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Based on the structure of the Stratum corneum (SC) the potential penetration/diffusion pathways of drugs and cosmetic actives through the SC are presented and discussed. The well-known lipophilic pathway across the SC is presented and relevant examples are used to show that highly lipophilic molecules such as glucocorticoids, coenzyme Q10 etc. are accumulated in the SC and penetrate into the inner liquid like layer of the SC lipid bilayer by lateral diffusion. The diffusion into and across the SC of highly hydrophilic drugs and active substances such as urea, amino acids and peptides is still under discussion. Another diffusion pathway for the highly hydrophilic molecules via the corneocytes and the corneodesmosomes is presented and discussed, the corneocytary diffusion pathway., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 The Author(s). Published by Elsevier B.V. All rights reserved.)

Free amino acids (FAAs) constitute the largest component (∼40 %) of the so-called natural moisturizing factors of the skin. Their level declines in dry skin conditions and one strategy to overcome this problem may involve the topical delivery of FAAs through appropriate strategy. The objective of the present study was therefore to identify alternative skin models and study the corneocyte-water partition coefficients (K COR/W ) and permeation coefficient (K P ) of 18 FAAs. The K COR/W was studied using standard protocols and the permeation studies were conducted using Franz diffusion cell. The results indicate that the FAAs have high partitioning behavior to the corneocytes. The K COR/W values of the human COR and that of pig ear skin were better correlated with each other than that of keratin isolated from chicken feathers. The presence of lipid in the stratum corneum (SC), initial concentration of the FAAs, and permeation enhancers affect the K COR/W . The FAAs have low permeation into the SC which suggests the need for permeation enhancers in designing dosage form containing these compounds. Even though the investigated mathematical models show good prediction of the Kp values, better prediction could be obtained by considering factors such as the possible entrapment of the FAAs by the CORs., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 The Author(s). Published by Elsevier B.V. All rights reserved.)

The objective of this study was to explore the benefits of transdermal drug delivery systems as an alternative option for patients who are unable to tolerate oral administration of drugs, such as ibuprofen (IB). To achieve this, nonionic surfactants and three cosolvents were employed to develop new microemulsions (MEs) that contained IB as nanocarriers. The aim was to enhance the solubility and bioavailability of the drug after transdermal administration. The MEs were characterised by droplet size, polydispersity index (PDI), and rheological properties. Furthermore, the flux of IB was evaluated by Franz diffusion cells using excised rat skin and in vivo bioavailability using rats. The results showed that the MEs had ideal viscosity and droplet size below 100 nm. Moreover, using the developed MEs, an improvement in the solubility (170 mg/mL) and flux through the rat skin (94.6 ± 8.0 µg/cm 2 .h) was achieved. In addition, IB demonstrated a maximum plasma level of 0.064 mg/mL after 8 h of transdermal administration in rats using the ME with an increase in the bioavailability of about 1.5 times in comparison to the commercial IB gel. In conclusion, the developed nonionic MEs containing IB can be ideal nanocarriers and promising formulations for the transdermal administration of IB., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023. Published by Elsevier B.V.)

Free amino acids constitute the largest portion (40%) of the natural moisturizing factor. Their level might decline and cause dry skin condition. The treatment strategy involves the replenishment of these components to the skin, and, to our knowledge, there are no reports that involve dermal delivery of free amino acids. The purpose of the current study was therefore to prepare and characterize different micro-emulsions, micro-emulsion-based hydrogels, and hydrophilic creams loaded with free amino acids for dermal delivery. Oil-in-water microemulsions were prepared using carefully selected formulation components. Poloxamer ® 407 and carbopol ® 934 were used to prepare the hydrogels. All the formulations were characterized for physico-chemical, permeation and cytotoxicity properties. The results showed that the prepared microemulsions had desired droplet size, size distribution, zeta potential, refractive index, and pH. In the gel preparations, the elastic properties prevailed over the viscous behavior. The hydrogels had non-Newtonian shear-thinning behavior with some thixotropic properties. The free amino acids permeated into the deeper layers of the stratum corneum from the microemulsions, and microemulsion-based hydrogels as compared to conventional hydrophilic cream. The hydrogels were more effective than the microemulsions to deliver the FAAs to the desired site of the skin in a sustained manner. Poloxamer-based hydrogel permeated into deeper skin layers than Carbopol-based hydrogel. Formulations prepared using standard free amino acids and those extracted and purified from oyster mushroom had similar characteristics. All the formulations were stable and safe to be applied topically. In conclusion, microemulsions and microemulsion-based hydrogels can be considered as safe carrier systems for dermal delivery of free amino acids.

Introduction: Heparin is a commonly used anti-coagulant administered either by intravenous or subcutaneous injection for a systemic effect or topically for the treatment of peripheral vascular disorders., Objective: This study aimed to formulate heparin in non-ionic colloidal carrier systems (CCSs) having enhanced percutaneous absorption for systemic and topical administration., Methods: Five CCSs were developed and characterized for their rheological properties, droplet size, and drug loading. The percutaneous absorption of heparin was evaluated in vitro using Franz diffusion cells with rats' skin and with the aid of a developed high-pressure chromatography method. Furthermore, the efficacy of two developed heparin CCSs was tested percutaneously in rats by measuring the response against the time in comparison to subcutaneous administration., Results: The rheograms and droplet size measurements showed that the developed drug delivery systems have Newtonian properties with a droplet size between 109 and 460 nm. As much as 500 mg of heparin could be loaded in around 5 mL of CCS. Furthermore, using Franz diffusion cells, a diffusion rate of 19.216 ± 2.01 USP U/cm2.h could be achieved for heparin-loaded CCSs. Moreover, the estimated percutaneous in vivo relative bioavailability in comparison to subcutaneous administration could reflect that at least more than 50% of the drug passed through the skin., Conclusion: The developed novel non-toxic CCSs containing heparin can be good candidates for percutaneous administration as alternative delivery systems for subcutaneous and intravenous invasive administration., (© 2022 S. Karger AG, Basel.)

The human skin provides a physiochemical and biological protective barrier due to the unique structure of its outermost layer known as the Stratum corneum. This layer consists of corneocytes and a multi-lamellar lipid matrix forming a composite, which is a major determining factor for the barrier function of the Stratum corneum. A substantiated understanding of this barrier is necessary, as controlled breaching or modulation of the same is also essential for various health and personal care applications such as topical drug delivery and cosmetics to a name few. In this study, we discuss the state-of-the-art of neutron diffraction techniques, using specifically deuterated lipids, combined with the information obtained from molecular models using molecular dynamics simulations, to understand the structure and barrier function of the Stratum corneum lipid matrix. As an example, the effect of ceramide concentration on a lipid lamella system consisting of CER[NP]/CER[AP]/Cholesterol/free fatty acid (deprotonated) is studied. This study demonstrates the usefulness of the combined approach of neutron diffraction and molecular dynamics simulations for effective analysis of the model systems created for the Stratum corneum lipid matrix. The optimization of force fields by comparison with experimental data is furthermore an important step in the direction of providing a predictive quality., (Copyright © 2022. Published by Elsevier B.V.)

In this study, insulin was loaded into non-ionic colloidal carrier systems (CCS) to be used as nano-sized drug delivery systems for transdermal administration. The CCS were characterized for their rheological properties, droplet size and drug loading. Also, the transdermal flux of insulin was estimated using Franz diffusion cells through the epidermis and all the layers of the rats' skin. The efficacy of the administration of the CCS was assessed in vivo transdermally in rats. Based on the rheological properties and droplet size results, the formulated fluids were identified as nano-sized systems having an aqueous colloidal phase, where the hydrophilic peptide is located. Also, a flux of insulin as high as 0.119 ± 0.016 and 1.328 ± 0.047 iu/cm 2. h through the rat's skin and epidermis, respectively, could be achieved using CCSIn2. Moreover, the monitoring of the blood sugar level over 6.5 h after a single transdermal administration of CCS exhibited a slight decrease. However, a significant drop in the blood sugar level was observed when they were administered once every two days over 10 days. The developed insulin-loaded CCS containing the penetration enhancer DMSO are nano-sized drug delivery systems and can induce a delayed therapeutic effect by repeating the administration., (Copyright © 2022 Elsevier B.V. All rights reserved.)

