Design of a phytosphingosine-containing, positively-charged nanoemulsion as a colloidal carrier system for dermal application of ceramides.

Positively charged oil/water (o/w) nanoemulsions (PN) are effective vehicles to change the permeability of the skin. This study focused on the preparation and characterisation of phytosphingosine (PS) containing PN (PPN) which serve as colloidal carriers for the dermal application of ceramide IIIB (CIIIB) and the stratum corneum (SC) lipids (PPNSC) such as ceramide III (CIII), cholesterol, and palmitic acid. The investigations were conducted using appropriate emulsification and homogenisation processing conditions to optimise PPNSC with regard to droplet size, physical stability, and solubility of PS, CIII and CIIIB. A decrease in droplet size was observed through eight homogenisation cycles at a pressure of 500 bar and a temperature of 50 degrees C. Above these optimal values, an increase in droplet size was observed. PS and ceramides have low solubilities in oil and water. When Lipoid E-80 (LE80) was added to the oil phase, the solubility of PS and ceramides increased, indicating some interactions shown by DSC measurements. SC lipids and CIIIB could be successfully incorporated in PPN without producing any physical instability. The high stability of PPNSC is probably due to the presence of a hydrophilic (Tween 80) and a lipophilic surfactant (LE80), supported by the lipophilic cosurfactant PS, at the o/w interface. It was shown that PS was responsible for the positive charge and thus supported the high physical stability of PPNSC. This optimised emulsion was selected for further skin absorption evaluation.     

Anti-aging efficacy of topical formulations containing niosomes entrapped with rice bran bioactive compounds

Context: Rice [Oryza sativa L. (Gramineae)] bran is a rich source of phytochemicals. Its oil also contains several bioactive components that exhibit antioxidative properties such as ferulic acid (F), γ-oryzanol (O), and phytic acid (P) which can be a new source of cosmetic raw materials.

Objective: To evaluate the anti-aging effects of the gel and cream containing niosomes entrapped with the rice bran bioactive compounds.

Materials and methods: The semi-purified rice bran extracts containing F, O, and P which indicated the growth stimulation of human fibroblasts and the inhibition of MMP-2 by sulforhodamine B and gelatin zymography, respectively, were entrapped in niosomes by supercritical carbon dioxide fluid (scCO₂) and incorporated in gel and cream formulations. The skin hydration, elasticity, thickness and roughness, and pigmentation in human volunteers after treated with these gel and creams were investigated by corneometer, cutometer, visiometer, and mexameter, respectively.

Results: Gel and cream containing the semi-purified rice bran extracts entrapped in niosomes gave no sign of erythema and edema detected within 72?h on the shaved rabbit skin by the closed patch test investigated by mexameter and visual observation, respectively. These formulations also demonstrated higher hydration enhancement and improvement of skin lightening, thickness, roughness, and elasticity on the skin of 30 human volunteers within the 28–day treatment not more than 9, 27, 7, 3, and 3 times, respectively.

Discussion and conclusions: The formulations containing niosomes entrapped with the rice bran bioactive compounds gave superior clinical anti-aging activity which can be applied as a novel skin product.     

Alteration of skin hydration and its barrier function by vehicle and permeation enhancers: a study using TGA, FTIR, TEWL and drug permeation as markers

