Structure and function of the epidermal barrier

Mild but effective skin cleansing-Evaluation of laureth-23 as a primary surfactant

OBJECTIVE

Skin cleansing products are among the main reasons for the development of hand eczema. Therefore, a mild but effective skin cleansing product is of particular interest, especially in the work place, where various contaminations frequently have to be removed from hands.

METHODS

In this study, the potential of laureth-23 as a primary surfactant was evaluated and compared to other fatty alcohol ethoxylates (FAEO). Also, different laureth-23 surfactant combinations were compared to each other. Therefore, transepidermal water loss, erythema and visual scoring were measured after occlusive patch testing in 24 healthy subjects (aged 18-55). Afterwards, the results were ranked from low to high irritant potential and an irritation score was calculated. Furthermore, the cleaning performance was tested using an automated cleansing device in 10 healthy subjects (aged 18-55).

RESULTS

The results confirmed the low irritant potential of laureth-23 and blends thereof. Within the different laureth-23 surfactant combinations, the combination of laureth-23 with a mild amphoteric and a mild anionic surfactant was superior to other laureth-23 surfactant combinations like laureth-23/anionic/anionic regarding skin compatibility as well as cleaning performance.

CONCLUSION

In conclusion, laureth-23 showed very good performance as a primary surfactant. Especially, the combination of laureth-23, cocamidopropyl betaine and disodium laureth sulfosuccinate was mild to the skin while also showing good cleansing performance.

Immunolabeling for filaggrin and acidic keratins in the granular layer of mammalian epidermis indicates that an acidic-basic interaction is involved in cornification

The soft epidermis of mammals derives from the accumulation of keratohyaline granules in the granular layer, before maturing into corneocytes. Main proteins accumulated in the granular layer are pro-filaggrin and filaggrin that determine keratin clumping and later moisturization of the stratum corneum that remains flexible. This soft epidermis allows the high sensitivity of mammalian skin. Presence and thickness of the stratum granulosum varies among different species of mammals and even between different body regions of the same animal, from discontinuous to multilayered. These variations are evident using antibodies for filaggrin, a large protein that share common epitopes among placentals. Here we have utilized filaggrin antibodies (8959 and 466) and an acidic keratin antibody (AK2) for labeling placental, marsupial and monotreme epidermis. AK2 labeling appears mainly to detect K24 keratin, and less likely other acidic keratins. Immunoreactivity for filaggrin is absent in platypus, discontinuous in Echidna and in the tested marsupials. In placentals, it is inconstantly or hardly detected in the thin epidermis of bat, rodents, and lagomorphs with a narrow, mono-stratified and/or discontinuous granular layer. In contrast, where the granular layer is continuous or even stratified, both filaggrin and AK2 antibodies decorate granular cells. The ultrastructural analysis using the AK2 antibody on human epidermis reveals that a weak labeling is associated with keratohyalin granules and filamentous keratins of transitional keratinocytes and corneocytes. This observation suggests that basophilic filaggrin interacts with acidic keratins like K24 and determines keratin condensation into corneocytes of the stratum corneum.

Nanocarrier-Integrated Microneedles: Divulging the Potential of Novel Frontiers for Fostering the Management of Skin Ailments

The various kinds of nanocarriers (NCs) have been explored for the delivery of therapeutics designed for the management of skin manifestations. The NCs are considered as one of the promising approaches for the skin delivery of therapeutics attributable to sustained release and enhanced skin penetration. Despite the extensive applications of the NCs, the challenges in their delivery via skin barrier (majorly stratum corneum) have persisted. To overcome all the challenges associated with the delivery of NCs, the microneedle (MN) technology has emerged as a beacon of hope. Programmable drug release, being painless, and its minimally invasive nature make it an intriguing strategy to circumvent the multiple challenges associated with the various drug delivery systems. The integration of positive traits of NCs and MNs boosts therapeutic effectiveness by evading stratum corneum, facilitating the delivery of NCs through the skin and enhancing their targeted delivery. This review discusses the barrier function of skin, the importance of MNs, the types of MNs, and the superiority of NC-loaded MNs. We highlighted the applications of NC-integrated MNs for the management of various skin ailments, combinational drug delivery, active targeting, in vivo imaging, and as theranostics. The clinical trials, patent portfolio, and marketed products of drug/NC-integrated MNs are covered. Finally, regulatory hurdles toward benchtop-to-bedside translation, along with promising prospects needed to scale up NC-integrated MN technology, have been deliberated. The current review is anticipated to deliver thoughtful visions to researchers, clinicians, and formulation scientists for the successful development of the MN-technology-based product by carefully optimizing all the formulation variables.

Advancements in transdermal drug delivery: A comprehensive review of physical penetration enhancement techniques

Transdermal drug administration has grown in popularity in the pharmaceutical research community due to its potential to improve drug bioavailability, compliance among patients, and therapeutic effectiveness. To overcome the substantial barrier posed by the stratum corneum (SC) and promote drug absorption within the skin, various physical penetration augmentation approaches have been devised. This review article delves into popular physical penetration augmentation techniques, which include sonophoresis, iontophoresis, magnetophoresis, thermophoresis, needle-free injection, and microneedles (MNs) Sonophoresis is a technique that uses low-frequency ultrasonic waves to break the skin's barrier characteristics, therefore improving drug transport and distribution. In contrast, iontophoresis uses an applied electric current to push charged molecules of drugs inside the skin, effectively enhancing medication absorption. Magnetophoresis uses magnetic fields to drive drug carriers into the dermis, a technology that has shown promise in aiding targeted medication delivery. Thermophoresis is the regulated heating of the skin in order to improve drug absorption, particularly with thermally sensitive drug carriers. Needle-free injection technologies, such as jet injectors (JIs) and microprojection arrays, offer another option by producing temporary small pore sizes in the skin, facilitating painless and effective drug delivery. MNs are a painless, minimally invasive method, easy to self-administration, as well as high drug bioavailability. This study focuses on the underlying processes, current breakthroughs, and limitations connected with all of these approaches, with an emphasis on their applicability in diverse therapeutic areas. Finally, a thorough knowledge of these physical enhancement approaches and their incorporation into pharmaceutical research has the potential to revolutionize drug delivery, providing more efficient and secure treatment choices for a wide range of health-related diseases.

A sequential tape stripping approach for the assessment of the impact of personal cleansing products on the stratum corneum surface layers' acid mantle properties and antimicrobial defense

BACKGROUND

Stratum corneum (SC) plays a critical role in skin barrier function for protection and defense in nature. The acidic skin pH, which is also known as the acid mantle, is very important in fighting against outer environmental threats, especially, bacteria. Furthermore, recent research has shown that the transient bacteria could potentially penetrate into deeper layer of the SC down to a few micrometers while posing an additional threat to the deeper layers of the skin.

AIM

To develop a sequential tape stripping method for assessing the impact of personal cleansing product on the SC surface layers' acid mantle properties and antimicrobial defense against transient bacteria.