The stratum corneum (SC) is the largest physical barrier of the human body. It protects against physical, chemical and biological damages, and avoids evaporation of water from the deepest skin layers. For its correct functioning, the homeostasis of the SC lipid matrix is fundamental. An alteration of the lipid matrix composition and in particular of its ceramide (CER) fraction can lead to the development of pathologies such as atopic dermatitis and psoriasis. Different studies showed that the direct replenishment of SC lipids on damaged skin had positive effects on the recovery of its barrier properties. In this work, cerosomes, i.e. liposomes composed of SC lipids, have been successfully prepared in order to investigate the mechanism of interaction with a model SC lipid matrix. The cerosomes contain CER[NP], D-CER[AP], stearic acid and cholesterol. In addition, hydrogenated soybean phospholipids have been added to one of the formulations leading to an increased stability at neutral pH. For the mode of action studies, monolayer models at the air-water interface and on solid support have been deployed. The results indicated that a strong interaction occurred between SC monolayers and the cerosomes. Since both systems were negatively charged, the driving force for the interaction must be based on the ability of CERs head groups to establish intermolecular hydrogen bonding networks that energetically prevailed against the electrostatic repulsion. This work proved for the first time the mode of action by which cerosomes exploit their function as skin barrier repairing agents on the SC., Competing Interests: The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (©e 8, 64289 Darmstadt, Germany .)

The stratum corneum represents the first skin barrier against chemical and physical damage. These unique properties are based on its peculiar lipid composition with ceramides (CERs) as the main protagonists. In this study, the structural and chemical properties of the α-OH phytosphingosine [AP] CER class have been investigated. α-OH CERs are present in the stratum corneum in their d-forms; however, in most model systems the diastereomer mixture with the synthetically produced l-form is used. The d-form is well-known to form a hydrogen bonding network that helps to reduce the permeability of the lipid matrix, while the l-form does not show any hydrogen bonding network formation. In this paper, 2D (monolayers) and 3D (aqueous dispersions) models have been used to thoroughly study the physical-chemical behaviors of CER[AP] diastereomers taking into account how the symmetry of the chain pattern influences the behavior of the molecules. The chains of both diastereomers arrange in an oblique unit cell, but only the d-CER[AP] forms a supramolecular lattice (subgel phase) in both model systems. Interestingly, the chain pattern does not play any role in structure formation since the hydrogen bonding network dictates the packing properties. The 1:1 mixture of the diastereomers phase separates into two domains: one is composed of practically pure d-form and the other one is composed of a mixture of the l-form with a certain amount of d-form molecules.

Background: Oral ivermectin can be used to treat scabies. Evidence for safe and effective use in young children in individual treatment situations has been developed and published. In order to also ensure a body weight-adapted dosage for children, an ivermectin-containing syrup was developed as an extemporaneous preparation., Materials and Methods: Since ivermectin is not available as a pure substance for the formulation, tablets containing active ingredient were used as a basic material for development. The formulation was designed according to pharmaceutical, regulatory and use-oriented criteria. An HPLC (high-pressure liquid chromatography) method was developed and validated to demonstrate chemical stability. In order to facilitate the practical implementation, information on suitable packaging material and application aids was also developed and the formulation was evaluated., Results: It has been demonstrated that the final formulation produced in the pharmacy was stable and can be stored for 3 weeks. No concerns were raised regarding the tolerability of the syrup formulation. The physicochemical properties and the taste of the formulation allow the intended use as a well-dosed syrup for children., Conclusion: The developed formulation meets the requirements of the Apothekenbetriebsordnung (Pharmacy Work Rules; Section 7 ApBetrO) and enables an exact, body weight-adapted dosage of oral ivermectin in young children. Studies on human pharmacokinetics or clinical studies to demonstrate tolerability and/or efficacy are not available for the formulation., (© 2021. The Author(s).)

Free amino acids (FAAs), the major constituents of the natural moisturizing factor (NMF), are very important for maintaining the moisture balance of human skin and their deficiency results in dry skin conditions. There is a great interest in the identification and use of nature-based sources of these molecules for such cosmeceutical applications. The objective of the present study was, therefore, to investigate the FAA contents of selected Ethiopian plant and fungi species; and select the best sources so as to use them for the stated purpose. About 59 different plant species and oyster mushroom were included in the study and the concentrations of 27 FAAs were analyzed. Each sample was collected, lyophilized, extracted using aqueous solvent, derivatized with Fluorenylmethoxycarbonyl chloride (Fmoc-Cl) prior to solid-phase extraction and quantified using Liquid Chromatography Electrospray Ionization Tandem Mass Spectrometric (LC-ESI-MS/MS) system. All the 27 FAAs were detected in most of the samples. The dominant FAAs that are part of the NMF were found at sufficiently high concentration in the mushroom and some of the plants. This indicates that FAAs that could be included in the preparations for the management of dry skin condition can be obtained from a single natural resource and the use of these resources for the specified purpose have both economic and therapeutic advantage in addition to fulfilling customer needs.

Transdermal drug delivery is a passive diffusion process of an active compound through the skin which is affected by drug solubility in the multilamellar lipidic matrix of the stratum corneum (SC). Widely used non-ionic surfactants (NIS) can be added into transdermal formulations to enhance the penetration of drugs by influencing the packing of the stratum corneum lipidic matrix. Objective of our study was to analyse the interaction between selected NIS and a simple SC lipidic matrix model system using a variety of surface-sensitive techniques based on the application of Langmuir monolayers. In this work, the well-known surfactant Polysorbate 80 was compared with a modern surfactant Sucrose monolaurate. Infrared reflection-absorption spectroscopy (IRRAS) and epifluorescence microscopy provide information about the effects of those surfactants on the SC model system. Monolayer isotherms of the SC model mixture indicate a very stiff and well-packed layer, however, packing defects are evidenced in epifluorescence studies. The injection of the two NIS underneath the SC monolayers proved their potential to penetrate into the SC model at the air-water interface having a maximum insertion pressure (MIP) above the assumed lateral pressure of biological membranes. The NIS adsorbed preferentially into packing defects seen in epifluorescence microscopy studies with Sucrose monolaurate being more active than Polysorbate 80 in disordering the SC monolayer., (Copyright © 2020. Published by Elsevier B.V.)

Ceramides (CERs) play a major role in skin barrier function and direct replacement of depleted skin CERs, due to skin disorder or aging, has beneficial effects in improving skin barrier function and skin hydration. Though, plants are reliable source of CERs, absence of economical and effective method of hydrolysis to convert the dominant plant sphingolipid, glucosylceramides (GlcCERs), into CERs remains a challenge. This study aims at exploring alternative GlcCERs sources and chemical method of hydrolysis into CERs for dermal application. GlcCERs isolated from lupin bean (Lupinus albus), mung bean (Vigna radiate) and naked barley (Hordium vulgare) were identified using ultra high performance liquid chromatography hyphenated with atmospheric pressure chemical ionization - high resolution tandem mass spectrometer (UHPLC/APCI-HRMS/MS) and quantified with validated automated multiple development-high performance thin layer chromatography (AMD-HPTLC) method. Plant GlcCERs were hydrolyzed into CERs with mild acid hydrolysis (0.1 N HCl) after treating them with oxidizing agent, NaIO 4, and reducing agent, NaBH 4 . GlcCERs with 4,8-sphingadienine, 8-sphingenine and 4-hydroxy-8-sphingenine sphingoid bases linked with C14 to C26 α-hydroxylated fatty acids (FAs) were identified. Single GlcCER (m/z 714.5520) was dominant in lupin and mung beans while five major GlcCERs species (m/z 714.5520, m/z 742.5829, m/z 770.6144, m/z 842.6719 and m/z 844.56875) were obtained from naked barley. The GlcCERs contents of the three plants were comparable. However, lupin bean contains predominantly (> 98 %) a single GlcCER (m/z 714.5520). Considering the affordability, GlcCER content and yield, lupin bean would be the preferred alternative commercial source of GlcCERs. CER species bearing 4,8-sphingadienine and 8-sphingenine sphingoid bases attached to C14 to 24 FAs were found after mild acid hydrolysis. CER species with m/z 552.4992 was the main component in the beans while CER with m/z 608.5613 was dominant in the naked barley. However, CERs with 4-hydroxy-8-sphingenine sphingoid base were not detected in UHPLC-HRMS/MS study suggesting that the method works for mainly GlcCERs carrying dihydroxy sphingoid bases. The method is economical and effective which potentiates the commercialization of plant CERs for dermal application., Competing Interests: Declaration of Competing Interest The authors declare no conflict of interest., (Copyright © 2020 Elsevier B.V. All rights reserved.)

