Epidermal barrier function in dry, flaky and sensitive skin: A narrative review.

The stratum corneum (SC)-the outermost layer of the epidermis-is the principal permeability and protective barrier of the skin. Different components of the SC, including corneocytes, natural moisturizing factor, a variety of enzymes and their inhibitors, antimicrobial peptides and lipids, work interactively to maintain barrier function. The main barrier properties of the SC are the limitation of water loss and the prevention of infection and contact with potentially harmful exogenous factors. Although the SC functions consistently as a protective barrier throughout the body, variations in functions and morphology occur across body sites with age and skin type. Healthy SC function also depends on the interplay between the chemosensory barrier, the skin's microbiome and the innate immune system. Dysregulation of SC barrier function can lead to the development of skin disorders, such as dry, flaky or sensitive skin, but the complete underlying pathophysiology of these are not fully understood. This review provides insight into the current literature and emerging themes related to epidermal barrier changes that occur in the context of dry, flaky and sensitive skin. Additional studies are needed to further elucidate the underlying aetiology of dry, flaky and sensitive skin and to provide tailored treatment.

Topical and transdermal botanical formulations of the Chinese pharmacopoeia-A review.

In pharmaceutics, ingredients are classified as active ingredients and excipients. In topical/transdermal phytomedicines, an ingredient may serve both functions. Published information on these dual-purpose ingredients and their pharmacological relevance is limited. An intriguing scenario arises in traditional Chinese medicine (TCM) formulations, where active ingredients and excipients are undifferentiated. This study analyzes ingredients in TCM topical/transdermal formulations, aiming at harmonization of understanding of TCMs. The most commonly recorded ingredients from such formulations in the Chinese pharmacopoeia 2020 (ChP 2020) are reviewed, aiming at developing innovative topical/transdermal phytomedicines. Current editions of Chinese historical documents were reviewed to explore the principles underlying the use of these ingredients. TCM formulations containing botanical drugs for topical/transdermal application were selected from the ChP 2020. The use of botanical materials in TCM formulations is guided by the "Jun-Chen-Zuo-Shi" principle rooted in Yin-Yang and the five elements' theories. In the ChP 2020, 155 botanical drugs, along with 40 excipients (from the "procedure" section, focusing on processing and technical parameters), were identified from 34 botanical formulations intended for topical/transdermal application. Pungent and aromatic botanical materials were the most frequently recorded. Adhesive plasters were the most commonly recorded TCM dosage form, employing specific matrix blends. This new perspective of study reveals the prevalence of pungent and aromatic botanical materials, the common use of adhesive plasters, multifunctional properties of botanical oils, and formulation adaptability in TCM topical/transdermal products. These insights should inform novel formulation designs for both pharmaceutical and phytopharmacological research.

The importance of stratum corneum ω-linoleoyloxyacylceramides in human skin barrier health: their biochemistry, processing enzymes and metabolites involved in corneocyte lipid envelope maturation.

Over the past 50 years there have been great strides made in the discovery of the composition and relevance of the total stratum corneum (SC) ceramide matrix. However, the focus of this review is on the free intercellular class of ω-linoleoyloxyacylceramides, corneocyte-bound ceramides and associated lipids known as the corneocyte lipid envelope (CLE) together with their processing enzymes involved in aiding ceramide attachment the corneocyte protein envelope (CPE). Two structural models and partially shared biosynthetic pathways have been proposed for the attachment of CPE-bound O-ceramides (ω-hydroxyceramides attached to glutamate residues of proteins in the (CPE) using the 12R-lipoxygenase (12R-LOX)/epidermal lipoxygenase-3 (eLOX3)/epoxide hydrolase-3 (EPHX3)/unknown esterase/ transglutaminase-1 (TG1) attachment pathway) and CPE-bound EO-ceramides (epoxy-enone ceramides attached to cysteine residues of proteins in the CPE using the 12R-LOX/eLOX3/short chain dehydrogenase/reductase family 9C member 7 (SDR9C7)/non-enzymatic attachment pathway), i.e. there is a bifurcation step beyond epidermal eLOX3. Their formation and structures will be discussed as well as their relevance in compromised skin barrier conditions together with our own work on SC maturation examined by proteomics, lipidomics, enzyme immunolocalization studies, mechanical fragility assays and Nile red staining of corneocyte envelopes (CE). Reduced levels of 12R-LOX, eLOX3, SDR9C7 and TG1 were observed in photodamaged skin of the cheeks that were associated with reduced SC maturation as evidenced by Nile red staining and increased CE fragility. In the severely photodamaged cheeks of Albino African SC we also observed increased levels of acylceramides. Concomitantly by reducing the activity of 12R-LOX by antibody inhibition and TG1 inhibition with a known chemical inhibitor, we demonstrated in a humidity-based ex vivo SC maturation model that these enzymes contributed to increased CE hydrophobicity and mechanical integrity. We hypothesize that at least the CPE-bound O-ceramide pathway is operational in the SC. Nevertheless, our understanding of the full complexity of ω-linoleoyloxyacylceramides and the composition of the CLE is limited particularly on cosmetically relevant body sites such as the face.

