Effects of water activity and low molecular weight humectants on skin permeability and hydration dynamics - a double-blind, randomized and controlled study

Evaluation of the Biological Activity of Hydrogel with Cornus mas L. Extract and Its Potential Use in Dermatology and Cosmetology

Due to the growing popularity of herbal extract-loaded hydrogels, this study assessed the biological activity of extracts and hydrogels containing three types (water (WE), water-ethanol (EE) and water-glycerin (GE)) of Cornus mas L. (dogwood) extracts. The content of biologically active compounds in the extracts was assessed using the UPLC-DAD-MS technique. Antioxidant properties were assessed by using DPPH and ABTS radicals and measuring the intracellular level of reactive oxygen species. Alamar Blue and Neutral Red tests were used to measure the cytotoxicity of the tested samples on skin cells-fibroblasts and keratinocytes. Cell migration and the anti-aging activity of the tested extracts and hydrogels were assessed. Transepidermal water loss and skin hydration after applying the hydrogels to the skin were also determined. A chromatographic analysis revealed that the extracts contained polyphenols, including gallic, caftaric, protocatechuic, chlorogenic, ellagic and p-coumaroylquinic acids, as well as iridoids, with loganic acid as the predominant component. Additionally, they contained cyanidin 3-O-galactoside, pelargonidin 3-O-glucoside and quinic acid. The obtained results show that the tested extracts and hydrogels had strong antioxidant properties and had a positive effect on the viability of skin cells in vitro. Additionally, it was shown that they stimulated the migration of these cells and had the ability to inhibit the activity of collagenase and elastase. Moreover, the tested hydrogels increased skin hydration and prevented transepidermal water loss. The obtained results indicate that the developed hydrogels may be effective delivery systems for phytochemicals contained in dogwood extracts.

Cosmeceutical formulations of pro-vitamin E phosphate: In-vitro release testing and dermal penetration into excised human skin

Long-term exposure to solar radiation can lead to skin damage such as photoageing, and photocarcinogenesis. This can be prevented by topically applying α-tocopherol phosphate (α-TP). The major challenge is that a significant amount of α-TP needs to reach viable skin layers for effective photoprotection. This study aims to develop candidate formulations of α-TP (gel-like, solution, lotion, and gel), and investigate formulation characteristics' effect on membrane diffusion and human skin permeation. All the formulations developed in the study had an appealing appearance and no signs of separation. All formulations had low viscosity and high spreadability except the gel. The flux of α-TP through the polyethersulfone membrane was the highest for lotion (6.63 ± 0.86 mg/cm²/h), followed by control gel-like (6.14 ± 1.76 mg/cm²/h), solution (4.65 ± 0.86 mg/cm²/h), and gel (1.02 ± 0.22 mg/cm²/h). The flux of α-TP through the human skin membrane was numerically higher for lotion compared to the gel-like (328.6 vs.175.2 µg/cm²/h). The lotion delivered 3-fold and 5-fold higher α-TP in viable skin layers at 3 h and 24 h, respectively, compared to that of the gel-like. The low skin membrane penetration rate and deposition of α-TP in viable skin layers were observed for the solution and gel. Our study demonstrated that dermal penetration of α-TP was influenced by characteristics of formulation such as formulation type, pH, and viscosity. The α-TP in the lotion scavenged higher DPPH free radicals compared to that of gel-like (almost 73% vs. 46%). The IC₅₀ of α-TP in lotion was significantly lower than that of gel-like (397.2 vs. 626.0 µg/mL). The preservative challenge test specifications were fulfilled by Geogard 221 and suggested that the combination of benzyl alcohol and Dehydroacetic Acid effectively preserved 2% α-TP lotion. This result confirms the suitability of the α-TP cosmeceutical lotion formulation employed in the present work for effective photoprotection.

Skin Barrier Enhancing Alternative Preservation Strategy of O/W Emulsions by Water Activity Reduction with Natural Multifunctional Ingredients

Water activity (aw) as an important parameter for self-preservation can help to control microbial growth in cosmetic formulations. However, high amounts of water-binding substances are required to lower the aw enough to affect microbial growth. Since consequences for the skin barrier have been poorly studied so far, we investigated the effect of aw-lowering agents on both the antimicrobial properties of o/w emulsions and skin physiological parameters. A combination of selected natural humectants (Sodium lactate, Propanediol, Erythritol, Betaine and Sodium PCA) with a total concentration of 28 wt% in an o/w emulsion was able to reduce its aw from 0.980 ± 0.003 to 0.865 ± 0.005. The challenge test results of the aw-lowered emulsion showed a convincing microbial count reduction in potentially pathogenic microorganisms. The addition of as little as 0.5% of the antimicrobial multifunctionals Glyceryl Caprylate and Magnolia Officinalis Bark Extract further enhanced the antimicrobial effect, resulting in adequate antimicrobial protection. Moreover, twice-daily application of the aw-lowered emulsion for a period of four weeks led to a skin barrier-enhancing effect: TEWL significantly decreased, and SC hydration significantly increased. Thus, we present an opportunity to replace conventional preservatives with a natural alternative preservation strategy that has been shown to offer benefits for the skin.