METHODS

Fifty-five subjects were recruited. High pH soap-based Product 1 and low pH synthetic surfactant-based Product 2 were applied on the left and right forearms of each subject. Sequential tape stripping was performed on the same spots to access multiple layers of the skin SC. Both antimicrobial defense property and skin pH of different skin layers were evaluated at baseline and 12 h after treatment.

RESULTS

The skin's antimicrobial defense was significantly higher 12 h after treatment of the low pH Product 2 as compared to the treatment of high pH Product 1. In fact, this trend was consistent across all three skin layers (Layer 1 to Layer 3) as measured in this study (p < 0.01). Furthermore, the skin surface pH of Layer 1 and Layer 3 were also lower 12 h after the treatment of low pH Product 2 as compared to that of the high pH Product 1 (p < 0.01).

CONCLUSION

The results of this investigation demonstrated the benefits of 12-h long lasting and deeper protection of SC acid mantle properties and antimicrobial defense using a low pH skin cleansing product as compared to a high pH product.

Advancements in Skin-Mediated Drug Delivery: Mechanisms, Techniques, and Applications

Skin-mediated drug delivery methods currently are receiving significant attention as a promising approach for the enhanced delivery of drugs through the skin. Skin-mediated drug delivery offers the potential to overcome the limitations of traditional drug delivery methods, including oral administration and intravenous injection. The challenges associated with drug permeation through layers of skin, which act as a major barrier, are explored, and strategies to overcome these limitations are discussed in detail. This review categorizes skin-mediated drug delivery methods based on the means of increasing drug permeation, and it provides a comprehensive overview of the mechanisms and techniques associated with these methods. In addition, recent advancements in the application of skin-mediated drug delivery are presented. The review also outlines the limitations of ongoing research and suggests future perspectives of studies regarding the skin-mediated delivery of drugs.

A systematic overview of metal nanoparticles as alternative disinfectants for emerging SARS-CoV-2 variants

Coronaviruses are a diverse family of viruses, and new strains can emerge. While the majority of coronavirus strains cause mild respiratory illnesses, a few are responsible for severe diseases such as Severe Acute Respiratory Syndrome (SARS) and Middle East Respiratory Syndrome (MERS). SARS-CoV-2, the virus responsible for COVID-19, is an example of a coronavirus that has led to a pandemic. Coronaviruses can mutate over time, potentially leading to the emergence of new variants. Some of these variants may have increased transmissibility or resistance to existing vaccines and treatments. The emergence of the COVID-19 pandemic in the recent past has sparked innovation in curbing virus spread, with sanitizers and disinfectants taking center stage. These essential tools hinder pathogen dissemination, especially for unvaccinated or rapidly mutating viruses. The World Health Organization supports the use of alcohol-based sanitizers and disinfectants globally against pandemics. However, there are ongoing concerns about their widespread usage and their potential impact on human health, animal well-being, and ecological equilibrium. In this ever-changing scenario, metal nanoparticles hold promise in combating a range of pathogens, including SARS-CoV-2, as well as other viruses such as norovirus, influenza, and HIV-1. This review explores their potential as non-alcoholic champions against SARS-CoV-2 and other pandemics of tomorrow. This extends beyond metal nanoparticles and advocates a balanced examination of pandemic control tools, exploring their strengths and weaknesses. The manuscript thus involves the evaluation of metal nanoparticle-based alternative approaches as hand sanitizers and disinfectants, providing a comprehensive perspective on this critical issue.

Topical drug delivery strategies for enhancing drug effectiveness by skin barriers, drug delivery systems and individualized dosing

Topical drug delivery is widely used in various diseases because of the advantages of not passing through the gastrointestinal tract, avoiding gastrointestinal irritation and hepatic first-pass effect, and reaching the lesion directly to reduce unnecessary adverse reactions. The skin helps the organism to defend itself against a huge majority of external aggressions and is one of the most important lines of defense of the body. However, the skin's strong barrier ability is also a huge obstacle to the effectiveness of topical medications. Allowing the bioactive, composition in a drug to pass through the stratum corneum barrier as needed to reach the target site is the most essential need for the bioactive, composition to exert its therapeutic effect. The state of the skin barrier, the choice of delivery system for the bioactive, composition, and individualized disease detection and dosing planning influence the effectiveness of topical medications. Nowadays, enhancing transdermal absorption of topically applied drugs is the hottest research area. However, enhancing transdermal absorption of drugs is not the first choice to improve the effectiveness of all drugs. Excessive transdermal absorption enhances topical drug accumulation at non-target sites and the occurrence of adverse reactions. This paper introduces topical drug delivery strategies to improve drug effectiveness from three perspectives: skin barrier, drug delivery system and individualized drug delivery, describes the current status and shortcomings of topical drug research, and provides new directions and ideas for topical drug research.

HPLC-TBARS-EVSC (high-performance liquid chromatography-thiobarbituric acid reactive substances-ex vivo stratum corneum) protocol: Selection of the subjects and approach to present the results

OBJECTIVE

Nowadays, it is recognized the need for improved safety and efficacy protocols to evaluate the human stratum corneum (SC) and its interaction with topical and cosmetic formulations by minimally or non-invasive methodologies. The aim of our research work was to streamline the HPLC-TBARS-EVSC (high-performance liquid chromatography-thiobarbituric acid reactive substances-ex vivo stratum corneum) methodology, by exploring the results of a group of 18 subjects.

METHODS

The study included nine women and nine men aged between 19 and 57 years old with phototypes from II to V. Sites in the forearm of each volunteer were randomly delimited, and the SC was collected by tape stripping. HPLC was used to quantify the MDA-TBA2 (malondialdehyde-thiobarbituric acid) adduct from the tape-stripped SC, irradiated and not by an ultraviolet (UV) simulator chamber.

RESULTS

Observing the findings of our present investigation, and the statistical approach applied, the use of the ratio between the treatment site and control would be an adequate strategy to better discriminate and evaluate the results. Additionally, an optimal selection of the volunteers to respond specifically to the purpose of the ex vivo assay also can be considered advantageous.

CONCLUSIONS

It seemed that in future studies focusing on the impact of SC UV-induced lipid peroxidation, determined by the HPLC-TBARS-EVSC, the most suitable subjects are females aged less than 35 years old, with phototype II.

Ameliorative effect of black tea extract on the skin of D-galactose-induced aging mice

Aging is a universal and irreversible process, and the skin is an important feature that reflects the aging of the organism. Skin aging has been a focus of attention in recent years because it leads to changes in an individual's external features and the loss of many important biological functions. This experiment investigated the improvement effect of black tea extract (BTE) on the skin of aging mice under D-galactose induction. After 6 weeks of administration, the changes in skin bio-chemical indices and tissue structure were compared with the blank and positive control groups. It was observed that BTE increased water and hyaluronic acid (HA) content, decreased malondialdehyde (MDA) content, enhanced superoxide dismutase (SOD), glutathione peroxidase (GSH-Px), and catalase (CAT) activities in the skin of aging mice, and improved the structure of aging damaged skin tissues and increased the content of total collagen. The experimental results showed that BTE can play a significant anti-aging effect on the skin, which can be used as a functional food for aging inhibition.