Ces 50 dernières années, de grandes avancées ont eu lieu dans la découverte de la composition de la matrice de céramides de toute la couche cornée et de son importance. Cependant, cette revue se concentre sur la classe intercellulaire libre des ω­linoléoyloxyacylcéramides, les céramides liés aux cornéocytes et les lipides associés appelés « enveloppe lipidique des cornéocytes ¼ (ELC), ainsi que sur leurs enzymes de transformation impliquées dans la fixation des céramides sur l'enveloppe protéique des cornéocytes (EPC). Deux modèles structurels et des voies de biosynthèse partiellement partagées ont été proposés pour la fixation des O­céramides liés à l'EPC (ω­hydroxycéramides fixés aux résidus glutamate des protéines dans l'[EPC] en utilisant la 12R­lipoxygénase [12R­LOX]/la lipoxygénase épidermique 3 [eLOX3]/l'époxyde hydrolase 3 [EPHX3]/une voie de fixation inconnue de l'estérase/de la transglutaminase 1 [TG1]) et les EO­céramides liés à l'EPC (céramides époxy­énone fixés aux résidus de cystéine des protéines de l'EPC utilisant la 12R­LOX/l'eLOX3/la déshydrogénase à chaîne courte/la réductase membre 7 de la famille 9C [SDR9C7]/une voie de fixation non enzymatique). En d'autres termes, il existe une étape de bifurcation au­delà de l'eLOX3 épidermique. Leur formation et leur structure, ainsi que leur importance dans des conditions de barrière cutanée compromises, font ici l'objet d'une discussion. Nous abordons également nos propres travaux sur la maturation de la couche cornée selon la protéomique, la lipidomique, les études d'immunolocalisation enzymatique, les tests de fragilité mécanique et la coloration au rouge du Nil des enveloppes cornées (EC). Des taux réduits de 12R­LOX, d'eLOX3, de SDR9C7 et de TG1, associés à une maturation réduite de la couche cornée, ont été observés sur la peau photo­lésée des joues, comme en témoigne la coloration au rouge du Nil et la fragilité accrue des EC. Nous avons également observé une augmentation des taux d'acylcéramides sur les joues de personnes africaines atteintes d'albinisme dont la couche cornée a été sévèrement photo­lésée. En réduisant l'activité de la 12R­LOX par inhibition des anticorps et du TG1 avec un inhibiteur chimique connu, nous avons pu démontrer, dans un modèle de maturation de la couche cornée ex vivo basé sur l'humidité, que ces enzymes contribuaient à accroître le caractère hydrophobe des EC, ainsi que leur intégrité mécanique. Nous émettons l'hypothèse qu'au moins la voie de l'O­céramide liée à l'EPC fonctionne dans la couche cornée. Néanmoins, notre compréhension de la complexité complète des ω­linoléoyloxyacylcéramides et de la composition de l'ELC reste limitée, en particulier à des parties du corps ou l'esthétique est importante, comme le visage.

Characterization of piroctone olamine for topical delivery to the skin.

OBJECTIVE: Dandruff and its more severe related condition, seborrheic dermatitis affects a high proportion of the population at some point in their life. Piroctone olamine, also known as Octopirox® (OPX) is the monoethanolamine salt of piroctone and is an antifungal agent widely used for the management of dandruff. The aim of the present work was to characterize the physicochemical properties of piroctone olamine and to conduct pre-formulation studies for the development of novel topical formulations of this active. METHODS: An HPLC method was developed and validated for the analysis of OPX. The melting point was determined using the DSC Q2000 (TA Instruments, USA). The distribution coefficient (logD(O/PBS) ) and partition coefficient (log Po/w ) was determined in phosphate-buffered saline (PBS) AND deionized (DI) water using the shake flask method. All experiments were performed at room temperature. The solubility was determined experimentally by adding amount of active to a solvent. The samples were kept at 32° ± 1°C for 48 h in a water bath. The stability of the compound was determined in a range of solvents by preparing solutions of 1 mg mL-1 in the relevant solvents. These solutions were kept and stirred throughout the experiment at 32 ± 1°C, and aliquots were taken at 24, 48 and 96 h. RESULTS: The HPLC method was developed successfully; however, samples at the lower end of the calibration curve showed lower degrees of precision and accuracy. Based on experiments with DSC, the melting point was observed at an onset temperature of 132.4°C. The LogD was determined to be 1.84. The compound had the highest solubility in methanol (278.4 mg mL-1 ) and propylene glycol (PG), with a value of 248.8 mg mL-1 . The lowest solubility for OPX was in dimethyl isosorbide (9.9 mg mL-1 ), Labrafac™ (3.6 mg mL-1 ) and isostearyl isostearate (0.5 mg mL-1 ). Over the 4 days, OPX showed stability in ethanol and PG, while a notable decrease in OPX was observed in PBS and DI water at 32 ± 1°C. CONCLUSION: The physicochemical properties of OPX were characterized to find suitable excipients able to target the epidermis for topical delivery. Building on these findings, future work will focus on the development of novel topical formulation of OPX.

