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Glycerol and the skin: Holistic approach to its origin and functions
Abstract
Glycerol is a trihydroxy alcohol that has been included for many years in topical dermatological preparations. In addition, endogenous glycerol plays a role in skin hydration, cutaneous elasticity and epidermal barrier repair. The aquaporin-3 transport channel and lipid metabolism in the pilosebaceous unit have been evidenced as potential pathways for endogenous delivery of glycerol and for its metabolism in the skin. Multiple effects of glycerol on the skin have been reported. The diverse actions of the polyol glycerol on the epidermis include improvement of stratum corneum hydration, skin barrier function and skin mechanical properties, inhibition of the stratum corneum lipid phase transition, protection against irritating stimuli, enhancement of desmosomal degradation, and acceleration of wound-healing processes. Even an antimicrobial effect has been demonstrated. Topical application of glycerol-containing products improves skin properties in diseases characterized by xerosis and impaired epidermal barrier function, such as atopic dermatitis. The increase of epidermal hydration by glycerol is critical in skin conditions aggravated by dry and cold environmental conditions, e.g. winter xerosis. This paper provides a review on effects of glycerol on the skin, the mechanisms of its action, and the potential applications of glycerol in dermatology.
... It is suited for superficial injections in facial rejuvenation [8,9]. Glycerol is a humectant known for its ability to enhance skin hydration, improve skin mechanical properties, reduce transepidermal water loss (TEWL), inhibit the stratum corneum lipid phase transition, provide anti-irritant and anti-inflammatory effects, accelerate wound healing, and exhibit antimicrobial actions [11,12]. ...
... The unique formulation of CPM-HA20G, which includes glycerol as a humectant, may contribute to its rapid and enhanced effects. Glycerol has been demonstrated to moisturize, strengthen, and provide protective benefits to the skin [11,12]. Physicochemical analysis of CPM-HA20G demonstrated an immediate release of glycerol, which can penetrate into the human dermis in an ex vivo study [26]. ...
... In the present study, improvements in skin redness were more apparent in subjects with inflammation-induced redness, such as rosacea and acne, than those with redness caused by aging or telangiectasia from sun exposure. This aligns with the known effects of HA and glycerol, which act as antioxidants to alleviate inflammatory conditions, potentially reducing skin redness [4,5,8,11,12,[16][17][18][19][20][21]. Skin brightness was also significantly improved with CPM-HA20G, likely due to the release of SDF-1 and perceived brighter skin resulting from smoother skin and reduced redness [2,5,22]. ...
Background
Intradermal injection of CPM‐HA20G, a low‐viscoelasticity hyaluronic acid (HA) dermal filler with glycerol, has been shown to be effective for facial rejuvenation in Caucasians, but research in Asians is limited.
Aims
This study aimed to evaluate the effectiveness and safety of CPM‐HA20G in enhancing facial skin quality in Korean women using a protocol developed by local aesthetic experts.
Patients/Methods
In this 24‐week prospective, single‐arm, open‐label study, 20 women received CPM‐HA20G injections in the immediate subdermal layer on the anterior cheek (1 mL per side; total 2 mL) in three sessions every 4 weeks. Evaluations included biophysical assessments covering the four emergent perceptual categories (EPCs) for skin quality and subjective assessment using the Global Aesthetic Improvement Scale.
Results
Significant improvements in skin glow (skin gloss, epidermal hydration), skin firmness (dermal elasticity, dermal hydration), skin surface evenness (average pore volume, pore area, pore density, pore count, maximum pore depth, total pore volume, skin roughness, sebum secretion, and skin depression volume), skin tone evenness (skin color brightness, skin redness), and transepidermal water loss were observed at Week 12 and Week 24 following the first injection with CPM‐HA20G. Most subjects and investigators reported improvements in overall aesthetic appearance with the treatment, with a 100% improvement rating from both groups at Week 12. No serious adverse reactions were observed.
Conclusions
Our study provides real‐world insights into the effectiveness and safety of CPM‐HA20G in improving facial skin quality in an Asian population, evaluated through both objective and subjective assessments.
... TEWL and MIX values were decreased 15 and 90 minutes after body cream application. This could be explained by the hydrating and moisturizing effect of the body cream due to the presence of substances, such as glycerol, white soft paraffin, liquid paraffin, and dimethicone 40,[45][46][47] . Additionally, these substances protect against water loss through the skin, which contributes to a decreased TEWL 40,45,47,48 . ...
... This could be explained by the hydrating and moisturizing effect of the body cream due to the presence of substances, such as glycerol, white soft paraffin, liquid paraffin, and dimethicone 40,[45][46][47] . Additionally, these substances protect against water loss through the skin, which contributes to a decreased TEWL 40,45,47,48 . Skin hydration decreases skin impedance at all frequencies, most likely due to better current conductivity 22 . ...
... Our observation of decreased TEWL is in contrast to previously documented increased TEWL after water exposure, supposedly due to evaporation of remaining water and disruption of SC intercellular lipid 29 . These contradictory results may be explained by the limited duration of water exposure (one minute in our study versus 30 minutes for five consecutive days in previous studies) and the hydrating properties of glycerin and sweet almond oil present in the soap used in this study 45 . Decreased MIX values after skin washing may be due to the hydrating properties of glycerin and sweet almond oil present in the soap and the role of water in altering extracellular resistive properties of superficial skin layers by filling pre-existing voids like hair follicles, sweat glands, and furrows 22 . ...
Skin barrier function assessment is commonly done by measuring transepidermal water loss (TEWL). An important limitation of this method is the influence of intrinsic and extrinsic factors. Electrical impedance spectroscopy (EIS) is a lesser-established method for skin barrier function assessment. Some influential factors have been described, but no guidelines exist regarding the standardization of these measurements. We evaluated the effects of daily routine activities on TEWL and EIS, as well as their correlation with age and anatomical differences.
... It is also used as a vehicle for many topical preparations. [31] The dermatologic uses of glycerol are summarized in Table 4. [31][32][33] ...
... It is also used as a vehicle for many topical preparations. [31] The dermatologic uses of glycerol are summarized in Table 4. [31][32][33] ...
This article describes evidence-based usage of common household items to treat dermatological diseases. We have compiled the rationale of their usage from various studies and practical ways to use items like household vinegar, bleach, and common salt, in diseases such as pseudomonas nail infections, other bacterial and fungal infections, pyogenic granuloma, etc.
... Its unique chemical property makes it prominent in the drug industry as an excellent vehicle for drug administration as it helps to maintain both moisture and smoothness of drugs (Van Rosendal et al., 2012) [29] . It also acts as a skin moisturizer, by forming a water layer on the skin surface, thereby preventing topical evaporation of water (Fluhr et al., 2008) [8] . In humans, Glycerin is widely used as a suppository to relieve occasional constipation and to clear the bowels before a rectal examination (Song, et al., 2008) [27] . ...
... Its unique chemical property makes it prominent in the drug industry as an excellent vehicle for drug administration as it helps to maintain both moisture and smoothness of drugs (Van Rosendal et al., 2012) [29] . It also acts as a skin moisturizer, by forming a water layer on the skin surface, thereby preventing topical evaporation of water (Fluhr et al., 2008) [8] . In humans, Glycerin is widely used as a suppository to relieve occasional constipation and to clear the bowels before a rectal examination (Song, et al., 2008) [27] . ...
The nutraceuticals in fruits and vegetables are among the major contributors of their therapeutic relevance to humans. This study evaluates the relevance of nutraceuticals obtained from the GC-MS analyses of dichloromethane extracts of unripe matured fruits of Musa paradisiaca, Musa acuminata and Musa balbisiana. Methodology: Unripe matured fruits of M. paradisiaca, M. acuminata and M. balbisiana harvested from their natural habitat and identified at the Plant Science Department of the University of Port Harcourt were separately washed and the epicarp were removed. The sliced mesocarp were dried and ground into fine powder. Ten grams each of the ground samples was weighed into different well stoppered bottle and 40 mls of dichloromethane was added. Each mixture was vigorously agitated and allowed to stand for 96 hours. The crude extracts collected by filtering was purified and concentrated to 2.0 ml for GC-MS analysis. Result: Results shows 97, 83, and 52 nutraceutical components in M. paradisiaca, M. acuminate and M. balbisiana respectively, with 1,4-Cyclohexadiene,1-methyl-4-(1-methylethyl)-, α-Pinene and Glycerin as highest nutraceutical components with percentage concentrations of 18.379, 11.874 and 17.889 respectively. Conclusion: The numerous therapeutic potentials of predominant nutraceuticals in these Musa species are of prominent in the development of broad-spectrum pharmaceuticals formulations for advancement of human wellbeing.
... 5 It has been shown to maintain SC integrity and enhance skin hydration through peroxisome proliferator-activated receptor α agonist (PPAR-α) that increase keratinocyte proliferation and lipid synthesis. 5 Moisturizing ingredients also help restore skin condition by forming an occlusive film on the skin surface, which controls the rate of water evaporation from the skin and by transporting hygroscopic substances capable of binding and retaining water into the SC. 6 The uses of glycerol and urea as potent endogenous humectants and moisturizers 7,8 are important components for reducing the severity of dry skin due to skin aging. Glycerol has been used as a major humectant in cosmetic products because it can spread easily on the skin and give a silky, soft, and nongreasy sensation favored by end consumers. ...
... The diverse effects of glycerol on the epidermis include increasing hydration barrier function and mechanical properties, inhibiting lipid phase transition, protecting against irritating stimuli, enhancing desmosomal degradation, and accelerating the wound-healing process. 8 Plant extracts are sometimes also added to antiaging formulations as ROS scavengers. Compounds isolated from natural products are preferred as there is a strong market trend toward formulating green and eco-friendly products. ...
We developed a facile preparation method of oil-in-water (O/ W) Pickering emulsion in an emollient formulation using basil extract (Ocimum americanum L.) as a solid particle stabilizer by fine-tuning the concentration and mixing steps of common cosmetic formulas, such as humectants (hexylene glycol and glycerol), surfactant (Tween 20), and moisturizer (urea). The hydrophobicity of the main phenolic compounds of basil extract (BE), namely, salvigenin, eupatorin, rosmarinic acid, and lariciresinol, supported high interfacial coverage to prevent coalescence of globules. Meanwhile, the presence of carboxyl and hydroxyl groups of these compounds provides active sites for stabilizing the emulsion using urea through the formation of hydrogen bonds. Addition of humectants directed the in situ synthesis of colloidal particles during emulsification. In addition, the presence of Tween 20 can simultaneously reduce the surface tension of the oil but tends to inhibit the adsorption of solid particles at high concentrations, which otherwise formed colloidal particles in water. The level of urea and Tween 20 determined the stabilization system of the O/W emulsion, whether interfacial solid adsorption (Pickering emulsion, PE) or colloidal network (CN). Variation of the partition coefficient of the phenolic compounds present in basil extract facilitated the formation of a mixed PE and CN system with better stability. The addition of excess urea induced interfacial solid particle detachment, which caused the oil droplet enlargement. The choice of stabilization system determined the control of antioxidant activity, diffusion through lipid membranes, and cellular antiaging effects in UV-B-irradiated fibroblasts. Particle sizes of less than 200 nm were found in both stabilization systems, which is beneficial for maximizing their effects. In conclusion, this study provides a technological platform to realize the demand for natural dermal cosmetic and pharmaceutical products with strong antiaging effects.
... This is called "swelling, " characterized by intracellular expansion of corneocytes and intercellular expansion between corneocytes. This mechanism probably results in improved skin barrier properties as well as water retention capacity in the skin, which results in a moisturizing effect [73]. Therefore, glycerine increases the bioavailability of phenolic acids by affecting membrane permeability [74]. ...
Background
Honey has been successfully used in wound care and cosmetics because of its effective biological properties, including antibacterial, antioxidant, and anti-inflammatory activities. Polyphenols, particularly phenolic acids, are key honey components responsible for these beneficial effects. In recent years, there has been a growing demand for natural, ecologically friendly, and biodegradable products in the modern cosmetics and wound care market. This study aimed to identify and quantify phenolic acids in four Polish honey samples of different botanical origins (heather, buckwheat, linden and rapeseed) and to assess for the first time the permeation of the identified phenolic acids through the skin and their accumulation after the application of pure honey samples, as well as honey-based hydrogel and emulsion formulations.
Methods
The honey samples’ antioxidant activity and total phenolic content were determined using the DPPH and ABTS assays and the Folin–Ciocalteu method, respectively. Phenolic acids and volatile compounds were identified and quantified in honey samples using the HPLC-UV and GC-MS method, respectively. The biocompatibility of the honey samples was evaluated using a murine fibroblast cell line (L929). A Franz-type vertical diffusion cell with porcine skin was used to assess phenolic acid’s permeation and skin accumulation from different honey-based pharmaceutical formulations. The biodegradability of the prepared formulations was also characterised.
