The effects of polar excipients transcutol and dexpanthenol on molecular mobility, permeability, and electrical impedance of the skin barrier

Cubosomes and hexosomes stabilized by sorbitan monooleate as biocompatible nanoplatforms against skin metastatic human melanoma

Nanoparticles have become versatile assets in the medical field, providing notable benefits across diverse medical arenas including controlled drug delivery, imaging, and immunological assays. Among these, non-lamellar lipid nanoparticles, notably cubosomes and hexosomes, showcase remarkable biocompatibility and stability, rendering them as optimal choices for theranostic applications. Particularly, incorporating edge activators like sodium taurocholate enhances the potential of these nanoparticles for dermal and transdermal drug delivery, overcoming the stratum corneum, a first line of defense in our skin. This study reports on the formulation of monoolein-based cubosomes and hexosomes incorporating taurocholate and stabilized by Span 80 and co-encapsulating Chlorin e6 and coenzyme QH for photodynamic therapy in skin metastatic melanoma. The formulations were optimized using small-angle X-ray scattering, and cryo-transmission electron microscopy confirmed the presence of cubosomes or hexosomes, depending on the ratio between taurocholate and Span 80. Furthermore, the co-loaded nanoparticles exhibited high encapsulation efficiencies for both Ce6 and the coenzyme QH. In vitro studies on human melanoma cells (Me45) demonstrated the biocompatibility and photodynamic activity of the loaded formulations. These findings show the possibility of formulating more biocompatible cubosomes and hexosomes for photodynamic therapy in skin cancer treatment.

Cryogenic probe technology enables multidimensional solid-state NMR of the stratum corneum without isotope labeling

Solid-state NMR has great potential for investigating molecular structure, dynamics, and organization of the stratum corneum, the outer 10-20 μm of the skin, but is hampered by the unfeasibility of isotope labelling as generally required to reach sufficient signal-to-noise ratio for the more informative multidimensional NMR techniques. In this preliminary study of pig stratum corneum at 35 °C and water-free conditions, we demonstrate that cryogenic probe technology offers sufficient signal boost to observe previously undetectable minor resonances that can be uniquely assigned to fluid cholesterol, ceramides, and triacylglycerols, as well as enables 1H-1H spin diffusion monitored by 2D 1H-13C HETCOR to estimate 1-100 nm distances between specific atomic sites on proteins and lipids. The new capabilities open up for future multidimensional solid-state NMR studies to answer long-standing questions about partitioning of additives, such as pharmaceutically active substances, between solid and liquid domains within the protein and lipid phases in the stratum corneum and the lipids of the sebum.

Skin Penetration and Permeation Properties of Transcutol® in Complex Formulations

Percutaneous delivery is explored as alternative pathway for addressing the drawbacks associated with the oral administration of otherwise efficacious drugs. Short of breaching the skin by physical means, the preference goes to formulation strategies that augment passive diffusion across the skin. One such strategy lies in the use of skin penetration and permeation enhancers notably of hydroxylated solvents like propylene glycol (PG), ethanol (EtOH), and diethylene glycol monoethyl ether (Transcutol®, TRC). In a previous publication, we focused on the role of Transcutol® as enhancer in neat or diluted systems. Herein, we explore its' role in complex formulation systems, including patches, emulsions, vesicles, solid lipid nanoparticles, and micro or nanoemulsions. This review discusses enhancement mechanisms associated with hydroalcoholic solvents in general and TRC in particular, as manifested in multi-component formulation settings alongside other solvents and enhancers. The principles that govern skin penetration and permeation, notably the importance of drug diffusion due to solubilization and thermodynamic activity in the vehicle (formulation), drug solubilization and partitioning in the stratum corneum (SC), and/or solvent drag across the skin into deeper tissue for systemic absorption are discussed. Emphasized also are the interplay between the drug properties, the skin barrier function and the formulation parameters that are key to successful (trans)dermal delivery.

Formulation and dermal delivery of a new active pharmaceutical ingredient in an in vitro wound model for the treatment of chronic ulcers

The aim of this study was to investigate dermal delivery of the new active pharmaceutical ingredient (API) TOP-N53 into diabetic foot ulcer using an in vitro wound model consisting of pig ear dermis and elucidate the impact of drug formulation and wound dressing taking into consideration clinical relevance in the home care setting and possible bacterial infection. Different formulation approaches for the poorly water-soluble API including colloidal solubilization, drug micro-suspension and cosolvent addition were investigated; moreover, the effect of (micro-)viscosity of hydrogels used as primary wound dressing on delivery was assessed. Addition of Transcutol® P as cosolvent to water improved solubility and was significantly superior to all other approaches providing a sustained three-day delivery that reached therapeutic drug levels in the tissue. Solubilization in micelles or liposomes, on the contrary, did not boost delivery while micro-suspensions exhibited sedimentation on the tissue surface. Microbial contamination was responsible for considerable metabolism of the drug leading to tissue penetration of metabolites which may be relevant for therapeutic effect. Use of hydrogels under semi-occlusive conditions significantly reduced drug delivery in a viscosity-dependent fashion. Micro-rheologic analysis of the gels using diffusive wave spectroscopy confirmed the restricted diffusion of drug particles in the gel lattice which correlated with the obtained tissue delivery results. Hence, the advantages of hydrogel dressings from the applicatory characteristic point of view must be weighed against their adverse effect on drug delivery. The employed in vitro wound model was useful for the assessment of drug delivery and the development of a drug therapy concept for chronic diabetic foot ulcer. Mechanistic insights about formulation and dressing performance may be applied to drug delivery in other skin conditions such as digital ulcer.

Unraveling UVB effects: Catalase activity and molecular alterations in the stratum corneum

AIM

Ultraviolet B (UVB) radiation can compromise the functionality of the skin barrier through various mechanisms. We hypothesize that UVB induce photochemical alterations in the components of the outermost layer of the skin, known as the stratum corneum (SC), and modulate its antioxidative defense mechanisms. Catalase is a well-known antioxidative enzyme found in the SC where it acts to scavenge reactive oxygen species. However, a detailed characterization of acute UVB exposure on the activity of native catalase in the SC is lacking. Moreover, the effects of UVB irradiation on the molecular dynamics and organization of the SC keratin and lipid components remain unclear. Thus, the aim of this work is to characterize consequences of UVB exposure on the structural and antioxidative properties of catalase, as well as on the molecular and global properties of the SC matrix surrounding the enzyme.

EXPERIMENTS

The effect of UVB irradiation on the catalase function is investigated by chronoamperometry with a skin covered oxygen electrode, which probes the activity of native catalase in the SC matrix. Circular dichroism is used to explore changes of the catalase secondary structure, and gel electrophoresis is used to detect fragmentation of the enzyme following the UVB exposure. UVB induced alterations of the SC molecular dynamics and structural features of the SC barrier, as well as its water sorption behavior, are investigated by a complementary set of techniques, including natural abundance 13C polarization transfer solid-state NMR, wide-angle X-ray diffraction, Fourier transform infrared (FTIR) spectroscopy, and dynamic vapor sorption microbalance.

FINDINGS

The findings show that UVB exposure impairs the antioxidative function of catalase by deactivating both native catalase in the SC matrix and lyophilized catalase. However, UVB radiation does not alter the secondary structure of the catalase nor induce any observable enzyme fragmentation, which otherwise could explain deactivation of its function. NMR measurements on SC samples show a subtle increase in the molecular mobility of the terminal segments of the SC lipids, accompanied by a decrease in the mobility of lipid chain trans-gauche conformers after high doses of UVB exposure. At the same time, the NMR data suggest increased rigidity of the polypeptide backbone of the keratin filaments, while the molecular mobility of amino acid residues in random coil domains of keratin remain unaffected by UVB irradiation. The FTIR data show a consistent decrease in absorbance associated with lipid bond vibrations, relative to the main protein bands. Collectively, the NMR and FTIR data suggest a small modification in the composition of fluid and solid phases of the SC lipid and protein components after UVB exposure, unrelated to the hydration capacity of the SC tissue. To conclude, UVB deactivation of catalase is anticipated to elevate oxidative stress of the SC, which, when coupled with subtle changes in the molecular characteristics of the SC, may compromise the overall skin health and elevate the likelihood of developing skin disorders.