Vehicles and permeation enhancers (PEs) used in transdermal drug delivery (TDD) of a drug can affect skin hydration, integrity and permeation of the solute administered. This investigation was designed to study the effect of the most commonly used vehicles and PEs on rat skin hydration, barrier function and permeation of an amphiphilic drug, imipramine hydrochloride (IMH). An array of well-established techniques were used to confirm the findings of the study. Thermogravimetric analysis (TGA) and Fourier transform infrared (FTIR) spectroscopy were used to determine changes in skin hydration. Alteration of the stratum corneum (SC) structure was investigated using FTIR studies. To monitor the barrier function alteration, transepidermal water loss (TEWL) measurement and permeation studies were performed. Our findings indicate that with hydration, there was an increase in the bound water content of the skin, and pseudoequilibrium of hydration (a drastic decrease in hydration rate) was achieved at around 12 h. Hydration increased the ratio between amide-I and amide-II peaks in FTIR and reduced the C-H stretching peak area. Both propylene glycol (PG) and ethanol (EtOH) dehydrated skin, with the latter showing a predominant effect. Furthermore, it was confirmed that PG and EtOH decreased the bound water content due to alteration in the protein domains and extraction of SC lipids, respectively. The effect of hydration on the SC was found to be similar to that reported for temperature. Permeation studies revealed that the dehydration caused by vehicles decreased IMH flux, whereas the flux was enhanced by PEs. The role of partition was predominant for the permeation of IMH through dehydrated skin. A synergistic effect was observed for PG and menthol in the enhancement of IMH. Further findings provided strong evidence that PG affects protein domains and EtOH extracts lipids from the bilayer. Both PG and EtOH, with or without PEs, increased TEWL. Initial TEWL was well correlated with the flux of IMH through the same skin. It was found that both PG and EtOH affect the permeation of solute and TEWL by dehydration. The experiments also proved that the initial TEWL value has a strong potential as a predictive tool for the permeation of the solute.     

In vivo comparison of various liposome formulations for cosmetic application

The interaction of liposome formulations, prepared with phospholipids of different origins (egg and soya), with skin were compared in terms of their effects on skin water content, skin barrier function, and skin elasticity. Short-term effect of four different liposome formulations and two references during 3.5 h was investigated non-occlusively on the volar side of the forearm of 10 volunteers, ranging in age from 24 to 32 years. Liposomes composed of different phospholipids showed differing effects on skin humidity. The maximal effect was achieved within 30 min and constant values were reached after 1.5 h for all formulations, however values remained significantly higher than without treatment (p<0.05) during the whole application time. The best results were obtained with liposome formulations prepared from egg phospholipids, which exhibited a 1.5-fold increase in skin water content (p<0.05), whereas liposome formulations prepared from soya phospholipids showed no advantage compared to the references. Skin barrier function showed greatest influence within 30 min after application and remained constant after 1.5 h for all formulations. Within the liposome formulations, egg phospholipids showed the highest transepidermal water loss values during the first 30 min, representing the strongest interactions with the skin barrier function, whereas for the other liposome formulations lower transepidermal water loss values were measured. Skin elasticity and tiring effect of the skin was not influenced by any of the formulations, due to the young skin tested. Long-term effect of two different liposome formulations mixed with base cream DAC in two different concentrations during 14 days was investigated non-occlusively on the volar side of the forearm of 10 volunteers, ranging in age from 20 to 25 years. Skin water content was measured daily and the results showed that skin humidity was increased significantly (p<0.05) for the formulation containing 20% egg phospholipids during 6 days. Liposome formulations prepared with egg phospholipids showed significantly higher (p<0.01) hydration effects during 3.5 h of application on human skin compared with liposome formulations prepared with soya phospholipids.     

Influence of DMPS on the water retention capacity of electroporated stratum corneum: ATR-FTIR study

Anionic lipids like phosphatidylserine are known to significantly enhance electroporation mediated transepidermal transport of polar solutes of molecular weights up to 10 kDa. The underlying mechanism of the effect of anionic lipids on transdermal transport is not fully understood. The main barrier to transdermal transport lies within the intercellular lipid matrix (ILM) of the stratum corneum (SC) and our previous studies indicate that dimyristoyl phosphatidylserine (DMPS) can perturb the packing of this lipid matrix. Here we report on our investigation on water retention in the SC following electroporation in the presence and the absence of DMPS. The water content in the outer most layers of the SC of full thickness porcine skin was determined using ATR-FTIR-spectroscopy. The results show that in the presence of DMPS, the SC remains in a state of enhanced hydration for longer periods after electroporation. This increase in water retention in the SC by DMPS is likely to play an important role in trans-epidermal transport, since improved hydration of the skin barrier can be expected to increase the partitioning of polar solutes and possibly the permeability.     