Results
Gallic acid, 3,4-dihydroxybenzoic acid, 2,5-dihydroxybenzoic acid, coumaric acid, and 3-hydroxybenzoic acid were identified and quantified in the honey samples. Heather honey exhibited significantly higher antioxidant activity and total polyphenol content than the other honey samples. Heather, linden and buckwheat honey samples significantly decreased cell viability at concentrations of 5% and 2.5%, while rapeseed honey sample markedly reduced fibroblast viability only at 5%. Among the tested formulations - pure honey, hydrogel, and emulsion - higher skin permeation and accumulation rates of phenolic acids were observed with the prepared honey-based hydrogels than with the pure honeys and emulsions. Additionally, the prepared formulations were classified as partially biodegradable.
Conclusions
The obtained results confirmed the effectiveness of two pharmaceutical formulations in the form of a hydrogel or emulsion containing honey after applied topically. The inclusion of honey in the vehicle, in particular hydrogel increased the penetration of phenolic acids through the skin.
... Lastly, the formula chassis included glycols and glycerin, to address the skin hydration and skin barrier component (25). The formula type chosen was a leave-on gel serum, with a non-greasy texture, thus it could be applied any time of the day without weighing down the hair. ...
Pruritus is prevalent among the population, with the scalp regarded as one of the most affected zones. The objective was to design and test a formulation for people experiencing regular skin discomfort on the scalp. Hallmarks of sensitive skin such as skin hydration, skin barrier, skin itching and skin redness were measured on the scalp before and up to 21 days of use. Skin hydration and skin barrier on the scalp were improved after a single use while itching intensity and scalp redness were reduced in the short and long term. By alleviating the burden of sensitive skin, these results are an example of “Skinification” of scalp care, where benefits traditionally expected for facial skin are expanded to other body parts.
... Chamomile is recognized for its well-established curative properties, including anti-inflammatory and antimicrobial activity [39]. Similarly, topical glycerol has been documented for its beneficial role in managing various skin conditions [40]. Nevertheless, it is essential to consider potential adverse effects and costs associated with the regular use of eyelid wipes, as reported in some studies [38]. ...
Background: Anterior blepharitis (AB) is a chronic eyelid inflammation with no definitive cure. Objectives: To assess the safety and efficacy of a 1% povidone-iodine (PVI) ophthalmic solution lid scrub compared to formulated eyelid wipes in treating AB. Design: A prospective, randomized, controlled, observer-masked, paired-eye trial. Methods: Sixty-three AB patients were randomly assigned to a 30-day treatment in which one eye underwent a daily lid scrub with 1% PVI solution (1% PVI group), while the fellow eye was treated with formulated eyelid wipes (control group). Clinical outcomes, such as blepharitis signs, tear breakup time, and corneal staining, were evaluated at study enrollment and exit visits. Symptom assessments utilized the visual analog scale (VAS) per eye and the ocular surface disease index (OSDI) questionnaire. Results: Fifty-two patients (mean age 62.3 years, 53.8% females) completed the treatment, while seven patients were lost to follow-up, three were non-compliant, and one sustained an eye trauma. After 30 days, both the 1% PVI and control groups exhibited significant improvements in symptoms, blepharitis signs, and corneal staining (p < 0.05). The 1% PVI scrubs were equally effective as eyelid wipes in most outcomes (p = 0.480) and superior in alleviating eyelid erythema (p = 0.007). Only the 1% PVI group showed a positive correlation between OSDI and VAS score improvements (r (52) = 0.353, p = 0.01). No adverse events related to either treatment modality were reported. Conclusions: A 1% PVI solution is an effective, safe, and well-tolerated treatment option for AB and is superior to formulated eyelid wipes in several subjective and objective measures.
... Glycerin has many other health benefits. It helps retain moisture in the skin [99], increases its hysteresis (creep phenomenon) and distensibility [100], and protects skin against irritants, inflammation, and microbes [99,101,102]. Glycerin can improve bowel movements and aid the passage of stool to relieve constipation and strengthen the gut, and it also improves hydration and cardiovascular functions [103,104]. In sports, the ingestion of glycerin in combination with excess fluid can lead to increased plasma osmolality, reduced urine volume, and expanded plasma volume [70]. ...
Dietary supplements are products taken orally, and they contain an ingredient intended to augment the diet. Many studies demonstrate clear alterations in microbe abundances and the production of microbiota-derived metabolites, such as short-chain fatty acids, following dietary changes. This review comprehensively explores the possible interactions among gut microbiota, lemon extracts, glycerin, and their mixture products. Lemon extracts/components are associated with a vast array of health benefits, including anti-inflammation, antioxidant, anti-atherosclerotic, and anti-diabetic effects. They are also associated with increased memory and decreased depression. Glycerin can reduce serum free fatty acids and mimic caloric restriction; its metabolites can function as a broad-spectrum antimicrobial. Additionally, glycerin has a dehydrating effect on the central nervous system and can reduce focal cerebral edema and improve performance by expanding plasma volume. However, it may also have side effects, such as hyperglycemia. Therefore, combined consumption of lemon extracts and glycerin may, in part, mitigate each other’s side effects while exerting their benefits. There is growing evidence that both lemon components and glycerin are metabolized by the gut microbiota and may modulate the intestinal microbiome composition. Therefore, gut microbiome alterations are also explored as an important mechanism in the gut–brain axis regulating various effects of these dietary supplements and their application in various noncommunicable neurological disorders.
... V0034CR (Dexeryl®; Pierre Fabre) is an emollient cream containing glycerol 15% and paraffin 10% in an oil-in-water emulsion. The combination of glycerol and paraffin was hypothesized to be pharmacologically relevant in xerosis, based on the moisturizing and barrier-repairing properties of glycerol, and the anti-irritant and occlusive properties of paraffin [6,13,14]. Indeed, the synergistic effects of V0034CR on skin hydration and transepidermal water loss were demonstrated in a study of healthy subjects with non-pathological dry skin [15], while other studies have shown the clinical benefits of V0034CR in patients with cutaneous xerosis [16] and related conditions including atopic dermatitis [17][18][19][20], ichthyosis [21,22], psoriasis [23], senile xerosis [24], and diabetic foot xerosis [25]. ...
There is an unmet need for effective topical therapies for patients with uremic xerosis and chronic kidney disease-associated pruritus (CKD-aP). The long-term efficacy and tolerability of an emollient containing glycerol 15% and paraffin 10% (V0034CR) was evaluated in a phase 3 study.
In this randomized, double-blind, two-parallel group, vehicle-controlled study, patients with moderate-to-severe uremic xerosis were randomized to once-daily application of V0034CR or vehicle control for 28 days (period I). This was followed by a treatment-free period of ≤ 21 days (period II), then all patients received open-label treatment with V0034CR for ≥ 84 days (period III). Outcomes included treatment response at the end of period I (El Gammal’s xerosis severity score), instrumental measures of scaling (D-Squame technique), time to relapse during period II, rate of recurrence during period III, pruritus severity over time, patient acceptability, and adverse events (AEs).
The intent-to-treat population comprised 235 patients randomized to V0034CR (n = 118) or vehicle control (n = 117) during period I. Treatment response at the end of period I was achieved by 71 patients (60.2%) in the V0034CR group versus 48 (41.0%) with vehicle control (p = 0.0041). This coincided with greater reductions in the total surface area of squames (p = 0.001 vs vehicle control). Xerosis relapsed progressively without treatment in period II; however, remission was durable under maintenance therapy in period III. Improvements in pruritus severity were comparable between V0034CR and vehicle control, suggesting that the antipruritic effect of V0034CR was mainly exerted by its oil-in-water emulsion base. V0034CR had high patient acceptability and was well tolerated; the most common treatment-related AEs were irritation or erythema (2.1%), exacerbated pruritus (1.3%), and vesicles at the application site (0.9%).
These data support the use of V0034CR, with its hydrating and occlusive properties, for the long-term management of patients with moderate-to-severe uremic xerosis and CKD-aP.
ClinicalTrials.gov identifier NCT01084148; EudraCT number 2006-002201-31.
... Glycerol, which is present at 1.55% in USE-B and 1.08% in USE-S, is an important ingredient in the cosmetics industry as a humectant and skin protectant. Its high moisture-retaining capacity maintains skin hydration and provides a protective barrier against external factors [47]. The primary monosaccharide identified was L-fucose (2.93% in USE-S), known for its anti-inflammatory and anticancer effects, particularly in modulating the immune response and reducing inflammation [48]. ...
The subcritical water extraction of Undaria pinnatifida (blade, sporophyll, and root) was evaluated to determine its chemical properties and biological activities. The extraction was conducted at 180 °C and 3 MPa. Root extracts exhibited the highest phenolic content (43.32 ± 0.19 mg phloroglucinol/g) and flavonoid content (31.54 ± 1.63 mg quercetin/g). Sporophyll extracts had the highest total sugar, reducing sugar, and protein content, with 97.35 ± 4.23 mg glucose/g, 56.44 ± 3.10 mg glucose/g, and 84.93 ± 2.82 mg bovine serum albumin (BSA)/g, respectively. The sporophyll contained the highest fucose (41.99%) and mannose (10.37%), whereas the blade had the highest galactose (48.57%) and glucose (17.27%) content. Sporophyll had the highest sulfate content (7.76%). Key compounds included sorbitol, glycerol, L-fucose, and palmitic acid. Root extracts contained the highest antioxidant activity, with IC50 values of 1.51 mg/mL (DPPH), 3.31 mg/mL (ABTS+), and 2.23 mg/mL (FRAP). The root extract exhibited significant α-glucosidase inhibitory activity with an IC50 of 5.07 mg/mL, indicating strong antidiabetic potential. The blade extract showed notable antihypertensive activity with an IC50 of 0.62 mg/mL. Hence, subcritical water extraction to obtain bioactive compounds from U. pinnatifida, supporting their use in functional foods, cosmetics, and pharmaceuticals is highlighted. This study uniquely demonstrates the variation in bioactive compound composition and bioactivities across different parts of U. pinnatifida, providing deeper insights. Significant correlations between chemical properties and biological activities emphasize the use of U. pinnatifida extracts for chronic conditions.
... Water-polyol mixtures have unique properties and wide-ranging applications. These solutions are used in various fields, such as automotive industry, as cryoprotective agents (CPA) [1][2][3][4][5][6], skincare products [7][8][9][10][11] and food or tissues cryopreservation. [12][13][14][15][16][17] Among the polyol molecules, glycerol has been demonstrated to be an excellent cryoprotectant. ...
Glycerol acts as a natural cryoprotectant by depressing the temperature of ice nucleation and slowing down the dynamics of water mixtures. In this work we characterize dynamics -- diffusion, viscosity, and hydrogen-bond dynamics -- as well as density anomaly and structure of water mixtures with 1\% to 50\% w/w glycerol at low temperatures via molecular dynamics simulations using all-atom and coarse-grained models. Simulations reveal distinct violations of the Stokes-Einsten relation in the low temperature regime for water and glycerol. Deviations are positive for water at all concentrations, and positive for glycerol in very dilute solutions but turning negative in concentrated ones. The all-atom and coarse-grained models reveal an unexpected crossover in the dynamics of the 1% and 10 % w/w glycerol at the lowest simulated temperatures. This crossover manifests in the diffusion coefficients of water and glycerol, as well as in the viscosity and lifetime of hydrogen-bonds in water. We interpret that the crossover originates on the opposing dependence with glycerol concentration of the two factors controlling the solution's slow-down: the increase in tetrahedrally coordinated water and the dynamics and clustering of the glycerol molecules. We anticipate that this dynamic crossover will also occur for solution of water with other polyols.
... Glycerol, another name for glycerin, is a straightforward polyol substance with the chemical formula C3H8O3. It is a colorless, odorless, sweet-tasting liquid that is used in a number of food, personal care, and medicinal products [Fluhr et al. 2008]. Glyoxal is a chemically defined organic substance having the formula OCHCHO. ...
In this study, Oriental beech (Fagus orientalis L.) wood was treated with 0.5%, 1.5% and 4.5% concentrations of two different dimensional stability chemicals (glyoxal and glycerol), two different fire-retardant salts (sodium acetate and sodium pentaborate), and their mixtures (1:1; weight/weight). The thermal degradation properties of wood samples treated with different types and concentrations of compounds were investigated using thermogravimetric analysis (TGA). When only glyoxal or glycerol was used, they had an adverse effect on the thermal properties of samples. The use of these chemicals together improved the thermal properties, due to the formation of longer polymer chains compared with the control group. Sodium acetate and sodium pentaborate salts, both singly and in a mixture, improved the char yield. The highest char yield (72.13%) was obtained using sodium pentaborate at 4.5% concentration.