EHO-85: A Multifunctional Amorphous Hydrogel for Wound Healing Containing Olea europaea Leaf Extract: Effects on Wound Microenvironment and Preclinical Evaluation

The prevalence of chronic wounds is increasing due to the population aging and associated pathologies, such as diabetes. These ulcers have an important socio-economic impact. Thus, it is necessary to design new products for their treatment with an adequate cost/effectiveness ratio. Among these products are amorphous hydrogels. Their composition can be manipulated to provide a favorable environment for ulcer healing. The aim of this study was to evaluate a novel multifunctional amorphous hydrogel (EHO-85), containing Olea europaea leaf extract, designed to enhance the wound healing process. For this purpose, its moistening ability, antioxidant capacity, effect on pH in the wound bed of experimental rats, and the effect on wound healing in a murine model of impaired wound healing were assessed. EHO-85 proved to be a remarkable moisturizer and its application in a rat skin wound model showed a significant antioxidant effect, decreasing lipid peroxidation in the wound bed. EHO-85 also decreased the pH of the ulcer bed from day 1. In addition, in mice (BKS. Cg-m +/+ Leprdb) EHO-85 treatment showed superior wound healing rates compared to hydrocolloid dressing. In conclusion, EHO-85 can speed up the closure of hard-to-heal wounds due to its multifunctional properties that are able to modulate the wound microenvironment, mainly through its remarkable effect on reactive oxygen species, pH, and moistening regulation.

Evaluation of Antioxidant and Wound-Healing Properties of EHO-85, a Novel Multifunctional Amorphous Hydrogel Containing Olea europaea Leaf Extract

The excess of free radicals in the wound environment contributes to its stagnation during the inflammatory phase, favoring hard-to-heal wounds. Oxidative stress negatively affects cells and the extracellular matrix, hindering the healing process. In this study, we evaluated the antioxidant and wound-healing properties of a novel multifunctional amorphous hydrogel-containing Olea europaea leaf extract (OELE). Five assessments were performed: (i) phenolic compounds characterization in OELE; (ii) absolute antioxidant activity determination in OELE and hydrogel (EHO-85); (iii) antioxidant activity measurement of OELE and (iv) its protective effect on cell viability on human dermal fibroblasts (HDFs) and keratinocytes (HaCaT); and (v) EHO-85 wound-healing-capacity analysis on diabetic mice (db/db; BKS.Cg-m+/+Leprdb). The antioxidant activity of OELE was prominent: 2220, 1558, and 1969 µmol TE/g by DPPH, ABTS, and FRAP assays, respectively. Oxidative stress induced with H2O2 in HDFs and HaCaT was normalized, and their viability increased with OELE co-treatment, thus evidencing a protective role. EHO-85 produced an early and sustained wound-healing stimulating effect superior to controls in diabetic mice. This novel amorphous hydrogel presents an important ROS scavenger capacity due to the high phenolic content of OELE, which protects skin cells from oxidative stress and contributes to the physiological process of wound healing.

Understanding humectant behaviour through their water-holding properties

OBJECTIVE

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Nanostructured lipid carriers containing chitosan or sodium alginate for co-encapsulation of antioxidants and an antimicrobial agent for potential application in wound healing

The high incidence and costs of chronic wounds in the elderly have motivated the search for innovations to improve product performance and the healing process while reducing costs. In this study, bioadhesive nanostructured lipid carriers (NLC) were developed for the co-encapsulation of compounds with antioxidant (α-tocopherol and quercetin) and antimicrobial (tea tree oil) activity for management of wounds. The NLC was produced with shea butter and argan oil, and modified with sodium alginate or chitosan to confer bioadhesive properties. Spherical nanoparticles of ~307-330 nm and zeta potential varying from -21.2 to +11.8 mV were obtained. Thermal analysis demonstrated that the lipid matrix reduced tea tree oil thermal loss (~1.8-fold). Regardless of the type of polysaccharide employed, the NLCs promoted cutaneous localization of antioxidants in damaged (subjected to incision) skin, with a ~74 to 180-fold higher delivery into the skin compared to percutaneous delivery. This result is consistent with the similar bioadhesive properties of chitosan or sodium alginate-modified NLC. Nanoencapsulation of tea tree oil did not preclude its antimicrobial effects against susceptible and resistant strains of S. aureus and P. aeruginosa, while co-encapsulation of antioxidants increased the NLC-induced fibroblasts migration, supporting their potential usefulness for management of wounds.