OBJECTIF: la production de pellicules et la maladie plus grave qui y est apparentée, la dermatite séborrhéique, touchent une grande partie des personnes à un moment donné de leur vie. La piroctone olamine, également connue sous le nom d'Octopirox® (OPX), est le sel de monoéthanolamine de la piroctone. Il s'agit d'un agent antifongique largement utilisé pour le traitement des pellicules. L'objectif de ce travail était de caractériser les propriétés physicochimiques de la piroctone olamine et de mener des études de préformulation pour le développement de nouvelles formulations topiques de ce principe actif. MÉTHODES: une méthode de chromatographie liquide à haute performance (CLHP) a été développée et validée pour l'analyse de l'OPX. Le point de fusion a été déterminé à l'aide du calorimètre à balayage différentiel (Differential Scanning Calorimetry, DSC) Q2000 (TA Instruments, États-Unis). Le coefficient de distribution (logD(Octanol/PBS) ) et le coefficient de partage (log Poctanol/eau , ou log Poe ) ont été déterminés dans le tampon phosphate salin (phosphate buffered saline, PBS) et dans l'eau désionisée (deionised, DI) à l'aide de la méthode par agitation en flacon. Toutes les expériences ont été réalisées à température ambiante. La solubilité a été déterminée de manière expérimentale. Une certaine quantité du principe actif a été ajoutée au solvant. Les échantillons ont été conservés à une température de 32 °C ± 1 °C pendant 48 h dans un bain-marie. La stabilité du composé a été déterminée à l'aide d'une gamme de solvants. Des solutions de 1 mg mL−1 ont été préparées dans les solvants correspondants. Les solutions ont été conservées et agitées tout au long de l'expérience à une température de 32°C ± 1°C. Des aliquotes ont été prélevées après 24, 48 et 96 h. RÉSULTATS: la méthode CLHP a été développée avec succès. Toutefois, les échantillons situés dans la partie inférieure de la courbe d'étalonnage ont montré des degrés inférieurs de précision et d'exactitude. Sur la base des expériences avec le DSC, le point de fusion a été observé à une température initiale de 132,4°C. Le LogD a été déterminé à 1,84. Le composé présentait la solubilité la plus élevée dans le méthanol (278,4 mg mL−1 ) et le propylène glycol (PG), avec une valeur de 248,8 mg mL−1 . L'OPX présentait la solubilité la plus faible dans l'isosorbide de diméthyle (9,9 mg.mL−1 ), le LabrafacTM (3,6 mg mL−1 ) et l'isostéarate d'isostéaryle (0,5 mg mL−1 ). Sur les 4 jours, l'OPX a montré une stabilité dans l'éthanol et le PG, tandis qu'il a diminué de manière notable dans le PBS et l'eau désionisée à une température de 32°C ± 1°C. CONCLUSION: les propriétés physicochimiques de l'OPX ont été caractérisées afin de trouver des excipients appropriés capables de cibler l'épiderme dans le cadre d'une administration topique. En s'appuyant sur ces résultats, les travaux futurs se concentreront sur le développement d'une nouvelle formulation topique de l'OPX.

Investigation of piroctone olamine delivery to the skin from single, binary and ternary solvent systems.

OBJECTIVE: Disruption of the protective stratum corneum barrier increases the skin's vulnerability to microorganisms and facilitates conditions such as dandruff. Dandruff is a disorder of the scalp that causes increased scaling of the SC and is associated with Malassezia fungus. Consequently, many anti-dandruff commercial products use anti-fungal active ingredients such as piroctone olamine also known as Octopirox (OPX). OPX is an active ingredient used in a number of topical preparations for the management of dandruff. The characterization of the physicochemical properties of OPX was previously reported. The aim of the present work was to investigate a range of solvent systems for their effects on OPX interaction with human skin. METHODS: The solvents used in this study were propylene glycol (PG), diethylene glycol monoethyl ether or Transcutol® (TC), PG monolaurate (PGML), isopropyl myristate (IPM), caprylic/capric triglyceride or Labrafac™ Lipophile WL 1349 (LAB), PG caprylate or Capryol® 90 (CAP), isostearyl isostearate (ISIS) and Plurol® Oleique CC 497 (PIOI). The single solvent systems evaluated were PG, TC, PGML, IPM, ISIS and CAP. For the binary solvent systems, PG and TC were examined. Ternary solvent systems consisted of: PG, TC and LAB; PG, PGML and LAB; and PG, TC and IPM. The concentration of OPX used was 1% (w/v). Heat-separated human epidermis was used for 24 h permeation experiments performed under finite dose conditions; mass balance studies were also conducted. RESULTS: For the six single solvents examined no permeation was evident. Skin permeation of OPX was observed for binary and ternary solvent systems. The highest permeation for all PG:TC binary solvent system ratios tested was from the PG:TC (75:25) system. For the ternary solvent systems investigated, highest cumulative permeation of OPX was observed for PG:PGML:LAB (60:30:10). Considering all systems, PG:TC (75:25) delivered the greatest amount of OPX through the skin. Although OPX is deposited in the skin following the application of neat solvents, higher skin retention values were generally observed for binary and ternary systems. CONCLUSION: To our knowledge, this is the first study to examine the permeation behaviour of OPX for a range of single, binary and ternary solvent systems.