... The effect of site and gender studied is explained in Figure S6 (Appendix S2). Scores and loadings plot show the trend of aminoacids, bioamine, glycerol 43 and sebaceous lipids in the SGP areas compared to SGR ones ( Figure S7, Appendix S2). ASCA model also F I G U R E 1 ASCA analysis on the effect matrix for lipid metabolites (pmol/tape) investigated in sebum from foreheads (upper panels) and cheeks (lower panels) in hC, fnAD, and fyAD groups. ...
Atopic dermatitis (AD) is a composite disease presenting disruption of the skin permeability barrier (SPB) in the stratum corneum (SC). Recent evidence supports derangement of the sebaceous gland (SG) activity in the AD pathomechanisms. The objective of this study was to delineate profiles of both sebaceous and epidermal lipids and of aminoacids from SG‐rich (SGR) and SG‐poor (SGP) areas in AD. Both sebum and SC were sampled from SGR areas, while SC was sampled also from SGP areas in 54 adult patients with AD, consisting of 34 and 20 subjects, respectively with and without clinical involvement of face, and in 44 age and sex‐matched controls. Skin biophysics were assessed in all sampling sites. Disruption of the SBP was found to be associated with dysregulated lipidome. Abundance of sapienate and lignocerate, representing, respectively, sebum and the SC type lipids, were decreased in sebum and SC from both SGR and SGP areas. Analogously, squalene was significantly diminished in AD, regardless the site. Extent of lipid derangement in SGR areas was correlated with the AD severity. The abundance of aminoacids in the SC from SGR areas was altered more than that determined in SGP areas. Several gender‐related differences were found in both controls and AD subgroups. In conclusion, the SG activity was differently compromised in adult females and males with AD, in both SGR and SGP areas. In AD, alterations in the aminoacidome profiles were apparent in the SGR areas. Lipid signatures in association with aminoacidome and skin physical properties may serve the definition of phenotype clusters that associate with AD severity and gender.
... Because bacteria contains with chemoreceptors for l-aspartic acid on its membrane, due to this reason they can express chemotaxis behavior towards l-aspartic acid-containing nanotherapeutic. This property of a therapeutic agent can facilitate rapid infection recovery from the target site [38,39]. For preparation of nanotherapeutic, 10 μg/ml concentration of nanoformulation was prepared in 5% ethanol solution by properly mixing for 2 h with random sonication. ...
Aim: To develop a biocompatible conjugated ciprofloxacin-PEG-FeO nanodelivery system with increased efficacy of available therapeutics in a controlled manner. Materials & methods: FeO nanoparticles were synthesized by chemical and biological methods and modified as ciprofloxacin-PEG-FeO nanoformulations. After initial antibacterial and cytotoxicity studies, the effective and biocompatible nanoformulations was further fabricated as nanotherapeutics for in vivo studies in mouse models. Results: Chemically synthesized ciprofloxacin-PEG-FeO nanoformulations demonstrated boosted antibacterial activity against clinically isolated bacterial strains. Nanoformulations were also found to be compatible with baby hamster kidney 21 cells and red blood cells. In in vivo studies, nanotherapeutic showed wound-healing effects with eradication of Staphylococcus aureus infection. Conclusion: The investigations indicate that the developed nanotherapeutic can eradicate localized infections and enhance wound healing with controlled cytotoxicity.
... Shu et al. (2013) showed for the first time the impact of SCFAs produced by commensal C. acnes against S. aureus USA300, a community-associated MRSA lineage that is the predominant cause of skin and soft tissue infections in the USA [48]. SCFAs produced through fermentation of glycerol, a carbon source naturally found on the skin [49], decreased USA300 colonization of skin lesions, due to a decrease in intracellular pH, affecting bacterial growth [26]. This seems to be a mechanism used by C. acnes to outcompete S. aureus, conferring it some advantage, as it is known that both species can ferment the same carbon source, competing when in the same niche [50]. ...
The skin is the largest human organ and is responsible for many important functions, such as temperature regulation, water transport, and protection from external insults. It is colonized by several microorganisms that interact with each other and with the host, shaping the microbial structure and community dynamics. Through these interactions, the skin microbiota can inhibit pathogens through several mechanisms such as the production of bacteriocins, proteases, phenol soluble modulins (PSMs), and fermentation. Furthermore, these commensals can produce molecules with antivirulence activity, reducing the potential of these pathogens to adhere to and invade human tissues. Microorganisms of the skin microbiota are also able to sense molecules from the environment and shape their behavior in response to these signals through the modulation of gene expression. Additionally, microbiota-derived compounds can affect pathogen gene expression, including the expression of virulence determinants. Although most studies related to microbial interactions in the skin have been directed towards elucidating competition mechanisms, microorganisms can also use the products of other species to their benefit. In this review, we will discuss several mechanisms through which microorganisms interact in the skin and the biotechnological applications of products originating from the skin microbiota that have already been reported in the literature.
... Furthermore, previous studies demonstrated that cucumber-derived products provided phytosterols, phenolic acids, fatty acids, and cucurbitacins, improving skin regeneration [15,27]. Further contributing to the wetting and cosmetic requirements demanded in skin-designed formulations that are absent when using pure glycerol [28], as evidenced here. Interestingly, the hydroglycolic extracts protect against uV-A and uV-B rays, mainly by acting as an adjuvant in inhibiting skin's deterioration due to DNA damage and lipid peroxidation [29,30]. ...
The Coronavirus disease 2019 (COVID-19) outbreak increased the usage of hand rub disinfectants, resulting in skin damage. The World Health Organization (WHO) proposed hand rubs formulations incorporating glycerine due to its moisturizing effect; nonetheless, glycerine can reduce the antimicrobial activity of alcohol-based hand rubs. Here we demonstrated that incorporating hydroglycolic extract as a substitute for glycerol in hand rub formulations reduces epidermis damage while improving antimicrobial effectiveness. We applied the hydroglycolic extracts from Cucumis sativus L., Fragaria sp. and Calendula officinalis instead of glycerol to modify the formula proposed by the WHO. The antimicrobial activity and the healing skin action were evaluated using the agar diffusion test and a human skin tolerability trial. Furthermore, we assessed the cytotoxicity and wound repair capability of the formulated hydroglycolic extracts against human gingival fibroblasts (HGFs) and the phenotype of murine macrophages. The hand rubs containing Fragaria sp. and C. officinalis hydroglycolic extracts showed improved antimicrobial activity even after six months of fabrication. Moreover, the formulated hand rubs had similar cellular viability behaviour to glycerol. Interestingly, the tolerability and acceptability response were promoted by the C. sativus extract, showing skin protection and increased integrity by up to 14.12%. Our results represent an alternative, ecofriendly and cost-effective option for formulating new potential hand rubs that improve skin protection without compromising the disinfection functionality.
... 46 Pathways for endogenous delivery of glycerol and metabolism in the skin involve the aquaporin-3 transport channel and lipid metabolism in the pilosebaceous unit. 47 It is possible that the initial boost in skin barrier observed in this study could be from the glycerin in the placebo. The placebo effect did not appear to maintain for the course of the study. ...
Introduction
Improvement of skin barrier strength could lead to healthy and youthful appearance. “Beauty inside‐out” approach using nutraceuticals such as tomato derived carotenoids to support skin barrier strength could be of benefit to the ageing population.
Method
A panel of 60 female subjects were provided with the Lumenato capsules (containing carotenoids) or placebo capsules as nutritional supplements for 3 months. Skin health and barrier function were observed using evaporimeter which measures trans epidermal water loss (TEWL). Barrier strength was determined by study of the number of strippings required to disrupt skin barrier and barrier repair was observed in terms of TEWL a few hours after barrier disruption. Cutometer was used to observe skin firmness and elasticity. Measurements were obtained before treatment and after 4 and 12 weeks of use.
Results
Results indicated a statistically significant improvement (p < 0.05) in skin barrier strength; a higher number of strippings were required to disrupt skin barrier after 12 weeks of supplement use. There was also a significant improvement in skin firmness and elasticity as observed with a cutometer.
Conclusion
Based on the confines and conditions of this study, oral supplementation with Lumenato resulted in significant improvement in skin barrier as well as skin firmness and elasticity.
... In comparison to the CMG-2 film, the CMG-3 film showed a 23.07 % decrease in the MC and a 23.52 % decrease in WS. Chitosan, MCC, and glycerol are highly hydrophilic materials with hygroscopic properties [61][62][63]. This is due to the presence of numerous amino (in chitosan) and hydroxyl groups in these molecules. ...
... It is indicated in the literature that glycerol moisturizes the stratum corneum of the skin, increases elasticity, protects against external irritants and improves wound healing. There is indicative data that glycerol can also have an antimicrobial effect [23,24]. Plant extracts are widely used in the world and are of great importance not only for human health but also animal health [25]. ...
Simple Summary
Bovine mastitis is one of the most widespread cow diseases, which causes high economic losses. Local treatment using natural ingredients instead of the systematic use of antibiotics can decrease the development of antimicrobial resistance. The aim of the study was to determine the physico-chemical properties, stability and antimicrobial effect of a newly formulated biocide for post-milking udder hygiene containing a thickener made from hydroxypropyl guar gum, an antiseptic chlorhexidine digluconate and teat skin-friendly components, including glycerol, Mentha Arvensis herbal oil and Aesculus hippocastanum extract. The product remains stable and homogenous for at least 12 months. The product also has good antimicrobial properties against the main mastitis pathogens, including Staphylococcus aureus, Streptococcus uberis, Escherichia coli, Candida albicans and Aspergillus niger.
Abstract
Despite much focus on mastitis as an endemic disease, clinical and subclinical mastitis remains an important problem for many herds. Reducing the usage of antibiotics for mastitis treatment allows the risks to be minimized related to the development of antimicrobial resistance and the excretion of antibiotics into the environment. The aim of the study was to determine the physico-chemical properties, stability and antimicrobial effect of a newly formulated biocide for post-milking udder hygiene containing a thickener made from hydroxypropyl guar gum, an antiseptic chlorhexidine digluconate and teat skin-friendly components including glycerol, Mentha Arvensis herbal oil and Aesculus hippocastanum extract. Hydroxypropyl guar gum was used as a thickener to provide the physical parameters and to retain the viscosity at 1438 mPa.s. The physical and chemical properties of the product, including the 12-month stability, were tested in long-term and accelerated stability studies. The product was effective against the primary mastitis pathogens, including Staphylococcus aureus, Streptococcus uberis, Escherichia coli, Candida albicans and Aspergillus niger.
... When the body requires energy, the triacylglycerol stored in the cells is broken down into glycerol and fatty acids under the action of lipase. Glycerol is decomposed by the glycolic pathway or glucose is generated by the gluconeogenic pathway to provide energy for cells, whereas fatty acids are decomposed into acetyl-CoA under sufficient oxygen supply and are thoroughly oxidized into CO2 and H2O, releasing a large amount of energy [19]. Most tissues can oxidize fatty acids, except the brain tissues, because fatty acids cannot pass through the blood-brain barrier [20]. ...
Epidemiological data have shown a positive correlation between lipid levels and tumor occurrence, such as the correlation between tumor frequency and aggressiveness, and cardiovascular disease, obesity, type 2 diabetes mellitus, and hyperinsulinemia. Therefore, reducing fat accumulation or weakening lipid metabolism may affect the carcinogenic processes of cells. Many studies have shown that traditional Chinese Medicine (TCM) has obvious advantages over traditional therapies in terms of fewer side effects, lower toxicity, and lower economic burden. This paper reviews the mechanism by which TCM regulates lipid metabolism and its antitumor effect through this regulation, with the aim of elucidating the bioactive compounds in TCM with good efficacy and few side effects that can provide promising therapeutic drugs for targeting lipid metabolism reprogramming in cancer.
... In the case of Veg Col-A, the "collagen-like" active ingredient was combined with glycerin. Glycerin is known to have good plastic properties in the skin [45]. When it is combined with Ch, its single hydrogen bonding site can break down the inter-and intramolecular hydrogen bonding networks of, thus leaving hydrophobic C-H ending groups to limit intermolecular hydrogen bond formation and allowing free motion of the chitosan chains [46]. ...