Effects of serine palmitoyltransferase inhibitor ISP-I on the stratum corneum of intact mouse skin

Serine palmitoyltransferase (SPT) is involved in the ceramide synthesis pathway. We investigated the effects of ISP-I, a potent inhibitor of SPT, on the stratum corneum (SC) of hairless mouse skin. Application of ISP-I for one week resulted in a significant decrease in the amount of ceramide, which was associated with a decrease in SC hydration. However, there was an increase in the number of SC layers and less transepidermal water loss than control. Transmission Electron Microscopy observation revealed that the number of desmosome-like structures in the layers immediately above the stratum granulosum (SG) was significantly increased in ISP-I-treated skin compared to vehicle-treated skin. The activity of serine protease-an enzyme associated with the process of desquamation-was lower in the SC of ISP-I-treated skin than control. Furthermore, immunoelectronmicroscopy revealed that glucosylceramide and corneodesmosin tended to remain in corneocytes and were not secreted into the intercellular spaces of the SC in the ISP-I-treated skin. These results indicate that the application of ISP-I decreases ceramide and skin hydration, while at the same time increases the number of SC layers. The accumulation of corneocyte layers may originate from an aberrant desquamation process related to the decrease in the serine protease activity as well as an alteration in the transport of desquamation-related proteases by lamellar bodies.     

Controlled penetration of ceramides into and across the stratum corneum using various types of microemulsions and formulation associated toxicity studies

Several skin diseases such as psoriasis and atopic dermatitis are associated with the depletion or disturbance of stratum corneum (SC) lipids such as ceramides (CERs), free fatty acids and cholesterol. Studies suggested that replenishment of these lipids might help to treat diseased, affected or aged skin. With this premises in mind, there are some formulations in the market that contain SC lipids and currently, to facilitate permeation of the lipids deep into the SC, various CERs, and other SC lipid microemulsions (MEs) were developed and characterised using lecithin or TEGO® CARE PL 4 (TCPL4) as base surfactants. However, to date, there are no reports that involve the permeability of SC lipids into and across the SC, and therefore, the penetration of CER [NP] as a model ceramide from various formulations was investigated ex vivo using Franz diffusion cell. Besides, the toxicity of the MEs was assessed using hen’s egg test chorioallantoic membrane (HET-CAM). The results of the study showed that CER [NP] could not permeate into deeper layers of the SC from a conventional hydrophilic cream. Unlike the cream, CER [NP] permeated into the deeper layers of the SC from both type of MEs, where permeation of the CER was more and into deeper layers from droplet type and lecithin-based MEs than bicontinuous (BC) type and TCPL4 based MEs, respectively. The CER also permeated into deeper layers from ME gels which was, however, shallow and to a lesser extent when compared with the MEs. The results of HET-CAM showed that both MEs are safe to be used topically, with lecithin-based MEs exhibiting better safety profiles than TCPL4 based MEs. Concluding, the study showed that the MEs are safe to be used on the skin for the controlled penetration of CER [NP] deep into the SC.     

Study of the potential of stratum corneum lipids and exogenous molecules interaction by fluorescence spectroscopy for the estimation of percutaneous penetration

Considering that the skin barrier properties are closely linked to the ceramides composition and conformation within the SC, our work focused on developing a new evaluation criterion in complement of the Log Pow and MW: lipids retentive role within the SC. We developed an in vitro model to study exogenous molecules (Mol) and SC lipids interaction by fluorescence spectroscopy. As ceramides do not fluoresce, fluorescence probes that emit a fluorescence signal in contact with lipidic chains were selected for the study. A protocol was developed based on the exogenous molecule (cosmetic actives) affinity for the SC lipids. A fluorescence criterion (ΔI) was calculated from our results and compared to ex vivo skin penetration measurements realized with a Franz cell device. Our results indicated that polarity seems to be very representative of the ceramide and exogenous molecule interaction for most of the molecules tested. However, the ΔI calculated highlighted the particular interaction of some exogenous molecules with ceramides and their skin distribution. This particular behavior was not initially possible to estimate with the Log Pow and MW. This work aimed to develop a new alternative method to enhance the percutaneous penetration estimation of exogenous molecules for the risk analysis.     