Natural phospholipid (PL) excipients are native, biocompatible and relatively inexpensive alternatives to synthetic emulsifiers. A well-known PL excipient is lecithin, which primarily contains phosphatidylcholine (PC) and (depending on the purity grade) also contains a well-defined mixture of other PLs with a fatty acid composition, which reflects their natural source. Since all of these lipid species are emulsifiers, natural PLs can be considered as a mixture of (co-) emulsifiers. Many different HLB values for lecithins are given in the literature, which is why this needs to be clarified. To assess this, HLB values of thirteen different plant derived PLs differing in PC content were determined using a centrifugation stress method to determine the relative stability of an emulsion with the respective emulsifier and different oil phases. It could be shown that the studied PLs can be characterized by a broad HLB range, which may be linked to the composition of the PLs and the oil used. In order to emphasize the results of the HLB determination, it could be demonstrated that stable emulsions could be prepared with a wide range of oils using the plant-based PLs and that the preparation method of the emulsions is important in order to obtain stable emulsions. Therefore, assigning a specific exact HLB value to natural PLs instead of a wider range is inappropriate. The broad HLB ranges indicate the suitability of the studied PL emulsifiers for the preparation of oil-in-water emulsions for a wide range of oils: It is recommended to experimentally evaluate the suitability of these natural emulsifiers for the preparation of stable emulsions and to benefit from the wide range of HLB values of these emulsifiers instead of relying on inaccurate and confusing HLB values in the literature.

Celluloses were extracted from teff straw (TS), enset fiber (EF), sugarcane bagasse (SB) and coffee hull (CH) agro-industrial byproducts generated in large quantities in Ethiopia. The present study aimed to explore these plant byproducts as alternative sources of cellulose for potential industrial applications, using various eco-friendly chlorine-free treatment conditions to obtain an optimum cellulose extraction condition. The byproducts and the as-extracted celluloses were analyzed for chemical compositions, yield, chemical functionality, crystallinity, thermal stability and morphology. EF yielded the highest cellulose content (60.0%), whereas CH the least (35.5%). FTIR spectra and ESEM morphological studies of the celluloses indicated progressive removal of non-cellulosic constituents. XRD analyses showed EF cellulose had the highest crystallinity index (CrI) (85.56%), crystallite size (5.52 nm), and proportion of crystallite interior chains of 200 plane (0.629), exhibiting unique physicochemical properties. The byproducts and the as-extracted celluloses showed Cellulose I β crystal lattice, while celluloses from EF and SB also displayed (partial) polymorphic transition into Cellulose II. TGA studies revealed enhanced stability of the as-extracted celluloses. On the basis of the physicochemical characteristics of the celluloses, all the byproducts studied could be considered as alternative sources of cellulose for potential value-added industrial applications., Competing Interests: Declaration of competing interest None., (Copyright © 2020. Published by Elsevier B.V.)

This review is the second part of a series which presents the state of the art in stratum corneum (SC) lipid matrix (LM) research in depth. In this part, the various hypothetical models which were developed to describe the structure and function of the SC LM as the skin's barrier will be discussed. New as well as a cumulative assortment of older results which change the view on the different models are considered to conclude how well the different models are holding up today. As a final conclusion, a model, factoring in as much of the known data as possible, is concluded, unifying the varying different models into one which can be developed further, as new results are found in the future. So far, the model is described with a single crystalline or gel-like phase with a certain amount of nanocrystallites of concentrated ceramides (CERs) and free fatty acids and more fluid nanodomains caused by a fluidizing effect of the cholesterol. These domains are dynamically resolved and reformed and do not impair the barrier function. The chain conformation is not completely clear yet; however, an equilibrium of fully extended and hairpin-folded CERs with ratios depending on the properties of each individual CER species is proposed as most likely. An overlapping middle layer as described for the tri-layer model in part I of this series would be present for both conformations. The macroscopic broad-narrow-broad layering, observed in electron micrographs, is explained by an external templating by the lipid envelope, and an internal templating by short and long lipid chains each preferentially show a homophilic association, forming thicker and thinner bilayers, respectively. The degree of influence of the very long ω-hydroxy-CERs is discussed as well., (© 2020 The Author(s) Published by S. Karger AG, Basel.)

Introduction: Coenzyme Q10 (CoQ10) has been widely used in topical and cosmeceutical products due to its cutaneous antioxidant and energizer effects. CoQ10 is found in a higher concentration in the epidermis compared to dermis. The epidermal level of CoQ10 can be reduced due to several factors such as skin UV irradiation and photoaging. Various dermal nano-formulations have been investigated to overcome the skin barrier and enhance the poor penetration of CoQ10. The nanocarriers are designed to target and concentrate the CoQ10 in the viable epidermis. Most of these studies, however, failed to show the depth and extent of penetration of CoQ10 from the various carrier systems., Objective: The distribution of CoQ10 across the various skin layers has to be shown using skin slices representing the different skin layers., Methods: To realize this objective, a sensitive and selective HPLC method was developed and validated for the quantification of CoQ10 in the different skin slices. The method applicability to skin penetration (using excised human skin) as well as stability studies was investigated using CoQ10-loaded lecithin-based microemulsion (ME) and hydrophilic cream formulations., Results: It could be shown that the highest concentration of CoQ10 in the viable epidermis, the target skin layer for CoQ10, was observed after application of the CoQ10 in the hydrophilic cream. This cream contains 10% of 2-ethylhexyl laurate which works obviously as a penetration enhancer for CoQ10. In contrast, the penetration of CoQ10 was lower from the ME. Just in the deeper dermis, a certain amount of CoQ10 could be detected., Conclusions: The HPLC method quantified the trace quantities of the CoQ10 distributed across the various skin layers and, hence, can be used to investigate the skin penetration of CoQ10 from various dermal standard and nano-formulations., (© 2020 The Author(s) Published by S. Karger AG, Basel.)

To optimize dermal and transdermal administration of drugs, the barrier function of the skin, particularly the stratum corneum (SC), needs to be reduced reversibly. For this purpose, penetration/diffusion enhancers such as DMSO can be applied. However, there is the question whether DMSO is an aggressive penetration/diffusion enhancer in pharmaceutical and cosmetical relevant concentrations? Until now, it is unclear if this penetration/diffusion enhancement is caused by an interaction with the SC lipid matrix or related to effects within the corneocytes. Therefore, the effects of the hydrophilic enhancer DMSO on SC models with different dimensionality ranging from bilayers (liposomes) via oligo-layers to multilayers have been investigated in this study. The effects of DMSO should be compared to that of other relevant hydrophilic enhancers such as urea and taurine. An innovative spectrum of methods was applied to ascertain the mode of action of DMSO in relevant concentrations on a molecular scale. The experiments reveal that there is no specific interaction of 10% and 30% DMSO solutions with the SC model systems. Hence, if DMSO is applied in pharmaceutically and cosmetically relevant concentrations, it has no influence on the SC model systems used. Neither an additional water uptake in the head group region nor a decrease of the lipid chain packing density have been observed. The leakage studies on liposomes show that 10% DMSO is causing just a very slight leakage of 8%, lower than the leakage of 19.4% caused by 10% urea (Müller et al., 2016). Consequently, the interactions of DMSO with the SC model lipids used are very low in concentrations of 10% and 30%, respectively. Since the lipid composition in native SC lipid matrix is far more complex than this model mixture, the results can not be directly transferred to the native SC lipid matrix. However, the outcome of this study, together with various findings in the literature give rise to the assumption that the enhancing effect of DMSO concerning the diffusion of relevant hydrophilic drugs and actives appears to be realized via the corneocytes., (Copyright © 2019 Elsevier B.V. All rights reserved.)