The use of animal testing in the cosmetic industry is already prohibited in more than 40 countries, including those of the EU. The pressure for it to be banned worldwide in the future is increasing, so the need for animal alternatives is of great interest today. In addition, using animals and humans in scientific research is ethically reprehensible. This study aimed to prove some of the anti-aging properties of elastin (EL), hydrolyzed collagen (HC), and two vegan collagen-like products (Veg Col) in a tri-layered chitosan membrane that was ionically crosslinked with sodium tripolyphosphate (TPP). In the first approach, as a way of representing different layers of a biological system, such as the epidermis and the two dermis sublayers, EL, HC, or Veg Col were independently introduced into the two inner layers (2L(i+b)). Their effects were compared with those of their introduction into three layers (3L). Different experiments were performed on the membrane to test its elasticity, hydration, moisture retention, and pore reduction at different concentrations of EL, HC, and Veg Col, and the results were normalized vs. a blank membrane. This new alternative to animal or human testing can be suitable for proving certain efficacy claims for active ingredients or products in the pharmaceutical, nutritional, and cosmetic fields.
... Although the presence of glycerol did not affect the gel formation, its addition needs to be optimised to individuate the optimal glycerol percentage enabling it to obtain the desired performances of the hydrogel structure. Indeed, glycerol has been included for many years in topical preparations thanks to its hydrating effect [69]; therefore, its inclusion in the hydrogel structure represented the first approach for the design of new cosmetics and cosmeceuticals. However, further work is needed to better understand fundamental aspects regarding the characteristics of HPP starch-based hydrogels, particularly, the relationship between the gel strength and the behaviour during the release of the bioactive compounds included in the formulation. ...
This work aimed to carry out a preliminary study on the release of bioactive compounds loaded into starch-based hydrogels produced by high-pressure processing (HPP). As a study case, the experiments were carried out on rice starch HPP hydrogels. Rice starch (20% w/w) and green tea extract (2% w/w), suspended in distilled water, were treated by HPP at processing conditions enabling starch gelatinisation, namely 600 MPa for 15 min at room temperature. Additional experiments were carried out on samples that were further loaded with glycerol (5% w/w). Gel formation was assessed by analysing the gelatinisation extent, structuring level, and swelling power of the samples. At the processing conditions utilised, stable hydrogels were obtained even in the presence of the extract and/or the glycerol in the starch suspension. As expected, the colour of the hydrogels formed was affected by the addition of green tea extract in the starch solution. HPP starch hydrogels were characterised by Fourier transform infrared spectroscopy (FT-IR) to determine the interactions between the different compounds utilised in the formulation. Moreover, the release kinetics of bioactive compounds from HPP rice starch hydrogels was evaluated using a vertical Franz diffusion cells system, simulating a transdermal pattern. The diffusion of bioactive compounds was measured spectrophotometrically and via HPLC analysis. A controlled release of bioactive compounds from the hydrogel structure was detected, suggesting that small molecules, such as polyphenols, positively interacted with the rice starch HPP hydrogel network that allowed a smooth and constant release of these bioactive compounds over time.
... Glycerin penetrates the skin rapidly, retains water in the stratum corneum, promotes wound healing and improves skin barrier function. 21 Our study showed that topical glycerin alone had anti-inflammatory, anti-apoptotic and collagen-enhancing effects during PU formation, and those beneficial effects were significantly strengthened by 10% (v/v) TTO dissolved in glycerin. Besides, many other beneficial effects of TTO have already been reported, such as its antimicrobial, anti-inflammatory and antioxidant properties, 4,5 and has been used to treat various skin diseases. ...
Objective: The effects of topical tea tree oil (TTO) on the healing of pressure ulcers (PUs) in an animal model was evaluated.
Method: To induce PUs, ischaemia-reperfusion cycles were performed by the external application of magnetic plates, with an ischaemic period of eight hours and a reperfusion period of 16 hours. Male and female Wistar rats were divided into three equally sized groups (n=20): one group received topical glycerin twice daily, another group received topical 10% (volume/volume (v/v)) TTO in glycerin twice daily; and the remaining group was untreated. The animals were assessed after one, four, seven and 14 cycles of ischaemia-reperfusion by thermal camera imaging, and then euthanised and sampled to investigate the degree of inflammation, collagen synthesis and apoptosis in the PUs.
Results: Although topical glycerin alone suppressed local inflammation and apoptosis, this suppressive effect was accentuated at all timepoints by the application of topical TTO + glycerin. Similarly, an increase in collagen synthesis was observed in the glycerin group and this was accentuated by TTO at all timepoints. Parallel to the histological findings, the local temperature had decreased significantly on days 4 and 7 for both treatment groups (glycerin and TTO+glycerin).
Conclusion: In this study, treatment with 10% (v/v) TTO in glycerin effectively suppressed skin inflammation and apoptosis, while it increased collagen synthesis during PU formation.
Background: The study compared the effectiveness of kojic acid and arbutin-containing lotion (alone) with arbutin-containing facewash and kojic acid and arbutin-containing lotion in the reduction of pigmentation. Methods: The study compared the test product (lotion) and the test regime (lotion + facewash) over a period of 45 days. In both test groups, a thin layer of advance body lotion was applied to the face, neck, and upper trunk. In the test regime group (TRG), these areas were washed with advance facewash before the lotion was applied. Both groups used sunscreen (with a sun protection factor of 50). The primary outcomes measured were (i) skin radiance and skin pigmentation, (ii) skin gloss, and (iii) skin hydration. The secondary outcomes measured were clinical evaluation and a subjective self-assessment for tolerance and perception of the product. Results: The study included 61 participants. The TRG showed a statistically significant increase in skin hydration (at 21 days) and skin gloss compared to the test product group (TPG) (at 21 and 45 days) (p<0.05). The majority of participants in both groups reported a visible reduction in pigmentation and improved facial glow and hydration as compared to baseline. No serious adverse effects were reported. Conclusions: The use of kojic acid and arbutin-containing lotion alone and arbutin-containing facewash with the lotion led to significant improvements in skin radiance, lightening, gloss, and hydration as compared to the baseline, with the TRG showing significantly better clinical results than the TPG in terms of skin hydration and gloss.
Objective:
Atopic dermatitis (AD) is characterized by compositional and structural changes to the skin at lesional sites. Alteration to the levels and organization of both protein and lipid components are associated with disease status and lead to impaired barrier and hydration. Corneodesmosin (CDSN) and the arrangement and length of the intercellular lipid lamellae (ICLL) are altered in disrupted skin states. The aim of this research was to profile the distribution of CDSN and the ICLL in the stratum corneum (SC) at lesional and non-lesional sites in AD-prone skin and to investigate the impact of an eczema calming lotion containing petroleum jelly, fatty acids, and colloidal oatmeal.
Methods:
An IRB-approved study was conducted with participants with active AD. From a small subset of participants, tape strips were collected from lesional and non-lesional sites on the arm, prior to and after twice daily application, over 4 weeks of an eczema calming lotion containing petroleum jelly, fatty acids, and colloidal oatmeal. Fluorescent antibody staining was used to investigate the distribution of CDSN. Transmission electron microscopy (TEM) was used to characterize the ICLL.
Results:
The distribution/coverage of CDSN was similar between lesional and non-lesional sites at baseline; application of the lotion resulted in a more defined honeycomb/peripheral distribution. Normalized ICLL (nICLL) was lower in baseline samples from lesional sites relative to non-lesional sites. Application of the lotion increased this parameter by the end of the study at all sites.
Conclusion:
The eczema calming lotion containing petroleum jelly, fatty acids and colloidal oatmeal provided changes in corneodesmosomal proteins distribution and ICLL, consistent with improvements in corneocyte maturation and improved barrier function in the skin of individuals with atopic dermatitis.
Balancing stretchability and degradability in batteries based on the primary battery principle, while maintaining robust discharging performance, poses a significant challenge for sustainable wearable technologies. Current reports adopting a layered stack structure often suffer from inadequate interlayer adhesion, leading to problems such as out‐of‐plane bending and delamination, as well as insufficient power density and energy density. In this context, a novel and straightforward methodology is introduced, employing in situ oxidation of molybdenum foil, a customized kirigami‐island‐bridge (KIB) structure, and an overall cast molding technique. This approach facilitates the integration of degradable primary batteries with enhanced power density (3.41 mW cm⁻²) and energy density (3.54 mWh cm⁻²). Furthermore, the battery sustains an output of 50 µA cm⁻² under cyclic 20% strain stretching for ≈3 h, showcasing its specific stretchability performance, and is successfully implemented in sensors for real‐time monitoring of body movements. This study presents a novel approach to the development of wearable, biodegradable, and medical electronics, offering potential pathways for sustainable technological advancement.
The current incidence of chronic kidney disease‐associated pruritus (CKD‐aP) in patients with end‐stage renal disease (ESRD) is approximately 70%, especially in those receiving dialysis, which negatively affects their work and private lives. The CKD‐aP pathogenesis remains unclear, but uremic toxin accumulation, histamine release, and opioid imbalance have been suggested to lead to CKD‐aP. Current therapeutic approaches, such as opioid receptor modulators, antihistamines, and ultraviolet B irradiation, are associated with some limitations and adverse effects. The skin barrier is the first defense in preventing external injury to the body. Patients with chronic kidney disease often experience itch due to the damaged skin barrier and reduced secretion of sweat and secretion from sebaceous glands. Surprisingly, skin barrier‐repairing agents repair the skin barrier and inhibit the release of inflammatory cytokines, maintain skin immunity, and ameliorate the micro‐inflammatory status of afferent nerve fibers. Here, we summarize the epidemiology, pathogenesis, and treatment status of CKD‐aP and explore the possibility of skin barrier repair in CKD‐aP treatment.
Background
Melasma is a chronic skin disorder that is characterized by the accumulation of irregular brown pigments in the skin. Lesions are usually seen on the forehead, temples, upper lip, and cheeks. This disease is one of the most common reasons for women to visit dermatologists.
Aim
The present study was conducted to determine the clinical and epidemiological characteristics of melasma in women referred to the dermatology clinic.
Methods
This is a cross-sectional study that was conducted on 100 women who were referred to the dermatology clinic of Imam Khomeini Hospital in Jiroft City in the first half of 2021 using a convenient sampling method. Data were collected using a researcher-made checklist and analyzed using SPSS-v20 statistical software and descriptive and inferential tests at a significance level of p˂0.05.
Results
The average age of women with melasma was 32.8±0.64 years. The majority of clients had skin type four (57%) and skin type three (30%). The spread of pigmentation was mainly centro facial (62%), and there was a positive family history in 43% of cases. Moreover, it was found that melasma is not related to any of the variables of age, number of children, duration of the disease, marital status, family history, history of hormonal treatment, history of pregnancy and subsequent exacerbation, thyroid disease and polycystic ovary syndrome, and use of night creams and sunscreen.
Conclusion
Melasma is a relatively common disease in Iran. Additional studies are needed to find the epidemiological and underlying variables and treatment of melasma.
Moisturization causes physiological changes that improve the barrier function of human skin and mechanical changes, including skin friction characteristics. This study evaluated petrolatum- or silicone oil-treated human skin to determine the effect of moisturizing on the friction dynamics. The friction force on the human skin was measured using a contact probe with a sinusoidal motion. The contact probe was used to rub the skin of the upper arm of 20 subjects. The water content of the stratum corneum, softness, and barrier function of the skin were measured using a corneometer, cutometer, and tewameter, respectively. Both oils reduce the frictional force on the human skin. Simultaneously, silicone oil also reduced the delay time δ, which is the standardized time difference between the frictional force response to contact probe movement. Three typical friction patterns were also discovered, which were significantly changed by the treatment with oil. These changes were attributed to the lubrication effect and elimination of adhesion at the true contact point between the skin and the contact probe.
graphical abstract Fullsize Image
The stratum corneum (SC)—the outermost layer of the epidermis—is the principal permeability and protective barrier of the skin. Different components of the SC, including corneocytes, natural moisturizing factor, a variety of enzymes and their inhibitors, antimicrobial peptides and lipids, work interactively to maintain barrier function. The main barrier properties of the SC are the limitation of water loss and the prevention of infection and contact with potentially harmful exogenous factors. Although the SC functions consistently as a protective barrier throughout the body, variations in functions and morphology occur across body sites with age and skin type. Healthy SC function also depends on the interplay between the chemosensory barrier, the skin's microbiome and the innate immune system. Dysregulation of SC barrier function can lead to the development of skin disorders, such as dry, flaky or sensitive skin, but the complete underlying pathophysiology of these are not fully understood. This review provides insight into the current literature and emerging themes related to epidermal barrier changes that occur in the context of dry, flaky and sensitive skin. Additional studies are needed to further elucidate the underlying aetiology of dry, flaky and sensitive skin and to provide tailored treatment.