Anti-inflammatory and skin-hydrating properties of a dietary supplement and topical formulations containing oligomeric proanthocyanidins

BACKGROUND: Anti-inflammatory and skin hydration properties of a dietary supplement and 2 topical formulations (Anthogenol) with oligomeric proanthocyanidins were investigated. METHODS: Forty-two subjects were randomized into 2 groups: one taking the dietary supplement (100 mg/day) and the other without supplement. After 4 weeks, erythema was induced using UV radiation followed by treatment with topical cream or lotion. Erythema was measured for up to 72 h after irradiation. Skin hydration after 1 and 2 weeks of application of the cream and lotion was also measured in separate test fields. RESULTS: Both topical formulations led to a significant suppression of erythema formation and the dietary supplement led to an additional slightly stronger suppression. Thus 72 h after UV exposure and compared to the control fields of patients that had not taken a dietary supplement, erythema was slightly (13.2%) lower in the subjects that had taken a dietary supplement. The cream resulted in a maximal reduction of erythema of 45.9% (p = 0.0015), while the lotion resulted in a maximal reduction of 53.1% (p = 0.0002). Both topical formulations also increased skin hydration (by nearly 20%; p < 0.002 for all combinations of dietary supplementation and topical treatment) and the hydration was higher in the group taking the dietary supplement. CONCLUSION: The regular use of Anthogenol products may help to protect from free-radical-mediated skin inflammation and to increase skin hydration.     

Endogenous phospholipid metabolite containing topical product inhibits ultraviolet light-induced inflammation and DNA damage in human skin

BACKGROUND: N-palmitoylethanolamine (PEA) and organic osmolytes are endogenous components of the human epidermis and are generated from phospholipids in the stratum granulosum. PEA has been shown to exert potent antioxidant and anti-inflammatory activities. The endogenous organic osmolytes such as betaine and sarcosine control skin humidity, but have also been shown to inhibit ultraviolet (UV) light-induced oxidative stress in keratinocytes. OBJECTIVES: To investigate the effect of a PEA- and organic osmolyte-containing topical product (Physiogel AI) on the development of UV light-induced erythema, thymine dimer formation and p53 tumor suppressor gene activation, as well as intercellular adhesion molecule 1 (ICAM-1) and Ki67 expression in normal human skin. METHODS: The UV-induced erythema was measured by a spectrofluorometric method. Thymine dimers, p53, ICAM-1 and Ki67 were detected in skin biopsies using immunohistochemistry. RESULTS: Physiogel AI cream significantly inhibited the development of UV light-induced erythema and thymine dimer formation in normal human skin, but did not alter the number of Ki67+ proliferating keratinocytes and the expression of p53 and ICAM-1. CONCLUSIONS: Our results suggest that PEA and organic osmolytes might represent a new generation of compounds which suppress UV-induced photodamage.     

In vitro and in vivo evaluations of topically applied capsaicin and nonivamide from hydrogels

The purpose of this study was designed to investigate the in vitro and in vivo skin absorption of capsaicin and nonivamide from hydrogels. Various commercialized creams of capsaicin were also compared with hydrogels. Both skin stripping technique and Mexameter were applied to evaluate the level of capsaicin and nonivamide retained in stratum corneum (SC) and skin erythema in vivo. The partition of drug between skin and the hydrogel matrix was considered to play an important role in the permeation process. The in vitro permeation of capsaicin from hydrogels depends on the physicochemical nature and the concentration of the polymer used. The incorporation of nonionic Pluronic F-127 polymer into hydrogels resulted in a retarded release of capsaicin. On the other hand, the in vitro capsaicin permeation showed higher levels in cationic chitosan and anionic carboxymethyl cellulose (CMC) hydrogels than cream bases. The permeation of nonivamide was retarded at the late stage of in vitro application. The inter-subject variation was more significant in the in vivo study than in vitro skin permeation experiments. The cream induced in vivo skin erythema depending on the drug concentration, however, the dose-dependence was not observed in hydrogels. Nonivamide-treated skin showed stronger erythema than capsaicin-treated skin. The present study indicates that there is a moderate correlation between in vitro skin permeation and in vivo erythema responses of topically applied capsaicin and nonivamide. The correlation between drug amount in SC and skin erythema test in vivo was also observed.     

