the face (forehead, cheek) and the volar forearm was observed. No obvious difference was observed between percutaneous absorption in young and post-menopausal women, but this could be due to the limited number of subjects. CONCLUSION: This tape stripping protocol is now to be deployed to address many other factors, such as percutaneous absorption in other anatomical areas (e.g. abdomen, axilla, etc.), impact of repeated applications and effect of formulation.

Melanoma: How and when to consider clinical diagnostic technologies.

In response to rising rates of melanoma worldwide, novel noninvasive melanoma detection techniques are emerging to facilitate the early detection of melanoma and decrease unnecessary biopsies of benign pigmented lesions. Because they often report similar study findings, it may be difficult to determine how best to incorporate these technologies into clinical practice based on their supporting studies alone. The first article in this continuing medical education series provides practical advice on how and when to use various noninvasive melanoma detection techniques in clinical practice.

Characterization and ex vivo evaluation of excised skin samples as substitutes for human dermal barrier in pharmaceutical and dermatological studies.

BACKGROUND: Excised animal and human skins are frequently used in permeability testing in pharmaceutical research. Several factors exist that may have influence on the results. In the current study some of the skin parameters that may affect drug permeability were analysed for human, mouse, rat and pig skin. MATERIALS AND METHODS: Classic biophysical skin parameters were measured (e.g. pH, hydration, permittivity, transepidermal water loss). Physiological characteristics of the skins were also analysed by confocal Raman spectroscopy, scanning electron microscopy and two-photon microscopy. RESULTS: Based on biophysical testing, skin barrier function was damaged in psoriatic mouse skin and in marketed pig skin. Hydration and pH values were similar among the species, but freezing and thawing reduced the water content of the skins and shifted the surface pH to acidic. Aging reduced hydration and permittivity, resulting in impaired barrier function. Mechanical sensitization used in permeability studies resulted in proportional thinning of dead epidermis. DISCUSSION: Results indicate that depending on the scientific question it should be considered whether fresh or frozen tissue is used, and for certain purposes rodent skins are well usable. The structure of the skin tissue (ceramide, cholesterol, keratin, natural moisturizing factor or urea) is similar in rats and mice, but due to the higher skin thickness the lipid distribution is different in porcine skin. Psoriasis led to irregular chemical composition of the skin. CONCLUSION: A comprehensive evaluation of skin samples of four species was performed. The biophysical and microscopic observations should be considered when selecting drug penetration models and experimental conditions.

The transcriptome of hand eczema assessed by tape stripping.

BACKGROUND: No biomarkers have been identified that can classify subtypes of hand eczema (HE). Although skin biopsies represent the gold standard for investigations of the skin, the invasive technique is not favorable when investigating skin from sensitive areas. Recent advances in the use of skin-tape strips for molecular investigations enable noninvasive investigations of HE. OBJECTIVE: By using whole transcriptome sequencing (WTS), the molecular profile of HE according to different localizations on the hands, etiologies, and clinical/morphological subtypes was investigated. METHODS: Thirty adult, Danish HE patients, 12 with and 18 without concurrent atopic dermatitis (AD), as well as 16 controls were included. Tape strip samples were collected from lesional, nonlesional, and healthy skin. Total RNA was extracted and WTS was performed. RESULTS: The largest molecular difference of HE patients with and without AD was found in nonlesional skin areas and included a downregulation of CXCL8 for HE patients without AD. Differences between allergic and irritant contact dermatitis included epidermal biomarkers such as EPHA1. CONCLUSION: Skin tape strip samples could be used to assess the gene expression profile of HE on different localizations of the hands. The skin tape strip method identified new molecular markers that showed promising result for the identification of HE subtypes.

Challenges in Noninvasive Skin Biomarker Measurements in Daily Practice: A Longitudinal Study on Skin Surface Protein Detection by the Transdermal Analysis Patch in Pediatric Psoriasis.