Interactions between Malassezia and New Therapeutic Agents in Atopic Dermatitis Affecting Skin Barrier and Inflammation in Recombinant Human Epidermis Model

Several studies have reported the pathogenic role of Malassezia in atopic dermatitis (AD); the significance of Malassezia’s influence on AD needs to be further investigated. Dupilumab, a monoclonal antibody to anti-Interleukin (IL) 4Rα, and ruxolitinib, a Janus kinase (JAK)1/2 inhibitor, are the first approved biologics and inhibitors widely used for AD treatment. In this study, we aimed to investigate how Malassezia Restricta (M. restricta) affects the skin barrier and inflammation in AD and interacts with the AD therapeutic agents ruxolitinib and anti-IL4Rα. To induce an in vitro AD model, a reconstructed human epidermis (RHE) was treated with IL-4 and IL-13. M. restricta was inoculated on the surface of RHE, and anti-IL4Rα or ruxolitinib was supplemented to model treated AD lesions. Histological and molecular analyses were performed. Skin barrier and ceramide-related molecules were downregulated by M. restricta and reverted by anti-IL4Rα and ruxolitinib. Antimicrobial peptides, VEGF, Th2-related, and JAK/STAT pathway molecules were upregulated by M. restricta and suppressed by anti-IL4Rα and ruxolitinib. These findings show that M. restricta aggravated skin barrier function and Th2 inflammation and decreased the efficacy of anti-IL4Rα and ruxolitinib.

Effect of Ultraviolet Radiation and Benzo[a]pyrene Co-Exposure on Skin Biology: Autophagy as a Potential Target

The skin is the outermost protective barrier of the human body. Its role is to protect against different physical, chemical, biological and environmental stressors. The vast majority of studies have focused on investigating the effects of single environmental stressors on skin homeostasis and the induction of several skin disorders, such as cancer or ageing. On the other hand, much fewer studies have explored the consequences of the co-exposure of skin cells to two or more stressors simultaneously, which is much more realistic. In the present study, we investigated, using mass-spectrometry-based proteomic analysis, the dysregulated biological functions in skin explants after their co-exposure to ultraviolet radiation (UV) and benzo[a]pyrene (BaP). We observed that several biological processes were dysregulated, among which autophagy appeared to be significantly downregulated. Furthermore, immunohistochemistry analysis was carried out to validate the downregulation of the autophagy process further. Altogether, the output of this study provides an insight into the biological responses of skin to combined exposure to UV + BaP and highlights autophagy as a potential target that might be considered in the future as a novel candidate for pharmacological intervention under such stress conditions.

Epicutaneous Sensitization and Food Allergy: Preventive Strategies Targeting Skin Barrier Repair-Facts and Challenges

Food allergy represents a growing public health and socio-economic problem with an increasing prevalence over the last two decades. Despite its substantial impact on the quality of life, current treatment options for food allergy are limited to strict allergen avoidance and emergency management, creating an urgent need for effective preventive strategies. Advances in the understanding of the food allergy pathogenesis allow to develop more precise approaches targeting specific pathophysiological pathways. Recently, the skin has become an important target for food allergy prevention strategies, as it has been hypothesized that allergen exposure through the impaired skin barrier might induce an immune response resulting in subsequent development of food allergy. This review aims to discuss current evidence supporting this complex interplay between the skin barrier dysfunction and food allergy by highlighting the crucial role of epicutaneous sensitization in the causality pathway leading to food allergen sensitization and progression to clinical food allergy. We also summarize recently studied prophylactic and therapeutic interventions targeting the skin barrier repair as an emerging food allergy prevention strategy and discuss current evidence controversies and future challenges. Further studies are needed before these promising strategies can be routinely implemented as prevention advice for the general population.

Soap or alcohol-based products? The effect of hand hygiene on skin characteristics during the COVID-19 pandemic

BACKGROUND

Different strategies for hand skin hygiene have been used to prevent the spread of SARS-CoV-2. However, frequent hand sanitization has been associated with skin damage. The present study aimed to evaluate hand hygiene habits during the COVID-19 pandemic and the effect of the repetitive use of soap or alcohol-based products on skin characteristics.

METHODS

We conducted a survey regards hand hygiene habits acquired during the COVID-19 pandemic. Also, we performed cutometry in a cohort of individuals who cleansed their volar forearms every 30 min, during 4 h, using soap or alcohol-based products.

RESULTS

We received 138 responses from people with medium-high educational level who reported a 2.5-time increase in the frequency of hand cleansing (p < 0.0001) that resulted in skin damage. An in vivo analysis of skin moisture and elasticity was also performed among 19 health workers and students. In general, skin moisture decreased with every cleansing, mainly after 2 h of washing with soap (p < 0.01), while skin elasticity only reduced after 4 h of treatment (p < 0.05). Alcohol-based solution or alcohol-based gel (70% ethanol, both) did not affect skin moisture or elasticity during testing.

CONCLUSION

It is known that the excessive use of soap or alcohol-based products causes dermatological issues. The present study demonstrates that non-medicated soap significantly affects skin moisture and elasticity, probably because the soap removes the hydrolipidic protective barrier, favoring transepidermal water loss, where the lack of the appropriate stratum corneum hydration also affects skin elasticity, mainly associated with changes in epidermal structure.

The UV-induced uptake of melanosome by skin keratinocyte is triggered by α7 nicotinic acetylcholine receptor-mediated phagocytosis

The melanosome is an organelle that produces melanin for skin pigmentation, which is synthesized by epidermal melanocytes, subsequently transported and internalized by epidermal keratinocytes. Exposure to ultraviolet (UV) from sunlight radiation is a major stimulator of melanosome uptake by keratinocytes. Acetylcholine (ACh) is known to be released by keratinocytes under UV exposure, which regulates melanin production in melanocytes by participating in which has been named as 'skin synapse'. Here, the role of cholinergic molecules, i.e. ACh and α7 nicotinic acetylcholine receptor (nAChR), in regulating melanosome uptake through phagocytosis by keratinocytes was illustrated. In cultured keratinocytes (HaCaT cells), the fluorescent beads at different sizes imitating melanosomes, or melanosomes, were phagocytosed under UV exposure. The UV-induced phagocytosis in keratinocytes was markedly increased by applied ACh, an acetylcholinesterase (AChE) inhibitor or an α7 nAChR agonist. By contrast, the antagonist of α7 nAChR was able to fully block the UV-induced phagocytosis, suggesting the role of α7 nAChR in this event. The intracellular Ca⁺⁺ mobilization was triggered by UV exposure, accounting for the initiation of phagocytosis. The blockage of UV-mediated Ca⁺⁺ mobilization, triggered by BAPTA-AM or α7 nAChR antagonist, resulted in a complete termination of phagocytosis. Besides, the phosphorylation of cofilin, as well as expression and activation of RhoA, accounting for phagocytosis was induced by UV exposure: the phosphorylation was blocked by BAPTA-AM or α7 nAChR antagonist. The result suggests that the cholinergic system, especially α7 nAChR, is playing a regulatory role in modulating melanosome uptake in keratinocytes being induced by UV exposure.

