The effect of vehicle on skin absorption of Mg2+ and Ca2+ from thermal spring water.

OBJECTIVE: Thermal spring waters (TSW) are commonly used as active ingredients in cosmetics. Their biological activities directly depend on the ionic composition of the spring. However, in order to exhibit beneficial properties, the minerals need to reach viable skin layers. The present study addresses the incorporation of marketed TSW in model cosmetic formulations and the impact of the formulation on skin absorption of magnesium and calcium ions that are known to improve skin barrier function. METHODS: Marketed TSW was introduced into five formulations. Liposomes were prepared using saturated or unsaturated phospholipids mixed with cholesterol by the thin layer evaporation technique. Emulsions water-in-oil (W/O), oil-in-water (O/W) or double: water-in-oil-in-water (W/O/W) were prepared by high-shear mixing. Skin absorption of Mg2+ and Ca2+ from those formulations was studied in vitro using static Franz diffusion cells under infinite dose condition and under occlusion of the apparatus. RESULTS: Mg2+ and Ca2+ penetrate skin samples from TSW. Encapsulating TSW into double emulsion (TSW/O/W) increased skin absorption of both cations of interest and kept the Ca2+ /Mg2+ ratio equal to that of TSW in each skin layer. The dermal absorption of Mg2+ from the double emulsion departs from both single emulsions. Application of liposome suspension improved the skin absorption of Ca2+ while keeping constant that of Mg2+ , leading to unbalanced Ca2+ /Mg2+ ratio inside skin. CONCLUSION: The beneficial effects of TSW are not only due to their action on the skin surface. Their active components, especially Ca2+ and Mg2+ cations, reach viable skin layers in a formulation-dependent manner. The distribution of ions inside skin depends on the type of formulation.

OBJECTIFS: Les eaux thermales sont couramment utilisées comme substances actives dans les formulations cosmétiques. Leurs activités biologiques dépendent directement de leur composition en ions. L'action des ions s'exerce à différents niveaux dans la peau, mais bien souvent dans les couches profondes, au-delà du stratum corneum, qu'ils doivent donc atteindre. L'objectif de cet article est d'étudier l'absorption des ions magnésium et calcium, reconnus pour leur effet bénéfique sur la fonction barrière de la peau, depuis différentes formes galéniques formulées avec une eau thermale. METHODES: Une eau thermale commerciale a été utilisée comme phase aqueuse dans 5 formulations différentes : des liposomes formulés avec des phospholipides saturés et insaturés et du cholestérol ; des émulsions de différents sens, eau thermale/huile (TSW/O) et huile/eau thermale (O/TSW) ; une émulsion multiple eau thermale/huile/eau (TSW/O/W). L'absorption cutanée du calcium et du magnésium a été étudiée depuis ces différentes formulations, en utilisant la méthode des cellules de Franz, en dose infinie, et en fermant les cellules pour prévenir toute évaporation. RESULTATS: Les ions magnésium et calcium pénètrent dans la peau depuis l'eau thermale, utilisée comme contrôle. L'encapsulation de l'eau thermale dans les gouttelettes internes de l'émulsion double (TSW/O/W) permet de promouvoir la pénétration des deux ions d'intérêt dans chaque couche de la peau tout en respectant le rapport Ca2+ /Mg2+ obtenu avec l'eau thermale, contrairement aux émulsions simples. Les liposomes augmentent la pénétration cutanée des ions calcium, tandis que celle des ions magnésium reste constante, ce qui conduit à des rapports Ca2+ /Mg2+ élevés dans la peau. CONCLUSION: Les effets thérapeutiques des eaux thermales ne sont pas seulement dus à une action de surface. Les ions comme le calcium et le magnésium pénètrent dans la peau et exercent une action en profondeur qui dépend de la formulation dans laquelle ils sont formulés. En effet, leur distribution ions dépend de la formulation qui les contient.

Formulation of survival acceptor medium able to maintain the viability of skin explants over in vitro dermal experiments.

OBJECTIVE: In vitro assessments of skin absorption of xenobiotics are essential for toxicological evaluations and bioavailability studies of cosmetic and pharmaceutical ingredients. Since skin metabolism can greatly contribute to xenobiotic absorption, experiments need to be performed with skin explants kept viable in suitable survival media. Existing protocols for non-viable skin are modified to consider those conditions. The objective was to design a survival medium used as an acceptor fluid in Franz cells for testing cutaneous penetration of hydrophilic or lipophilic molecules. Their metabolism inside skin may be investigated under the same conditions. The determining factors involved in survival mechanisms in vitro are discussed. The consequences of short-term skin preservation at 4°C were also evaluated. METHODS: The metabolic activity of fresh skin samples mounted in Franz cells was studied by measurement of lactate release over 24 h in order to assess the impacts of pH, buffering, osmolality, ionic strength, initial glucose supply and the addition of ethanol or non-ionic surfactant in the acceptor part of Franz cells. CONCLUSION: Survival media must maintain physiological pH (>5.5) be isotonic with skin cells (300 mOsm kg-1 ) and contain at least 0.5 g L-1 glucose. Several compositions able to preserve skin metabolism are reported. Storage of skin explants overnight at 4°C impairs skin metabolic activity. The present work provides guidelines for designing survival media according to constraints related to the scientific requirements of the experiments.