Amino acids (AAs), important constituents of natural moisturizing factors (NMFs) of the skin are decreased in diseased conditions such as psoriasis and atopic dermatitis. No study so far investigated the uptake of AAs into isolated corneocytes (COR). The present study was performed using 19 AAs, including taurine (TAU), to measure their amount diffused into the COR and binding of these AAs to keratin. Incubation of alanine, aspartic acid, asparagine, glutamine, glutamic acid, histidine, proline, serine and TAU with the isolated COR showed uptake after 24 h of 51.6, 95.4, 98.6, 94.1, 95.6, 90.1, 94.6, 72.9 and 57.8 %, respectively, into the COR but no binding with keratin. Uptake of TAU was validated by time dependent in-vitro diffusion models 'without COR and 'with COR'. The time dependent curve fitting showed that in in-vitro diffusion model 'without COR' there was no change in the total concentration of TAU until 72 hours, while in diffusion model 'with COR' the total conc. decreased to 37.8 % after 72 hours. The Pearson's correlation coefficient 'r' between the conc. curves of both in-vitro diffusion models was -0.54 that was an evidence of significant amount of TAU uptake by the COR. AAs as part of the NMFs have a great potential to be diffused into the COR. This property of the AAs can be employed in further dermatological research on diseased or aged skin conditions with NMFs deficiency.

In a previous study, it was shown, that shed snake skin is a good alternative model membrane for the human stratum corneum (SC). In this study, the influence of the enhancers dimethyl sulfoxide (DMSO), 1,2-propanediol, 1,3-butanediol, 1,2-pentanediol, 1,2-hexanediol and 1,2-octanediol in a concentration of 10 % on the permeation of l-prolyl- l-lysyl-l-α-glutamyl-l-lysin (PKEK) through shed snake skin was conducted. Pharmacokinetic parameters (diffusion coefficient, permeation coefficient, t-lag, Flux) were calculated. All examinations were performed on the skin of an individual and thus allowed a very good comparability of the data. All enhancers have overcome the shed snake skin and could be proven in the acceptor. DMSO does not affect the permeability of the membrane. Nevertheless, PKEK permeates faster in the presence of DMSO than PKEK being used alone. PKEK permeated the same, no matter if an auxiliary material was added or not. Without their addition, in all other enhancers no significant difference towards permeation could be determined.

A method for selective and sensitive quantification of amino acids is described. The combination of established derivatization procedures of secondary and primary amino groups with 9-fluorenylmethoxycarbonyl chloride (Fmoc-Cl) and subsequent detection of derivatized amino acids by LC-ESI-MS/MS using multiple reaction monitoring provides high selectivity. The attachment of an apolar moiety enables purification of derivatized amino acids from matrix by a single solid-phase extraction step, which increases sensitivity by reduced ion suppression during LC-ESI-MS/MS detection. Additionally, chromatography of all amino acids can be performed on reversed-phase HPLC columns using eluents without additives, which are known to cause significant decreases in signal to noise ratios. The method has been routinely applied for amino acid profiling of low amounts of liquids and tissues of various origins with a sample throughput of about 50-100 samples a day. In addition to a detailed description of the method, some representative examples are presented.

Background/aims: Free amino acids (FAAs) and urea, present inside the corneocytes, can be important indicators of skin condition. However, due to the lack of a standard extraction protocol for FAAs from corneocytes, conflicting research results have been reported. Therefore, the purpose of this study was (1) to standardize the extraction protocol and (2) to investigate FAA profiles in healthy young and healthy old volunteers, as well as in psoriasis and atopic dermatitis patients., Methods: Skin samples were collected from four groups (healthy young, healthy old, and psoriasis and atopic dermatitis patients) with 5 volunteers per group. Corneocytes were isolated and examined microscopically. FAAs and urea were extracted from the isolated corneocytes, and their amounts were quantified using LC-ESI/MS/MS (after derivatization with Fmoc-Cl) and colorimetric methods, respectively., Results: The micrographs of the corneocytes showed no morphological features attributable to age or disease conditions. The highest and lowest concentrations of total FAAs and urea were observed in the healthy old group and the healthy young group, respectively. Unlike the other FAAs and urea, citrulline was found at a higher level in the healthy young group than in the disease groups., Conclusion: This study suggests that the levels of FAAs and urea in the skin are affected by age and skin conditions (healthy/diseased). However, further studies are needed to show the effects of different skin conditions on the levels of FAAs and urea., (© 2019 S. Karger AG, Basel.)

The main barrier of the human skin is the stratum corneum (SC). Its properties (also depending on the health and age of the individual) and its influence on improved penetration of active ingredients into the skin are the subject of many research projects. Since the availability of human skin, as the ideal model membrane, is limited, the aim of this study was to find a suitable alternative model membrane from the animal kingdom. The alternative model membrane should be used in subsequent permeation experiments with the Teflon diffusion cell instead of human SC. Previous studies have already investigated the permeation properties of pig, snake, and human skin, but not in a Teflon diffusion cell using ATR. Therefore, it first had to be proven that comparable results can be achieved with animal membranes even under these measurement conditions. This is the precondition for meaningful future permeation experiments with potential enhancers. For this purpose, permeation experiments on various model membranes (human isolated SC, sunburned SC, pig isolated SC, and shed snake skin) by means of FTIR-ATR in a Teflon diffusion cell containing the acceptor and the donor compartment as well as the model membrane were conducted and concentration-time courses of the model peptide PKEK determined. These concentration-time courses were used to calculate and compare the pharmacokinetic parameters (permeation coefficients, lag time, and flux). The starting point was a 10% PKEK solution in D2O. It turned out that snake skin is the appropriate alternative model membrane for this type of permeation test., (© 2019 S. Karger AG, Basel.)

This study used neutron diffraction to investigate a ceramide-[NP] C24/[AP] C24 /[EOS]-br C30/cholesterol/lignoceric acid (0.6: 0.3: 0.1: 0.7: 1) based stratum corneum modelling system. By adding specifically deuterated ceramides-[NP]-D 3 , [AP]-D 3 , and [EOS]-br-D 3 , detailed information on the lamellar and the nanostructure of the system was obtained. For the short periodicity phase a natural-like lamellar repeat distance of 5.47 ± 0.02 nm was observed, similar to the [NP]/[AP] base system without the [EOS]-br. Unlike in this system the ceramides here were slightly tilted, hinting towards a slightly less natural arrangement. Due to the deuteration it was possible to observe that the long ceramide chains were overlapping in the lamellar mid-plane. This is considered to be an important feature for the natural stratum corneum. Despite the presence of a ceramide [EOS] analogue - able to form a long phase arrangement - no distinct long periodicity phase was formed, despite a slightly higher than natural ω-acyl ceramide ratio of 10 mol%. The deuterated variant of this ceramide determined that the very long ceramide was integrated into the short periodicity phase, spanning multiple layers instead. The - compared to the base system - unchanged repeat distance highlights the stability of this structure. Furthermore, the localisation of the very long ceramide in the short periodicity phase indicates the possibility of a crosslinking effect and thus a multilayer stabilizing role for the ceramide [EOS]. It can be concluded, that additionally to the mere presence of ceramide-[EOS] more complex conditions have to be met in order to form this long phase. This has to be further investigated in the future., (Copyright © 2018 Elsevier B.V. All rights reserved.)