INTRODUCTION: Skin surface proteins are potential biomarkers in psoriasis and can be measured noninvasively with the transdermal analysis patch (TAP). This study aimed to assess markers measured by TAP over time in daily clinical practice, explore their correlation with disease severity in pediatric psoriasis, and compare the TAP and tape stripping detection capability. METHODS: In this prospective observational daily clinical practice study, pediatric psoriasis patients (aged >5 to <18 years) were followed during 1 year. At each visit, TAPs were applied to lesional (n = 2), peri-lesional (n = 2), and non-lesional (n = 1) sites. Post-lesional skin was sampled if all lesions on the arms, legs, or trunk cleared. Treatment and psoriasis severity data were collected. IL-1RA, hBD-2, IL-1α, IL-8, VEGF, CXCL-1/2, CCL-27, IL-23, hBD-1, IL-22, IL-17A, KLK-5, and IL-4 levels were quantified by spot-ELISA. For the statistical analysis, Wilcoxon signed rank tests, Mann-Whitney U tests, and Spearman correlations were used. Detection capability of the TAP was compared to tape stripping in a separate cohort of adult psoriasis patients. RESULTS: 32 patients (median age 15.0 years, median Psoriasis Area and Severity Index [PASI] 5.2) were followed for a mean of 11.3 (±3.4) months with a total of 104 visits. In lesional skin (n = 197), significantly higher IL-1RA, hBD-2, IL-8, VEGF, CXCL-1/2, IL-23, hBD-1, IL-22, CCL-27, and IL-17A levels were found compared to non-lesional skin (n = 104), while IL-1α was higher in non-lesional skin. Marker levels were highly variable over time and did not correlate with disease severity measured by PASI or SUM scores. Comparison of the TAP and tape strip detection capability in adult psoriasis patients (n = 10) showed that lesional hBD-2, IL1-α, IL-8, and VEGF and non-lesional IL-1RA, hBD-2, IL-8, and VEGF were more frequently detected in tape extracts than TAPs. CONCLUSION: Due to the lack of correlation with clinical disease severity and the current detection capability of the markers measured by TAP in psoriasis, its use in regular practice is still a bridge too far.

Nanoemulsions for enhanced skin permeation and controlled delivery of chlorohexidine digluconate.

Chlorhexidine digluconate (CHG) is a widely used antiseptic for skin disinfection, as it exhibits poor skin permeability. Therefore, aim of the present study was preparation and evaluation of CHG nanoemulsions (NEs) using high-speed homogenisation (HSH) combined with ultra-probe sonication to improve skin permeability. CHG-NEs were prepared using eucalyptus oil (EO) and olive oil (OO), with a surfactant-to-cosurfactant ratio of 2:1. Optimised NEs had a mean droplet diameter of 257.5 ± 12.4 nm and PDI of 0.56 ± 0.13. In In vitro permeation studies EO based NEs delivered more CHG into the skin, 6.15 ± 0.12 µg/mg compared to 3.01 ± 0.02 µg/mg for a control solution. Additionally NEs were incorporated into an in situ forming dressing and results showed controlled delivery of CHG within skin. Together, these findings bring new possibilities for topical antimicrobial treatment and prophylactic strategies in wound management.

Profiling the Atopic Dermatitis Epidermal Transcriptome by Tape Stripping and BRB-seq.

Tape stripping is a non-invasive skin sampling technique, which has recently gained use for the study of the transcriptome of atopic dermatitis (AD), a common inflammatory skin disorder characterized by a defective epidermal barrier and perturbated immune response. Here, we performed BRB-seq-a low cost, multiplex-based, transcriptomic profiling technique-on tape-stripped skin from 30 AD patients and 30 healthy controls to evaluate the methods' ability to assess the epidermal AD transcriptome. An AD signature consisting of 91 differentially expressed genes, specific for skin barrier and inflammatory response, was identified. The gene expression in the outermost layers, stratum corneum and stratum granulosum, of the skin showed highest correlation between tape-stripped skin and matched full-thickness punch biopsies. However, we observed that low and highly variable transcript counts, probably due to low RNA yield and RNA degradation in the tape-stripped skin samples, were a limiting factor for epidermal transcriptome profiling as compared to punch biopsies. We conclude that deep BRB-seq of tape-stripped skin is needed to counteract large between-sample RNA yield variation and highly zero-inflated data in order to apply this protocol for population-wide screening of the epidermal transcriptome in inflammatory skin diseases.