The implications of lipid mobility, drug-enhancers (surfactants)-skin interaction, and TRPV1 activation on licorice flavonoid permeability

Licorice flavonoids (LFs) are derived from perennial herb licorice and have been attaining a considerable interest in cosmetic and skin ailment treatments. However, some LFs compounds exhibited poor permeation and retention capability, which restricted their application. In this paper, we systematically investigated and compared the enhancement efficacy and mechanisms of different penetration enhancers (surfactants) with distinct lipophilicity or "heat and cool" characteristics on ten LFs compounds. Herein, the aim was to unveil how seven different enhancers modified the stratum corneum (SC) surface and influence the drug-enhancers-skin interaction, and to relate these effects to permeation enhancing effects of ten LFs compounds. The enhancing efficacy was evaluated by enhancement ratio (ER)permeation, ERretention, and ERcom, which was conducted on the porcine skin. It was summarized that heat capsaicin (CaP) and lipophilic Plurol® Oleique CC 497 (POCC) caused the most significance of SC lipid fluidity, SC water loss, and surface structure alterations, thereby resulting in a higher permeation enhancing effects than other enhancers. CaP could completely occupied drug-skin interaction sites in the SC, while POCC only occupied most drug-skin interactions. Moreover, the enhancing efficacy of both POCC and CaP was dependent on the log P values of LFs. For impervious LFs with low drug solubility, enhancing their drug solubility could help them permeate into the SC. For high-permeation LFs, their permeation was inhibited ascribed to the strong drug-enhancer-skin strength in the SC. More importantly, drug-surfactant-skin energy possessed a good negative correlation with the LFs permeation amount for most LFs molecules. Additionally, the activation of transient receptor potential vanilloid 1 (TRPV1) could enhance LFs permeation by CaP. The study provided novel insights for drug permeation enhancement from the viewpoint of molecular pharmaceutics, as well as the scientific utilization of different enhancers in topical or transdermal formulations.

The vitamin B5/coenzyme A axis: A target for immunomodulation?

Coenzyme A (CoA) serves as a vital cofactor in numerous enzymatic reactions involved in energy production, lipid metabolism, and synthesis of essential molecules. Dysregulation of CoA-dependent metabolic pathways can contribute to chronic diseases, such as inflammatory diseases, obesity, diabetes, cancer, and cardiovascular disorders. Additionally, CoA influences immune cell activation by modulating the metabolism of these cells, thereby affecting their proliferation, differentiation, and effector functions. Targeting CoA metabolism presents a promising avenue for therapeutic intervention, as it can potentially restore metabolic balance, mitigate chronic inflammation, and enhance immune cell function. This might ultimately improve the management and outcomes for these diseases. This review will more specifically focus on the contribution of pathways regulating the availability of the CoA precursor Vitamin B5/pantothenate in vivo and modulating the development of Th17-mediated inflammation, CD8-dependent anti-tumor immunity but also tissue repair processes in chronic inflammatory or degenerative diseases.

Topical dexpanthenol effects on physiological parameters of the stratum corneum by Confocal Raman Microspectroscopy

BACKGROUND

Topical use of dexpanthenol presents well-established moisturizing properties and maintenance and repair of the skin barrier function, however, its exact action mechanisms are not completely elucidated. In this context, Confocal Raman Microspectroscopy is an optical method that enables non-invasive and non-destructive in vivo analysis with the sensitive acquisition of molecular changes in different skin layers. Herein, the aim was to evaluate the effects of topical dexpanthenol on the components and physiological parameters of the stratum corneum (SC).

MATERIALS AND METHODS

Ten healthy female subjects underwent skin evaluation by means of a Confocal Raman Spectrometer Skin Analyzer 3510. Spectral data were obtained from the skin of the anterior forearm region, before and 2 h after applying a cosmetic formulation containing or not containing 5% dexpanthenol.

RESULTS

Semiquantitative analysis of the natural moisturizing factor showed a significant decrease in content after 2 h of topical dexpanthenol application, while the analysis of the lamellar organization of intercellular lipids and the secondary structure of keratin showed a significant increase in hexagonal organization of lipids at the first half of the SC and a significant increase in β-pleated sheet conformation of keratin.

CONCLUSION

Effects of topical dexpanthenol on SC suggest a contribution in increasing fluidity of both lipidic and protein components of the SC and are compatible with dexpanthenol activity in maintaining adequate physiological conditions and preventing transepidermal water loss. This study also contributes to the elucidation of action mechanisms and other concurrent biochemical processes.

How to Promote Skin Repair? In-Depth Look at Pharmaceutical and Cosmetic Strategies

Skin repair encompasses epidermal barrier repair and wound healing which involves multiple cellular and molecular stages. Therefore, many skin repair strategies have been proposed. In order to characterize the usage frequency of skin repair ingredients in cosmetics, medicines, and medical devices, commercialized in Portuguese pharmacies and parapharmacies, a comprehensive analysis of the products' composition was performed. A total of 120 cosmetic products, collected from national pharmacies online platforms, 21 topical medicines, and 46 medical devices, collected from INFARMED database, were included in the study, revealing the top 10 most used skin repair ingredients in these categories. A critical review regarding the effectiveness of the top ingredients was performed and an in-depth analysis focused on the top three skin repair ingredients pursued. Results demonstrated that top three most used cosmetic ingredients were metal salts and oxides (78.3%), vitamin E and its derivatives (54.2%), and Centella asiatica (L.) Urb. extract and actives (35.8%). Regarding medicines, metal salts and oxides were also the most used (47.4%) followed by vitamin B5 and derivatives (23.8%), and vitamin A and derivatives (26.3%). Silicones and derivatives were the most common skin repair ingredients in medical devices (33%), followed by petrolatum and derivatives (22%) and alginate (15%). This work provides an overview of the most used skin repair ingredients, highlighting their different mechanisms of action, aiming to provide an up-to-date tool to support health professionals' decisions.

Topical hydrophilic gel with itraconazole-loaded polymeric nanomicelles improves wound healing in the treatment of feline sporotrichosis

Sporotrichosis is a superficial fungal disease that can affect animals and humans. The high number of infected cats has been associated with zoonotic transmission and contributed to sporotrichosis being considered by the World Health Organization as one of the main neglected tropical fungal diseases for 2021-2030. Oral administration of itraconazole (ITZ) is the first choice for treatment, but it is expensive, time-consuming, and often related to serious adverse effects. As a strategy to optimize the treatment, we proposed the development of a hydrophilic gel with nanomicelles loaded with ITZ (HGN-ITZ). The HGN-ITZ was developed using an I-optimal design and characterized for particle size, Zeta potential, drug content, microscopic aspects, viscosity, spreadability, in vitro drug release, in vitro antifungal activity, and clinical evaluation in cats. The HGN-ITZ showed a high content of ITZ (97.3 ± 2.1 mg/g); and characteristics suitable for topical application (viscosity, spreadability, globules size, Zeta potential, controlled drug release). In a pilot clinical study, cats with disseminated sporotrichosis were treated with oral ITZ or HGN-ITZ + oral ITZ. A mortality rate of 21.3% was observed for the oral ITZ group compared to 5.3% for the HGN-ITZ + oral ITZ group. In a cat with a single lesion, topical treatment alone (HGN-ITZ) provided complete healing of the lesion in 45 days. No signs of topical irritation were observed during the treatments, suggesting that HGN-ITZ can be a promising strategy in the treatment of sporotrichosis.