Stratum Corneum Lipids of Human Epidermal Keratinocyte Air-Liquid Cultures: Implications for Barrier Function

Purpose. The purpose of this study is to investigate the permeability barrier, i.e., the stratum corneum (SC) lipids, of human epidermal keratinocyte air-liquid cultures and compare them with those of human SC. Methods. The SC lipids composition was analyzed by TLC technique, the organization by electron microscopic procedure, and the phase transition temperature by Infrared spectroscopic method. Results. Electron microscopy demonstrated that The SC lipids of cultures were largely retained inside the corneocytes, and that the intercellular lipids lack both the basic unit repetition (i.e., broad : narrow : broad : broad : narrow : broad of electron lucent bands) and the covalently-bound lipid envelope normally found in human SC. These characteristics are similar to those found in SC from patients with atopic dermatitis or psoriasis, or from animals with essential fatty acid deficiency, suggesting that the cultures may be hyperproliferative. In addition, the high free sterol content and the altered fatty acid/ceramide composition of these cultures argue that the compromised barrier function is linked to hyperproliferation and lipid synthesis, or vice versa. Infrared spectroscopic analyses confirm that there are major conformational differences between the lipids of human and cultured SC. Conclusions. The profound differences in SC lipid composition, organization and conformational properties attest that permeability alone is not a sufficiently sensitive marker to define barrier equivalence between cultures and human skin.     

Photostability and efficacy studies of topical formulations containing UV-filters combination and vitamins A, C and E

It is already known that the photostability of a sunscreen is important for its performance on human skin. On the other hand, there are many formulations besides sunscreens containing combinations of UV-filters and daily use active substances with other claims like hydration and anti-aging effects. Vitamins A, C and E are frequently added in these kinds of products and it is not known if the UV-filters have some influence on the hydration and anti-aging effects of these vitamins on the skin as well as on their stability mainly when photounstable UV-filters like avobenzone and octyl methoxycinnamate are present in the formulation. Thus, the aim of this study was to evaluate the influence of two different UV-filters combinations, a photostable and a photounstable one, on the photostability as well as on the efficacy of a formulation containing vitamin A, C and E derivatives. The formulations that were investigated contained or not (vehicle: formulation 1) a combination of 0.6 % (w/w) vitamin A palmitate (1,700,000 UI/g), 2 % (w/w) vitamin E acetate and 2% (w/w) ascorbyl tetraisopalmitate (formulation 2) supplemented with a photounstable UV filter combination octyl methoxycinnamate (OMC), avobenzone (AVB) and 4-methylbenzilidene camphor (MBC) (formulation 3) or with a photostable UV filter combination OMC, benzophenone-3 (BP-3) and octocrylene (OC) (formulation 4). In the photostability studies, all formulations were spread onto a glass plate and exposed to UVA/UVB irradiation. The filter components and vitamins were quantified by HPLC analysis with detection at 325 and 235 nm and by spectrophotometry. To simulate the effects of these formulations daily use, all of them (formulations 1-4) were applied on the dorsum of hairless mice, which were submitted to a controlled light-dark cycle (and were not irradiated), once a day for 5 days. Transepidermal water loss (TEWL), water content of the stratum corneum and viscoelastic properties of the skin were analyzed by using different non-invasive Biophysics Techniques in order to evaluate hydration and anti-aging effects of these formulations as well as erythema to assess skin irritation. Histopathology, viable epidermal thickness as well as the number of epidermal cell layers were also evaluated. It was observed that both UV filters combinations (photounstable one containing OMC, AVB and MBC and photostable one containing OMC, BP-3 and OC) enhanced vitamin A photostability and F4 was more photostable than F3, in terms of vitamin A. In vivo efficacy studies showed that F2, F3 and F4 enhanced the viable epidermal thickness, the number of epidermal cell layers, TEWL and Uv/Ue parameter, when compared to the vehicle, which can suggest that they enhanced viable epidermis hydration and acted in cell renewal. However formulation 2 (containing only vitamins), which was the most photounstable formulation, provoked an irritation on hairless mouse skin, and consequently it cannot be considered as safe as the other formulations. It can be concluded that both UV filters combinations did not influence the hydration and anti-aging effects of the formulations containing the vitamins under study and reduced the skin irritation observed when the vitamins were present in the formulation. In addition, the photostable UV-filters combination had the highest recovery of vitamin A in the photostability studies. Finally, it could be suggested that the presence of UV-filters can be considered interesting for the reduction of skin irritation and the most suitable formulation was the one containing the combinations of vitamins A, C and E with photostable UV-filters.     