OBJECTIF: La perturbation de la barrière protectrice de la couche cornée augmente la vulnérabilité de la peau aux micro-organismes et facilite des affections telles que les pellicules. Les pellicules sont un trouble du cuir chevelu qui provoque une augmentation de la desquamation de la couche cornée et qui est associé au champignon Malassezia. Par conséquent, de nombreux produits commerciaux antipelliculaires utilisent des principes actifs antifongiques, tels que la piroctone olamine, également appelée Octopirox (OPX). L'OPX est un principe actif utilisé dans un certain nombre de préparations topiques pour la prise en charge des pellicules. La caractérisation des propriétés physicochimiques de l'OPX a été précédemment rapportée. L'objectif de ce travail était d'étudier un éventail de systèmes de solvants pour leurs effets sur l'interaction de l'OPX avec la peau humaine. MÉTHODES: Les solvants utilisés dans cette étude étaient le propylène glycol (PG), l'éther monoéthylique de diéthylèneglycol ou Transcutol® (TC), le monolaurate de propylène glycol (PGML), le myristate d'isopropyle (IPM), le triglycéride caprylique/caprique ou Labrafac™ lipophile WL 1349 (LAB), le caprylate de propylène glycol ou Capryol® 90 (CAP), l'isostéarate d'isostéaryle (ISIS) et Plurol® Oleique CC 497 (PIOI). Les systèmes à solvant unique évalués étaient le PG, le TC, le PGML, l'IPM, l'ISIS et le CAP. Pour les systèmes de solvants binaires, le PG et le TC ont été examinés. Les systèmes de solvants ternaires comprenaient : PG, TC et LAB ; PG, PGML et LAB ; et PG, TC et IPM. La concentration d'OPX utilisée était de 1 % (p/v). L'épiderme humain séparé par la chaleur a été utilisé pour des expériences de perméation de 24 heures réalisées dans des conditions de dose finie ; des études d'équilibre de masse ont également été menées. RÉSULTATS: Pour les six solvants uniques examinés, aucune perméation n'était manifeste. Une perméation cutanée de l'OPX a été observée pour les systèmes de solvants binaires et ternaires. La perméation la plus élevée pour tous les rapports du système de solvant binaire PG:TC testés a été obtenue avec le système PG:TC (75:25). Pour les systèmes de solvants ternaires étudiés, la perméation cumulée la plus élevée d'OPX a été observée pour PG:PGML:LAB (60:30:10). Parmi tous les systèmes, PG:TC (75:25) a délivré la plus grande quantité d'OPX à travers la peau. Bien que l'OPX se dépose dans la peau après l'application de solvants purs, des valeurs de rétention cutanée plus élevées ont généralement été observées pour les systèmes binaire et ternaire. CONCLUSION: À notre connaissance, il s'agit de la première étude visant à examiner le comportement de perméation de l'OPX pour un éventail de systèmes de solvants uniques, binaires et ternaires.

A comparison of the in vitro permeation of 3-O-ethyl-l-ascorbic acid in human skin and in a living skin equivalent (LabSkin™).

OBJECTIVES: The safety assessment of personal care products often entails determining dermal absorption of their ingredients. Such experiments are typically performed in human or animal skin in vitro; however, ethical and safety considerations are associated with obtaining these tissues. Several human skin equivalent models (HSEs) have been developed as alternatives to human tissue. The barrier function of such models however, is normally less developed than human skin. Here, we examine the permeability of the HSE LabSkinTM to a model compound, 3-O-ethyl-l-ascorbic acid (EA) compared with human skin. METHODS: Skin uptake and permeation of EA was investigated in vitro using heat-separated human epidermis and LabSkinTM . Finite dose (5 µL cm-2 ) Franz-diffusion studies were conducted using 2 % (w/w) EA in a ternary solvent mixture comprising propylene glycol (PG), propylene glycol monolaurate (PGML), and isopropyl myristate (IPM). These excipients are commonly used in cosmetic products and they have been reported to promote permeation of EA in a different model, namely porcine skin. RESULTS: Permeation of EA through LabSkinTM was evident from 2 h; however, EA permeation in human skin was not detected until 5 h. Similar amounts of EA permeated through the two membranes at time points 8, 10, 12 and 24 h (p > 0.05). The cumulative amounts of EA delivered through LabSkinTM at 24 h were 41.3 ± 2.0 µg cm-2 , corresponding to 55.1 ± 1.8 % of the applied dose. Similar amounts permeated across human skin, 49.4 ± 4.1 µg cm-2 , accounting for 58.0 ± 4.2 % of the dose applied (p > 0.05). CONCLUSION: The permeation of EA in LabSkinTM compared well with results for human epidermis in terms of the permeation profiles and the cumulative amounts of EA that permeated. The data suggest that the skin barrier of the two models was similar with regard to their overall permeability to the hydrophilic active EA. The findings are promising for the use of LabSkinTM as a surrogate for human skin in permeability testing. Future studies will focus on exploring the reproducibility and robustness of LabSkinTM for delivery of other actives that span a range of physicochemical properties.