Impact of solid lipid nanoparticles on 3T3 fibroblasts viability and lipid profile: The effect of curcumin and resveratrol loading

This study focused on the impact in 3T3 fibroblasts of several types of empty and curcumin- and resveratrol-loaded solid lipid nanoparticles (SLN) on cell viability and lipid metabolism in relation to their lipid content and encapsulated drug. SLN, prepared by hot homogenization/ultrasonication, were characterized with respect to size, polydispersity index, and zeta potential. Compritol® 888 ATO at different concentrations (4%, 5%, and 6% wt/wt) was chosen as lipid matrix while Poloxamer 188 (from 2.2% to 3.3% wt/wt) and Transcutol (TRC; 2% or 4%) were added as nanoparticle excipients. Prepared SLN were able to encapsulate high drug amount (encapsulation efficiency percentage of about 97-99%). All empty SLN did not show cytotoxicity (by MTT assay, at 24 h of incubation) in 3T3 cells independently of the lipid and TRC amount, while a viability reduction in the range 5-11% and 12-27% was observed in 3T3 cells treated with curcumin-loaded and resveratrol-loaded SLN, respectively. SLN without TRC did not affect cell lipid metabolism, independently from the lipid content. Empty and loaded SLN formulated with 4% of Compritol and 4% of TRC significantly affected, after 24 h of incubation at the dose of 5 μl/ml, cell polar lipids (phospholipids and free cholesterol) and fatty acid profile, with respect to control cells. Loaded compounds significantly modulated the impact of the corresponding empty formulation on cell lipids. Therefore, the combined impact on lipid metabolism of SLN and loaded drug should be taken in consideration in the evaluation of the toxicity, potential application, and therapeutic effects of new formulations.

Lip Mesotherapy with Dexpanthenol as a Novel Approach to Prevent Isotretinoin-Associated Cheilitis

INTRODUCTION

Isotretinoin (ISO)-associated cheilitis is the most common side effect and the most common reason for discontinuation of ongoing therapy. So, various lip balms are also routinely recommended for all patients.

OBJECTIVES

We aimed to investigate the effectiveness of local intradermal injections (mesotherapy) of dexpanthenol into the lips to prevent ISO-associated cheilitis.

METHODS

This pilot study was conducted on patients over the age of 18 using ISO (about 0.5 mg/kg/day). All patients were prescribed only hamamelis virginiana distillate in ointment form as a lip balm. In the mesotherapy group (n=28), 0.1 ml of dexpanthenol was injected into each lip tubercle (4 points total) to the submucosal level. The patients in the control group (n=26) used only the ointment. "ISO cheilitis grading scale (ICGS)" was used in the evaluation of ISO-associated cheilitis. The patients were followed for 2 months.

RESULTS

Although there was an increase in ICGS scores in the mesotherapy group compared to the baseline, no statistically significant change was observed after treatment (p=0.545). However, in the control group, there was a statistically significant increase in ICGS scores in the 1st and 2nd months compared to the baseline (p<0.001). Lip balms were needed significantly less frequently in the mesotherapy group compared to the control, both in the 1st and 2nd months (p=0.006, p=0.045; respectively).

CONCLUSIONS

Lip mesotherapy with dexpanthenol will be a useful option for preventing ISO-associated cheilitis because of its easy application, cost-effectiveness, low complication risk, and high patient satisfaction.

Development and Characterisation of a Topical Methyl Salicylate Patch: Effect of Solvents on Adhesion and Skin Permeation

The advent of skin patch formulation design and technology has enabled the commercialisation of methyl salicylate (MS) as a topical patch. However, the most fundamental aspect of skin permeation is unknown at present. The study aims to investigate the effect of solvent choice on the skin permeation of MS in a neat solvent system and patch formulation with an emphasis on patch adhesion. MS in six selected solvents (propylene glycol (PG), Transcutol^®, isopropyl myristate, Labrasol^®, Plurol^® oleique CC 497 and Maisine^® CC) was characterised and in vitro permeation studies were also performed. An ATR-FTIR analysis on solvent-treated skin was conudcted. Patch formulation was prepared and characterised for adhesion, in vitro drug release and skin permeation studies. The highest MS permeation was found in neat PG over 24 h (~90 μg/cm²) due to its strong skin protein conformation effect. Transcutol^® and isopropyl myristate showed better skin deposition and formulation retention, respectively. Nevertheless, PG enhanced the patch adhesion despite having a lower cumulative amount of MS permeated (~80 μg/cm²) as compared with Transcutol^® and Maisine^® (~110-150 μg/cm²). These two solvents, however, demonstrated better skin deposition and formulation retention but a lower patch adhesion. The unpredictable influence of the solvent on patch adhesion highlights the importance of the trade-off between patch adhesion and skin permeation during formulation design.

Parabens Permeation through Biological Membranes: A Comparative Study Using Franz Cell Diffusion System and Biomimetic Liquid Chromatography

Parabens (PBs) are used as preservatives to extend the shelf life of various foodstuffs, and pharmaceutical and cosmetic preparations. In this work, the membrane barrier passage potential of a subset of seven parabens, i.e., methyl-, ethyl-, propyl- isopropyl, butyl, isobutyl, and benzyl paraben, along with their parent compound, p-hydroxy benzoic acid, were studied. Thus, the Franz cell diffusion (FDC) method, biomimetic liquid chromatography (BLC), and in silico prediction were performed to evaluate the soundness of both describing their permeation through the skin. While BLC allowed the achievement of a full scale of affinity for membrane phospholipids of the PBs under research, the permeation of parabens through Franz diffusion cells having a carbon chain > ethyl could not be measured in a fully aqueous medium, i.e., permeation enhancer-free conditions. Our results support that BLC and in silico prediction alone can occasionally be misleading in the permeability potential assessment of these preservatives, emphasizing the need for a multi-technique and integrated experimental approach.

Exploratory evaluation of tolerability, performance, and cosmetic acceptance of dexpanthenol-containing dermo-cosmetic wash and sun-care products for tattoo aftercare

Background and Aims

Tattoo prevalence has significantly increased over the last decades. Proper tattoo aftercare, such as cleansing, moisturizing, and protection against sunlight, is essential to prevent complications and to keep the beauty of the tattoo. The tolerability, performance, and cosmetic acceptability of two dexpanthenol-containing dermo-cosmetic products, a wash and a sun-care, were investigated on tattooed skin in two separate trials.

Methods

Two single-center, exploratory, open-label cosmetic studies were conducted between August and November 2020 to evaluate the dexpanthenol-containing dermo-cosmetic products. In the first study, healthy adults applied the 2.5% dexpanthenol-containing wash right after their tattoo session daily for 14 consecutive days. In the second study, healthy adults applied the 2.5% dexpanthenol-containing sun-care sun protection factor 50+ cream on existing tattoos that were daily exposed to sunlight for 28 consecutive days. Clinical examination by a dermatologist and self-assessment through subject questionnaires were used to assess the tolerability, acceptance, ease of use, and cosmetic outcomes of both products. Additionally, transepidermal water loss and moisturization assessments were performed to evaluate skin hydration after use of the sun-care product.

Results

Both study products were well tolerated, and no product related adverse events were reported during the studies. At least 90% of the study participants appreciated the performance of the dexpanthenol-containing wash and sun-care product, including moisturizing properties, relief of unpleasant sensations, and preservation of the cosmetic appearance of the tattoo. For the sun-care, it was shown that its application supported maintaining the skin barrier of tattooed skin, while keeping it hydrated.