Vehicles for atopic dermatitis therapies: more than just a placebo

A topical vehicle is a 'carrier system' for an active pharmaceutical (or cosmetic) substance, referred to hereafter as the drug, but a vehicle may also be used on its own as an emollient to ameliorate dry skin. It is well established that the vehicle plays an important role in determining the bioavailability of a given drug at its ultimate target within the skin. Yet in the treatment of atopic eczema/dermatitis (AD), wherein the structure and function of the skin's outer barrier play a pivotal role in the development and course of the condition, the interaction of the vehicle with this barrier carries a particular importance. It is now clear that the often-considered inert excipients of a vehicle bring about changes within the skin at the molecular level that promote barrier restoration and enhance innate immune defenses with therapeutic value to AD patients. Moreover, the vehicle control in randomized controlled trials (RCTs) increasingly displays significant efficacy. In light of this, we consider the implications of vehicle design in relation to AD pathophysiology and the role vehicles play as controls in RCTs of new drug treatments for this condition.

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

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

Topical urea in skincare: A review

Alterations in barrier function are associated with a number of skin diseases, including xerosis, atopic dermatitis, and psoriasis. Urea, a component of the natural moisturizing factor of the skin, plays an important role in the preservation of skin hydration and integrity. Several studies have investigated the effects of urea in the clinical setting. Here, we summarize the available clinical evidence regarding the effects of urea in the maintenance of healthy skin and management of skin disorders. At lower doses (≤10%), urea-containing topical formulations act as a skin moisturizer, while at higher concentrations (>10% urea), urea-based preparations exert a keratolytic action. Urea is also useful in combination therapies with anti-inflammatory and anti-fungal drugs, due to its activity as a penetration enhancer.

In vivo uptake of iodine from a Fucus serratus Linnaeus seaweed bath: does volatile iodine contribute?

Seaweed baths containing Fucus serratus Linnaeus are a rich source of iodine which has the potential to increase the urinary iodide concentration (UIC) of the bather. In this study, the range of total iodine concentration in seawater (22-105 µg L-1) and seaweed baths (808-13,734 µg L-1) was measured over 1 year. The seasonal trend shows minimum levels in summer (May-July) and maximum in winter (November-January). The bathwater pH was found to be acidic, average pH 5.9 ± 0.3. An in vivo study with 30 volunteers was undertaken to measure the UIC of 15 bathers immersed in the bath and 15 non-bathers sitting adjacent to the bath. Their UIC was analysed pre- and post-seaweed bath and corrected for creatinine concentration. The corrected UIC of the population shows an increase following the seaweed bath from a pre-treatment median of 76 µg L-1 to a post-treatment median of 95 µg L-1. The pre-treatment UIC for both groups did not indicate significant difference (p = 0.479); however, the post-treatment UIC for both did (p = 0.015) where the median bather test UIC was 86 µg L-1 and the non-bather UIC test was 105 µg L-1. Results indicate the bath has the potential to increase the UIC by a significant amount and that inhalation of volatile iodine is a more significant contributor to UIC than previously documented.

Evidence That P-glycoprotein Inhibitor (Elacridar)-Loaded Nanocarriers Improve Epidermal Targeting of an Anticancer Drug via Absorptive Cutaneous Transporters Inhibition

Because P-glycoprotein (P-gp) plays an absorptive role in the skin, its pharmacological inhibition represents a strategy to promote cutaneous localization of anticancer agents that serve as its substrates, improving local efficacy while reducing systemic exposure. Here, we evaluated the ability of a nanoemulsion (NE) coencapsulating a P-gp inhibitor (elacridar) with the antitumor drug paclitaxel to promote epidermal targeting. Loaded NE displayed a nanometric size (45.2 ± 4.0 nm) and negative zeta potential (-4.2 ± 0.8 mV). Elacridar improved NE ability to inhibit verapamil-induced ATPase activity of P-gp; unloaded NE-inhibited P-gp when used at a concentration of 1500 μM, while elacridar encapsulation decreased this concentration by 3-fold (p <0.05). Elacridar-loaded NE reduced paclitaxel penetration into the dermis of freshly excised mice skin and its percutaneous permeation by 1.5- and 1.7-fold (p <0.05), respectively at 6 h, whereas larger drug amounts (1.4-fold, p <0.05) were obtained in viable epidermis. Assessment of cutaneous distribution of a fluorescent paclitaxel derivative confirmed the smaller delivery into the dermis at elacridar presence. In conclusion, we have provided novel evidence that NE containing elacridar exhibited a clear potential for P-gp inhibition and enabled epidermal targeting of paclitaxel, which in turn, can potentially reduce adverse effects associated with systemic exposure to anticancer therapy.