Mesoscopic Monitoring of Human Skin Explants Viscoelastic Properties

The investigation of the mechanical properties of skin is of great interest for monitoring physiological and pathological changes in the cutaneous barrier function for dermatological and cosmetic issues. Skin constitutes a complex tissue because of its multi-layered organisation. From a rheological point of view, it can be considered to be a soft tissue with viscoelastic properties. In order to characterise ex vivo mechanical properties of skin on the mesoscopic scale, a biosensor including a thickness shear mode transducer (TSM) in contact with a skin explant was used. A specific experimental set-up was developed to monitor continuously and in real-time human skin explants, including the dermis and the epidermis. These were kept alive for up to 8 days. Skin viscoelastic evolutions can be quantified with a multi-frequency impedance measurement (from 5 MHz to 45 MHz) combined with a dedicated fractional calculus model. Two relevant parameters for the non-destructive mesoscopic characterisation of skin explants were extracted: the structural parameter αapp and the apparent viscosity ηapp. In this study, the validity of the biosensor, including repeatability and viability, was controlled. A typical signature of the viscoelastic evolutions of the different cutaneous layers was identified. Finally, monitoring was carried out on stripped explants mimicking a weakened barrier function.

Arginine-fructose-glucose from red ginseng extract reduces stiffness of keratin fiber in corneocyte of skin

PURPOSE

The moisture content of the stratum corneum of the skin changes depending on the external environment. The structure of keratinous fiber protein in corneocyte of the skin changes depending on the amount of moisture. As the moisture decreases, the population of the alpha-helix increases, the beta-sheet deceases, and the stiffness increases accordingly. Here, we investigated the effect of humectants from ginseng on the keratin structure.

METHODS

Corneocyte was prepared from dry porcine skin with disc tape and measured through ATR-FT-IR. The signal from amide I of the keratin protein in corneocyte was detected, and the change in the ratio of alpha-helix and beta-sheet was calculated. The test samples were treated on the exfoliated corneocyte, and the degree of change was checked.

RESULT

Arginine-fructose-glucose (AFG)-enriched extract of red ginseng was effective in changing the keratin structure and was superior to humectants such as glycerin. However, arginine, mono sugar were not effective, and the AFG form in which two sugars were bound to one amino acid could perform its function.

CONCLUSION

The present study suggests that AFG, when applied to cosmetics, is expected to improve skin texture in a different way from existing moisturizers represented by glycerin by reducing the alpha-helix structure of corneocyte keratin.

Effects of indoor summer dehumidification and winter humidification on the physiological and subjective responses of the elderly

The purpose of this study was to clarify the physiological and subjective responses of the elderly to dehumidification in a humid summer and humidification in a dry winter compared with the young. Sixteen elderly and sixteen young subjects participated in the dehumidification experiment (DE) and 13 elderly and 15 young subjects participated in the humidification experiment (HE). The air temperature in the climate chamber was set at 28 °C, and humidity was decreased from 70% relative humidity (RH) to 50% RH for 90 min in the DE. The air temperature was set at 25 °C, and the humidity was increased from 30% RH to 50% RH for 90 min in the HE. Skin temperature, body weight, transepidermal water loss (TEWL), skin hydration state, saccharin clearance time (SCT), and blinking frequency were measured during exposure; whereby we evaluated humidity sensation, thermal sensation, and thermal comfort. Dehumidification caused a significant decrease in skin temperature in both age groups owing to greater insensible perspiration. Humidification significantly shortened the SCT in both age groups. TEWL increased significantly in the DE and decreased in the HE. For the physiological responses (skin temperature, skin physiology, SCT, and blinking frequency) to dehumidification and humidification, no distinct differences between the age groups were observed. However, subjective responses suggested that the elderly were less sensitive to humidity differences than the young in both the DE and HE.

Multidimensional quantitative characterization of the tumor microenvironment by multicontrast nonlinear microscopy

Characterization of the microenvironment features of tumors, such as its microstructures, biomolecular metabolism, and functional dynamics, may provide essential pathologic information about the tumor, tumor margin, and adjacent normal tissue for early and intraoperative diagnosis. However, it can be particularly challenging to obtain faithful and comprehensive pathological information simultaneously from unperturbed tissues due to the complexity of the microenvironment in organisms. Super-multiplex nonlinear optical imaging system emerged and matured as an attractive tool for acquisition and elucidation of the nonlinear properties correlated with tumor microenvironment. Here, we introduced a nonlinear effects-based multidimensional optical imaging platform and methodology to simultaneously and efficiently capture contrasting and complementary nonlinear optical signatures of freshly excised human skin tissues. The qualitative and quantitative analysis of autofluorescence (FAD), collagen fiber, and intracellular components (lipids and proteins) illustrated the differences about morphological changes and biomolecular metabolic processes of the epidermis and dermis in different skin carcinogenic types. Interpretation of multi-parameter stain-free histological findings complements conventional H&E-stained slides for investigating basal cell carcinoma and pigmented nevus, validates the platform's versatility and efficiency for classifying subtypes of skin carcinoma, and provides the potential to translate endogenous molecule into biomarker for assisting in rapid cancer screening and diagnosis.

Grifola frondosa Extract Containing Bioactive Components Blocks Skin Fibroblastic Inflammation and Cytotoxicity Caused by Endocrine Disrupting Chemical, Bisphenol A

Grifola frondosa (GF), a species of Basidiomycotina, is widely distributed across Asia and has been used as an immunomodulatory, anti-bacterial, and anti-cancer agent. In the present study, the pharmacological activity of the GF extract against an ecotoxicological industrial chemical, bisphenol A (BPA) in normal human dermal fibroblasts (NHDFs), was investigated. GF extract containing naringin, hesperidin, chlorogenic acid, and kaempferol showed an inhibitory effect on cell death and inflammation induced by BPA in the NHDFs. For the cell death caused by BPA, GF extract inhibited the production of reactive oxygen species responsible for the unique activation of the extracellular signal-regulated kinase. In addition, GF extract attenuated the expression of apoptosis-related proteins (Bax, Bcl-2, and cleaved caspase-3) and the pro-inflammatory cytokine IL-1β by the suppression of the redox-sensitive transcription factor, nuclear factor-kappa B (NF-κB) in BPA-treated NHDFs. For the inflammation triggered by BPA, GF extract blocked the inflammasome-mediated caspase-1 activation that leads to the secretion of IL-1β protein. These results indicate that the GF extract is a functional antioxidant that prevents skin fibroblastic pyroptosis induced by BPA.

Development of Safirinium dyes for new applications: fluorescent staining of bacteria, human kidney cells, and the horny layer of the epidermis

Low-molecular synthetic fluorophores are convenient tools in bioimaging applications. Several derivatives of Safirinium dyes as well as their reactive N-hydroxysuccinimide (NHS) esters bearing diverse substituents were synthesized and evaluated experimentally in terms of their lipophilicity by means of reverse-phase and immobilized artificial membrane high-performance liquid chromatography. Subsequently, the selected compounds were employed as novel cellular imaging agents for staining Gram-positive and Gram-negative bacteria, human kidney cell line, as well as human skin tissue. The analyzed dyes allowed for visualization of cellular structures such as mitochondria, endoplasmic reticulum, and cellular nuclei. They proved to be useful in fluorescent staining of stratum corneum, especially in the aspect of xenobiotic exposure and its penetration into the skin. The best results were obtained with the use of moderately lipophilic NHS esters of Safirinium Q. The development of Safirinium dyes is a promising alternative for commercially available dyes since the reported molecules have low molecular masses and exhibit efficient staining and remarkable water solubility. Moreover, they are relatively simple and low-cost in synthesis.