OBJECTIFS: L'évaluation de la sécurité des produits de soins personnels implique souvent de déterminer l'absorption cutanée de leurs ingrédients. Ces expérimentations sont généralement réalisées in vitro sur la peau humaine ou animale ; cependant, des considérations éthiques et de sécurité sont associées à l'obtention de ces tissus. Plusieurs modèles équivalents de peau humaine (Human Skin Equivalent, HSE) ont été développés comme alternatives au tissu humain. La fonction barrière de ces modèles est cependant normalement moins développée que la peau humaine. Ici, nous examinons la perméabilité du HSE LabSkin™ à un composé modèle, l'acide 3-O-éthyl-l-ascorbique (EA) en le comparant à la peau humaine. MÉTHODES: L'absorption cutanée et la perméation de l'EA ont été étudiées in vitro à l'aide d'épiderme humain séparé par la chaleur et de LabSkin™. Des études de diffusion de Franz à dose limitée (5 µL cm-2 ) ont été réalisées en utilisant 2 % (p/p) d'EA dans un mélange de solvant ternaire contenant du propylène glycol (PG), du propylène glycol monolaurate (PGML) et du myristate d'isopropyle (IPM). Ces excipients sont fréquemment utilisés dans les produits cosmétiques et il a été rapporté qu'ils favorisent la perméation de l'EA dans un modèle différent, à savoir la peau porcine. RÉSULTATS: La perméation de l'EA par LabSkin™ était évidente dès 2 h ; cependant, la perméation de l'EA dans la peau humaine n'a pas été détectée avant 5 h. Des quantités similaires d'EA ont pénétré les deux membranes aux points temporels 8, 10, 12 et 24 h (p > 0,05). Les quantités cumulées d'EA délivrées par LabSkin™ à 24 h étaient de 41,3 ± 2,0 µg cm-2 , correspondant à 55,1 ± 1,8 % de la dose appliquée. Des quantités similaires ont pénétré la peau humaine, 49,4 ± 4,1 µg cm-2 , représentant 58,0 ± 4,2 % de la dose appliquée (p > 0,05). CONCLUSION: La perméation de l'EA dans LabSkin™ a bien soutenu la comparaison quant aux résultats concernant l'épiderme humain en termes de profils de perméation et de quantités cumulées d'EA qui ont pénétré. Les données suggèrent que la barrière cutanée des deux modèles était similaire en ce qui concerne leur perméabilité globale à l'EA hydrophile actif. Les résultats sont prometteurs pour l'utilisation de LabSkin™ en tant que substitut de la peau humaine dans les tests de perméabilité. Les études futures se concentreront sur l'exploration de la reproductibilité et de la robustesse de LabSkin™ pour la délivrance d'autres principes actifs qui couvrent un éventail de propriétés physicochimiques.

Monitoring Drug Crystallization in Percutaneous Penetration Using Localized Nanothermal Analysis and Photothermal Microspectroscopy.

Drug crystallization on and in the skin has been reported following application of topical or transdermal formulations. This study explored novel probe-based approaches including localized nanothermal analysis (nano-TA) and photothermal microspectroscopy (PTMS) to investigate and locate drug crystals in the stratum corneum (SC) of porcine skin following application of simple ibuprofen (IBU) formulations. We also conducted in vitro skin permeation studies and tape stripping. The detection of drug crystals in the SC on tape strips was confirmed using localized nano-TA, based on the melting temperature of IBU. The melting of IBU was also evident as indicated by a double transition and confirmed the presence of drug crystals in the SC. The single point scans of PTMS on the tape strips allowed collection of the photothermal FTIR spectra of IBU, confirming the existence of drug crystals in the skin. The combined methods also indicated that drug crystallized in the SC at a depth of ∼4-7 µm. Future studies will examine the potential of these techniques to probe crystallization of other commonly used actives in topical and transdermal formulations.

Use of buccal morphine in the management of pain in children with life-limiting conditions: Results of a laboratory study.

BACKGROUND: Children and infants with impaired swallow or compromised enteral absorption require alternative routes for administration of analgesia. Recent clinical guidance and practice for paediatric palliative care teams, who often treat such children, supports buccal morphine sulphate as a fast acting, effective and easily administered agent for pain relief. However, a consideration of the physicochemical properties and potency of morphine would suggest that it is not a suitable candidate for delivery via the transmucosal route, raising questions about its use in children and infants. AIM: To explore the permeability of buccal morphine sulphate in an established ex vivo porcine buccal mucosa as a necessary step in examining efficacy for use in children with life-limiting conditions and life-threatening illnesses. DESIGN: A permeation study conducted with morphine sulphate in an ex vivo porcine buccal tissue model. Flux values and pharmacokinetic data were used to calculate the plasma values of morphine that would result following buccal administration in a 20kg child. RESULTS: Results show that the estimated steady state plasma values of morphine sulphate following buccal administration in this model do not achieve minimum therapeutic concentration. CONCLUSION: These data strongly suggest that morphine sulphate is not suitable for buccal administration and that further research is needed to establish its efficacy in relief of pain in children with life-limiting conditions and life-threatening illnesses.