The control of bleaching reaction is important in hair bleaching and laundry detergents to ensure quality of the final product. A better understanding of the reaction mechanisms is needed to minimize product failures. 31 P NMR-spectroscopy-based spin trap technique was employed to detect and quantify the free radical species that were generated in different bleaching solutions. These solutions contained the key actives in an alkaline hair colorant/bleaching product, an ammonium salt and hydrogen peroxide at pH = 10. Generally, the main radical species detected in hair oxidative coloring or bleaching processes, were hydroperoxyl/superoxide radicals HO 2 ·/O 2 .- , amino radicals ·NH 2 and hydroxyl radicals ·OH. Their amounts showed a variation based on the chemical composition of the bleaching systems and the metal ion content. The generation of free radicals from reactions between transition metal ions, such as copper, and hydrogen peroxide at pH = 10 was evaluated. In the absence of chelating agents, the copper ions generated a significant level of hydroxyl radicals in a Fenton-like reaction with hydrogen peroxide at pH = 10. Besides that, an increase in copper ion content led to an increase of amino radical ·NH 2 , whereas the concentration of superoxide radical O 2 ·- decreased which was not yet well reported in the previous literature. The effect of chelating agents like ethylenediaminetetraacetic acid (EDTA), tetrasodium-iminodisuccinate (IDS), a mixture of basic amino acids and dicarboxylic acid on free radical formation was investigated in the presence of binary Cu 2+ -Ca 2+ bleaching systems. As expected, in the binary Cu 2+ -Ca 2+ ion system EDTA did not suppress hydroxyl radical formation effectively, but the mixture containing sodium succinate, lysine and arginine reduced hydroxyl radical formation, whereas IDS (nearly) completely inhibited hydroxyl radical formation. The results indicated that each bleaching solution has its characteristic performance and damage profile. Whereas the reactivity can be controlled by the usage of chelating agents., (Copyright © 2018 Elsevier Inc. All rights reserved.)

This review is summarizing an important part of the state of the art in stratum corneum research. A complete overview on discoveries about the general biophysical and physicochemical properties of the known ceramide species' is provided. The ceramides are one of the three major components of the lipid matrix and mainly govern its properties and structure. They are shown to exhibit very little redundancy, despite the minor differences in their chemical structure. The results are discussed, compared to each other as well as the current base of knowledge. New interesting aspects and concepts are concluded or suggested. A novel interpretation of the 3-dimensional structure of the lipid matrix and its influence on the barrier function will be discussed. The most important conclusion is the presentation of a new and up to date theoretical model of the nanostructure of the short periodicity phase. The model suggests three perpendicular layers: The rigid head group region, the rigid chain region and, a liquid-like overlapping middle layer. The general principle of the skin barrier function is highlighted in regard to this structure and the ceramides biophysical and physicochemical properties. As a result of these considerations, the entropy vs. enthalpy principle is introduced, shedding light on the function as well as the effectiveness of the skin barrier. Additionally, general ideas to effectively overcome this barrier principle for dermal and transdermal delivery of actives or how to use it for specific targeting of the stratum corneum are proposed., (Copyright © 2018 Elsevier B.V. All rights reserved.)

Dermal application of peptides as drugs is an interesting and growing field in therapeutics. Besides therapy, they are increasingly used as cosmetic agents. Peptide delivery into the skin is highly challenging since they provide disadvantageous properties like a high molecular weight, hydrophilicity, polarity and susceptibility to enzymatic degradation. The aim of the presented study was to improve the bioavailability of a dermal administered tetrapeptide GEKG (amino acid sequence in one-letter notation). A nano-sized carrier system (microemulsion, ME) of w/o type was therefore developed since ME provide excellent penetration enhancing properties. Furthermore, enhancers were used to increase the penetration capacity of GEKG. The penetration of GEKG from the ME and enhancer-containing emulsions was compared to the penetration from a standard formulation. For this purpose ex vivo penetration studies with human skin were performed, which provide insights into dermal penetration and also localization and distribution of the active substances in each skin layer as well as the influence of vehicle variations. Experiments with three incubation times (30, 100, 300 min) and 5000 ppm GEKG in the formulations clearly show that the nano-sized carrier system is significantly better suited to transport GEKG rapidly into upper and deeper vital skin layers as well as through the skin compared to the standard cream. Studies with o/w emulsions containing 5% glyceryl caprylate/caprate 2.0× or 1.5× as enhancer and 50 ppm peptide revealed only a tendency to increased penetration into the SC and for the formulation with glyceryl caprylate/caprate 1.5× into the vital epidermis compared to the standard cream without additional enhancer. Significant better penetration rates were observed for the ME with 50 ppm GEKG. It can be concluded that liquid nano-sized systems are significantly more effective as carriers for extremely hydrophilic peptides used in cosmetics and also in therapeutics than classic cosmetic emulsions or enhancer-containing emulsions., Chemical Compounds: Tetrapeptide-21 (CAS: 960608-17-7) glyceryl caprylate/caprate (CAS: 73398-61-5) sorbitan oleate (CAS: 1338-43-8) polyglyceryl-4 laurate (CAS: 75798-42-4) butylene glycol (CAS: 107-88-0) isopropyl palmitate (CAS: 142-91-6)., (Copyright © 2018 Elsevier B.V. All rights reserved.)

Ceramides (CERs) are the backbone of the intercellular lipid lamellae of the stratum corneum (SC), the outer layer of the skin. Skin diseases such as atopic dermatitis, psoriasis, and aged skin are characterized by dysfunctional skin barrier and dryness which are associated with reduced levels of CERs. Replenishing the depleted epidermal CERs with exogenous CERs has been shown to have beneficial effects in improving the skin barrier and hydration. The exogenous CERs such as phyto-derived CERs (PhytoCERs) can be delivered deep into the SC using novel topical formulations. This, however, requires investigating the rate and extent of skin permeation of CERs. In this study, an LC/APCI-MS method to detect and quantify PhytoCERs in different layers of the skin has been developed and validated. The method was used to investigate the skin permeation of PhytoCERs using Franz diffusion cells after applying an amphiphilic cream containing PhytoCERs to the surface of ex vivo human skin. As plant-specific CERs are not commercially available, well-characterized CERs isolated from oat (Avena abyssinica) were used as reference standards for the development and validation of the method. The method was linear over the range of 30-1050 ng/mL and sensitive with limit of detection and quantification of 10 and 30 ng/mL, respectively. The method was also selective, accurate, and precise with minimal matrix effect (with mean matrix factor around 100%). Even if more than 85% of oat CERs in the cream remained in the cream after the incubation periods of 30, 100, and 300 min, it was possible to quantify the small quantities of oat CERs distributed across the SC, epidermis, and dermis of the skin indicating the method's sensitivity. Therefore, the method can be used to investigate the skin permeation of oat CERs from the various pharmaceutical and cosmeceutical products without any interference from the skin constituents such as the epidermal lipids. Graphical abstract ᅟ.

For this study mixtures based on the ceramides [NS] (NS = non-hydroxy-sphingosine) and [AP] (AP = α-hydroxy-phytosphingosine) in a 2:1 and 1:2 ratio, together with cholesterol and lignoceric acid, were investigated. These mixtures are modelling the uppermost skin layer, the stratum corneum. Neutron diffraction, utilizing specifically deuterated ceramide molecules, was used to obtain a maximum amount of experimental detail. Highly detailed molecular dynamics simulations were used to generate even more information from the experimental data. It was possible to observe a single lamellar phase for both systems. They had a lamellar repeat distance of 5.43 ± 0.05 nm for the [NS]/[AP] 2:1 and a slightly shorter one of 5.34 ± 0.05 nm for the 1:2 system. The structure and water content was uninfluenced by excess humidity. Both the experimental and simulation data indicated slightly tilted ceramides, with their C24 chains overlapping in the lamellar mid-plane. This arrangement is well comparable to systems investigated before. The structure of both systems, except for the differing repeat distance, looks similar at first. However, on a smaller scale there were various distinct differences, demonstrating only low redundancy between the different ceramide species, despite only minor chemical differences. The mainly ceramide [AP] determined 1:2 system has a slightly smaller repeat distance. This is a result of a tighter arrangement of the lipids chain along the bilayer normal and increased overlapping of the long chains in the lamellar middle. For the CER[NS] some novel features could be shown, despite it being the overall most investigated ceramide. These include the low adaptability to changed lateral interactions, leading to an increased chain opening. This effect could explain its low miscibility with other lipids. The investigated model systems allows it to directly compare results from the literature which have used ceramide [NS] to the most recent studies using the phytosphingosine ceramides such as ceramide [AP]., (Copyright © 2018 Elsevier B.V. All rights reserved.)