Skin Dialogues in Atopic Dermatitis

Atopic dermatitis (AD) is a chronic skin disorder associated with significant quality-of-life impairment and increased risk for allergic and non-allergic comorbidities. The aim of this review is to elucidate the connection between AD and most common comorbidities, as this requires a holistic and multidisciplinary approach. Advances in understanding these associations could lead to the development of highly effective and targeted treatments.

Landmark-based retrieval of inflamed skin vessels enabled by 3D correlative intravital light and volume electron microscopy

The nanometer spatial resolution of electron microscopy imaging remains an advantage over light microscopy, but the restricted field of view that can be inspected and the inability to visualize dynamic cellular events are definitely drawbacks of standard transmission electron microscopy (TEM). Several methods have been developed to overcome these limitations, mainly by correlating the light microscopical image to the electron microscope with correlative light and electron microscopy (CLEM) techniques. Since there is more than one method to obtain the region of interest (ROI), the workflow must be adjusted according to the research question and biological material addressed. Here, we describe in detail the development of a three-dimensional CLEM workflow for mouse skin tissue exposed to an inflammation stimulus and imaged by intravital microscopy (IVM) before fixation. Our aim is to relocate a distinct vessel in the electron microscope, addressing a complex biological question: how do cells interact with each other and the surrounding environment at the ultrastructural level? Retracing the area over several preparation steps did not involve any specific automated instruments but was entirely led by anatomical and artificially introduced landmarks, including blood vessel architecture and carbon-coated grids. Successful retrieval of the ROI by electron microscopy depended on particularly high precision during sample manipulation and extensive documentation. Further modification of the TEM sample preparation protocol for mouse skin tissue even rendered the specimen suitable for serial block-face scanning electron microscopy (SBF-SEM).

Ethosomes as dermal/transdermal drug delivery systems: applications, preparation and characterization

Transdermal drug delivery systems (TDDSs) have gained substantial attention during the last decade. TDDS are versatile delivery systems in which active components are delivered to skin for local effects or systemic delivery of active pharmaceutical through the skin. Overcoming stratum corneum is the most challenging step of delivering drugs through the skin. Lipid-based vesicular delivery systems due to the capability of the delivery of both hydrophilic and hydrophobic drugs are becoming more popular during the recent years. Ethosomes are innovative, biocompatible, biodegradable and non-toxic form of lipid-based vesicles that efficiently enable to entrap drugs of various physicochemical properties. These are other forms of liposome which contain high amounts of ethanol in their structure that enabling ethosomes to efficiently penetrate through deeper layers of skin. Ethosomes have various compositions based on their type but are mainly composed of phospholipids, ethanol, water and the active components. Ethosomes are easily manufactured and they are superior compared to liposomes in terms of different aspects due to the presence of ethanol. The purpose of this review is to thoroughly focus on various aspects of ethosomes, including mechanism of penetration, advantages and disadvantages, characterisation and applications.

A Review of Moisturizers; History, Preparation, Characterization and Applications

Moisturizers are one of the most widely used preparations in cosmetics and have been extensively used to soften the skin for consumers. Moisturizers work effectively in combating dry skin which may cause pain, tightness, itch, stinging, and/or tingling. The aim of this review is to evaluate published studies on the history, ingredients, preparation processes, characteristics, uses, and applications of moisturizers. Moisturizers bridge the gap between medicine and consumer goods by being used to make the skin more beautiful and healthy. In the future, in moisturizer therapy, the capacity to adapt specific agents to specific dermatological demands will be crucial. Cosmetically, moisturizers make the skin smooth by the mechanism of increasing the water content in the stratum corneum, hence exerting its most vital action, which is moisturizing action and maintaining a normal skin pH.

Euphorbia hirta Leaf Ethanol Extract Suppresses TNF-α/IFN-γ-Induced Inflammatory Response via Down-Regulating JNK or STAT1/3 Pathways in Human Keratinocytes

Skin inflammation may cause allergic diseases such as allergic rhinitis, asthma, and atopic dermatitis. Euphorbia hirta (E. hirta) is a member of the Euphorbiaceae family and is well-known for its anti-asthma effects. E. hirta has traditionally been used to treat respiratory ailments, dysentery, jaundice, and digestive problems. However, its effects on skin inflammation remain unclear. Here, we determined the effects of 70% ethanol extract of E. hirta leaves (ELE) in vitro using human keratinocyte HaCaT cells, which constitute most epidermal skin cells. We determined the inhibitory effects of ELE on the inflammation caused by tumor necrosis factor (TNF)-α/interferon (IFN)-γ in keratinocytes using ELISA, immunoblotting, and qRT-PCR assay. ELE was found to reduce the production and mRNA expression of pro-inflammatory cytokines such as TNF-α or interleukin-6 and the expression of various proteins, including signal transducers, activators of transcription 1/3, and mitogen-activated protein kinase. Expression levels of these proteins were found to be upregulated in the TNF-α/IFN-γ-stimulated condition and downregulated by ELE treatment. These results indicate that ELE protects HaCaT cells against TNF-α/IFN-γ-induced skin inflammation.

Formulation and Testing of Antioxidant and Protective Effect of Hyalurosomes Loading Extract Rich in Rosmarinic Acid Biotechnologically Produced from Lavandula angustifolia Miller

Culture of plant cells or tissues is a scalable, sustainable, and environmentally friendly approach to obtain extracts and secondary metabolites of uniform quality that can be continuously supplied in controlled conditions, independent of geographical and seasonal variations, environmental factors, and negative biological influences. In addition, tissues and cells can be extracted/obtained from the by-products of other industrial cultivations such as that of Lavandula angustifolia Miller (L. angustifolia), which is largely cultivated for the collection of flowers. Given that, an extract rich in rosmarinic acid was biotechnologically produced starting from cell suspension of L. angustifolia, which was then loaded in hyalurosomes, special phospholipid vesicles enriched with sodium hyaluronate, which in turn are capable of both immobilizing and stabilizing the system. These vesicles have demonstrated to be good candidates for skin delivery as their high viscosity favors their residence at the application site, thus promoting their interaction with the skin components. The main physico-chemical and technological characteristics of vesicles (i.e., mean diameter, polydispersity index, zeta potential and entrapment efficiency of extract in vesicles) were measured along with their biological properties in vitro: biocompatibility against fibroblasts and ability to protect the cells from oxidative stress induced by hydrogen peroxide. Overall, preliminary results disclosed the promising properties of obtained formulations to be used for the treatment of skin diseases associated with oxidative stress and inflammation.