Caffeic acid phenethyl ester is protective in experimental ulcerative colitis via reduction in levels of pro-inflammatory mediators and enhancement of epithelial barrier function.

BACKGROUND: Inhibition of the nuclear factor kappa beta (NF-κß) pathway has been proposed as a therapeutic target due to its key role in the expression of pro-inflammatory genes, including pro-inflammatory cytokines, chemokines, and adhesion molecules. Caffeic acid phenethyl ester (CAPE) is a naturally occurring anti-inflammatory agent, found in propolis, and has been reported as a specific inhibitor of NF-κß. However, the impact of CAPE on levels of myeloperoxidases (MPO) and pro-inflammatory cytokines during inflammation is not clear. The aims of this study were to investigate the protective efficacy of CAPE in the mouse model of colitis and determine its effect on MPO activity, pro-inflammatory cytokines levels, and intestinal permeability. METHOD: Dextran sulphate sodium was administered in drinking water to induce colitis in C57/BL6 mice before treatment with intraperitoneal administration of CAPE (30 mg kg-1 day-1). Disease activity index (DAI) score, colon length and tissue histology levels of MPO, pro-inflammatory cytokines, and intestinal permeability were observed. RESULTS: CAPE-treated mice had lower DAI and tissue inflammation scores, with improved epithelial barrier protection and significant reduction in the level of MPO and pro-inflammatory cytokines. CONCLUSION: Our results show that CAPE is effective in suppressing inflammation-triggered MPO activity and pro-inflammatory cytokines production while enhancing epithelial barrier function in experimental colitis. Thus, we conclude that CAPE could be a potential therapeutic agent for further clinical investigations for treatment of inflammatory bowel diseases in humans.

Developing Transdermal Applications of Ketorolac Tromethamine Entrapped in Stimuli Sensitive Block Copolymer Hydrogels.

PURPOSE: In order to obtain dermal vehicles of ketorolac tromethamine (KT) for the local treatment of inflammation and restrict undesirable side effects of systemic levels hydrogels (HGs) of poloxamer and carbomer were developed. METHODS: KT poloxamer based HG (KT-P407-HG) and KT carbomer based HG (KT-C940-HG) were elaborated and characterized in terms of swelling, degradation, porosity, rheology, stability, in vitro release, ex vivo permeation and distribution skin layers. Finally, in vivo anti-inflammatory efficacy and skin tolerance were also assessed. RESULTS: HGs were transparent and kept stable after 3 months exhibiting biocompatible near neutral pH values. Rheological patterns fitted to Herschel-Bulkley for KT-C940-HG and Newton for KT-P407-HG due to its low viscosity at 25°C. Rapid release profiles were observed through first order kinetics. Following the surface the highest concentration of KT from C940-HG was found in the epidermis and the stratum corneum for P407-HG. Relevant anti-inflammatory efficacy of KT-P407-HG revealed enough ability to provide sufficient bioavailability KT to reach easily the site of action. The application of developed formulations in volunteers did not induce any visual skin irritation. CONCLUSIONS: KT-P407-HG was proposed as suitable formulation for anti-inflammatory local treatment without theoretical systemic side effect.

Effect of allergens and irritants on levels of natural moisturizing factor and corneocyte morphology.

BACKGROUND: The irritant sodium lauryl sulfate (SLS) is known to cause a decrease in the stratum corneum level of natural moisturizing factor (NMF), which in itself is associated with changes in corneocyte surface topography. OBJECTIVE: To explore this phenomenon in allergic contact dermatitis. METHODS: Patch testing was performed on patients with previously positive patch test reactions to potassium dichromate (Cr), nickel sulfate (Ni), methylchloroisothiazolinone (MCI)/methylisothiazolinone (MI), or p-phenylenediamine. Moreover, a control (pet.) patch and an irritant (SLS) patch were applied. After 3 days, the stratum corneum from tested sites was collected, and NMF levels and corneocyte morphology, expressed as the amount of circular nanosize objects, quantified according to the Dermal Texture Index (DTI), were determined. RESULTS: Among allergens, only MCI/MI reduced NMF levels significantly, as did SLS. Furthermore, only MCI/MI caused remarkable changes at the microscopic level; the corneocytes were hexagonal-shaped with pronounced cell borders and a smoother surface. The DTI was increased after SLS exposure but not after allergen exposure. CONCLUSIONS: MCI/MI significantly decreased NMF levels, similarly to SLS. The altered corneocyte morphology suggests that skin barrier damage plays a role in the pathogenesis of MCI/MI contact allergy. The DTI seems to differentiate reactions to SLS from those to the allergens tested, as SLS was the only agent that caused a DTI increase.

A Hexa-Herbal TCM Decoction Used to Treat Skin Inflammation: An LC-MS-Based Phytochemical Analysis.