Conclusion

The 2.5% dexpanthenol-containing wash and sun-care products are well tolerated and appreciated by tattooed subjects. Hence, they represent valid options for tattoo aftercare in line with current recommendations and practice.

The effects of glycols on molecular mobility, structure, and permeability in stratum corneum

The skin provides an attractive alternative to the conventional drug administration routes. Still, it comes with challenges as the upper layer of the skin, the stratum corneum (SC), provides an efficient barrier against permeation of most compounds. One way to overcome the skin barrier is to apply chemical permeation enhancers, which can modify the SC structure. In this paper, we investigated the molecular effect of three different types of glycols in SC: dipropylene glycol (diPG), propylene glycol (PG), and butylene glycol (BG). The aim is to understand how these molecules influence the molecular mobility and structure of the SC components, and to relate the molecular effects to the efficiency of these molecules as permeation enhancers. We used complementary experimental techniques, including natural abundance ¹³C NMR spectroscopy and wide-angle X-ray diffraction to characterize the molecular consequences of these compounds at different doses in SC at 97% RH humidity and 32 °C. In addition, we study the permeation enhancing effects of the same glycols in comparable conditions using Raman spectroscopy. Based on the results from NMR, we conclude that all three glycols cause increased mobility in SC lipids, and that the addition of glycols has an effect on the keratin filaments in similar manner as Natural Moisturizing Factor (NMF). The highest mobility of both lipids and amino acids can be reached with BG, which is followed by PG. It is also shown that one reaches an apparent saturation level for all three chemicals in SC, after which increased addition of the compound does not lead to further increase in the mobility of SC lipids or protein components. The examination with Raman mapping show that BG and PG give a significant permeation enhancement as compared to SC without any added glycol at corresponding conditions. Finally, we observe a non-monotonic response in permeation enhancement with respect to the concentration of glycols, where the highest concentration does not give the highest permeation. This is explained by the dehydration effects at highest glycol concentrations. In summary, we find a good correlation between the molecular effects of glycols on the SC lipid and protein mobility, and macroscopic permeation enhances of the same molecules.

Preparation of topical bimatoprost with enhanced skin infiltration and in vivo hair regrowth efficacy in androgenic alopecia

To prepare a topical formulation of bimatoprost (BIM) with high skin permeability, we designed a solvent mixture system composed of ethanol, diethylene glycol monoethyl ether, cyclomethicone, and butylated hydroxyanisole, serving as a volatile solvent, nonvolatile co-solvent, spreading agent, and antioxidant, respectively. The ideal topical BIM formulation (BIM–TF#5) exhibited 4.60-fold higher human skin flux and a 529% increase in dermal drug deposition compared to BIM in ethanol. In addition, compared to the other formulations, BIM–TF#5 maximally activated human dermal papilla cell proliferation at a concentration of 5 μM BIM, equivalent to 10 μM minoxidil. Moreover, BIM–TF#5 (0.3% [w/w] BIM) significantly promoted hair regrowth in the androgenic alopecia mouse model and increased the area covered by hair at 10 days by 585% compared to the vehicle-treated mice, indicating that entire telogen area transitioned into the anagen phase. Furthermore, at day 14, the hair weight of mice treated with BIM–TF#5 (5% [w/w] BIM) was 8.45- and 1.30-fold greater than in the 5% (w/w) BIM in ethanol and 5% (w/v) minoxidil treated groups, respectively. In the histological examination, the number and diameter of hair follicles in the deep subcutis were significantly increased in the BIM–TF#5 (0.3 or 5% [w/w] BIM)-treated mice compared to the mice treated with vehicle or 5% (w/w) BIM in ethanol. Thus, our findings suggest that BIM–TF#5 is an effective formulation to treat scalp alopecia, as part of a novel therapeutic approach involving direct prostamide F2α receptor-mediated stimulation of dermal papilla cells within hair follicles.

Single-center, assessor-blind study to evaluate the efficacy and safety of DA-5520 topical gel in patients with acne scars: A pilot study

BACKGROUND

Unlike various topical treatment options for acne vulgaris, options for acne scars mostly involve invasive interventions. So far, only a few clinical trials have investigated the effects of topical treatment for acne scars.

OBJECTIVES

We evaluated the safety and efficacy of DA-5520, a recently developed topical gel for the treatment of different types of acne scars.

METHODS

A 12-week prospective, randomized, active-controlled, evaluator-blind, single-center study involving 36 participants with acne scars was performed. Participants were randomized into four different groups at a 1:1:1:1 ratio: laser resurfacing with DA-5520 application (test 1); laser resurfacing without DA-5520 application (control 1); comedone extraction with DA-5520 application (test 2); and comedone extraction without DA-5520 application (control 2). For 12 weeks, participants in the two test groups applied DA-5520 twice daily, while participants in the control groups applied moisturizers alone. Participants in the test 1 and control 1 groups received a single session of laser resurfacing at visit 1 (week 0). All participants were followed up at 1, 4, 8, and 12 weeks, and objective scar evaluation using the échelle d'évaluation clinique des cicatrices d'acné (ECCA) score was performed at each visit.

RESULTS

Clinical improvement of acne scars, confirmed by the ECCA grading scale (1 for atrophic scar and 2 for hypertrophic scar), was observed after using DA-5520 when combined with laser resurfacing or individually, and no associated adverse reactions were noted.

CONCLUSIONS

Preliminary results of this study revealed that DA-5520 may be a promising new formulation for treating all type of acne scars.

Catalase Activity in Keratinocytes, Stratum Corneum, and Defatted Algae Biomass as a Potential Skin Care Ingredient

The generation of reactive oxygen species presents a destructive challenge for the skin organ and there is a clear need to advance skin care formulations aiming at alleviating oxidative stress. The aim of this work was to characterize the activity of the antioxidative enzyme catalase in keratinocytes and in the skin barrier (i.e., the stratum corneum). Further, the goal was to compare the activity levels with the corresponding catalase activity found in defatted algae biomass, which may serve as a source of antioxidative enzymes, as well as other beneficial algae-derived molecules, to be employed in skin care products. For this, an oxygen electrode-based method was employed to determine the catalase activity and the apparent kinetic parameters for purified catalase, as well as catalase naturally present in HaCaT keratinocytes, excised stratum corneum samples collected from pig ears with various amounts of melanin, and defatted algae biomass from the diatom Phaeodactylum tricornutum. Taken together, this work illustrates the versatility of the oxygen electrode-based method for characterizing catalase function in samples with a high degree of complexity and enables the assessment of sample treatment protocols and comparisons between different biological systems related to the skin organ or algae-derived materials as a potential source of skin care ingredients for combating oxidative stress.

Three New Dexpanthenol-Containing Face Creams: Performance and Acceptability after Single and Repeated Applications in Subjects of Different Ethnicity with Dry and Sensitive Skin

Three novel face creams containing dexpanthenol with different lipid contents were developed for dry skin sufferers: a day face cream (DFC), a day face cream with sun protection (DFC-SPF), and a night face cream (NFC). Three identically designed studies (N = 42–44 each) were conducted with healthy adults of three ethnicities (African, Asian, Caucasian) with dry/sensitive skin. Effects on stratum corneum (SC) hydration, SC lipid content, and skin elasticity were quantified by established noninvasive methods during the 4-week studies. After single and repeated once-daily applications of the face creams, facial hydration significantly increased from baseline. On day 28, the mean increments in skin hydration amounted to 27%, 26%, and 27% (p < 0.0001 each) for DFC, DFC-SPF, and NFC, respectively. Favorable effects of DFC, DFC-SPF, and NFC on facial moisturization were observed in all three ethnic groups. The enhancements in SC hydration were not paralleled by improvements in skin elasticity parameters but lipid analyses showed significant increases in SC cholesterol, SC free fatty acid, and/or SC ceramide levels. All three face creams were well tolerated and achieved a high product satisfaction and acceptability by study participants. Our findings support the once-daily use of the face creams in adults of different ethnicities with dry and sensitive skin.