A detailed insight on the molecular and cellular mechanism of action of the antifungal drugs used in the treatment of superficial fungal infections

Background:

Dermatomycosis, a type of fungal infection that can infect human skin, hair, and nails; day by day the growth of fungal infections ranging from superficial to systemic infection is alarming. Common causative agents included are Candida, Cryptococcus, Aspergillus, and Pneumocystis species.

Objective:

The effective treatment of the fungal infection includes the use of proper antifungal drug therapy. Antifungal drugs are classified into various classes. This paper focuses on understanding and interpreting the detailed molecular and cellular mechanism of action of various classes of an anti-fungal drug along with their important characteristics along with the safety and efficacy data of individual drugs of the particular class.

Methods:

The data selection for carrying out the respective study has been done by studying the combination of review articles and research papers from different databases like Research Gate, PubMed, MDPI, Elsevier, Science Direct, and Med Crave ranging from the year 1972 to 2019 by using the keywords like “anti-fungal agents”, “dermatophytes”, “cutaneous candidiasis”, “superficial fungal infections”, “oral candidiasis”, “amphotericin”, “echinocandins”, “azoles”, “polyenes” “ketoconazole”, “terbinafine”, “griseofulvin”, “azoles”.

Result:

Based on interpretation, we have concluded that the different classes of antifungal drugs follow the different mechanisms of action and target the fungal cell membrane, and are efficient in reducing fungal disease by their respective mechanism.

Conclusion:

The prevention and cure of fungal infections can be done by oral or topical antifungal drugs that aim to destroy the fungal cell membrane. These drugs show action by their respective pathways that are either preventing the formation of ergosterol or squalene or act by inhibiting β-1,3-glucan synthase enzyme. All the drugs are effective in treating fungal infections.

Leaky Gum: The Revisited Origin of Systemic Diseases

The oral cavity is the gateway for microorganisms into your body where they disseminate not only to the directly connected respiratory and digestive tracts but also to the many remote organs. Oral microbiota, travelling to the end of the intestine and circulating in our bodies through blood vessels, not only affect a gut microbiome profile but also lead to many systemic diseases. By gathering information accumulated from the era of focal infection theory to the age of revolution in microbiome research, we propose a pivotal role of “leaky gum”, as an analogy of “leaky gut”, to underscore the importance of the oral cavity in systemic health. The oral cavity has unique structures, the gingival sulcus (GS) and the junctional epithelium (JE) below the GS, which are rarely found anywhere else in our body. The JE is attached to the tooth enamel and cementum by hemidesmosome (HD), which is structurally weaker than desmosome and is, thus, vulnerable to microbial infiltration. In the GS, microbial biofilms can build up for life, unlike the biofilms on the skin and intestinal mucosa that fall off by the natural process. Thus, we emphasize that the GS and the JE are the weakest leaky point for microbes to invade the human body, making the leaky gum just as important as, or even more important than, the leaky gut.

Snout cutis of the domestic pig (Sus scrofa domesticus, Linnaeus, 1758): Using light and transmission electron microscopy

The current study was designed to give microscopic view on the snout skin of the domestic pig (Sus scrofa domesticus) to clear its adaptations with the function of exploring for the food and pushing the objects. This study carried out on the snout skin of apparently healthy 1 year five pigs (Sus Scrofa) and examined under the light and transmission electron microscopy. Our results clarify that the snout skin cutis composed of the epidermis and the dermis. The epidermis consisted of stratum corneum, stratum granulosum, stratum spinosum, and stratum basale. The stratum corneum and the stratum spinosum appeared thicker than other parts. The dermis consisted of a reticular and a papillary dermis. For tightness junction between the dermis and the epidermis, the hemidesmosomes were observed, while the desmosomes were presented in abundant numbers at the level of stratum basale to ensure the adhesion between the keratinocytes. The merocrine sweat glands were observed in abundant numbers to provide the wetness of the snout to avoid its injury from friction during food exploring or pushing of the objects. We concluded that the adaptation of the snout skin with the environmental condition surrounding the studied domestic pig.

Nanodelivery Strategies for Skin Diseases with Barrier Impairment: Focusing on Ceramides and Glucocorticoids

The human epidermis has a characteristic lipidic composition in the stratum corneum, where ceramides play a crucial role in the skin barrier homeostasis and in water-holding capacity. Several skin diseases, such as atopic dermatitis and psoriasis, exhibit a dysfunction in the lipid barrier with altered ceramide levels and increased loss of transepidermal water. Glucocorticoids are normally employed in the therapeutical management of these pathologies. However, they have shown a poor safety profile and reduced treatment efficiency. The main objective of this review is to, within the framework of the limitations of the currently available therapeutical approaches, establish the relevance of nanocarriers as a safe and efficient delivery strategy for glucocorticoids and ceramides in the topical treatment of skin disorders with barrier impairment.

Analysis of immune response induction mechanisms implicating the dose-sparing effect of transcutaneous immunization using a self-dissolving microneedle patch

Transcutaneous immunization (TCI) is an effective vaccination method that is easier and less painful than the conventional injectable vaccination method. We previously developed self-dissolving microneedle patches (sdMN) and demonstrated that this TCI method has a high vaccination efficacy in mice and humans. To elucidate the mechanism of immune response induction, which is the basis for the efficacy and safety of TCI with sdMN, we examined the local reaction of the skin where sdMN was applied and the kinetics and differentiation status of immune cells in the draining lymph nodes (DLNs). We found that gene expression of the proinflammatory cytokine Il1b and the downstream transcription factor Irf7 was markedly upregulated in skin tissues after sdMN application. Moreover, activation of Langerhans cells and CD207^- dermal dendritic cells, which are subsets of antigen-presenting cells (APCs) in the skin, and their migration to the DLNs were promoted. Furthermore, the activated APC subsets promoted CD4⁺ T cell and B cell differentiation and the formation of germinal centers, which are the sites of high-affinity antibody production. These phenomena associated with sdMN application may contribute to the efficient production of antigen-specific antibodies after TCI using sdMN. These findings provide essential information regarding immune response induction mechanisms for the development and improvement of TCI preparations.

Microneedle-Mediated Vaccination: Innovation and Translation

Vaccine administration by subcutaneous or intramuscular injection is the most commonly prescribed route for inoculation, however, it is often associated with some deficiencies such as low compliance, high professionalism, and risk of infection. Therefore, the application of microneedles for vaccine delivery has gained widespread interests in the past few years due to its high compliance, minimal invasiveness, and convenience. This review focuses on recent advances in the development and application of microneedles for vaccination based on different delivery strategies, and introduces the current status of microneedle-mediated vaccination in clinical translation. The prospects for its application including opportunities and challenges are further discussed.