Introduction
The removal of unwanted hair is a widespread grooming practice adopted by both males and females. Although many depilatory techniques are now available, shaving remains the most common, despite its propensity to irritate skin. Current techniques to investigate the impact of shaving regimes on skin health rely on costly and lengthy clinical trials, which hinge on recruitment of human volunteers and can require invasive biopsies to elucidate cellular and molecular-level changes.
Methods
Well-characterised human skin equivalent technology was combined with a commonplace dermatological technique of tape stripping, to remove cellular material from the uppermost layer of the skin ( stratum corneum ). This method of exfoliation recapitulated aspects of razor-based shaving in vitro , offering a robust and standardised in vitro method to study inflammatory processes such as those invoked by grooming practices.
Results
Tape strip insult induced inflammatory changes in the skin equivalent such as: increased epidermal proliferation, epidermal thickening, increased cytokine production and impaired barrier function. These changes paralleled effects seen with a single dry razor pass, correlated with the number of tape strips removed, and were attenuated by pre-application of shaving foam, or post-application of moisturisation.
Discussion
Tape strip removal is a common dermatological technique, in this study we demonstrate a novel application of tape stripping, to mimic barrier damage and inflammation associated with a dry shave. We validate this method, comparing it to razor-based shaving in vitro and demonstrate the propensity of suitable shave- and skin-care formulations to mitigate damage. This provides a novel methodology to examine grooming associated damage and a platform for screening potential skin care formulations.
Objective
This study aimed to assess the effect of 1,3‐propanediol at different concentrations (5%, 10%, or 15%), either applied alone or in combination with butylene glycol (5%) and/or glycerol (5%), on skin hydration and skin barrier function. The measurements were conducted using capacitance to determine skin hydration and trans epidermal water loss (TEWL) rates to evaluate skin barrier function.
Methods
A total of 30 healthy female subjects participated in the study. Capacitance and TEWL measurements were conducted at multiple time points, including before application and at 15 minutes, 2 hours, and 8 hours after the humectants were applied to the forearms of the subjects. All subjects provided written informed consent.
Results
The 1,3‐propanediol in all concentrations and in all combinations (with butylene glycol and/or glycerol) increased skin hydration and improved skin barrier function 15 minutes, 2 hours, and 8 hours after application. Glycerol increased the hydration performance of 1,3‐propanediol. The application of 1,3‐propanediol at a concentration of 15%, either alone or in combination with other humectants, reduced the TEWL to a greater extent than lower concentrations of 1,3‐propanediol. Furthermore the addition of glycerol to 1,3‐propanediol 15% improved the skin barrier and reduced TEWL when compared with 1,3‐propanediol alone and with the combination of1,3‐propanediol + butylene glycol.
Conclusion
The humectants significantly improved skin hydration and reduced TEWL throughout the 8‐hour time course. The increase in 1,3‐propanediol concentration, as well as its combination with glycerol, provided a greater benefit to the skin, improving both hydration and the skin barrier function.
Wearing masks is used as an effective way to prevent the spread of viruses. However, the effect of wearing masks on skin health requires further assessment. In this study, a non-invasive D-squame sampling method coupled with an untargeted metabolomics analysis by liquid chromatography high-resolution mass spectrometry was developed to identify the changes in the skin metabolome caused by wearing masks. D-squame method was found to have advantages over the commonly used sterile gauze method, especially for the lipids and lipid-like molecules. A total of 356 skin metabolites were putatively identified from the stratum corneum of 10 volunteers, and 17 differential metabolites were significantly downregulated after wearing surgical masks or N95 respirators. The downregulation of metabolites such as phosphatidylethanolamine and sphingomyelin might be related to hypoxia or increased skin moisture caused by wearing masks. Changes in skin metabolomics indicated a potential risk of skin barrier disruption and skin inflammation. Intermittent removal of the masks can effectively alleviate changes in the skin metabolome.
This study used Raman spectroscopy to develop a new approach to evaluate the effects of solar radiation on the stratum corneum (SC). The method measures the SC's hydration and dehydration kinetics by calculating the vOH/vCH ratio to monitor the relative water content during the drying process. The study also investigated the role of skin surface lipids (SSLs) in protecting the SC from solar radiation. The SSLs film is a complex mixture of free fatty acids, triglycerides, wax esters, squalene, free and esterified cholesterols, that play a crucial role in the skin's barrier function. The results showed that solar radiation alters the water content and balance within the SC, and SSLs provide protection by acting as an optical filter by absorbing some of the energy of the solar light. This is confirmed by high temperature gas chromatography coupled to mass spectrometry analyses by revealing a decrease in specific lipids after irradiating the SSLs. his article is protected by copyright. All rights reserved.
Objective: The effects of topical tea tree oil (TTO) on the healing of pressure ulcers (PUs) in an animal model was evaluated.
Method: To induce PUs, ischaemia-reperfusion cycles were performed by the external application of magnetic plates, with an ischaemic period of eight hours and a reperfusion period of 16 hours. Male and female Wistar rats were divided into three equally sized groups (n=20): one group received topical glycerin twice daily, another group received topical 10% (volume/volume (v/v)) TTO in glycerin twice daily; and the remaining group was untreated. The animals were assessed after one, four, seven and 14 cycles of ischaemia-reperfusion by thermal camera imaging, and then euthanised and sampled to investigate the degree of inflammation, collagen synthesis and apoptosis in the PUs.
Results: Although topical glycerin alone suppressed local inflammation and apoptosis, this suppressive effect was accentuated at all timepoints by the application of topical TTO + glycerin. Similarly, an increase in collagen synthesis was observed in the glycerin group and this was accentuated by TTO at all timepoints. Parallel to the histological findings, the local temperature had decreased significantly on days 4 and 7 for both treatment groups (glycerin and TTO+glycerin).
Conclusion: In this study, treatment with 10% (v/v) TTO in glycerin effectively suppressed skin inflammation and apoptosis, while it increased collagen synthesis during PU formation.
Glycerol (Gly) is a well-known, FDA-approved molecule posing three hydroxyl groups. Since Gly is biocompatible, here, it was aimed to prepare poly(Glycerol) (p(Gly)) particles directly for the first time for the delivery of therapeutic agents. Micrometer-sized particles of p(Gly) were successfully synthesized via the micro-emulsion method with an average size of 14.5 ± 5.6 µm. P(Gly) microparticles up to 1.0 g/mL concentrations were found biocompatible with 85 ± 1% cell viability against L929 fibroblasts. Moreover, p(Gly) microparticles were tested for hemocompatibility, and it was found that up to 1.0 mg/mL concentrations the particles were non-hemolytic with 0.4 ± 0.1% hemolysis ratios. In addition, the blood compatibility index values of the prepared p(Gly) particles were found as 95 ± 2%, indicating that these microparticles are both bio-and hemocompatible. Furthermore, Quercetin (QC) flavonoid, which possessed high antioxidant properties, was loaded into p(Gly) microparticles to demonstrate drug-carrying properties of the particles with improved bioavailability, non-toxicity, and high biocompatibility. The results of this study evidently revealed that p(Gly) particles can be directly prepared from a cost-effective and easily accessible glycerol molecule and the prepared particles exhibited good biocompatibility, hemocompatibility, and non-toxicity. Therefore, p(Gly) particles were found as promising vehicles for drug delivery systems in terms of their higher loading and release capability as well as for sustained long term release profiles.
As an on‐skin electronic device, artificial skin shows great potential in medical monitoring and personal electronics, which also holds promise to develop human‐machine merging interfaces. However, merging artificial skins with human bodies is largely restricted by the dissimilarity of material compositions in existing artificial skins and biological tissues. Naturally conductive protein is a potential material candidate for artificial skins, nevertheless, it suffers from the critical issue of dehydration which harms its proton conductivity. Inspired by the sebum membrane of human skin, herein, a protein‐based bioprotonic hydrogel (PBH) with reliable water retention ability is reported for artificial skins. The bovine serum albumin with natural proton conductivity is utilized in the PBH, and the glycerol that originally presents on human skin surface is used as an artificial sebum membrane to retain water. The PBH can act as a bioprotonic skin (B‐skin) for collecting electrophysiological signals and self‐powered sensing. Based on the B‐skin, intelligent robot and cellphone control systems are demonstrated. Compared with present artificial skins, this B‐skin is all made out of biological materials that are consistent with material components of human skin tissues including proteins, endogenous glycerol, and water. Such a B‐skin may enable the development of next‐generation human‐machine merging interfaces.
Aquaporins (AQPs) are transmembrane water channel proteins that regulate the movement of water through the plasma membrane in various tissues including cornea. The cornea is avascular and has specialized microcirculatory mechanisms for homeostasis. AQPs regulate corneal hydration and transparency for normal vision. Currently, there are 13 known isoforms of AQPs that can be subclassified as orthodox AQPs, aquaglyceroporins (AQGPs), or supraquaporins (SAQPs)/unorthodox AQPs. AQPs are implicated in keratocyte function, inflammation, edema, angiogenesis, microvessel proliferation, and the wound-healing process in the cornea. AQPs play an important role in wound healing by facilitating the movement of corneal stromal keratocytes by squeezing through tight stromal matrix and narrow extracellular spaces to the wound site. Deficiency of AQPs can cause reduced concentration of hepatocyte growth factor (HGF) leading to reduced epithelial proliferation, reduced/impaired keratocyte migration, reduced number of keratocytes in the injury site, delayed and abnormal wound healing process. Dysregulated AQPs cause dysfunction in osmolar homeostasis as well as wound healing mechanisms. The cornea is a transparent avascular tissue that constitutes the anterior aspect of the outer covering of the eye and aids in two-thirds of visual light refraction. Being the outermost layer of the eye, the cornea is prone to injury. Of the 13 AQP isoforms, AQP1 is expressed in the stromal keratocytes and endothelial cells, and AQP3 and AQP5 are expressed in epithelial cells in the human cornea. AQPs can facilitate wound healing through aid in cellular migration, proliferation, mitigation, extracellular matrix (ECM) remodeling and autophagy mechanism. Corneal wound healing post-chemical injury requires an integrative and coordinated activity of the epithelium, stromal keratocytes, endothelium, ECM, and a battery of cytokines and growth factors to restore corneal transparency. If the chemical injury is mild, the cornea will heal with normal clarity, but severe injuries can lead to partial and/or permanent loss of corneal functions. Currently, the role of AQPs in corneal wound healing is poorly understood in the context of chemical injury. This review discusses the current literature and the role of AQPs in corneal homeostasis, wound repair, and potential therapeutic target for acute and chronic corneal injuries.
Background and Objective
Hyper-osmotic chemical agents were used to study the effects of transient tissue scattering on the remitted fluorescence emission intensity from a target placed under a tissue sample.Study Design/Materials and MethodsA fluorescent film was placed underneath in vitro and in vivo samples of hamster skin, and the remitted fluorescent signal traveling to the tissue surface was monitored over time as the tissue was treated with an osmotically active agent.ResultsThe detected fluorescent signal increased as the scattering in tissue samples was substantially reduced. The increase was greater for dimethyl sulfoxide than glucose or glycerol. It was not statistically different between in vivo skin and in vitro skin.Conclusions
The study shows how chemical agents can be used to improve the detected signal for a specific optical application. It could be useful in a number of optical therapeutic and diagnostic applications that can benefit from an increase in the penetration depth of light. Lasers Surg. Med. 29:213–220, 2001. © 2001 Wiley-Liss, Inc.
A method to increase light transport deeply into target areas of tissue would enhance both therapeutic and diagnostic laser applications. The effects of a hyperosmotic agent on the scattering properties of rat and hamster skin were investigated.
A hyperosmotic agent, glycerol, was applied in vitro and in vivo to rat and hamster skin to assess the changes in tissue optical properties. Changes in the reduced scattering coefficient after application of the agent in vitro to rat skin and after the skin has been rehydrated were assessed to evaluate the effect of the agent on tissue.
Experimental results showed a transient change in the optical properties of in vitro rat skin. A 50% increase in transmittance and decrease in diffuse reflectance occurred within 5-10 min after the introduction of anhydrous glycerol. In addition, reduction of light scattering with this technique increased depth of visibility with optical coherence tomography. Injection of glycerol under the skin allowed in vivo visualization of blood vessels.
The application of the agent reduces the amount of refractive mismatch found in the tissue and markedly reduces random scattering, thereby making the skin less turbid for visible wavelengths for a controlled period of time.