Deficiency or altered composition of stratum corneum (SC) lipids such as ceramides (CERs), causing skin barrier dysfunction and skin dryness, have been associated with skin diseases such as atopic dermatitis and psoriasis, and ageing. Replenishing the depleted native CERs with exogenous CERs has also been shown to have beneficial effects in restoring the skin barrier. Phyto-derived CERs such as oat CERs were shown to be potential for skin barrier reinforcement. To effect this, however, the oat CERs should overcome the SC barrier and delivered deep into the lipid matrix using the various novel formulations. In an attempt to demonstrate the potential use of oat CERs, lecithin-based microemulsions (MEs) and starch-based nanoparticles (NPs) were formulated and characterized. Besides, ME gel and NP gel were also prepared using Carbopol®980 as a gelling agent. The in vitro release and penetration (using artificial four-layer membrane system) and ex vivo permeation (using excised human skin) of oat CERs from the various formulations were investigated. The results revealed ME enhanced the in vitro release and penetration oat CERs compared to the other formulations. On the other hand, the NPs retarded the release of oat CERs and small quantities of oat CERs incorporated into NP gel penetrated into the deeper layers of the multilayer membranes. The penetration-enhancing effect of ME was also observed in the ex vivo permeation studies where significant quantities of oat CERs were found in the acceptor compartment. Compared to the ME, the ME gel exhibited reduced depth and extent of oat CERs permeation. As compared to NP gel, ME gel enhanced the degree of permeation of oat CERs into the deeper layer of the skin. Generally the gel formulations were effective in concentrating oat CERs in the SC where they are needed to be., (Copyright © 2018 Elsevier B.V. All rights reserved.)

Due to the lipophilic properties of the uppermost skin layer of the stratum corneum (SC) it is highly challenging to reach therapeutic concentrations of cosmetic actives and drugs. Particularly, the hydrophilic ones penetrate poorly across the SC. The purpose of this study was to improve the topical bioavailability of the hydrophilic, polar tetrapeptide PKEK (amino acid sequence in one-letter notation). A nano-sized carrier system (microemulsion, ME) was therefore developed since MEs provide excellent penetration enhancing properties. The penetration of PKEK from the ME was compared to the penetration from a standard formulation. For the two preparations the penetration of the tetrapeptide in ex vivo human skin was investigated. This allows to make statements regarding dermal penetration, localization and distribution of the active substances in each skin layer as well as the influence of vehicle variations, in this case the incorporation of PKEK into a ME system. Relatively high amounts between 40 and 58% of the tetrapeptide PKEK penetrated from the standard cream into the skin. The major proportion of PKEK, which penetrated from the standard cream, remained in the SC and did not reach the target compartment within the skin. Penetration of PKEK from the ME was comparable with the cream for the shortest test time. However, very high PKEK amounts penetrated form the nano-sized carrier system (ME) into the human skin after 100 min (94%) and after 300 min (88%). The largest proportion did not remain in the skin, but permeated into the acceptor compartment. Therefore, the relative peptide content in the viable skin layers was predominantly comparable for the cream and the ME. For some samples a tendency could be observed that slightly higher amounts of PKEK were detected after the application of the standard cream. The absolute peptide concentrations gave a similar conclusion. The results indicate that liquid nano-sized systems are very effective carriers for extremely hydrophilic peptides used in cosmetics and also in therapeutics., (Copyright © 2017 Elsevier B.V. All rights reserved.)

Neutron diffraction was used as a tool to investigate the lamellar as well as molecular nanostructure of ceramide-[NP]/ceramide-[AP]/cholesterol/lignoceric acid model systems with a nativelike 2:1 ratio and a 1:2 ratio to study the influence of the ceramide-[AP]. By using mixtures together with cholesterol and free fatty acids as well as a humidity and temperature chamber while measuring, natural conditions were simulated as closely as possible. Despite its simplicity, the system simulated the native stratum corneum lipid matrix fairly closely, showing a similar lamellar thickness with a repeat distance of 5.45 ± 0.1 nm and a similar arrangement with overlapping long C24 chains. Furthermore, despite the very minor chemical difference between ceramide-[NP] and ceramide-[AP], which is only a single OH group, it was possible to demonstrate substantial differences between the structural influence of the two ceramides. Ceramide-[AP] could be concluded to be arranged in such a way that its C24 chain in both ratios is somehow shorter than that of ceramide-[NP], not overlapping as much with the opposite lamellar leaflet. Furthermore, in the unnatural 1:2 ratio, the higher ceramide-[AP] content causes an increased tilt of the ceramide acyl chains. This leads to even less overlapping within the lamellar midplane, whereas the repeat distance stays the same as for the ceramide-[NP]-rich system. In this nativelike 2:1 ratio, the chains are arranged mostly straight, and the long C24 chains show a broad overlapping region in the lamellar midplane.

Three new glucosylceramides (GluCers) named malusides I-III (1-3) were isolated from apple (cultivars of Malus domestica) pomace (fruit material remaining after juice extraction). An unusual oxo/hydroxy group pattern within the sphingadienine (d18:2) type sphingoid base was observed. All compounds contained the same α-hydroxylated fatty acid (h16:0) and a β-D-glucose moiety. Their structures were assigned on the basis of one- and two-dimensional (1D and 2D) nuclear magnetic resonance (NMR) spectroscopic analyses and mass spectrometry (MS) measurements.

Of particular importance for Stratum corneum (SC) lipids are the free fatty acids (FFAs). Age-related changes of the SC structure lead to diminished capacity for barrier compensation. The aims of this cross-sectional study were to identify even-numbered especially odd-numbered FFAs within the intercorneocytic lamellar lipid structures of the SC and to explore age- and diabetes-related changes in FFAs. Gas chromatography - flame ionisation detection was used to qualitatively and quantitatively assess FFAs extracted from the SC. 110 subjects aged over 60 years (elderly/healthy), 110 subjects aged 18-40 (young/healthy) and 38 subjects with diabetes mellitus aged 18-40 (young/diabetic) were investigated. Overall, odd-numbered FFAs comprised about 21, 23 and 24% of total FFAs in subgroups elderly/healthy, young/healthy and young/diabetic. The most abundant short-chain FFAs were C16: 0 and C18: 0 and long-chain FFAs were C24: 0 and C26: 0. Only levels of C15: 0 and C17: 0 decreased with age. In contrast, levels of C18: 2 and C19 were significantly decreased and levels of C15, C17, C18: 1 and C23 were significantly increased in young diabetic subjects. In general, compared with younger healthy subjects, FFA composition was only partly significantly altered in older healthy subjects but was significantly altered in younger diabetic subjects., (© 2018 S. Karger AG, Basel.)

The pH value is identified as an essential determinant for the lipid synthesis in the stratum corneum (SC). The activity of the enzymes that catalyse the transformation of lipid precursors into ceramides, free fatty acids or cholesterol highly depends on pH value. Additionally, there are substantial indications for pH conditions to have a direct effect on the molecular structure of the membranes and their properties. Knowledge about the sigmoidal pH gradient within the corneal layer also provides understanding of the pathological processes in a dysfunctional barrier. Shifting the pH environment from acidic into alkaline does not only inhibit the regenerating metabolic pathways but also activates enzymes that accelerate desquamation of the SC., (© 2018 S. Karger AG, Basel.)