The Modulatory Influence of Plant-Derived Compounds on Human Keratinocyte Function

The plant kingdom is a rich source of secondary metabolites with numerous properties, including the potential to modify keratinocyte biology. Keratinocytes are important epithelial cells that play a protective role against various chemical, physical and biological stimuli, and participate in reactive oxygen scavenging and inflammation and wound healing processes. The epidermal cell response may be modulated by phytochemicals via changes in signal transduction pathways. Plant extracts and single secondary compounds can possess a high antioxidant capacity and may suppress reactive oxygen species release, inhibit pro-apoptotic proteins and apoptosis and activate antioxidant enzymes in keratinocytes. Moreover, selected plant extracts and single compounds also exhibit anti-inflammatory properties and exposure may result in limited production of adhesion molecules, pro-inflammatory cytokines and chemokines in keratinocytes. In addition, plant extracts and single compounds may promote keratinocyte motility and proliferation via the regulation of growth factor production and enhance wound healing. While such plant compounds may modulate keratinocyte functions, further in vitro and in vivo studies are needed on their mechanisms of action, and more specific toxicity and clinical studies are needed to ensure their effectiveness and safety for use on human skin.

Interaction between SARS-CoV-2 spike glycoprotein and human skin models: a molecular dynamics study

The possibility of contamination of human skin by infectious virions plays an important role in indirect transmission of respiratory viruses but little is known about the fundamental physico-chemical aspects of the virus-skin interactions. In the case of coronaviruses, the interaction with surfaces (including the skin surface) is mediated by their large glycoprotein spikes that protrude from (and cover) the viral envelope. Here, we perform all atomic simulations between the SARS-CoV-2 spike glycoprotein and human skin models. We consider an "oily" skin covered by sebum and a "clean" skin exposing the stratum corneum. The simulations show that the spike tries to maximize the contacts with stratum corneum lipids, particularly ceramides, with substantial hydrogen bonding. In the case of "oily" skin, the spike is able to retain its structure, orientation and hydration over sebum with little interaction with sebum components. Comparison of these results with our previous simulations of the interaction of SARS-CoV-2 spike with hydrophilic and hydrophobic solid surfaces, suggests that the "soft" or "hard" nature of the surface plays an essential role in the interaction of the spike protein with materials.

The Use of Calcium Phosphates in Cosmetics, State of the Art and Future Perspectives

Calcium phosphates (CaPs) belong to a class of biomimetic materials widely employed for medical applications thanks to their excellent properties, such as biodegradability, biocompatibility and osteoinductivity. The recent trend in the cosmetics field of substituting potentially hazardous materials with natural, safe, and sustainable ingredients for the health of consumers and for the environment, as well as the progress in the materials science of academics and chemical industries, has opened new perspectives in the use of CaPs in this field. While several reviews have been focused on the applications of CaP-based materials in medicine, this is the first attempt to catalogue the properties and use of CaPs in cosmetics. In this review a brief introduction on the chemical and physical characteristics of the main CaP phases is given, followed by an up-to-date report of their use in cosmetics through a large literature survey of research papers and patents. The application of CaPs as agents in oral care, skin care, hair care, and odor control has been selected and extensively discussed, highlighting the correlation between the chemical, physical and toxicological properties of the materials with their final applications. Finally, perspectives on the main challenges that should be addressed by the scientific community and cosmetics companies to widen the application of CaPs in cosmetics are given.

Bioprinting Technology in Skin, Heart, Pancreas and Cartilage Tissues: Progress and Challenges in Clinical Practice

Bioprinting is an emerging additive manufacturing technique which shows an outstanding potential for shaping customized functional substitutes for tissue engineering. Its introduction into the clinical space in order to replace injured organs could ideally overcome the limitations faced with allografts. Presently, even though there have been years of prolific research in the field, there is a wide gap to bridge in order to bring bioprinting from "bench to bedside". This is due to the fact that bioprinted designs have not yet reached the complexity required for clinical use, nor have clear GMP (good manufacturing practices) rules or precise regulatory guidelines been established. This review provides an overview of some of the most recent and remarkable achievements for skin, heart, pancreas and cartilage bioprinting breakthroughs while highlighting the critical shortcomings for each tissue type which is keeping this technique from becoming widespread reality.

Nanostructured Lipid Carriers for the Formulation of Topical Anti-Inflammatory Nanomedicines Based on Natural Substances

The main function of the skin is to protect the body from the external environment. However, the skin can undergo inflammatory processes, due to genetic, hormonal, or environmental factors. When the defense system is overloaded, there is an increase in pro-inflammatory mediators and reactive oxygen species (ROS), which results in skin disorders. Among the substances used to treat these inflammatory processes, many natural substances with anti-inflammatory and antioxidant properties are being studied: nature is yet an abundant source to obtain diverse pharmacological actives. The treatment of skin diseases is usually focused on topical application, as it reduces the risk of systemic side effects and prevents drug degradation by first-pass metabolism. Thus, the properties of drug delivery vehicles can facilitate or inhibit its permeation. Due to the hydrophobic nature of the skin, a promising strategy to improve dermal drug penetration is the use of lipid-based nanoparticles, such as nanostructured lipid carriers (NLC). Therefore, in this review, we present NLC as a tool to improve dermal administration of natural substances with anti-inflammatory properties.

Nanocarriers for Skin Applications: Where Do We Stand?

Skin penetration of active molecules for treatment of diverse diseases is a major field of research owing to the advantages associated with the skin like easy accessibility, reduced systemic‐derived side effects, and increased therapeutic efficacy. Despite these advantages, dermal drug delivery is generally challenging due to the low skin permeability of therapeutics. Although various methods have been developed to improve skin penetration and permeation of therapeutics, they are usually aggressive and could lead to irreversible damage to the stratum corneum. Nanosized carrier systems represent an alternative approach for current technologies, with minimal damage to the natural barrier function of skin. In this Review, the use of nanoparticles to deliver drug molecules, genetic material, and vaccines into the skin is discussed. In addition, nanotoxicology studies and the recent clinical development of nanoparticles are highlighted to shed light on their potential to undergo market translation.

Nanosystems in Cosmetic Products: A Brief Overview of Functional, Market, Regulatory and Safety Concerns

Nanosystems exhibit various innovative physico-chemical properties as well as a range of cosmetic functions, including increased skin retention for loaded compounds. The worldwide nano-market has therefore been consistently extensive in recent decades. This review summarizes the most important properties of nanosystems that are employed in cosmetics, including composition, functions and interactions with skin, with particular attention being paid to marketed products. Moreover, the worldwide regulatory landscape of nanomaterials used as cosmetic ingredients is considered, and the main safety concerns are indicated. In general, advanced physico-chemical characterization is preliminarily needed to assess the safety of nanomaterials for human health and the environment. However, there is currently a shortfall in global legislation as a universally accepted and unambiguous definition of a nanomaterial is still lacking. Therefore, each country follows its own regulations. Anyhow, the main safety concerns arise from the European context, which is the most restrictive. Accordingly, the poor dermal permeation of nanomaterials generally limits their potential toxic effects, which should be mainly ascribed to unwanted or accidental exposure routes.