Two studies were performed to evaluate the influence of glycerol on the recovery of damaged stratum corneum barrier function. Measurements of transepidermal water loss and capacitance were conducted in a 3-day follow-up after tape stripping (study 1) and a 7-day follow-up after a barrier damage due to a repeated washing with sodium lauryl sulphate. In study 1 a faster barrier repair (transepidermal water loss) was monitored in glycerol-treated sites. Significant differences between glycerol open vs. untreated and glycerol occluded vs. untreated were observed at day 3. Stratum corneum hydration showed significantly higher values in the sites treated with glycerol+occlusion, compared with all other sites. In study 2 a faster barrier repair was seen in glycerol-treated sites, with significant differences against untreated and base-treated sites 7 days after the end of the treatment. Stratum corneum hydration showed highest values in the glycerol treated sites after 3 days of treatment. Glycerol creates a stimulus for barrier repair and improves the stratum corneum hydration; stratum corneum hydration is not strictly related to barrier homeostasis and can be optimized by different mechanisms and pathways. The observed effects were based on the modulation of barrier repair and were not biased by the humectant effect of glycerol. As the glycerol-induced recovery of barrier function and stratum corneum hydration were observed even 7 days after the end of treatment, glycerol can be regarded as a barrier stabilizing and moisturizing compound.
Gylcerol was discovered in 1779 by the Swedish chemist Scheele and is among the most effective humectant polyols such as sorbitol and mannitol. It is a versatile chemical, and moisturization is due to its high degree of hydroxyl groups, which bind and retain water. Glycerol is found in baby care products and in embalming fluids used by morticians, in glues and explosives; in throat lozenges and in suppositories. Glycerol is a colorless, viscous liquid, and stable under most conditions. Glycerin is nontoxic, easily digested, and is environmentally safe. It has a pleasant taste and odor, which makes it an ideal ingredient in food and cosmetic applications.1
Repetitive washing with 0.01 mol/l sodium lauryl sulphate solution for one week was followed by a measurable skin function disorder as evaluated by corneometry, laser Doppler flowmetry, and transepidermal water loss (TEWL) measurements. The application of commercially available barrier creams (Marly Skin®, Saniwip®, Tactosan®) as well as the application of well-defined oil-in-water emulsions containing 10% urea or 10% glycerol, respectively, significantly reduced skin function deterioration following repetitive washings. Urea and glycerol containing oil-in-water emulsions were at least as effective as the most effective commercial barrier cream Tactosan and had the additional advantage of better user acceptance.
The dependence of the effects of urea and glycerol on their concentration, the dependence of their efficacy on the vehicle and the influence of glycerol on the penetration of hydrocortisone were investigated. The study was based on the known hydrating effects of urea and glycerol on the stratum corneum when applied in basic formulations for external use, the penetration enhancing effect of urea for corticosteroids applied in dermatology, and the penetration enhancing effect of glycerol for hexyl nicotinate which was demonstrated before. 49 test persons were studied. The hydration was measured with the help of corneometry and the Skicon method. The penetration of hydrocortisone was detected by the blanching effect. The studies showed that urea and glycerol have a comparable hydrating effect in all w/o and o/w basic formulations tested. An increase in the concentration of urea from 5 to 10% did not yield any advantage, whereas 10% glycerol was more efficient than 5%, independent of the basic formulation used. Urea enhanced the penetration of steroids only in an o/w emulsion with a high water content but not in the other vehicles tested. Glycerol showed no influence on the penetration of hydrocortisone in this study.
The influence of a monotherapy with glycerol and urea, respectively, on the stratum corneum hydration against exsiccation by a tenside solution and on the skin-smoothing effect was investigated in comparison with a combination therapy with glycerol and urea. Here, an increase of 5% in the dose of urea in an oil-in-water-emulsion did not produce significant advantages with regard to the stratum corneum hydration and the protective effect against the dehydration by tenside solutions. In contrast to this an increase in the dose of glycerol of over 5% in an oil-in-water-emulsion proved to be efficient under both criteria. With regard to the stratum corneum hydration and the protective effect against exsiccation by tendides, the combination of 5% glycerin and 5% urea was superior to a monotherapy, with exception of the oil-in-water-emulsion containing 10% glycerin. With regard to the smoothing effect only the combination of 5% urea and 5% glycerin produced a significant advantage.
Objectives: To investigate in more details the mechanism of action of a newly developed skin protection cream containing 5 % glycerol and 5 % aluminium chlorohydrate as active components. Methods: In 20 healthy volunteers, the skin of the inner forearm was treated with a solvent mixture, to extract surface lipids and to create an "atopic-like" skin surface. Thereafter, a controlled washing was performed three times daily with aqueous sodium laurylsulfate (SLS) at low concentration (0.25 %). After each washing, the skin was treated with the O/W vehicle alone or containing one of the active components, with the newly developed skin protection cream, and with a commercially available standard skin protection cream. Before, during, and after treatment, the hydration of the horny layer and the transepidermal water loss (TEWL) were measured. Results and conclusion: The combination of glycerol with aluminium chlorohydrate in a suitable O/W emulsion lead to the same hydration grade of the horny layer as the O/W vehicle alone. On the other side, 5 % glycerol in the same vehicle significantly enhanced horny layer hydration. However, the skin protection effect of the combination is greater than the effect of glycerol alone. This may be an advantage if protection gloves are to be used and in individuals suffering from hyperhidrosis.
Two studies were performed to evaluate the influence of glycerol on the recovery of damaged stratum corneum barrier function. Measurements of transepidermal water loss and capacitance were conducted in a 3-day follow-up after tape stripping (study 1) and a 7-day follow-up after a barrier damage due to a repeated washing with sodium lauryl sulphate. In study 1 a faster barrier repair (transepidermal water loss) was monitored in glycerol-treated sites. Significant differences between glycerol open vs. untreated and glycerol occluded vs. untreated were observed at day 3. Stratum corneum hydration showed significantly higher values in the sites treated with glycerol + occlusion, compared with all other sites. In study 2 a faster barrier repair was seen in glycerol-treated sites, with significant differences against untreated and base-treated sites 7 days after the end of the treatment. Stratum corneum hydration showed highest values in the glycerol treated sites after 3 days of treatment. Glycerol creates a stimulus for barrier repair and improves the stratum corneum hydration; stratum corneum hydration is not strictly related to barrier homeostasis and can be optimized by different mechanisms and pathways. The observed effects were based on the modulation of barrier repair and were not biased by the humectant effect of glycerol. As the glycerol-induced recovery of barrier function and stratum corneum hydration were observed even 7 days after the end of treatment, glycerol can be regarded as a barrier stabilizing and moisturizing compound.
The epidermis functions as a barrier against the environment by means of several layers of terminally differentiated, dead keratinocytes - the cornified layer, which forms the endpoint of epidermal differentiation and death. The cornified envelope replaces the plasma membrane of differentiating keratinocytes and consists of keratins that are enclosed within an insoluble amalgam of proteins, which are crosslinked by transglutaminases and surrounded by a lipid envelope. New insights into the molecular mechanisms and the physiological endpoints of cornification are increasing our understanding of the pathological defects of this unique form of programmed cell death, which is associated with barrier malfunctions and ichthyosis.
The sorption of water by polyhydroxyalkanes and polyalkylene glycols has been studied at 35 °C and 75% relative humidity. The solubilities in water of these compounds were taken from the literature or measured by us, and found to be predictable from Yalkowski's expression and to correlate with the water sorption ability, with some notable exceptions, rationalized with reference to the configurations of the compounds in question. In very concentrated aqueous solutions all the water is bound to the polyols; in dilute solutions two or four molecules of water are bound per oxygen atom of the polyhydroxyalkanes and polyethylene glycols, respectively.
Previous studies have shown that barrier disruption increases epidermal mRNA levels of interleukin-1α (IL-1α). We used immunohistochemistry to examine IL-1α expression in hairless mouse skin under basal conditions and following barrier abrogation. In untreated mice, IL-1α was present in the dermis and nucleated epidermal layers in a diffuse, generalized pattern. In essential fatty acid deficient mice IL-1α was present in all epidermal layers and the dermis, with prominent staining in the stratum corneum. After acute barrier disruption with tape-stripping, IL-1α increased in the epidermis and dermis within 10 mm, remained elevated at 2 and 4 h, and decreased to near basal levels by 24 h. Moreover, intense, perinuclear, basal cell staining appeared at 10 mm, persisting until 4 h after barrier disruption. Since the increase in IL-1α immunostaining after acute barrier abrogation precedes the increase in mRNA, we hypothesized that the IL-1α might derive from a prefonned pool. Prolonged occlusion of normal skin, a treatment that specifically reduces epidermal mRNA levels of IL-1α, decreased basal immunostaining for IL-1α and blunted the increase in IL-1α usually seen following barrier disruption. Moreover, tape-stripping of skin, maintained ex vivo at 4°C, resulted in increased IL-1α immunostaining within the upper nucleated epidermal layers, as well as release of mature IL-1α into the medium, as measured by Western blotting and enzyme-linked immunosorbent assay. In addition, the stratum corneum attached to the tape contained IL-1α. These studies show that acute barrier disruption induces both the immediate release and dispersion of IL-1α from a pre-formed, epidermal pool, as well as increased IL-1α synthesis; both mechanisms are consistent with a role for IL-1α in the regulation of proinflammatory and homeostatic processes in the skin.
Preparations containing the humectant glycerol were applied topically to the skin of young adults, and the physical effects of glycerol on the stratum comeurn were examined using instrumental techniques. Reductions in transepidermal water loss and electrical impedance, smoothing of the skin surface profile, and an increase in the coefficient of friction were found to accompany an improvement in the expertly assessed condition of the skin. Such changes, found to last for periods in excess of eight hours, were similar to those observed transiently after the topical application of distilled water.
in the lower stratum comeurn but underwent degradation towards the upper surface of the stratum corneum. These observations contrasted with xerotic skin, which had disorganized lipid bilayers in the upper stratum corneum, although apparently normal lipid bilayers in the deeper tissue regions. Also, desmosomes remained undegraded in the upper layers of the xerotic stratum corneum, a finding corrobo- rated by western blotting showing increased levels of desmoglein 1. Chromatographic analysis of stratum comeurn lipids showed decreased ceramide and increased fatty acid levels in subjects with xerosis compared with normal individuals, particularly in the outer stratum corneum layers. Although ceramides were lost from the stratum comeurn, the increased levels of fatty acids may be due in part to the deposition of soap fatty acids. Our results support previous studies demonstrating the importance of desmosomal degradation in desquamation. Furthermore, we have been able to show changes in the normal membrane structure of intracellular lipids in the desquamating layers of the stratum comeurn. These studies also provide new insights into soap-induced winter xerosis, revealing abnormalities in stratum comeurn lipid composition and organization together with reduced desmosomal degradation.
To understand the biochemical abnormalities that underlie the reduced desquamation observed in dry skin, we analyzed corneodesmosome degradation in normal and winter xerosis skin. Western blotting of total proteins from corneocytes obtained by varnish-strippings from the legs of 56 volunteers with normal (26) or xerotic (30) skin was performed using antibodies specific for (corneo)desmosome proteins. In the whole population, the amounts of desmoglein 1 and plakoglobin were found to be correlated, but were not related to the amounts of corneodesmosin. This suggests simultaneous proteolysis for the former proteins differing from that of corneodesmosin. Neither entire desmoplakins nor any proteolysis-derived fragments were detected. The amounts of corneodesmosin, desmoglein 1, and plakoglobin detected were found to be significantly higher in xerotic compared with normal skin extracts. Conventional and freeze-fracture electron microscopy showed the absence of nonperipheral corneodesmosomes in the upper stratum corneum of normal skin but the presence of a significant number of these structures in the same layer of winter xerosis skin. These results provide a more precise description of the proteolysis of corneodesmosome components in the upper cornified layer of the epidermis. They support previous studies demonstrating the importance of corneodesmosome degradation in desquamation and reveal that the nonperipheral corneodesmosomes, which are totally degraded during maturation of the stratum corneum in normal skin, persist in winter xerosis, probably leading to abnormal desquamation.Keywords: desmosomes, epidermis, keratinocytes, proteases
Allogeneic split skin grafts are used widely in the treatment of burns. The relative simplicity of glycerol preservation of skin suggests it will be used increasingly in areas of high HIV-1 seroprevalence. The ability of glycerol preservation to inactivate HIV-1 present in skin graft infected in vitro was determined using a macrophage tropic strain HIV-1 as a cell-free virus suspension, within infected PBMCs, or within in vitro HIV-1 infected fresh cadaveric split skin. Different temperatures and concentrations of glycerol were used and infectivity determined by coculture with mitogen activated peripheral blood mononuclear cells (PBMCs) and measurement of reverse transcriptase activity after 7–10 days. Cell-free HIV-1 was inactivated within 30 min at 4°C in glycerol concentrations of 70% or higher. During similar exposure cell- or skin-associated HIV-1 titer was reduced but not eliminated with 70% and 85% glycerol at 4°C. HIV-1 was recovered consistently from skin stored in 85% glycerol at 4°C for up to 72 hr but virus isolation was infrequent after storage for more than 5 days. At 20°C or 37°C, 70% or 85% glycerol could inactivate cell- or skin-associated HIV-1 within 8 hr. The initial glycerolization procedures and the storage at 4°C eliminated effectively HIV-1 from skin. J. Med. Virol. 60:182–188, 2000. © 2000 Wiley-Liss, Inc.