Are Water Permeability Measurements Sufficient to Characterize in Vitro Cultured Human Skin Surrogates?

Abstract

We have found previously that human neonatal foreskin keratinocyte air/liquid (A/L) cultures developed normal-appearing epidermis, and that water flux was only two to three times higher than that found with intact human skin. To understand further the barrier properties of these A/L cultures, we have analyzed the composition and the gross conformational structures of the cultured stratum corneum (SC) lipids, and compared them with those of human SC. Electron microscopic examination demonstrated that cultured SC has high intracellular lipid content, but that it lacks both the basic unit repetition (e.g., broad/narrow/broad/broad/narrow/ broad pattern of electronlucent bands) normally found in human SC intercellular lipids and the covalently bound lipid envelope. These results indicate that the cultures are hyperproliferative, with characteristics similar to those found in SC obtained from patients with atopic dermatitis or psoriasis, or from animals whose diets lack essential fatty acids. In addition, the high free sterol content and the altered fatty acid/ceramide composition of these cultures argue that the compromised barrier function is linked to hyperproliferation and lipid synthesis, or vice versa. Infrared spectroscopic analysis of the SC lipid thermal transitions confirm that there are major conformational differences between the lipids of cultured and human SC, which clearly have an impact on permeability. The hyperproliferative state of growth and the profound differences between cultured and human SC in their lipid structural, compositional, and conformational properties together attest that water permeability alone is not a sufficiently sensitive marker of keratinocyte terminal differentiation for in vitro culture systems. It is not completely obvious how these differences in the cultured SC may influence the utility of this surrogate in studies involving skin biochemistry, pharmacology, permeability, metabolism, and toxicology. Nevertheless, it is clear that one needs to characterize the end product fully before one can judiciously interpret any results obtained from this or other similar skin surrogates.     

Increase of skin-ceramide levels in aged subjects following a short-term topical application of bacterial sphingomyelinase from Streptococcus thermophilus

Several studies have demonstrated that ceramides play an essential role in both the barrier and water-holding functions of healthy stratum corneum, suggesting that the dysfunction of the stratum corneum associated with ageing as well that observed in patients with several skin diseases could result from a ceramide deficiency. In a previous study our group reported a significant increase in skin ceramide levels in healthy subjects after treatment in vivo with a cream containing a preparation of Streptococcus thermophilus. The presence of high levels of neutral sphingomyelinase activity in this organism was responsible for the observed increase of stratum corneum ceramide levels, thus leading to an improvement in barrier function and maintenance of stratum corneum flexibility. The aim of the present work is to investigate the effects of the topical treatment of a Streptococcus thermophilus-containing cream on ceramide levels of stratum corneum of healthy elderly women. The ceramide levels, transepidermal water loss and capacitance were evaluated on stratum corneum sheets from the forearms of 20 healthy female subjects treated with a base cream or the same cream containing a sonicated preparation of the lactic acid bacterium Streptococcus thermophilus. A 2-week topical application of a sonicated Streptococcus thermophilus preparation led to significant and relevant increase of stratum corneum ceramide levels. Moreover, the hydration values of the treated forearm of each subject was significantly higher than control sites. These results suggest that the experimental cream was able to improve the lipid barrier and to increase a resistance against ageing-associated xerosis.     

Moisturizing and Antiinflammatory Properties of Cosmetic Formulations Containing Centella asiatica Extract

Centella asiatica extract is a rich source of natural bioactive substances, triterpenoid saponins, flavonoids, phenolic acids, triterpenic steroids, amino acids and sugars. Thus, many scavenging free radicals, exhibit antiinflammatory activity and affect on the stratum corneum hydration and epidermal barrier function. The aim of the present study was to evaluate the in vivo moisturizing and antiinflammatory properties of cosmetic formulations (oil-in-water emulsion cream and hydrogel) containing different concentrations of Centella asiatica extract. The study was conducted over four weeks on a group of 25 volunteers after twice a day application of cosmetic formulations with Centella asiatica extract (2.5 and 5%, w/w) on their forearms. The measurement of basic skin parameters (stratum corneum hydration and epidermal barrier function) was performed once a week. The in vivo antiinflammatory activity based on the methyl nicotinate model of microinflammation in human skin was evaluated after four weeks application of tested formulations. In vivo tests formulations containing 5% of Centella asiatica extract showed the best efficacy in improving skin moisture by increase of skin surface hydration state and decrease in transepidermal water loss as well as exhibited antiinflammatory properties based on the methyl nicotinate model of microinflammation in human skin. Comparative tests conducted by corneometer, tewameter and chromameter showed that cosmetic formulations containing Centella asiatica extract have the moisturizing and antiinflammatory properties.     