Extraction of natural moisturizing factor from the stratum corneum and its implication on skin molecular mobility

The natural moisturizing factor (NMF) is a mixture of small water-soluble compounds present in the upper layer of the skin, stratum corneum (SC). Soaking of SC in water leads to extraction of the NMF molecules, which may influence the SC molecular properties and lead to brittle and dry skin. In this study, we investigate how the molecular dynamics in SC lipid and protein components are affected by the removal of the NMF compounds. We then explore whether the changes in SC components caused by NMF removal can be reversed by a subsequent addition of one single NMF component: urea, pyrrolidone carboxylic acid (PCA) or potassium lactate. Samples of intact SC were investigated using NMR, X-ray diffraction, infrared spectroscopy and sorption microbalance. It is shown that the removal of NMF leads to reduced molecular mobility in keratin filaments and SC lipids compared to untreated SC. When the complex NMF mixture is replaced by one single NMF component, the molecular mobility in both keratin filaments and lipids is regained. From this we propose a general relation between the molecular mobility in SC and the amount of polar solutes which does not appear specific to the precise chemical identify of the NMF compounds.

Understanding humectant behaviour through their water-holding properties

OBJECTIVE

Humectants perform essential roles in the formulation of topical moisturizing products in terms of delivery of active ingredients, consumer experience and biophysical behaviour. How they retain and release water is key to understanding their behaviour.

METHODS

Dynamic vapour sorption (DVS) was used to monitor the dehydration kinetics of three humectants widely used in topical formulations-glycerine, dexpanthenol and urea. Model aqueous solutions with concentrations of 20% w/w were tested and compared against pure deionized water.

RESULTS

The three humectants varied in their ability to retain water during the dehydration process. Dexpanthenol was able to retain water most efficiently during the latter stages of dehydration. Urea demonstrated evidence of crystallization during the final stage of water loss, which was not shown by glycerine or dexpanthenol.

CONCLUSIONS

Humectants perform vital roles in the formulation of consumer acceptable topical products including the delivery of actives to the skin. Their ability to influence water movement in the skin is also essential for the maintenance of stratum corneum flexibility. DVS assessment of aqueous solutions has demonstrated how the behaviour of three commonly used humectants differs. Knowledge of the mechanisms by which these humectants operate enables the formulator to develop topical products optimized for the roles for which they are intended.

Skin hydration as a tool to control the distribution and molecular effects of intermediate polarity compounds in intact stratum corneum

The barrier function of the skin is mainly assured by its outermost layer, stratum corneum (SC), which consists of dead keratin-filled cells embedded in a lipid matrix. The skin is daily exposed to an environment with changing conditions in terms of hydration and different chemicals. Here we investigate how a molecule that has reasonable solubility in both hydrophobic and hydrophilic environments can be directed to certain regions in SC by changing the skin hydration. We use 1,2,3-trimethoxy propane (TMP) as a model substance and solid-state NMR on natural abundance ¹³C to obtain atomically resolved information on the molecular dynamics of TMP as well as SC lipid and protein components at varying hydration conditions. Upon dehydration, TMP redistributes from the hydrophilic corneocytes to the hydrophobic SC lipid regions. In this way, TMP can act to prevent the fluid-solid lipid transition in drying conditions and be present in the corneocytes in more humid conditions. Hydration can thereby be used as a switch to control the location and action of TMP or similar compounds in complex materials like SC. The general principles described here can also have impact on other applications including lipid-based formulations in food, drug delivery and cosmetics.

Two New Dexpanthenol-Containing Wash Gels: Skin Hydration, Barrier Function and Cosmetic Performance upon Single and Repeated Usage in Subjects with Dry Skin

Two novel body/face wash gels enriched with emollient ingredients (including dexpanthenol) were developed for the daily care of dry skin. Two similarly designed 2-week studies (N = 42 each) were conducted to assess the biophysical and cosmetic performance of each of the new wash gels in healthy adults with dry skin. Instrumental measurements quantified the effects of the wash gels on stratum corneum (SC) hydration and transepidermal water loss (TEWL) (with and without a previous sodium lauryl sulfate (SLS) challenge) after single and repeated usage. Following single and repeated applications of the face wash gel to facial skin, as well as to dry SLS-undamaged and SLS-damaged skin of the forearm, skin hydration significantly increased. Similarly, after single and repeated usage of the body wash gel to dry SLS-undamaged and SLS-damaged skin of the forearm, skin moisturization increased significantly from baseline; comparisons with control areas provided inconsistent results for SLS-undamaged skin. No effects on TEWL were observed for either product. Both wash gels were well tolerated and the cosmetic performances were appreciated by the subjects. The study results suggest that daily use of the new wash gels was associated with significant skin-moisturizing effects without adversely affecting skin barrier function and repair.

Performance and Tolerability of a New Topical Dexpanthenol-Containing Emollient Line in Subjects with Dry Skin: Results from Three Randomized Studies

Three studies were conducted with three new dexpanthenol-containing emollients containing increasing lipid contents (Emollients 1–3) to assess their performances in healthy adults with dry skin. All three studies (N = 42 each) followed virtually the same design. A single skin application of the study product was performed followed by once-daily usage. Skin hydration, transepidermal water loss (TEWL), skin biomechanical properties, and lipid content of the stratum corneum (SC) were regularly assessed over the 28-day study period; a subset (N = 22) underwent a sodium lauryl sulfate (SLS) challenge prior to product application. All three emollients were well tolerated and showed good performances with only minor differences in instrumental measurements. After single and prolonged once-daily applications of Emollients 1–3 to dry skin and dry SLS-damaged skin, skin hydration significantly increased from baseline (BL) (by 38.1–72.4% in unchallenged skin, p < 0.001 for all three). This was paralleled by significant increases in skin elasticity parameters. Usage of Emollients 1 and 3 caused increases from BL in SC cholesterol (by 9.8–12.5%, p < 0.05 for both) and SC free fatty acid levels (by 3.7–26.3%, p < 0.05 for both) at the end of the study. No sustained effects on TEWL were recorded. Our findings support the once-daily use of all three emollients in adults with dry skin.

Non-invasive skin sampling of tryptophan/kynurenine ratio in vitro towards a skin cancer biomarker

The tryptophan to kynurenine ratio (Trp/Kyn) has been proposed as a cancer biomarker. Non-invasive topical sampling of Trp/Kyn can therefore serve as a promising concept for skin cancer diagnostics. By performing in vitro pig skin permeability studies, we conclude that non-invasive topical sampling of Trp and Kyn is feasible. We explore the influence of different experimental conditions, which are relevant for the clinical in vivo setting, such as pH variations, sampling time, and microbial degradation of Trp and Kyn. The permeabilities of Trp and Kyn are overall similar. However, the permeated Trp/Kyn ratio is generally higher than unity due to endogenous Trp, which should be taken into account to obtain a non-biased Trp/Kyn ratio accurately reflecting systemic concentrations. Additionally, prolonged sampling time is associated with bacterial Trp and Kyn degradation and should be considered in a clinical setting. Finally, the experimental results are supported by the four permeation pathways model, predicting that the hydrophilic Trp and Kyn molecules mainly permeate through lipid defects (i.e., the porous pathway). However, the hydrophobic indole ring of Trp is suggested to result in a small but noticeable relative increase of Trp diffusion via pathways across the SC lipid lamellae, while the shunt pathway is proposed to slightly favor permeation of Kyn relative to Trp.