OBJECTIFS: Les études d'absorption cutanée sont indispensables pour les évaluations toxicologiques et les études de biodisponibilité des ingrédients cosmétiques et pharmaceutiques. Etant donné que le métabolisme cutané peut contribuer à l'absorption cutanée des xénobiotiques, les études doivent être parfois menées sur les explants cutanés maintenus en survie à l'aide d'un milieu adapté. Les protocoles classiques utilisés avec des explants congelés non viables sont souvent modifiés pour prendre en compte ces conditions particulières. L'objectif de cette étude est d'étudier les conditions nécessaires à appliquer au milieu receveur des cellules de Franz pour maintenir la viabilité des explants, dans les études de pénétration cutanée de molécules hydrophiles et lipophiles. Leur métabolisme dans la peau peut être étudié dans ces mêmes conditions. Les facteurs déterminants à prendre en compte pour assurer la viabilité des explants in vitro sont discutés. Les conséquences de la conservation des explants cutanés durant une courte durée à 4°C, avant utilisation, ont été également évaluées. METHODES: L'activité métabolique des échantillons de peau, montés en cellules de Franz, a été évaluée grâce aux mesures du lactate produit durant 24h, durée de l'expérience. L'impact du pH, de solutions « tampon ¼, de l'osmolalité, de la force ionique, de la concentration initiale en glucose et de l'addition d'éthanol ou de tensioactifs non-ioniques, dans le milieu receveur de la cellule de Franz, a été étudié. CONCLUSION: Le milieu de survie doit maintenir un pH physiologique (>5.5), être isotonique par rapport aux cellules de la peau (300 mOsm kg-1 ) et contenir au moins 0.5 g L-1 de glucose. Plusieurs compositions capables de maintenir le métabolisme cutané sont décrites. La conservation des explants cutanés à 4°C, durant une nuit, perturbe l'activité métabolique de la peau. Ces travaux permettent de mettre en évidence des prérequis pour la formulation de milieux de survie adaptés aux expériences.

Confocal Raman microspectroscopy for evaluating the stratum corneum removal by 3 standard methods.

BACKGROUND/AIMS: Stratum corneum (SC) removal is needed in biopharmaceutical studies or in evaluating the barrier function. The most common technique is the tape stripping method. However, it results in neither a homogeneous nor a complete removal. METHODS: The removal qualities of tape stripping, cyanoacrylate skin surface biopsy and trypsinization were estimated in vitro via histological imaging and confocal Raman microspectroscopy (CRM) and compared. In addition, the potential of the noninvasive CRM as a replacement method is discussed. RESULTS: Comparison between the 3 methods showed, as expected, that the tape stripping method did not result in a uniform removal over the whole surface even after 28 strips. The trypsinization and cyanoacrylate skin surface biopsies allowed a complete and uniform removal of the SC after defining a standard protocol (2 cyanoacrylate strips with a polymerization time of 15 min). CONCLUSION: The feasibility of CRM to control SC removal was demonstrated in vitro. Tape stripping is a simple method, but it is influenced by many extrinsic factors and axial drug quantification is difficult. With trypsinization and cyanoacrylate methods, the entire SC is removed so that quantification over the whole SC is possible but not an axial drug screening.

rhEGF microsphere formulation and in vitro skin evaluation.

An optimized process for protein encapsulation was applied to formulate epidermal growth factor (rhEGF)-poly-epsilon-caprolactone microspheres. Microparticles mean size was 3.8 microm +/- 0.2 and the encapsulation efficiency was 41.9% +/- 2.6. rhEGF recovery after the encapsulation process was approximately 70% (41.9% inside the microspheres and 30% still active in the external phase). In vitro release experiments in McIlvaine buffered solution showed a rhEGF sustained release over 4 days. Skin absorption studies conducted on full-thickness human skin using the Franz cell method showed that 20% rhEGF was released from the microspheres after 24 h exposure. Microspheres accumulated in the stratum corneum where they may act as a rhEGF reservoir. Therefore, rhEGF-PCL microparticles seemed to be promising systems due to their ability to provide locally a sustained release of rhEGF in skin layers.

Skin absorption studies of octyl-methoxycinnamate loaded poly(D,L-lactide) nanoparticles: estimation of the UV filter distribution and release behaviour in skin layers.