Co-encapsulation of paclitaxel and C6 ceramide in tributyrin-containing nanocarriers improve co-localization in the skin and potentiate cytotoxic effects in 2D and 3D models

Considering that tumor development is generally multifactorial, therapy with a combination of agents capable of potentiating cytotoxic effects is promising. In this study, we co-encapsulated C6 ceramide (0.35%) and paclitaxel (0.50%) in micro and nanoemulsions containing tributyrin (a butyric acid pro-drug included for potentiation of cytotoxicity), and compared their ability to co-localize the drugs in viable skin layers. The nanoemulsion delivered 2- and 2.4-fold more paclitaxel into viable skin layers of porcine skin in vitro at 4 and 8h post-application than the microemulsion, and 1.9-fold more C6 ceramide at 8h. The drugs were co-localized mainly in the epidermis, suggesting the nanoemulsion ability for a targeted delivery. Based on this result, the nanoemulsion was selected for evaluation of the nanocarrier-mediated cytotoxicity against cells in culture (2D model) and histological changes in a 3D melanoma model. Encapsulation of the drugs individually decreased the concentration necessary to reduce melanoma cells viability to 50% (EC₅₀) by approximately 4- (paclitaxel) and 13-fold (ceramide), demonstrating an improved nanoemulsion-mediated drug delivery. Co-encapsulation of paclitaxel and ceramide further decreased EC₅₀ by 2.5-4.5-fold, and calculation of the combination index indicated a synergistic effect. Nanoemulsion topical administration on 3D bioengineered melanoma models for 48h promoted marked epidermis destruction, with only few cells remaining in this layer. This result demonstrates the efficacy of the nanoemulsion, but also suggests non-selective cytotoxic effects, which highlights the importance of localizing the drugs within cutaneous layers where the lesions develop to avoid adverse effects.

Potential of Non-aqueous Microemulsions to Improve the Delivery of Lipophilic Drugs to the Skin

In this study, non-aqueous microemulsions were developed because of the challenges associated with finding pharmaceutically acceptable solvents for topical delivery of drugs sparingly soluble in water. The formulation irritation potential and ability to modulate the penetration of lipophilic compounds (progesterone, α-tocopherol, and lycopene) of interest for topical treatment/prevention of skin disorders were evaluated and compared to solutions and aqueous microemulsions of similar composition. The microemulsions (ME) were developed with BRIJ, vitamin E-TPGS, and ethanol as surfactant-co-surfactant blend and tributyrin, isopropyl myristate, and oleic acid as oil phase. As polar phase, propylene glycol (MEPG) or water (MEW) was used (26% w/w). The microemulsions were isotropic and based on viscosity and conductivity assessment, bicontinuous. Compared to drug solutions in lipophilic vehicles, MEPG improved drug delivery into viable skin layers by 2.5-38-fold; the magnitude of penetration enhancement mediated by MEPG into viable skin increased with drug lipophilicity, even though the absolute amount of drug delivered decreased. Delivery of progesterone and tocopherol, but not lycopene (the most lipophilic compound), increased up to 2.5-fold with MEW, and higher amounts of these two drugs were released from MEW (2-2.5-fold). Both microemulsions were considered safe for topical application, but MEPG-mediated decrease in the viability of reconstructed epidermis was more pronounced, suggesting its higher potential for irritation. We conclude that MEPG is a safe and suitable nanocarrier to deliver a variety of lipophilic drugs into viable skin layers, but the use of MEW might be more advantageous for drugs in the lower range of lipophilicity.

Improvement of hand sensibility resulting from application of anaesthetic cream on the forearm: importance of dose and time

Introduction

A local anaesthetic cream, EMLA®, applied temporarily to the forearm can improve sensory functions in the hands, both in healthy individuals and in patients with nerve injury. The treatment concept is an example of guided plasticity where the dynamic capacity of the central nervous system is used for therapeutic purposes. However, the optimal dose and duration of the anaesthetic cream is not known and this is addressed here.

Methods

Sixty healthy volunteers participated in this experimental study. They were randomised to one of six groups of 10 and received either 10 g or 20 g of EMLA® on the volar part of the forearm for either 60, 90 or 120 min, respectively. Outcome measures were touch thresholds and discriminative touch in digits II and V.

Results

There was a statistically significant improvement in touch threshold as well as discriminative touch in all six groups. However, there were no statistically significant differences between the six different dose and duration combinations.

Conclusions

It is concluded that 10 g of EMLA® applied to the volar part of the forearm for 60 min may be adequate to induce improved hand sensibility.