Foray into Concepts of Design and Evaluation of Microemulsions as a Modern Approach for Topical Applications in Acne Pathology

With a fascinating complexity, governed by multiple physiological processes, the skin is considered a mantle with protective functions which during lifetime are frequently impaired, triggering dermatologic disorders. As one of the most prevalent dermatologic conditions worldwide, characterized by a complex pathogenesis and a high recurrence, acne can affect the patient's quality of life. Smart topical vehicles represent a good option in the treatment of a versatile skin condition. By surpassing the stratum corneum known for diffusional resistance, a superior topical bioavailability can be obtained at the affected place. In this direction, the literature study presents microemulsions as a part of a condensed group of modern formulations. Microemulsions are appreciated for their superior profile in matters of drug delivery, especially for challenging substances with hydrophilic or lipophilic structures. Formulated as transparent and thermodynamically stable systems, using simplified methods of preparation, microemulsions have a simple and clear appearance. Their unique structures can be explained as a function of the formulation parameters which were found to be the mainstay of a targeted therapy.

Visualisation of H2O2 penetration through skin indicates importance to develop pathway-specific epidermal sensing

Elevated amounts of reactive oxygen species (ROS) including hydrogen peroxide (H₂O₂) are observed in the epidermis in different skin disorders. Thus, epidermal sensing of H₂O₂ should be useful to monitor the progression of skin pathologies. We have evaluated epidermal sensing of H₂O₂ in vitro, by visualising H₂O₂ permeation through the skin. Skin membranes were mounted in Franz cells, and a suspension of Prussian white microparticles was deposited on the stratum corneum face of the skin. Upon H₂O₂ permeation, Prussian white was oxidised to Prussian blue, resulting in a pattern of blue dots. Comparison of skin surface images with the dot patterns revealed that about 74% of the blue dots were associated with hair shafts. The degree of the Prussian white to Prussian blue conversion strongly correlated with the reciprocal resistance of the skin membranes. Together, the results demonstrate that hair follicles are the major pathways of H₂O₂ transdermal penetration. The study recommends that the development of H₂O₂ monitoring on skin should aim for pathway-specific epidermal sensing, allowing micrometre resolution to detect and quantify this ROS biomarker at hair follicles.Graphical abstract.

Development of Microemulsions Containing Glochidion wallichianum Leaf Extract and Potential for Transdermal and Topical Skin Delivery of Gallic Acid

Glochidion wallichianum (GW) is a good source of antioxidants, including gallic acid, promoting its development as a microemulsion. We constructed five pseudo-ternary phase diagrams comprising isopropyl myristate (IPM), water, and surfactant mixture (Smix)—i.e., Labrasol®:HCO-40® (1:1) with Transcutol® (1:1, 2:1, 3:1), and Tween80:Span80 (3:2) with Transcutol® or propylene glycol:ethanol (1:1). Additionally, blank and GW extract-loaded microemulsions were prepared at an IPM:Water:Smix ratio of 10:30:60 (high water content) and 30:10:60 (high oil content) from each Smix. The physical characteristics, skin permeation, and disposition were evaluated. The formulations with high water content and conductivities provided higher gallic acid permeation and disposition than those with high oil content. The Smix of Labrasol®:HCO-40® (1:1) and Transcutol® (1:1) promoted the highest gallic acid permeation (enhancement ratio 1.78 ± 0.12) and was suitable for transdermal delivery. However, the 1% hydroxypropyl methylcellulose control gel, the microemulsion with Smix of Labrasol®:HCO-40® (1:1) with Transcutol® (2:1), and Smix of Tween80:Span80 (3:2) with propylene glycol:ethanol (1:1) could provide higher skin accumulation of gallic acid than that with other formulations. The microstructures, ratio of surfactant:cosurfactant, and compositions of microemulsions were found to affect the skin permeation and disposition of gallic acid and require optimization to act as transdermal or topical delivery carriers.

A comparison of Myribase and Doublebase gel: Does qualitative similarity of emollient products imply their direct interchangeability in everyday practice?

Emollients are acknowledged as a part of standard care in therapeutic and prevention protocols as well as a part of everyday skin care routine. When it comes to making a final decision between two emollient products, the ingredient list, that is, the formulation composition could be the determining factor. In such cases the consumer, and some healthcare providers, believe that products with the same qualitative composition (ingredient list) must have the same efficacy. In this study, we have investigated the skin hydration performance of two emollient preparations (DBG and MBG), which appear to contain the same ingredients, and hence, could be considered interchangeable in everyday practice. Our studies showed that the effects of DBG were overall superior to the ones attributed to MBG at each investigated time point (1, 2, 4, and 24 h post application) when tested on normal and dry skin. Consequently, it is shown that two apparently qualitatively identical products do not necessarily provide matching efficacy.

Skin hydration dynamics investigated by electrical impedance techniques in vivo and in vitro

Skin is easily accessible for transdermal drug delivery and also attractive for biomarker sampling. These applications are strongly influenced by hydration where elevated hydration generally leads to increased skin permeability. Thus, favorable transdermal delivery and extraction conditions can be easily obtained by exploiting elevated skin hydration. Here, we provide a detailed in vivo and in vitro investigation of the skin hydration dynamics using three techniques based on electrical impedance spectroscopy. Good correlation between in vivo and in vitro results is demonstrated, which implies that simple but realistic in vitro models can be used for further studies related to skin hydration (e.g., cosmetic testing). Importantly, the results show that hydration proceeds in two stages. Firstly, hydration between 5 and 10 min results in a drastic skin impedance change, which is interpreted as filling of superficial voids in skin with conducting electrolyte solution. Secondly, a subtle impedance change is observed over time, which is interpreted as leveling of the water gradient across skin leading to structural relaxation/changes of the macromolecular skin barrier components. With respect to transdermal drug delivery and extraction of biomarkers; 1 h of hydration is suggested to result in beneficial and stable conditions in terms of high skin permeability and extraction efficiency.

Dexpanthenol in Wound Healing after Medical and Cosmetic Interventions (Postprocedure Wound Healing)

With the availability of new technologies, the number of subjects undergoing medical and cosmetic interventions is increasing. Many procedures (e.g., ablative fractional laser treatment) resulting in superficial/minor wounds require appropriate aftercare to prevent complications in wound healing and poor cosmetic outcome. We review the published evidence of the usefulness of topical dexpanthenol in postprocedure wound healing and the associated mechanisms of action at the molecular level. A search in the PubMed and Embase databases was performed to query the terms dexpanthenol, panthenol, superficial wound, minor wound, wound healing, skin repair, and postprocedure. Search results were categorized as clinical trials and in vitro studies. In vitro and clinical studies provided evidence that topically applied dexpanthenol promotes superficial and postprocedure wound healing. Latest findings confirmed that dexpanthenol upregulates genes that are critical for the healing process. The gene expression data are of clinical relevance as evidenced by prospective clinical studies indicating that topical dexpanthenol accelerates wound healing with rapid re-epithelialization and restoration of skin barrier function following skin injury. It can therefore be inferred that topical dexpanthenol represents an appropriate and state-of-the-art treatment option for superficial postprocedure wounds, especially when applied early after the superficial skin damage.