New formulation strategies have to be developed to limit the skin penetration of UV-filter. Nanoparticles (NP) are very suitable for that purpose. In this study, the skin distribution, at different times (1, 2 and 3 h), of octyl-methoxycinnamate (OMC) from loaded PLA-nanoparticles was compared to a classical formulation containing non-encapsulated OMC, using the Franz cell method. The results showed that the OMC penetration was clearly impeded by stratum corneum and that the major part of the OMC-NP was accumulated at the skin surface (> 80%). A significant lower OMC amount was quantified in viable skin with NP compared to the OMC emulgel. To accurately determine the real OMC amount in close contact with viable skin layers two solvents were used to extract OMC from the skin compartments. Acetone (ACET) allowed quantifying both OMC in NP and OMC released from the particles, while isopropylmyristate (IPM), a non-solvent of the NP polymer (PLA), allowed quantifying only OMC released from the particles. Using IPM as an extraction solvent, it appeared that the OMC released from NP, in contact with viable skin, was 3-fold lower than free OMC diffused from the emulgel. Lastly, a sustained release was observed when nanoparticles were used.

Percutaneous release of caffeine from microemulsion, emulsion and gel dosage forms.

The transport of caffeine to the hypodermis by an alcohol-free o/w microemulsion was investigated and compared with an aqueous gel and an o/w emulsion. The microemulsion was well characterized and in vitro diffusion measurements through pig skin having the hypodermis either kept or removed were performed in static Franz cells. The microemulsion allowed delivery of a large fraction of the caffeine in the hypodermis: 23% of caffeine reached the hypodermis after 24h diffusion, 1.3-fold larger than from the emulsion and gel dosage forms. Half this amount was stored in the hypodermis, the other half continuing its diffusion to the receptor compartment of the Franz cell.

Assessment of oil polarity: comparison of evaluation methods.

In multiple emulsion systems, oily or aqueous transfers may occur between the dispersed droplets through the continuous phase. These transfers are controlled by both the surfactant system (micellar transport), and the partial solubility of one phase in another (molecular transport). The latter could be anticipated from the knowledge of oil polarity, if this information could easily be obtained. In this work, the relative polarity of eight oils used for various purposes has been evaluated from the comparison of their dielectric requirement for solubilization, their interfacial tension and chromatographic analysis. The results showed the complementarities of HPLC analysis and interfacial tension measurements and their superiority over the solubilization method for classifying oils as a function of their polarity.

Actinide-contaminated Skin: Comparing Decontamination Efficacy of Water, Cleansing Gels, and DTPA Gels.

Skin contamination by alpha-emitting actinides is a risk to workers during nuclear fuel production and reactor decommissioning. Also, the list of items for potential use in radiological dispersal devices includes plutonium and americium. The actinide chemical form is important and solvents such as tributyl phosphate, used to extract plutonium, can influence plutonium behavior. This study investigated skin fixation and efficacy of decontamination products for these actinide forms using viable pig skin in the Franz cell diffusion system. Commonly used or recommended decontamination products such as water, cleansing gel, diethylenetriamine pentaacetic acid, or octadentate hydroxypyridinone compound 3,4,3-LI(1,2-HOPO), as well as diethylenetriamine pentaacetic acid hydrogel formulations, were tested after a 2-h contact time with the contaminant. Analysis of skin samples demonstrated that more plutonium nitrate is bound to skin as compared to plutonium-tributyl phosphate, and fixation of americium to skin was also significant. The data show that for plutonium-tributyl phosphate all the products are effective ranging from 80 to 90% removal of this contaminant. This may be associated with damage to the skin by this complex and suggests a mechanical/wash-out action rather than chelation. For removal of americium and plutonium, both Trait Rouge cleansing gel and diethylenetriamine pentaacetic acid are better than water, and diethylenetriamine pentaacetic acid hydrogel is better than Osmogel. The different treatments, however, did not significantly affect the activity in deeper skin layers, which suggests a need for further improvement of decontamination procedures. The new diethylenetriamine pentaacetic acid hydrogel preparation was effective in removing americium, plutonium, and plutonium-tributyl phosphate from skin; such a formulation offers advantages and thus merits further assessment.

Improvement of a bovine serum albumin microencapsulation process by screening design.

The first objective of this study was to prepare microspheres containing a model protein by double emulsion-solvent evaporation/extraction method. This method was modified to consider the fragile nature of proteins. These modifications related to the reduction of polymer loss, of agitation duration and of contact time between protein and solvent. The polymer used was poly(epsilon-caprolactone) and the model protein was bovine serum albumin. The control of the microsphere properties constituted a second objective of this project. A screening design methodology was used to evaluate the effects of the process and formulation variables on microsphere properties. Twelve operating factors were retained, and the particle properties considered were the mean size, the encapsulation efficiency, and the surface state. The statistical analysis of the results allowed determining the most influent factors. Considering the whole results, it appeared that the polymer concentration, the osmotic pressure equilibrium and the volume of the inner, outer and organic phases were the most important parameters. Following this screening study, it was possible to produce particles of small size with high entrapment efficiency (near to 80%) and smooth surface. A good batch to batch reproductibility was obtained.