Calendula extract: effects on mechanical parameters of human skin

The aim of this study was to evaluate the effects of newly formulated topical cream of Calendula officinalis extract on the mechanical parameters of the skin by using the cutometer. The Cutometer 580 MPA is a device that is designed to measure the mechanical properties of the skin in response to the application of negative pressure. This non-invasive method can be useful for objective and quantitative investigation of age related changes in skin, skin elasticity, skin fatigue, skin hydration, and evaluation of the effects of cosmetic and antiaging topical products. Two creams (base and formulation) were prepared for the study. Both the creams were applied to the cheeks of 21 healthy human volunteers for a period of eight weeks. Every individual was asked to come on week 1, 2, 3, 4, 5, 6, 7, and 8 and measurements were taken by using Cutometer MPA 580 every week. Different mechanical parameters of the skin measured by the cutometer were; R0, R1, R2, R5, R6, R7, and R8. These were then evaluated statistically to measure the effects produced by these creams. Using ANOVA, and t-test it was found that R0, and R6 were significant (p <0.05) whereas R1, R2, R5, R7, R8 were insignificant (p > 0.05). The instrumental measurements produced by formulation reflected significant improvements in hydration and firmness of skin.     

Hydration Effects on Skin Microstructure as Probed by High-Resolution Cryo-Scanning Electron Microscopy and Mechanistic Implications to Enhanced Transcutaneous Delivery of Biomacromolecules

Although hydration is long known to improve the permeability of skin, penetration of macromolecules such as proteins is limited and the understanding of enhanced transport is based on empirical observations. This study uses high-resolution cryo-scanning electron microscopy to visualize microstructural changes in the stratum corneum (SC) and enable a mechanistic interpretation of biomacromolecule penetration through highly hydrated porcine skin. Swollen corneocytes, separation of lipid bilayers in the SC intercellular space to form cisternae, and networks of spherical particulates are observed in porcine skin tissue hydrated for a period of 4–10 h. This is explained through compaction of skin lipids when hydrated, a reversal in the conformational transition from unilamellar liposomes in lamellar granules to lamellae between keratinocytes when the SC skin barrier is initially established. Confocal microscopy studies show distinct enhancement in penetration of fluorescein isothiocyanate-bovine serum albumin (FITC-BSA) through skin hydrated for 4–10 h, and limited penetration of FITC-BSA once skin is restored to its natively hydrated structure when exposed to the environment for 2–3 h. These results demonstrate the effectiveness of a 4–10 h hydration period to enhance transcutaneous penetration of large biomacromolecules without permanently damaging the skin. © 2009 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 99:730–740, 2010     

Combined effect of liposomalization and addition of glycerol on the transdermal delivery of isosorbide 5-nitrate in rat skin

In this report, we investigated the combined effect of drug liposomalization and addition of glycerol on the transdermal delivery of isosorbide 5-nitrate (ISN) in rat abdominal skin in vitro. Occlusive application of both liposomal and aqueous ISN solution, with and without addition of 5% glycerol, showed that drug liposomalization and addition of glycerol has far-reaching implications for ISN permeation and accumulation in 4 and 8 weeks old rat abdominal skin. Using 8 weeks old rat abdominal skin, the optimal concentration of glycerol to be added to liposomal ISN was found to be 5%. The ISN mean values permeated through and accumulated in stripped 8 weeks old rat abdominal skin from those formulations described above were not significant different, which might indicate the combined effect of glycerol and liposomal ISN resides solely in the stratum corneum (SC). Based on previous reports, the enhancement effect of glycerol might be due to an increase in the SC hydration, and perhaps due to subtle changes in the lipid organization caused by penetration of liposomal lipids within the SC intercellular spaces. These data might provide evidence that glycerol action on SC is useful to facilitate skin permeation and accumulation of drugs formulated in liposome.