In dermatology and cosmetics, moisturizers are used to soften skin. The objectives of this study were to compare the influence of three different moisturizers on skin hydration and skin mechanics by various non-invasive test methods and to determine the relationship between the methods used.
In 27 test subjects, four test areas in each were treated over 3 days, three times a day. An oil-in-water (o/w) emulsion was applied without moisturizer, the same with 10% glycerol, with 10% urea, or with 10% propylene glycol, respectively. Three hours after the last treatment results were measured by using the following instruments: Corneometer CM 820, Skicon 200, Frictionmeter, and Cutometer.
In all procedures a significant effect, in the sense of an increase in the data recorded, could be demonstrated by glycerol-treatment. During Corneometer, Frictionmeter, and Cutometer measurements, an additional unidirectional effect caused by the basic emulsion was seen. With all test methods, the influence of urea and propylene glycol was not significant compared to the basic emulsion. For all pretreatments there was a correlation between Corneometer data and Skicon data. Because of the low correlation coefficients between hydration parameters and mechanical parameters, it is to be assumed that other effects of glycerol- and basic-emulsion-treatment-independent from the hydration effect – have an additional influence on the data obtained by using the Frictionmeter and the Cutometer. This indicates that the clinical effect of emulsions should not be evaluated exclusively on the basis of electrical measurements of hydration.
Background/aims: Moisturising creams are useful treatment adjuncts in inflammatory dermatoses and have beneficial effects in the treatment of dry, scaly skin. The effects on dryness and skin permeability of a new moisturising cream with 20% glycerine was compared with its placebo and with a medicinally authorised cream with 4% urea (combined with 4% sodium chloride) in the treatment of dry skin.
Methods: Patients ( n =109) with atopic dermatitis were treated for 30 days with a moisturiser in a randomised, parallel and double‐blind fashion. Transepidermal water loss (TEWL) and skin capacitance were assessed instrumentally, and changes in the dryness of the skin were assessed by the dermatologist.
Results: No difference in TEWL was found between glycerine treatment and its placebo, whereas a lower value was found in the urea‐treated area compared to the glycerine‐treated area. No difference in skin capacitance was found. The clinical assessment of dryness showed urea to be superior to glycerine in treating the condition.
Conclusions: Moisturising creams are different, not only with respect to composition but also with respect to their influence on skin as a barrier to water in patients with atopic dermatitis.
Human cadaveric skin allografts are used in the treatment of burns and can be preserved in glycerol at high concentrations. Previously, glycerol has been attributed some antimicrobial effect. In an experimental set-up, we aimed at investigating this effect of prolonged incubation of bacteria in 85% glycerol. Staphylococcus epidermidis, Staphylococcus aureus, Pseudomonas aeruginosa, and Bacillus subtilis were incubated in 85% glycerol. The influence of duration of incubation and temperature on ultrastructure and viability were investigated. Unstressed cultures served as controls. Survival was studied after 24¿36 h and 10 days incubation in 85% glycerol at 4°C and 36°C with transmission electron microscopy (TEM) and flow cytometry using viability stains indicating membrane damage (SYTO9, propidium iodide) or esterase activity (carboxyfluorescein diacetate). TEM clearly demonstrated variability in morphological changes of bacteria suggesting different mechanisms of damage. Viability stains supported these findings with faster declining viable cell populations in 85% glycerol at 36°C compared with 4°C. Both methods demonstrated that Gram-negative species were more susceptible than Gram-positive species. In conclusion, 85% glycerol may have some additional antimicrobial effect. Temperature is an important factor herein and Gram-negatives are most susceptible. The latter finding probably reflects the difference in cell wall composition between Gram-positive and Gram-negative bacteria.
Synopsis
Topically applied water, occlusion and topically applied glycerol were used to investigate and characterize some of the changes which occur in the hydrated stratum corneum. The effects of these treatments were monitored using non‐invasive techniques under controlled conditions.
The Servomed Evaporimeter was used to determine natural water flux from the skin surface before and after treatment. The performance of the Evaporimeter in this type of study had previously been improved by attaching a paper baffle to the detector. This eliminated the variance in output caused by atmospheric movement. Experiments were carried out at temperatures below the threshold of thermal sweating and emotional sweating was minimized.
Skin surface topography was characterized by means of a new type of profilometer. The instrument's design allowed a diamond stylus to traverse the living skin surface without significantly altering its structure. Changes in skin surface roughness were further elucidated using scanning electron microscopy and macrophotography.
In vivo penetration of glycerol was assessed by chemical analysis of stratum corneum layers of treated skin. Samples were obtained by sequential stripping of the stratum corneum using adhesive tape.
Topically applied water produced only a transient benefit because of rapid evaporation. More prolonged hydration was achieved by suppressing transepidermal water loss with polyethylene film. This occlusive hyperhydration was characterized by a significant reduction in profile roughness and by a smoother macroscopic appearance.
Glycerol achieved the same effects by reducing the magnitude of the natural water flux from the skin surface and by reducing the rate of evaporation of water from applied aqueous glycerol solution or cosmetic product. Both effects were seen as the result of lowered water activity in the proximity of glycerol.
Smoothing effects of glycerol on the skin surface, and improved appearance, persisted for at least 24 h. This persistence was explained by evidence for diffusion of glycerol into the stratum corneum where it formed a reservoir.
Hydration of the skin is known to affect its barrier function and thereby exert a profound effect on penetration of both lipophilic and hydrophilic molecules. Clinically, this effect may be achieved using liberal applications of occlusive petroleum jelly and ointments. The results presented in this paper suggest that the use of humectants could achieve useful hydration using cosmetically acceptable materials.
In water soluble substances obtained by water extraction from human skin surface, free glycerol was detected by gas chromatography mass spectrometry. A selected ion monitoring method was employed to measure low concentration of free glycerol and the mean amounts were found to be about 0.7 microgram cm-2 on the cheek and 0.2 microgram cm-2 on the forearm and sole.
We recently developed a pig skin model to determine the role of corneosomes (modified desmosomes in the stratum corneum) and extracellular lipids in desquamation. The present study provides control morphometric data on the morphological changes in desmosomes and corneosomes leading to desquamation in adult pig epidermis in vivo. The extracellular space within desmosomes gradually widened from the basal to the granular layer, and decreased slightly in the stratum corneum. Mid-dense line broadening, and increased electron density of the distal light layers, coincided with membrane-coating granule extrusion in the outer granular layer. Corneocyte attachment correlated with corneosome distribution. Compactum packing was relatively tight and corneosomes were numerous. Cohesion was mainly peripheral in the disjunctum, and corneosomes were restricted to corneocyte edges. Adhesion had a tongue-and-groove appearance with corneosomes riveting corneocyte peripheries into a lipped groove on adjoining cells. Cells shed by peeling radially towards the lipped groove, and corneosomes decreased from lower to upper disjunctum. Corneosome breakdown commenced with an electron lucent band forming between the plug and lipid envelope. The plug was then unzipped from the lipid envelope and degraded. Corneosomes did not form squamosomes.
Filaggrin is a specific epidermal protein which is the precursor of the free amino acids, urocanic acid and pyrrolidone carboxylic acid which are largely responsible for the ability of the stratum corneum of the skin to remain hydrated at low environmental humidity. The distribution of filaggrin shown by immunofluorescence in the stratum corneum of the rat changed dramatically during the first hours of postnatal life. During late foetal development, filaggrin accumulated through the entire thickness of the stratum corneum, indicating that there was a block on the subsequent processing of the protein which normally would convert it to free amino acids. Immediately after birth this block was lifted and normal proteolysis of the filaggrin took place in the outer part of the stratum corneum, leaving the normal adult pattern of a thin zone of cells containing filaggrin at the bottom of the stratum corneum. This activation of filaggrin proteolysis was dependent on the drop in external water activity caused by the transition from an aqueous environment in utero to a dryer environment after birth and it could be blocked by maintaining a 100% humidity atmosphere around the newborn rat after birth. In isolated stratum corneum in vitro, filaggrin proteolysis took place only between 80 and 95% relative humidity, both higher and lower relative humidity blocked the proteolysis. Application of occlusive patches to adult rats prevented the normal proteolysis of filaggrin, indicating that this mechanism controls not only the massive filaggrin proteolysis occurring after birth but also the proteolysis occurring during normal stratum corneum maturation. The stratum corneum therefore has the ability to respond to changes in external humidity by altering the level of the stratum corneum where it converts its reserves of filaggrin into water binding amino acids, such that under humid conditions water binding components will be produced in only the most superficial stratum corneum, or even not produced at all.
Glycerol stabilizes the triple-helical structure of solubilized calf skin collagen. The equilibrium melting temperature of the protein increased linearly from 38.0 degrees C in AS buffer (0.01 M NaOAc and 0.02 M NaCl, pH 4.0) to 43.0 degrees C in AS and 6 M glycerol buffer. To understand the thermodynamic basis of this effect on the equilibrium melting temperature and the glycerol inhibition of collagen self-association, the preferential interactions of native and denatured calf skin collagens in AS buffer containing 1.5, 3, and 4.5 M glycerol were measured with a precision densimeter. The results indicated that native collagen binds glycerol preferentially whereas denatured collagen neither binds nor repels glycerol. The preferential binding of glycerol by native collagen, when interpreted in terms of the three-component solution thermodynamics, suggests that the surface interaction of native collagen with glycerol is energetically more favorable than its interaction with water. By use of the Wyman linked function, the negative chemical potential change of collagen derived from its preferential binding of glycerol can account for both the glycerol stabilization of the triple-helical structure of collagen and the inhibition of in vitro self-association of monomers into fibrils.
Low-humidity dermatoses arise in the work place as a result of low water content of the air. At a relative humidity of 10% or less, the horny layer becomes rigid and brittle. The combination of low humidity, high temperature, and, frequently, rapid air movement dehydrates the outer stratum corneum. This leads to pruritus and, finally, to low-grade eczema. A roughened, scaly stratum corneum becomes more susceptible to mechanical trauma. Microtrauma from small particles can aggravate the dry scaly dermatosis. Low-humidity lesions resolve quickly with the simple expedients of routine use of moisturizers and/or raising the relative humidity.
The mechanical parameters, work of fracture, ultimate breaking strength and elongation at fracture, were determined from the stress-strain characteristics of normal human stratum corneum conditioned in various physicochemical environments. These biomechanical properties were found to be highly dependent on the conditioning relative humidity (RH) and solvent extraction history. Over the increasing 0 to 100% RH range, untreated stratum corneum breaking strength decreased 85%, while the work of fracture increased 600%. Elongation at fracture increased from 20% at 0% RH to 190% at 100% RH. Ether extraction increased the magnitude of the breaking strength at all RH's while having little influence on RH dependence of the % elongation at fracture as compared to untreated. Sequential ether-water extraction significantly decreased the fracture elongation at the higher RH's while breaking strengths were less dependent on RH than untreated. The lower extensibility of the ether-water treated samples relative to ether extracted or untreated is consistent with the suggested role of water soluble materials being responsible for the water binding necessary for membrane flexibility. The mechanism for the influence of ether extraction on the breaking strength remains unclear.
Glycerol protects bacterial cells and transforming DNA against both x rays and 365-nm ultraviolet light, but not against 254-nm ultraviolet light. The observation reinforces the concept that 365 nm and ionizing radiation mimic each other in their biological effects and appear more closely related than are 254- and 365-nm ultraviolet light.
Moisturizers are known to have occlusive, emollient and humectant properties, all of which help to alleviate the symptoms of skin xerosis. Although the biological mode of action of moisturizers is poorly understood, the recent observation that skin xerosis is associated with incomplete desmosome digestion suggests that moisturizers improve the desquamation process in such conditions. To examine the possibility that certain moisturizers act by facilitating desmosomal digestion, we investigated the ability of glycerol, a common humectant, to influence this process in stratum corneum in vitro. Examining desmosome morphology in isolated stratum corneum by electron microscopy, it was observed that the desmosomes were in more advanced stages of degradation in glycerol-treated tissue compared with control tissue. This enhanced desmosomal degradation in glycerol-treated tissue was confirmed by significant decreases in the levels of immunoreactive desmoglein 1, a marker of desmosome integrity. Desmosomal degradation was also shown to be a humidity-dependent event, being significantly reduced at low relative humidity. The effect of glycerol on desmosome digestion was emphasized further in two in vitro model systems. Firstly, glycerol increased the rate of corneocyte loss from the superficial surface of human skin biopsies in a simple desquamation assay. Secondly, measurement of the mechanical strength of sheets of stratum corneum, using an extensiometer, indicated a dramatic reduction in the intercorneocyte forces following glycerol treatment. These studies demonstrated the ability of glycerol to facilitate desmosome digestion in vitro. Extrapolating from these results, we believe that one of the major actions of moisturizers in vivo is to aid the digestion of desmosomes which are abnormally retained in the superficial layers of xerotic stratum corneum.