This study was able to investigate the different influence of the d- and l-ceramide [AP] on the lamellar as well as molecular nanostructure of stratum corneum simulating lipid model mixtures. In this case, neutron diffraction together with specifically deuterated ceramide was used as an effective tool to investigate the lamellar and the molecular nanostructure of the mixtures. It could clearly be demonstrated, that both isomers show distinctly different characteristics, even though the variation between both is only a single differently arranged OH-group. The l-ceramide [AP] promotes a crystalline like phase behaviour even if mixed with ceramide [NP], cholesterol and free fatty acids. The d-ceramide [AP] only shows crystalline-like features if mixed only with cholesterol and free fatty acids but adopts a native-like behaviour if additionally mixed with ceramide [NP]. It furthermore demonstrates that the l-ceramide [AP] should not be used for any applications concerning ceramide substitution. It could however possibly serve its own purpose, if this crystalline like behaviour has some kind of positive influence on the SC or can be utilized for any practical applications. The results obtained in this study demonstrate that the diastereomers of ceramide [AP] are an attractive target for further research because their influence on the lamellar as well as the nanostructure is exceptionally strong. Additionally, the results furthermore show a very strong influence on hydration of the model membrane. With these properties, the d-ceramide [AP] could be effectively used to simulate native like behaviour even in very simple mixtures and could also have a strong impact on the native stratum corneum as well as high relevance for dermal ceramide substitution. The unnatural l-ceramide [AP] on the other hand should be investigated further, to assess its applicability., (Copyright © 2017 Elsevier B.V. All rights reserved.)

The impaired epidermal barrier and skin dryness in chronic skin conditions such as atopic dermatitis, psoriasis and aged skin are associated with the depletion of ceramides (CERs) in the stratum corneum. Previously, the beneficial effects of phyto-CERs, mainly from wheat and rice, in replenishing the depleted epidermal CERs and restoring the skin barrier have been shown. However, very few efforts have been made to exploit CERs from other plants for dermal applications. In an attempt to explore alternative plant source of CERs, glucosylceramides (GlcCERs) were isolated from the lipid extract of Ethiopian oat grain (Avena abyssinica). The GlcCER species were separated on a reversed phase HPLC and the structure of individual GlcCERs were identified by tandem MS with atmospheric pressure chemical ionization interface. The glycosidic linkage of the GlcCERs was cleaved by acid treatment and the predominant CERs species were isolated using column chromatography and preparative LC-MS. Further structural characterization of the CERs was made by HR/ESI-MS and NMR analyses. All the detected oat-derived GlcCER species consisted of C18 dihydroxy sphingoid bases amide-linked with α-hydroxylated saturated fatty acids (C16-C24). The two predominant GlcCER species consisted of sphingenine (d18:1) amide-linked to hydroxypalmitic acid (h16:0) and hydroxyarachidic acid (h20:0). The molecular formulae of the two major CERs assigned by HR/ESI-MS were identical to the ones identified by LC/APCI-MS/MS. The structural information was also supported by 1 H, 13 C, 1 H COSY NMR and HMBC spectral analyses. The amount of GlcCERs in oat grain, quantified by HPTLC, was found to be 193.5mg/kg. The results indicated the similarity of oat CERs with commercial plant CERs (with comparable GlcCER content) suggesting its potential as source of CERs for oral (as dietary supplements) as well as topical applications., (Copyright © 2017 Elsevier B.V. All rights reserved.)

The skin offers an attractive way for dermal and transdermal drug delivery that is why the drug still needs certain qualities to transcend the outermost layer of the skin, the stratum corneum. The requirements are: drugs with a maximum molecular weight of 1kDa, high lipophilicity and a certain polarity. This would restrict the use of a transdermal delivery of macromolecules, which would make the drug more effective in therapeutic administration. Various studies have shown that macromolecules without support do not penetrate the human skin. This effect can be achieved using physical and chemical methods, as well as biological peptides. The most popular physical method is the use of microneedles to create micropores in the skin and release the active agent in different sections. But also, other methods have been tested. Microjets, lasers, electroporation, sonophoresis and iontophoresis are also promising methods to successfully deliver dermal and transdermal macromolecules. Additionally, there are different penetration enhancer groups and biological peptides, which are also considered to be interesting approaches of enabling macromolecules to travel along the skin. All these methods will be described and evaluated in this review article., (Copyright © 2017 Elsevier B.V. All rights reserved.)

The stratum corneum (SC) is the outermost layer of the skin and is composed of a multilayered assembly of mostly ceramids (Cer), free fatty acids, cholesterol (Chol), and cholesterol sulfate (Chol-S). Because of the tight packing of these lipids, the SC features unique barrier properties defending the skin from environmental influences. Under pathological conditions, where the skin barrier function is compromised, topical application of molecules that rigidify the SC may lead to a restored barrier function. To this end, molecules are required that incorporate into the SC and bring back the original rigidity of the skin barrier. Here, we investigated the influence of a novel dimeric ceramide (dim-Cer) molecule designed to feature a long, rigid hydrocarbon chain ideally suited to forming an orthorhombic lipid phase. The influence of this molecules on the thermotropic phase behavior of a SC mixture consisting of Cer[AP18] (55 wt %), cholesterol (Chol, 25 wt %), steric acid (SA, 15 wt %), and cholesterol sulfate (Chol-S, 5 wt %) was studied using a combination of neutron diffraction and 2 H NMR spectroscopy. These methods provide detailed insights into the packing properties of the lipids in the SC model mixture. Dim-Cer remains in an all-trans state of the membrane-spanning lipid chain at all investigated temperatures, but the influence on the phase behavior of the other lipids in the mixture is marginal. Biophysical experiments are complemented by permeability measurements in model membranes and human skin. The latter, however, indicates that dim-Cer only partially provides the desired effect on membrane permeability, necessitating further optimization of its structure for medical applications.

Ceramide [NP] is an integral component of the stratum corneum (SC) lipid matrix and is capable of forming tough and stable lamellar structures. It was proven, that in skin diseases as psoriasis or atopic dermatitis different ceramide (CER) classes, including [NP], are degraded. It is obvious that topically application of CER on impaired skin is useful for repairing the skin barrier but a tendency for low penetration due to its poor solubility in conventional dosage forms was observed. Therefore, a stable and physiologic compatible colloidal carrier system, a microemulsion (ME), was developed and characterized. The increasing knowledge of the new colloidal systems in this last decade shows their benefits in dermal application. Isosorbide (Polysorb P) was incorporated into the ME developed. It was expected that Polysorb P has a retarder potential in order to accumulate the CER in the SC, the outermost layer of the skin. Thereby the CER [NP] would be able to interact with the affected skin layers to strengthen the skin barrier. The release and penetration behavior of the CER [NP] from the ME was assessed ex vivo in a Franz diffusion cell. The results of the study showed that CER [NP] penetrate largely in the upper layers of the skin (from SC to stratum basale), which was the desired region. A recovery in the acceptor could not be detected that underlines an accumulation in upper layers. Furthermore, significantly increased values for the SC for the ME with retarder were not received. No differences in the concentrations of CER [NP] were observed. However, the toxicity of MEs was investigated using heńs egg test chorioallantoic membrane (HET-CAM). For the isosorbide-containing ME no difference was obtained in comparison to the non-containing. The results showed that both MEs are safe to be used on the skin for the controlled penetration of CER [NP] into the skin. The isosorbide had no effect on the irritating effect as well as on the penetration of the used CER.

Chronic skin conditions such as atopic dermatitis, psoriasis and aged skin are characterized by defective skin barrier and dryness which are associated with reduced levels of skin ceramides (CERs). The beneficial effects of plant-derived CERs for skin hydration and skin barrier recovery have been shown in several studies. Although plenty of glucosylceramide (GlcCER)-based dietary supplements meant for skin barrier improvement have been marketed, there are limited commercial sources of plant GlcCERs. In an attempt to explore alternative GlcCER sources, a reversed phase LC-MS/MS method with atmospheric pressure chemical ionization (APCI) interface was developed for separation and structural identification of GlcCERs isolated from three plants. The GlcCERs were extracted from the seeds of grass pea (Lathyrus sativus L.), Ethiopian mustard (Brassica carinata) and haricot bean (Phaseolus vulgaris) and purified by column chromatography and preparative LC-MS. The individual GlcCER species were further separated and qualitatively analyzed by LC/APCI-MS/MS. The amount of GlcCERs in each plant was quantified by HPTLC. All GlcCER species detected in the three plants consisted of C18 di/trihydroxy sphingoid bases amide linked with hydroxy fatty acids (C14-C24). The trihydroxy SBs were acylated with very long chain FAs (C22-C24). The major GlcCERs derived from grass pea, Ethiopian mustard and haricot bean are composed of sphingenine (d18:1) linked to hydroxypalmitic acid (h16:0), 4-hydroxy-8-sphingenine (t18:1) coupled with hydroxynervonic acid (h24:1) and sphingadienine (d18:2) joined with h16:0, respectively. The GlcCERs contents in haricot bean (161.2mg/kg) and grass pea (130.0mg/kg) were found to be higher compared to Ethiopian mustard (71.8mg/kg). This qualitative and quantitative information suggests that the two plants of the Fabaceae family (haricot bean and grass pea) are potential alternative sources of GlcCERs for their use in products meant for the recovery of skin barrier function. The LC/APCI-MS/MS method described here has proven to be reliable for the screening of other potential plants containing GlcCERs., (Copyright © 2017 Elsevier B.V. All rights reserved.)