Quantification of the amount of mobile components in intact stratum corneum with natural-abundance 13C solid-state NMR

The outermost layer of the skin is the stratum corneum (SC), which is mainly comprised of solid proteins and lipids. Minor amounts of mobile proteins and lipids are crucial for the macroscopic properties of the SC, including softness, elasticity and barrier function. Still this minor number of mobile components are not well characterized in terms of structure or amount. Conventional quantitative direct polarization (Q-DP) 13C solid-state NMR gives signal amplitudes proportional to concentrations, but fails to quantify the SC mobile components because of spectral overlap with the overwhelming signals from the solids. Spectral editing with the INEPT scheme suppresses the signals from solids, but also modulates the amplitudes of the mobile components depending on their values of the transverse relaxation times T2, scalar couplings JCH, and number of covalently bound hydrogens nH. This study describes a quantitative INEPT (Q-INEPT) method relying on systematic variation of the INEPT timing variables to estimate T2, JCH, nH, and amplitude for each of the resolved resonances from the mobile components. Q-INEPT is validated with a series of model systems containing molecules with different hydrophobicity and dynamics. For selected systems where Q-DP is applicable, the results of Q-INEPT and Q-DP are similar with respect to the linearity and uncertainty of the obtained molar ratios. Utilizing a reference compound with known concentration, we quantify the concentrations of mobile lipids and proteins within the mainly solid SC. By melting all lipids at high temperature, we obtain the total lipid concentration. These Q-INEPT results are the first steps towards a quantitative understanding of the relations between mobile component concentrations and SC macroscopic properties.

Optimal Support of Wound Healing: New Insights

BACKGROUND

The ultimate goal of wound healing following minor injury is to form a tissue regenerate that has functionality and visual appearance as close to the original skin as possible. The body's physiological response to any wound is traditionally characterised by three distinct steps: inflammation, proliferation and remodelling.

SUMMARY

New insights suggest that the three phases overlap (and even occur in parallel) in both time and space in the wound, necessitating a clinical approach that targets each stage simultaneously to ensure rapid repair and wound closure without further complications. Ingredients that exhibit activity across each of the three phases, such as dexpanthenol, are of value in the context of minor wound care and scar management. Key Messages: In addition to treatment and ingredient selection, it is also important to consider broader clinical best practices and self-care options that can be used to optimise the management of minor wounds. An individualised approach that can account for a patient's unique requirements and preferences is critical in achieving effective wound recovery.

Transcutol® P/Cremophor® EL/Ethyl Oleate-Formulated Microemulsion Loaded into Hyaluronic Acid-Based Hydrogel for Improved Transdermal Delivery and Biosafety of Ibuprofen

In the present study, a novel transdermal delivery system was developed and its advantages were demonstrated. Ibuprofen is a commonly used anti-inflammatory, antipyretic, and analgesic drug; however, because of its short biological half-life, it must be frequently administered orally and is highly irritating to the digestive tract. To prepare a novel transdermal delivery system for ibuprofen, a microemulsion was used as a drug carrier and dispersed in a hyaluronic acid-based hydrogel (ME/Gel) to increase percutaneous drug absorption while avoiding gastrointestinal tract irritation. The prepared microemulsion had a droplet size of ~ 90 nm, and the microemulsion had good stability in the hydrogel. Rheological tests revealed that the ME/Gel is a pseudoplastic fluid with decreased viscosity and increased shear rate. It displayed a certain viscoelasticity, and the microemulsion distribution displayed minor effects on the rheological characteristics of the hydrogel system. There was no significant difference in the rheology of the ME/Gel at 25°C and 32°C (normal skin surface temperature), which is beneficial for clinical application. Drug transdermal flux was significantly higher than that of the hydrogel and commercial cream groups (p < 0.01). The 24-h cumulative drug permeation amount was 1.42-fold and 2.52-fold higher than that of the hydrogel and cream groups, respectively. By loading into the ME/Gel, the cytotoxicity of the drug to HaCaT cells was reduced. These results indicate that the prepared ME/Gel can effectively improve transdermal ibuprofen delivery and the biosafety of the drug and could therefore have applicability as a drug delivery system.

Determination of panthenol enantiomers in cosmetic preparations using an achiral-chiral-coupled column HPLC system

A new high-performance liquid chromatography (HPLC) method for separation and determination of panthenol enantiomers in hair care products was developed. Two types of detectors, low-wavelength ultraviolet (UV) and polarimetric, were used. Optimized conditions consisted of coupled achiral, amino type, and chiral, amylose tris(3,5-dimethylphenylcarbamate), stationary phases, mixture of n-hexane/ethanol (60:40, v/v) as mobile phase under isocratic conditions and flow rate 0.8 cm³ min^-1 . The effect of column temperature on retention and resolution of enantiomers was studied. The analysis runtime was 10 minutes, and the average retention times for d- and l-panthenol were 7.10 ±0.1 minutes and 8.21 ±0.2 minutes, respectively. The resolution of enantiomers on coupled achiral-chiral columns was R_s = 2.7. The solid-phase extraction method was employed for extraction and purification of analytes. The validated method was selective, accurate, and linear (R² > .998) over the concentration range of 0.001 to 1.0 mg cm^-3 for both enantiomeric forms. The limits of detection (LOD) and quantitation (LOQ) of each enantiomer were 0.3 and 1.0 μg cm^-3 , respectively. The results demonstrated the occurrence of d-panthenol in hair care products.

Dry skin management: practical approach in light of latest research on skin structure and function

Dry skin is a common condition that is attributed to a lack of water in the stratum corneum. With the availability of new technologies, light has been shed on the pathophysiology of dry skin at the molecular level. With the aim to discuss implications of this latest research for the optimal formulation of emollients designed to treat dry skin, five specialists met in November 2017. Research on three topics thereby provided particularly detailed new insights on how to manage dry skin: research on the lipid composition and organization of the stratum corneum, research on natural moisturizing factors, and research on the peripheral nervous system. There was consensus that latest research expands the rationale to include physiological lipids in an emollient used for dry skin, as they were found to be essential for an adequate composition and organization in the stratum corneum but are reduced in dry skin. Latest findings also confirmed the incorporation of carefully selected humectants into a topical emollient for dry skin, given the reduced activity of enzymes involved in the synthesis of moisturizing factors when skin is dry. Overall, the group of specialists concluded that the previous concept of the five components for an ideal emollient for dry skin is well in accordance with latest research.

Safety assessment of the pharmacological excipient, diethylene glycol monoethyl ether (DEGEE), using in vitro and in vivo systems

BACKGROUND

Diethylene glycol monoethyl ether (DEGEE) is widely used as a solubilizer in cosmetics as well as in oral, topical, transdermal and injectable pharmaceutical formulations. Due to the unavailability of detailed toxicological studies on DEGEE, the Scientific Committee on Consumer Products (SCCP) found its toxicological reports to be unsatisfactory, comprising only summaries. Also, a few reports have raised concern on the use of DEGEE as it might cause damage to the kidneys.

OBJECTIVE

Safety assessment of DEGEE using in vitro and in vivo models.

METHODS

In vitro effects of DEGEE (0.5-25 mg/ml) were assessed in the HEK293 human embryonic kidney cells. In vivo effects were evaluated after single acute exposure of DEGEE via intraperitoneal route in Swiss albino mice and further, a 28 days subchronic exposure study was conducted where DEGEE was administered orally, once daily.

RESULTS

DEGEE was cytotoxic to HEK293 cells, and an IC50 of 15 mg/ml was established. An increase in the intracellular levels of ROS and alteration in the mitochondrial membrane potential led to nuclear fragmentation and induction of apoptosis in these cells. Survival rate of animals administered intraperitoneally with a single acute dose of 1000 mg/kg DEGEE was 100% with no significant changes in the behavioural and histological parameters. However, the dose of 3000 mg/kg and above led to total mortality within 14 days of acute exposure. Subchronic oral exposure of 500-2000 mg/kg DEGEE showed no significant changes in the hematological, biochemical and histopathological parameters.