Penetration and decontamination of americium-241 ex vivo using fresh and frozen pig skin.

Skin contamination is one of the most probable risks following major nuclear or radiological incidents. However, accidents involving skin contamination with radionuclides may occur in the nuclear industry, in research laboratories and in nuclear medicine departments. This work aims to measure the penetration of the radiological contaminant Americium (241Am) in fresh and frozen skin and to evaluate the distribution of the contamination in the skin. Decontamination tests were performed using water, Fuller's earth and diethylene triamine pentaacetic acid (DTPA), which is the recommended treatment in case of skin contamination with actinides such as plutonium or americium. To assess these parameters, we used the Franz cell diffusion system with full-thickness skin obtained from pigs' ears, representative of human skin. Solutions of 241Am were deposited on the skin samples. The radioactivity content in each compartment and skin layers was measured after 24 h by liquid scintillation counting and alpha spectrophotometry. The Am cutaneous penetration to the receiver compartment is almost negligible in fresh and frozen skin. Multiple washings with water and DTPA recovered about 90% of the initial activity. The rest remains fixed mainly in the stratum corneum. Traces of activity were detected within the epidermis and dermis which is fixed and not accessible to the decontamination.

Hairy skin exposure to VX in vitro: effectiveness of delayed decontamination.

The chemical warfare agents such as VX represent a threat for both military and civilians, which involves an immediate need of effective decontamination systems. Since human scalp is usually unprotected compared to other body regions covered with clothes, it could be a preferential site of exposure in case of terrorist acts. The purpose of this study was to determine if skin decontamination could be efficient when performed more than 1h after exposure. In addition, the impact of hairs in skin contamination was investigated. By using in vitro skin models, we demonstrated that about 75% of the applied quantity of VX was recovered on the skin surface 2h after skin exposition, which means that it is worth decontaminating even if contamination occurred 2h before. The stratum corneum reservoir for VX was quickly established and persistent. In addition, the presence of hairs modified the percutaneous penetration of the nerve agent by binding of VX to hairs. Hair shaft has thus to be taken into account in the decontamination process. Reactive Skin Decontamination Lotion (RSDL) and Fuller's Earth (FE) were active in the skin decontamination 45min post-exposure, but RSDL was more efficient in reducing the amount of VX either in the skin or in the hair.

Human scalp permeability to the chemical warfare agent VX.

The use of chemical warfare agents such as VX in terrorism act might lead to contamination of the civilian population. Human scalp decontamination may require appropriate products and procedures. Due to ethical reasons, skin decontamination studies usually involve in vitro skin models, but human scalp skin samples are uncommon and expensive. The purpose of this study was to characterize the in vitro permeability to VX of human scalp, and to compare it with (a) human abdominal skin, and (b) pig skin from two different anatomic sites: ear and skull roof, in order to design a relevant model. Based on the VX skin permeation kinetics and distribution, we demonstrated that (a) human scalp was significantly more permeable to VX than abdominal skin and (b) pig-ear skin was the most relevant model to predict the in vitro human scalp permeability. Our results indicated that the follicular pathway significantly contributed to the skin absorption of VX through human scalp. In addition, the hair follicles and the stratum corneum significantly contributed to the formation of a skin reservoir for VX.

Skin contamination by radiopharmaceuticals and decontamination strategies.

The aim of the present study was to evaluate the percutaneous penetration of five common radiopharmaceuticals ((99m)Tc, (67)Ga, (125)I, (111)In and (51)Cr) and to evaluate the effect of decontamination by a detergent solution dedicated to hospital institutions for that purpose. The skin kinetic profiles were established by using the in vitro Franz cell method over 24h. The skin distribution in each skin layer was quantified after 6h exposure time and the efficacy of the detergent solution to remove radionuclides was evaluated also after 6h. The most striking result was the repartition into two classes of kinetic profiles: (125)I and (99m)Tc permeated quickly (∼60% of applied activity after 24h) while the 3 other radionuclides permeated slowly (from ∼2.75% for (67)Ga to ∼10% of applied activity for (111)In). The lag times, i.e. the time necessary to cross the skin varied from 20min for (99m)Tc to 5h for (51)Cr, which accumulated in skin compartments. Skin washings with the detergent solution were particularly efficient for this radionuclide, contrary to the others for which the washing procedure should be applied earlier. The permeation of ions was dependent on their chemical and physical forms and on their salting-in or salting-out effects (coordination state and Hofmeister series).