The synthesis of specific deuterated derivatives of the long chained ceramides [EOS] and [EOP] is described. The structural differences with respect to the natural compounds are founded in the substitution of the 2 double bonds containing linoleic acid by a palmitic acid branched with a methyl group in 10-position. The specific deuteration is introduced both in the branched and in the terminal methyl group, which was realized by common methods of successive deuteration of carboxylic groups in 3 steps. These modified fatty acids resp. the corresponding ceramides [EOS] and [EOP] were prepared for neutron scattering investigations. First results of these investigations were presented in this manuscript showing that the deuterated compounds could be detected in the stratum corneum lipid model membranes. The deuterated ceramides [EOS] and [EOP] are valuable tools to investigate the influence of these long chained ceramide species on the nanostructure of stratum corneum lipid model membranes., (Copyright © 2017 John Wiley & Sons, Ltd.)

This work was aimed to explore the potential effect of hyaluronic acid (HA) initial concentration (7.0 - 14.0 % w/v) on cross-linking efficiency of HA hydrogels cross-linked with 1,4-butanediol diglycidyl ether (BDDE). The results revealed that the hydrogel prepared at 10.0 % HA concentration exhibited a slower degradation rate, a lower swelling ability and more regular porosity than those prepared at either lower or higher HA concentration. After four days incubating with hyaluronidase, the content of NAG (N-acetyl glucosamine) remaining in the 10.0 HA hydrogel was 25.1±1.9 % with respect to the total NAG content found in the original mass. In contrast, the hydrogels prepared at 7.0 % and 14.0 % HA concentration showed a less remaining content of NAG equaled to approximately 15.9±5.4 % and 19.5±2.6 % respectively. On the other hand, the swelling ability of tested hydrogels was steadily decreased with the increase of HA initial concentration until the 10.0 % HA hydrogel and then showed an opposite trend. Based on this finding, the 10.0 % HA hydrogel exhibited the lowest swelling ratio which was observed at 129±3.2 g/g in distilled water and at 116±2.4 g/g in phosphate buffer saline (PBS). The SEM images showed various morphologies within the entire range of tested hydrogels. However, the hydrogel prepared at 10.0 % HA concentration was more homogenous and appeared with narrower pore-size distribution ranged in diameter from less than 50 μm to approximately 300 μm. Finally, the effect of HA initial concentration was investigated by FTIR which confirmed that the 10.0 % HA hydrogel was subject to a greater loss of (- OH) at 3343 cm-1 than other hydrogels except the 11.0 % HA hydrogel. This phenomenon was probably attributed to the formation of pendants that allowed the 11.0 % HA hydrogel to appear with a lower peak intensity than the 10.0 % HA hydrogel in the FTIR spectra. In conclusion, the HA initial concentration plays a crucial role in determining the cross-linking efficiency of HA hydrogels cross-linked with BDDE.

The outer most layer of the skin, the stratum corneum, consists of corneocytes which are coated by a cornified envelope and embedded in a lipid matrix of ordered lamellar structure. It is responsible for the skin barrier function. Ceramides (CERs) are the backbone of the intercellular lipid membranes. Skin diseases such as atopic dermatitis and psoriasis and aged skin are characterized by dysfunctional skin barrier and dryness which are associated with reduced levels of CERs. Previously, the effectiveness of supplementation of synthetic and animal-based CERs in replenishing the depleted natural skin CERs and restoring the skin barrier function have been investigated. Recently, however, the barrier function improving effect of plant-derived CERs has attracted much attention. Phyto-derived CERs (phytoCERs) are preferable due to their assumed higher safety as they are mostly isolated from dietary sources. The beneficial effects of phytoCER-based oral dietary supplements for skin hydration and skin barrier reinforcement have been indicated in several studies involving animal models as well as human subjects. Ingestible dietary supplements containing phytoCERs are also widely available on the market. Nonetheless, little effort has been made to investigate the potential cosmetic applications of topically administered phytoCERs. Therefore, summarizing the foregoing investigations and identifying the gap in the scientific data on plant-derived CERs intended for skin-health benefits are of paramount importance. In this review, an attempt is made to synthesize the information available in the literature regarding the effects of phytoCER-based oral dietary supplements on skin hydration and barrier function with the underlying mechanisms., (© 2017 S. Karger AG, Basel.)

The outermost layer of the mammalian skin, the stratum corneum (SC), is a very thin structure and realizes simultaneously the main barrier properties. The penetration barrier for xenobiotica is mostly represented by a complex lipid matrix. There is great interest in the subject of getting information about the arrangement of the lipids, which are mainly ceramides (CER), free fatty acids (FFA) and cholesterol (CHOL). SC lipid model membranes containing synthetically derived lipids in a non-physiological ratio were investigated. To compare the study to a former experiment, a methyl-branched ceramide [EOS] species in presence of the ultra-long chain CER[AP], CHOL and behenic acid (23/10/33/33, wt%) was applied. The membrane structure was studied using the very versatile technique of neutron diffraction. We were able to identify a long-periodicity phase (LPP) with a size of 114Å or 118Å with CER[EOS]-br in a ratio of >60wt% of the ceramides. Furthermore, we figured out two additional coexisting short-periodicity phases (SPP) with repeat distances of 48Å and 45Å, respectively. Partial deuterations of CER[EOS]-br and CER[AP] enabled the localization of the molecules within the multiphase system. CER[EOS]-d3 was present in the LPP, but absent in both SPP. CER[AP]-d3 was determined in both short phases but not localized within the LPP. Besides, we revealed influences of humidity and time with respect to the long-periodicity phase., (Copyright © 2016 Elsevier B.V. All rights reserved.)

To optimize transdermal application of drugs, the barrier function of the skin, especially the stratum corneum (SC), needs to be reduced reversibly. For this purpose, penetration enhancers like urea or taurine are applied. Until now, it is unclear if this penetration enhancement is caused by an interaction with the SC lipid matrix or related to effects within the corneocytes. Therefore, the effects of both hydrophilic enhancers on SC models with different dimensionality, ranging from monolayers to multilayers, have been investigated in this study. Many sophisticated methods were applied to ascertain the mode of action of both substances on a molecular scale. The experiments reveal that there is no specific interaction when 10% urea or 5% taurine solutions are added to the SC model systems. No additional water uptake in the head group region and no decrease of the lipid chain packing density have been observed. Consequently, we suppose that the penetration enhancing effect of both substances might be based on the introduction of large amounts of water into the corneocytes, caused by the enormous water binding capacity of urea and a resulting osmotic pressure in case of taurine., (Copyright © 2016 Elsevier B.V. All rights reserved.)

Fourier transform infrared attenuated total reflectance (FTIR-ATR) spectroscopy was used to study directly the release of drug particles (ketoconazole) in a liquid medium (paraffinum liquidum). In the case of the release experiment, the formulation is placed on the ATR crystal and the acceptor membrane on the top of the ointment. The decrease of the drug content in the sediment near the interface ATR crystal-formulation in the course of the release process was quantified by monitoring the changes of the IR spectrum in relevant spectral ranges using multivariate analysis. A mathematical model based on Fick's second law with appropriate initial and boundary conditions was applied in order to determine the diffusion coefficient of the drug in the liquid medium. Knowing this value, it is possible to calculate the effective diffusion coefficient of the drug in heterogeneous semisolid formulation (Vaseline) as a function of the volume fraction of the solid phase.