In order to understand the chemical relationship between a traditional hexa-herbal Chinese medicine formula and botanical drugs it is derived from, an analytical platform comprising liquid chromatography coupled with triple quadrupole mass spectrometry and data mining was developed to separate and identify key chemical components. The hexa-herbal formula comprises the rootstock of Scutellaria baicalensis, Rheum tanguticum, Sophora flavescens, the root bark of Dictamnus dasycarpus, the bark of Phellodendron chinense, and the fruit of Kochia scoparia. Seventy-three compounds including alkaloids, anthraquinone derivatives, coumarins, coumarins derivatives, flavonoids, flavone glycosides, naphthalene derivatives, phenylbutanone glucopyranoside, phenolic acids, pterocarpans, stilbenes, stilbenes derivatives, and tannins were putatively identified based on mass measurement and characteristic fragment ions. Among the botanical drugs of the hexa-herbal Chinese medicine formula, the rootstock of R. tanguticum and S. flavescens, bark of P. chinense, and rootstock of S. baicalensis contributed to the majority of the extracted metabolites of the formula decoction. The developed method appeared to be a versatile tool for monitoring chemical constituents in extracts of a traditional Chinese medicine formula in a relatively comprehensive and systematic manner, and helped to understand the importance of the individual botanical drugs within a formulation.

Current challenges in bioequivalence, quality, and novel assessment technologies for topical products.

This paper summarises the proceedings of a recent workshop which brought together pharmaceutical scientists and dermatologists from academia, industry and regulatory agencies to discuss current regulatory issues and industry practices for establishing therapeutic bioequivalence (BE) of dermatologic topical products. The methods currently available for assessment of BE were reviewed as well as alternatives and the advantages and disadvantages of each method were considered. Guidance on quality and performance of topical products was reviewed and a framework to categorise existing and alternative methods for evaluation of BE was discussed. The outcome of the workshop emphasized both a need for greater attention to quality, possibly, via a Quality-By-Design (QBD) approach and a need to develop a "whole toolkit" approach towards the problem of determination of rate and extent in the assessment of topical bioavailability. The discussion on the BE and clinical equivalence of topical products revealed considerable concerns about the variability present in the current methodologies utilized by the industry and regulatory agencies. It was proposed that academicians, researchers, the pharmaceutical industry and regulators work together to evaluate and validate alternative methods that are based on both the underlying science and are adapted to the drug product itself instead of single "universal" method.

In vitro permeation testing for the evaluation of drug delivery to the skin.

This review considers the role of in vitro permeation testing (IVPT) for the evaluation of drug delivery from topical formulations applied to the skin. The technique was pioneered by Franz in the 1970's and today remains an important tool in the development, testing and optimization of such topical formulations. An overview of IVPT as well as selection of skin for the experiment, integrity testing of the membrane, and required number of replicate skin samples is discussed. In the literature many researchers have focused solely on permeation and have not reported amounts of the active remaining on and in the skin at the end of the IVPT. Therefore, a particular focus of this article is determination of the complete mass balance of the drug. It is noteworthy that for the evaluation of bioequivalence of topical formulations the draft guideline issued by the European Medicines Agency (EMA) requires the IVPT method to report on both the skin deposition and distribution of the active in the skin as well as amount permeated. Other aspects of current guidance from the EMA and United States Food and Drug Agency for IVPT are also compared and contrasted. Ultimately, harmonisation of IVPT protocols across the regulatory agencies will expedite the development process for novel topical formulations as well as the availability of generic products.

In vivo permeation of 2-phenoxyethanol in human skin.

A number of baby wipe formulations contain 2-phenoxyethanol (PE) as a preservative and cetylpyridinium chloride (CPC) as a surfactant with antimicrobial activity. Previously, we reported the skin absorption of PE in porcine skin and human skin in vitro. In the present work, the permeation of PE from preparations with CPC and without CPC was investigated in human skin in vivo. The studies were conducted using Confocal Raman Spectroscopy (CRS) and tape stripping (TS) methods. The CRS studies showed that the area under the curve (AUC) of PE for the formulation with and without CPC were not significantly different (p > 0.05). The TS data indicated no significant difference in the amounts of PE recovered from tapes 1-6 for the preparation with and without CPC (p > 0.05). When comparing the in vitro and in vivo data, a correlation was observed between the cumulative amount of PE permeated through human skin in vitro at 24 h and the AUC as measured by CRS (r2 = 0.97). In addition, the cumulative amount of PE permeated through human skin in vitro at 24 h was found to correlate with the amount of PE recovered from tape 1 to 6 in vivo (r2 = 0.95). Both CRS and TS techniques demonstrated limitations in assessing the distribution of PE and CPC in the skin in vivo, primarily attributed to the Raman signal intensities of compounds under investigation and the variability in the amount of SC collected by TS. Despite the limitations of CRS and TS, the results from the present study add further insights to the in vitro permeation data. Additionally, the findings of the present study encourage the further development and application of CRS for non-invasive evaluation of topical skin formulations in vivo.

Rational development of topical climbazole formulations.