Moisturizers and emollients do not only smooth the skin but also make it more supple. To clarify this effect, the short-term influence of tap water, paraffin oil, ethanol and glycerin on skin mechanics was studied. These substances are all common ingredients in moisturizers and emollients. Significant changes were seen already after 10 min of application. The distensibility and hysteresis (creep phenomenon) showed the most pronounced changes. Water and paraffin oil application caused significant (p < 0.03) increases after 10 min of application. The changes persisted for at least 10 min following paraffin oil application, while they disappeared sooner following water application. Application of ethanol had a negative effect on distensibility (p < 0.03). Glycerin appears to have a slow onset of action, but with the changes continuing even after application was stopped. The changes induced by glycerin appear to be similar to those induced by water and paraffin oil. The study shows that some of the most common ingredients in moisturizers and emollients are capable of inducing significant changes in the mechanical properties of human skin in vivo even after a 10-min application, suggesting that the outermost layers of the epidermis play an important role in skin mechanics.
Glycerol has been used for a long time as a viral preservation medium in tissue samples at a 50 per cent concentration, however after a limited time span viruses could no longer be detected. This fact combined with the dehydrating action of glycerol, raised the suspicion that glycerol in a higher concentration could be virucidal. To test this hypothesis, experiments were done at various concentrations of glycerol at three different temperatures (4, 20 and 37 degrees C), using the following viruses: herpes simplex virus, a virus with an envelope, comparable to human immunodeficiency virus; and poliovirus as an example of small, hard to inactivate viruses without an envelope. Glycerol will dehydrate the skin, the extracted water being replaced by glycerol, preserving the original structure. The remaining water is optimally distributed throughout the tissue. However, the possibility exists that glycerol influences the enzymatic processes of nucleic acid breakdown. Plasmid DNA pBR322 was added to HeLa-cells in the presence and absence of glycerol. The outcome of the experiments showed that glycerol has a strong virucidal action. Preservation in 85 per cent glycerol was preferred, because using this concentration the glycerolized allograft skin retained its suppleness and was easy to manipulate during operations.
Donor allograft skin preserved in 85 per cent glycerol has been used successfully as a temporary coverage for large burn wounds. The glycerol preservation is a method with low costs and has practical advantages such as antibacterial and virucidal effects. This report shows that the glycerol treatment did not affect the fundamental structural integrity of the skin. Intact keratinocytes and Langerhans cells with their characteristic Birbeck granules were still present in the glycerol-treated skin. After treatment with glycerol, the cells in the prepared epidermal cell suspensions were non-viable. MHC class II positive and CD1a positive cells could still be identified in situ and in the suspension.
Previous studies have shown that barrier disruption increases epidermal mRNA levels of interleukin-1 alpha (IL-1 alpha). We used immunohistochemistry to examine IL-1 alpha expression in hairless mouse skin under basal conditions and following barrier abrogation. In untreated mice, IL-1 alpha was present in the dermis and nucleated epidermal layers in a diffuse, generalized pattern. In essential fatty acid deficient mice IL-1 alpha was present in all epidermal layers and the dermis, with prominent staining in the stratum corneum. After acute barrier disruption with tape-stripping, IL-1 alpha increased in the epidermis and dermis within 10 min, remained elevated at 2 and 4 h, and decreased to near basal levels by 24 h. Moreover, intense, perinuclear, basal cell staining appeared at 10 min, persisting until 4 h after barrier disruption. Since the increase in IL-1 alpha immunostaining after acute barrier abrogation precedes the increase in mRNA, we hypothesized that the IL-1 alpha might derive from a pre-formed pool. Prolonged occlusion of normal skin, a treatment that specifically reduces epidermal mRNA levels of IL-1 alpha, decreased basal immunostaining for IL-1 alpha and blunted the increase in IL-1 alpha usually seen following barrier disruption. Moreover, tape-stripping of skin, maintained ex vivo at 4 degrees C, resulted in increased IL-1 alpha immunostaining within the upper nucleated epidermal layers, as well as release of mature IL-1 alpha into the medium, as measured by Western blotting and enzyme-linked immunosorbent assay. In addition, the stratum corneum attached to the tape contained IL-1 alpha. These studies show that acute barrier disruption induces both the immediate release and dispersion of IL-1 alpha from a pre-formed, epidermal pool, as well as increased IL-1 alpha synthesis; both mechanisms are consistent with a role for IL-1 alpha in the regulation of proinflammatory and homeostatic processes in the skin.
It is known that glycerol in an oil-in-water emulsion has a protective effect against irritating substances.
To answer the question: is the protection effect of glycerol based on a regenerative process?
Upon irritation by either tape stripping or acetone treatment, we applied glycerol to the skin surface under an occlusive dressing to create transepidermal water movement. As a control we used water under the occlusive dressing on the contralateral forearm. After 5 h we compared the barrier function using biological tests.
A significant improvement of the protective barrier function was observed in the glycerol-treated areas, as shown by the alkali resistance and by the irritant effect of dimethyl sulfoxide (DMSO) as well as sodium lauryl sulfate. Surprisingly, at the same time penetration of hexyl nicotinate improved on the glycerol-treated areas. A direct physicochemical protection effect on the surface of the skin was ruled out in additional studies using NaOH and DMSO.
Under the given conditions glycerol leads to a more rapid reconstitution of the protective skin barrier and initiates a regenerative skin protection. In contrast to that, it is acting as a penetration enhancer.
Cryopreservation and glycerol preservation are 2 successful methods for long-term preservation of human cadaver skin. Preservation is subjected to strict criteria to minimize the risk of disease transmission. This investigation compares the effects of glycerol preservation and cryopreservation on the inactivation of HIV-1. The effects of glycerol preservation and cryopreservation on inactivation of both extracellular and intracellular HIV-1Ba-L were investigated. After exposing HIV-1Ba-L-infected material to various concentrations of glycerol or to 10% dimethyl sulfoxide followed by cryopreservation, uninfected peripheral blood mononuclear cells were added to the treated material. At different time points during the culture, supernatants were taken to quantify HIV-1Ba-L and reverse transcriptase levels to determine HIV-1Ba-L infectivity. Cell-free HIV-1Ba-L was inactivated within 30 minutes in 70% and 85% glycerol. Also, intracellular HIV-1Ba-L in infected peripheral blood mononuclear cells or infected cadaver skin was completely inactivated by glycerol treatment in vitro. Cryopreservation did not show any extracellular or intracellular HIV-1Ba-L inactivation. Glycerol preservation--but not cryopreservation--of human cadaveric donor skin can inactivate both extracellular and intracellular HIV-1.
Application of water and glycerin is known to influence skin mechanics. The kinetics of these processes are of great interest. A study was performed to show the immediate changes in skin-mechanics. A Dermaflex machine (R) was used to study 23 healthy volunteers. Water or glycerin was applied to the flexorside of the forearm, and readings were made after 3, 6, 9, 12 and 15 min. Regional untreated skin served as baseline. In agreement with earlier studies both substances influenced hysteresis. Water caused a significant increase in hysteresis after 12 and 15 min of hydration (P<0.01). Glycerin caused significantly increased hysteresis after 3 min (P<0.05) and the effect continued to the end of the observation period. No significant differences were seen in the distensibility. The onset of action is rapid for both substances, and the effects are therefore supposed to take place in the outermost layers of epidermis. The effect of glycerin on the hysteresis is more rapid in onset than that of water. Comparing the permeability coefficients, the effect on the mechanical properties of the skin does not appear to be determined by the permeability coefficients as water has a higher permeability coefficient but induces smaller changes than glycerin. Water alone does not appear to be the optimal plasticiser of human skin and other substances soluble in both water and lipids may have an even greater influence on skin mechanics in vivo.
The epidermis functions as a barrier against the environment by means of several layers of terminally differentiated, dead keratinocytes — the cornified layer, which forms the endpoint of epidermal differentiation and death. The cornified envelope replaces the plasma membrane of differentiating keratinocytes and consists of keratins that are enclosed within an insoluble amalgam of proteins, which are crosslinked by transglutaminases and surrounded by a lipid envelope. New insights into the molecular mechanisms and the physiological endpoints of cornification are increasing our understanding of the pathological defects of this unique form of programmed cell death, which is associated with barrier malfunctions and ichthyosis.
Proteolytic enzymes play crucial roles in the formation of the stratum corneum barrier tissue and in its subsequent maturation. Despite this, the proteases involved in stratum corneum physiology are not well characterized. Hence, studies were performed to identify these proteolytic enzymes present in the peripheral layers of this tissue using a combination of tape stripping and zymography. Using this approach, a novel human cysteine protease was identified and characterized, and named stratum corneum thiol protease (SCTP). Gelatin zymography revealed that SCTP is composed of two variants with apparent molecular weights of 34 and 35 kDa which do not correspond to any previously described stratum corneum protease. Mechanistically SCTP belongs to the cysteine proteinase class as shown by: (1) acid protease activity, (2) a requirement for mild reducing conditions, and (3) the specific inhibition of activity by E64 and Z-phe-ala-diazomethylketone. Further analysis using concanavalin A affinity chromatography demonstrated that the two 34 and 35 kDa variants are both glycoproteins, which, after removal of the oligosaccharide sidechains with the specific enzyme N-glycopeptidase F, reveal a single active core protease of 32 kDa. SCTP did not crossreact with antibodies raised against the lysosomal cysteine proteases cathepsins B, H or L, thereby distinguishing it from the classical cysteine cathepsins. Localization studies revealed that SCTP is present at all depths in the stratum corneum, thereby precluding microbial contamination as the enzyme source. Moreover, it was also present at all body sites investigated, except for the hyperkeratotic palmoplantar stratum corneum. SCTP was found to be a product of late differentiation in cultured human keratinocytes; the enzyme was synthesized by differentiated calcium-switched cells and secreted into the medium, whereas nondifferentiated basal keratinocytes did not produce this protease. Moreover, human fibroblast cultures did not produce the enzyme, suggesting that SCTP is not produced by the dermis and hence is epidermal specific. The function of SCTP is unknown, but the observed gelatinolytic activity coupled with its secretion into the medium by cultured keratinocytes indicates that physiologically it is responsible for the degradation of extracellular structural proteins. Furthermore, the optimal activity at acid pH suggests that it can function in the acidic environment of the stratum corneum. It remains to be elucidated whether this enzyme has a role in desquamation.
Allogeneic split skin grafts are used widely in the treatment of burns. The relative simplicity of glycerol preservation of skin suggests it will be used increasingly in areas of high HIV-1 seroprevalence. The ability of glycerol preservation to inactivate HIV-1 present in skin graft infected in vitro was determined using a macrophage tropic strain HIV-1 as a cell-free virus suspension, within infected PBMCs, or within in vitro HIV-1 infected fresh cadaveric split skin. Different temperatures and concentrations of glycerol were used and infectivity determined by coculture with mitogen activated peripheral blood mononuclear cells (PBMCs) and measurement of reverse transcriptase activity after 7-10 days. Cell-free HIV-1 was inactivated within 30 min at 4 degrees C in glycerol concentrations of 70% or higher. During similar exposure cell- or skin-associated HIV-1 titer was reduced but not eliminated with 70% and 85% glycerol at 4 degrees C. HIV-1 was recovered consistently from skin stored in 85% glycerol at 4 degrees C for up to 72 hr but virus isolation was infrequent after storage for more than 5 days. At 20 degrees C or 37 degrees C, 70% or 85% glycerol could inactivate cell- or skin-associated HIV-1 within 8 hr. The initial glycerolization procedures and the storage at 4 degrees C eliminated effectively HIV-1 from skin.
To maintain a constant thickness of the stratum corneum the desquamation rate and the de novo production of corneocytes is delicately balanced. Using a plantar stratum corneum model we have obtained evidence that proteolysis is a central event in the desquamation process. A number of regulatory mechanisms for desquamation have been postulated based on our findings.
Keywords:moisturizers;glycerol;W/O emulsion;horny layer;hydration;prevention;skin-care products;long-term use