Increased Levels of Short-Chain Ceramides Modify the Lipid Organization and Reduce the Lipid Barrier of Skin Model Membranes

The skin barrier function is attributed to the stratum corneum (SC) intercellular lipid matrix, which is composed primarily of ceramides (CERs), free fatty acids, and cholesterol. These lipids are organized in two lamellar phases: the short and long periodicity phases (SPP and LPP), respectively. The LPP is considered important for the skin barrier function. High levels of short-chain CERs are observed in various inflammatory skin diseases and have been correlated with barrier dysfunction. In this research, we investigated how the increase in the fraction of the short-chain CER with a nonhydroxy C16 acyl chain linked to a C18 sphingosine base CER NS(C16) at the expense of the physiological chain length CER NS with a C24 acyl chain (CER NS(C24)) impacts the microstructure and barrier function of a lipid model that mimicked certain characteristics of the SC lipid organization. The permeability and lipid organization of the model membranes were compared with that of a control model without CER NS(C16). The permeability increased significantly when ≥50% of CER NS(C24) was substituted with CER NS(C16). Employing biophysical techniques, we showed that the lipid packing density reduced with an increasing proportion of CER NS(C16). Substitution of 75% of CER NS(C24) by CER NS(C16) resulted in the formation of phase-separated lipid domains and alteration of the LPP structure. Using deuterium-labeled lipids enabled simultaneous characterization of the C24 and C16 acyl chains in the lipid models, providing insight into the mechanisms underlying the reduced skin barrier function in diseased skin.

Cyanobacteria and microalgae bioactive compounds in skin-ageing: potential to restore extracellular matrix filling and overcome hyperpigmentation

As the largest organ in human body, skin acts as a physicochemical barrier, offering protection against harmful environmental stressors, such as chemicals, pathogens, temperature and radiation. Nonetheless, skins prominence goes further, with a significant psychosocial role in an increasingly ageing population. Prompted by consumers’ concern regarding skincare, cosmetic industry has been developing new formulas capable of lessening the most visible signs of ageing, including reduction in skin density and elasticity, wrinkling and hyperpigmentation. Allied to skincare is the rising importance set on natural products, sustainably obtained from less environmental impacting methods. Cyanobacteria and microalgae are adding importance in this field, given their ability to biosynthesize secondary metabolites with anti-ageing potential. In this review, we present an overview on the potential of cyanobacteria and microalgae compounds to overcome skin-ageing, essentially by exploring their effects on the metalloproteinases collagenase, elastase, gelatinase and hyaluronidase, and in other enzymes involved in the pigmentation process.

Review of the safety of application of cosmetic products containing parabens

Cosmetics are a source of lifetime exposure to various substances including parabens, being the most popular synthetic preservatives. Because the use of cosmetics shows an increasing trend and some adverse health outcomes of parabens present in these products have been reported, the present review focused on the safety of dermal application of these compounds. Special attention has been paid to the absorption of parabens and their retention in the human body in the intact form, as well as to their toxicological characteristics. Particular emphasis has been placed on the estrogenic potential of parabens. Based on the available published data of the concentrations of parabens in various kinds of cosmetics, the average ranges of systemic exposure dose (SED) for methylparaben, ethylparaben, propylparaben, and butylparaben have been calculated. Safety evaluations [margin of safety (MoS)] for these compounds, based on their aggregate exposure, have also been performed. Moreover, evidence for the negative impact of methylparaben on skin cells has been provided, and the main factors that may intensify dermal absorption of parabens and their impact on the skin have been described. Summarizing, the use of single cosmetics containing parabens should not pose a hazard for human health; however, using excessive quantities of cosmetic preparations containing these compounds may lead to the development of unfavorable health outcomes. Due to the real risk of estrogenic effects, as a result of exposure to parabens in cosmetics, simultaneous use of many cosmetic products containing these preservatives should be avoided.

Wound healing applications of creams and "smart" hydrogels

Although superficial wounds are often easy to treat for healthy individuals, there are some more severe types of wounds (burns, ulcers, diabetic wounds, etc.) that are a challenge for clinicians. A good therapeutic result is based on the delivery of a treatment at the right time, for the right patient. Our goal was to sum up useful knowledge regarding wound healing and wound treatments, based on creams and hydrogels with various active ingredients. We concluded that both preparations have application in preventing infections and promoting healing, but their efficacy is clearly conditioned by the type, depth, severity of the wound and patient profile. However, due to their superior versatility and capability of maintaining the integrity and functionality of the active ingredient, as well as it is controlled release at site, hydrogels are more suited for incorporating different active ingredients. New wound healing devices can combine smart hydrogel dressings with physical therapies to deliver a more efficient treatment to patients if the indications are appropriate.

Nano- and Micro-Porous Chitosan Membranes for Human Epidermal Stratification and Differentiation

The creation of partial or complete human epidermis represents a critical aspect and the major challenge of skin tissue engineering. This work was aimed at investigating the effect of nano- and micro-structured CHT membranes on human keratinocyte stratification and differentiation. To this end, nanoporous and microporous membranes of chitosan (CHT) were prepared by phase inversion technique tailoring the operational parameters in order to obtain nano- and micro-structured flat membranes with specific surface properties. Microporous structures with different mean pore diameters were created by adding and dissolving, in the polymeric solution, polyethylene glycol (PEG Mw 10,000 Da) as porogen, with a different CHT/PEG ratio. The developed membranes were characterized and assessed for epidermal construction by culturing human keratinocytes on them for up to 21 days. The overall results demonstrated that the membrane surface properties strongly affect the stratification and terminal differentiation of human keratinocytes. In particular, human keratinocytes adhered on nanoporous CHT membranes, developing the structure of the corneum epidermal top layer, characterized by low thickness and low cell proliferation. On the microporous CHT membrane, keratinocytes formed an epidermal basal lamina, with high proliferating cells that stratified and differentiated over time, migrating along the z axis and forming a multilayered epidermis. This strategy represents an attractive tissue engineering approach for the creation of specific human epidermal strata for testing the effects and toxicity of drugs, cosmetics and pollutants.

Atopic dermatitis: Role of the skin barrier, environment, microbiome, and therapeutic agents

Atopic dermatitis (AD) is a chronic, inflammatory skin disorder characterized by eczematous and pruritic skin lesions. In recent decades, the prevalence of AD has increased worldwide, most notably in developing countries. The enormous progress in our understanding of the complex composition and functions of the epidermal barrier allows for a deeper appreciation of the active role that the skin barrier plays in the initiation and maintenance of skin inflammation. The epidermis forms a physical, chemical, immunological, neuro-sensory, and microbial barrier between the internal and external environment. Not only lesional, but also non-lesional areas of AD skin display many morphological, biochemical and functional differences compared with healthy skin. Supporting this notion, genetic defects affecting structural proteins of the skin barrier, including filaggrin, contribute to an increased risk of AD. There is evidence to suggest that natural environmental allergens and man-made pollutants are associated with an increased likelihood of developing AD. A compromised epidermal barrier predisposes the skin to increased permeability of these compounds. Numerous topical and systemic therapies for AD are currently available or in development; while anti-inflammatory therapy is central to the treatment of AD, some existing and novel therapies also appear to exert beneficial effects on skin barrier function. Further research on the skin barrier, particularly addressing epidermal differentiation and inflammation, lipid metabolism, and the role of bacterial communities for skin barrier function, will likely expand our understanding of the complex etiology of AD and lead to identification of novel targets and the development of new therapies.