CONCLUSIONS

The in vitro findings indicate that the nephrotoxic potential of DEGEE cannot be ruled out. The results of the in vivo studies reveal that the degree of toxic effects shown by DEGEE varies, depending on the dose, duration of exposure and routes of administration. Therefore, the present findings are of relevance and thorough studies should be conducted before using this substance in clinical formulations. Graphical abstract Evaluation of the toxic potential of Diethylene glycol monoethyl ether.

The Effect of UVB Irradiation and Oxidative Stress on the Skin Barrier-A New Method to Evaluate Sun Protection Factor Based on Electrical Impedance Spectroscopy

Sunlight is vital for several biochemical processes of the skin organ. However, acute or chronic exposure to ultraviolet radiation (UVR) has several harmful effects on the skin structure and function, especially in the case of the failing function of antioxidative enzymes, which may lead to substantial tissue damage due to the increased presence of reactive oxygen species (ROS). The aim of this work was to investigate the combined effect of ultraviolet B (UVB) irradiation and oxidative stress on the skin barrier integrity. For this, we employed electrical impedance spectroscopy (EIS) to characterize changes of the electrical properties of excised pig skin membranes after various exposure conditions of UVB irradiation, oxidative stress, and the inhibition of antioxidative enzymatic processes. The oxidative stress was regulated by adding hydrogen peroxide (H₂O₂) as a source of ROS, while sodium azide (NaN₃) was used as an inhibitor of the antioxidative enzyme catalase, which is naturally present throughout the epidermis. By screening for the combined effect of UVB and oxidative stress on the skin membrane electrical properties, we developed a new protocol for evaluating these parameters in a simple in vitro setup. Strikingly, the results show that exposure to extreme UVB irradiation does not affect the skin membrane resistance, implying that the skin barrier remains macroscopically intact. Likewise, exposure to only oxidative stress conditions, without UVB irradiation, does not affect the skin membrane resistance. In contrast to these observations, the combination of UVB irradiation and oxidative stress conditions results in a drastic decrease of the skin membrane resistance, indicating that the integrity of the skin barrier is compromised. Further, the skin membrane effective capacitance remained more or less unaffected by UVB exposure, irrespective of simultaneous exposure of oxidative stress. The EIS results were concluded to be associated with clear signs of macroscopic tissue damage of the epidermis as visualized with microscopy after exposure to UVB irradiation under oxidative stress conditions. Finally, the novel methodology was tested by performing an assessment of cosmetic sunscreen formulations with varying sun protection factor (SPF), with an overall successful outcome, showing good correlation between SPF value and protection capacity in terms of skin resistance change. The results from this study allow for the development of new skin sensors based on EIS for the detection of skin tissue damage from exposure to UVB irradiation and oxidative stress and provide a new, more comprehensive methodology, taking into account both the influence of UVB irradiation and oxidative stress, for in vitro determination of SPF in cosmetic formulations.

Skin Penetration and Permeation Properties of Transcutol®-Neat or Diluted Mixtures

A heightened interest in (trans)dermal delivery is in part driven by the need to improve the existing skin therapies and also the demand for alternative routes of administration, notably for pharmaceutical actives with undesirable oral absorption characteristics. The premise of delivering difficult actives to the skin or via the skin however is weighed down by the barrier function properties of the stratum corneum. Short of disrupting the skin by physical means, scientists have resorted to formulation with excipients known to enhance the skin penetration and permeation of drugs. A vehicle that has emerged over the years as a safe solubilizer and enhancer for a broad range of drug actives is the highly purified NF/EP grade of diethylene glycol monoethyl ether (DEGEE) commercially known as Transcutol®. Whereas numerous studies affirm its enhancing effect on drug solubilization, percutaneous absorption rate, and/or drug retention in the skin, there are few publications that unite the body of the published literature in describing the precise role and mechanisms of action for Transcutol®. In view of the current mechanistic understanding of skin barrier properties, this paper takes on a retrospective review of the published works and critically evaluates the data for potential misses due to experimental variables such as formulation design, skin model, skin hydration levels, and drug properties. The goal of this review is to mitigate the incongruence of the published works and to construct a unified, comprehensive understanding of how Transcutol® influences skin penetration and permeation. Graphical Abstract Transcutol has affinity for the hydrophilic head groups of the stratum corneum structures.

Solid and fluid segments within the same molecule of stratum corneum ceramide lipid

The outer layer of the skin, stratum corneum (SC) is an efficient transport barrier and it tolerates mechanical deformation. At physiological conditions, the majority of SC lipids are solid, while the presence of a small amount of fluid lipids is considered crucial for SC barrier and material properties. Here we use solid-state and diffusion nuclear magnetic resonance to characterize the composition and molecular dynamics of the fluid lipid fraction in SC model lipids, focusing on the role of the essential SC lipid CER EOS, which is a ceramide esterified omega-hydroxy sphingosine linoleate with very long chain. We show that both rigid and mobile structures are present within the same CER EOS molecule, and that the linoleate segments undergo fast isotropic reorientation while exhibiting extraordinarily slow self-diffusion. The characterization of this unusual self-assembly in SC lipids provides deepened insight into the molecular arrangement in the SC extracellular lipid matrix and the role of CER EOS linoleate in the healthy and diseased skin.

Topical use of dexpanthenol: a 70th anniversary article

Approximately 70 years ago, the first topical dexpanthenol-containing formulation (Bepanthen™ Ointment) has been developed. Nowadays, various topical dexpanthenol preparations exist, tailored according to individual requirements. Topical dexpanthenol has emerged as frequently used formulation in the field of dermatology and skin care. Various studies confirmed dexpanthenol's moisturizing and skin barrier enhancing potential. It prevents skin irritation, stimulates skin regeneration and promotes wound healing. Two main directions in the use of topical dexpanthenol-containing formulations have therefore been pursued: as skin moisturizer/skin barrier restorer and as facilitator of wound healing. This 70th anniversary paper reviews studies with topical dexpanthenol in skin conditions where it is most frequently used. Although discovered decades ago, the exact mechanisms of action of dexpanthenol have not been fully elucidated yet. With the adoption of new technologies, new light has been shed on dexpanthenol's mode of action at the molecular level. It appears that dexpanthenol increases the mobility of stratum corneum molecular components which are important for barrier function and modulates the expression of genes important for wound healing. This review will update readers on recent advances in this field.

Tracking solvents in the skin through atomically resolved measurements of molecular mobility in intact stratum corneum

Solvents are commonly used in pharmaceutical and cosmetic formulations and sanitary products and cleansers. The uptake of solvent into the skin may change the molecular organization of skin lipids and proteins, which may in turn alter the protective skin barrier function. We herein examine the molecular effects of 10 different solvents on the outermost layer of skin, the stratum corneum (SC), using polarization transfer solid-state NMR on natural abundance ¹³C in intact SC. With this approach it is possible to characterize the molecular dynamics of solvent molecules when present inside intact SC and to simultaneously monitor the effects caused by the added solvent on SC lipids and protein components. All solvents investigated cause an increased fluidity of SC lipids, with the most prominent effects shown for the apolar hydrocarbon solvents and 2-propanol. However, no solvent other than water shows the ability to fluidize amino acids in the keratin filaments. The solvent molecules themselves show reduced molecular mobility when incorporated in the SC matrix. Changes in the molecular properties of the SC, and in particular alternation in the balance between solid and fluid SC components, may have significant influences on the macroscopic SC barrier properties as well as mechanical properties of the skin. Deepened understanding of molecular effects of foreign compounds in SC fluidity can therefore have strong impact on the development of skin products in pharmaceutical, cosmetic, and sanitary applications.