Dandruff, or pityriasis capitis simplex, is a common scalp condition associated with excessive flaking and scaling of the epidermal tissue. Other features include irregular corneocyte turnover, irritation, itching and an impaired skin barrier function. Previously we reported the characterization of climbazole (CBZ), an antifungal agent used in the management of dandruff. Skin permeation of CBZ from neat solvents was also investigated. In the present work we evaluated CBZ permeation in human skin in vitro from more complex formulations that better represent products used by consumers. The various systems studied were composed of propylene glycol (PG), Transcutol®P (TC), octyl salicylate (OSal) and isopropyl alcohol (IPA). As well as measurement of skin uptake and penetration of CBZ, where possible, the skin retention and permeation of the various solvents was also determined. All vehicles promoted skin permeation of CBZ but no significant differences in amount permeated were evident between the binary vehicles (PG:TC, TC:OSal) and the ternary vehicle studied (PG:IPA:OSal). The binary vehicles generally promoted more skin uptake of CBZ compared with the neat solvents (PG, TC, OSal) studied previously. Permeation and skin extraction of CBZ from the PG:TC vehicles increased with increasing PG content; a similar trend was evident for the PG:IPA:OSal systems. New methods were developed and validated for measurement of PG, TC and OSal. Analysis of the individual solvents indicated that PG permeation was also independent of the amounts of other solvents in the binary or ternary systems. Consistent with previous findings higher proportions of TC permeated compared with PG for the PG:TC binary systems; TC also permeated the skin more rapidly than PG from these vehicles. For OSal, skin extraction was generally higher for TC:OSal compared with the PG:IPA:OSal vehicle. However, increasing the content of OSal did not appear to influence CBZ skin uptake nor permeation. Interestingly, the effects of the various PG:TC vehicles on CBZ skin delivery contrast with results we previous reported for the same systems for a different active. This confirms that with reference to skin permeation, formulation effects and/or skin penetration enhancement should be expected to vary and may not be predicted for specific vehicles.

Nanoparticles do not penetrate human skin--a theoretical perspective.

The penetration of intact particles in the nanometer range (nanoparticles, [NP]) through human skin is a controversial topic, which has attracted much interest from both the pharmaceutical and the personal care industries. Concerns have also been raised about the possible implications that dermal exposure to NP may have for human health, particularly from physical sunblock formulations. Here we use a theoretical approach to determine the feasibility of NP penetration of healthy human skin. The maximum flux of NPs of various dimensions is calculated based on two algorithms that have been developed to model passive diffusion of molecules through skin. The results confirm that NPs are too large to permeate skin by this mechanism. Although components of NPs may dissolve in the skin and measurable amounts have been detected in body fluids, this is not indicative of actual NP transport through the skin. The possible roles for NP formulations in drug permeation enhancement are also considered but are not associated with the penetration of intact NP.

In vivo barrier challenge and initial recovery in human facial skin.

BACKGROUND: Many in vivo biophysical studies focus on parts of the body which are generally less exposed to the environment compared with facial skin. This study characterizes in vivo changes in the barrier function of cheek stratum corneum (SC) during controlled conditions of damage. OBJECTIVES: The objective was to investigate structural and compositional changes in cheek SC in vivo using tape stripping and Attenuated Total Reflectance Fourier Transform Infrared (ATR-FTIR) spectroscopy. METHODS: In vivo ATR-FTIR spectra of the cheek were collected before and after tape stripping. Trans epidermal water loss (TEWL) measurements from the same site were conducted before and after stripping. Data were also collected 24 h after the last tape strip to investigate any initial recovery process. RESULTS: Sequential tape stripping of the cheek progressively increases TEWL to twice baseline values but some barrier recovery is evident 24 h later. ATR-FTIR spectra show increasing water content within the SC with each tape strip with concomitant increase in lipid conformational order. CONCLUSIONS: Several structural and compositional parameters have been analyzed for cheek SC and these have been correlated with barrier function. The depth dependent changes in face SC map those in body skin but over a much shorter distance.

In vivo barrier challenge and long-term recovery in human facial skin.

Recently, we developed a biophysical approach to characterize in vivo facial cheek skin as a function of stratum corneum (SC) depth, barrier function and during a 24-h recovery period. The current study extends this work and characterizes the human facial cheek after barrier challenge and, for the first time, facial SC barrier recovery over a 4-week period. Changes in the corneocyte size over the 4-week recovery period, and correlations with changes in Trans-Epidermal Water Loss (TEWL) were monitored. This approach allows complete characterization of SC barrier function after a full biological regeneration of the SC barrier following tape stripping. The structural and compositional changes in facial cheek were investigated using Attenuated Total Reflectance-Fourier Transform Infra Red (ATR-FTIR) spectroscopy, tape stripping, TEWL measurements and image analysis combined with optical microscopy to characterize the SC depth profile during the tape stripping stress and over 4-week recovery period. TEWL increased significantly from baseline after sequential tape stripping. Corneocyte size decreased with successive tape stripping. An inverse direct correlation was determined between TEWL and corneocyte surface area. After 4 weeks, the corneocyte size and TEWL for the facial cheek recovered 100% from the tape stripping procedure. The in vivo ATR-FTIR data demonstrated that lipid and sebum components on the surface of the facial cheek SC recovered within 24 h post tape stripping, whereas protein (Amide II) and water components recovered after 1 week.