Zielsetzung dieser Arbeit war es, das Verhalten der in modernen Sonnenschutzmitteln eingesetzten Titandioxid-Mikropartikel mit quantitativen Methoden zu bestimmen, um Aussagen über ihre Eignung zu erhalten. Dabei stand die Frage nach der Verteilung der Substanz innerhalb des Stratum corneum im Mittelpunkt der Untersuchungen. Insbesondere war wegen der bekannten photokatalytischen Aktivität von Titandioxid zu klären, ob ein Kontakt mit den lebenden Bereichen der Haut ausgeschlossen werden kann. Für die Messungen wurden zwei kommerziell genutzte, unterschiedlich beschichtete Titandioxid-Mikropartikel eingesetzt. Eine wesentliche Voraussetzung für diese Untersuchungen war die Anwendung der Abrissmethode (Tape stripping) in Kombination mit der spektroskopischen Bestimmung der Extinktion im sichtbaren Bereich zur Berechnung des Hornschichtprofils. Die Konzentration der Titandioxid-Partikel wurde mit Hilfe von Röntgenfluoreszenz-Messungen bestimmt. So war es erstmals möglich, in vivo standardisierte und reproduzierbare Untersuchungen zum Penetrationsverhalten von beschichteten Titandioxid-Mikropartikeln in die Hornschicht der menschlichen Haut durchzuführen. Durch Langzeitapplikation der Substanzen und die Beobachtung der Titandioxid-konzentrationen in der Hornschicht über mehrere Tage konnten auch Aussagen zum Penetrationsverhalten der applizierten Mikropartikel gemacht werden. Es wurde eindeutig gezeigt, dass die untersuchten Substanzen unabhängig von ihrer Struktur, von ihrer Beschichtung und vom Probanden hauptsächlich in den obersten Schichten des Stratum corneum lokalisiert sind. Nach Klärung dieser grundsätzlichen Fragen war es notwendig, die Ursache für das Auftreten extrem geringer Titandioxid-Konzentrationen auf Abrissen zu bestimmen, die aus tieferen Schichten des Stratum corneum entnommen wurden. Durch die Kombination der Abrissmethode mit einem speziellen Färbeverfahren und der Laser-Scan-Mikroskopie ergaben sich deutliche Hinweise auf die Bedeutung der Follikelkanäle für das beobachtete Phänomen. Röntgenspektroskopische Untersuchungen an Biopsien zeigten, dass diese Mikropartikel in die Haarfollikel eindringen und damit Bereiche unterhalb des Stratum corneum erreichen. Hierbei wurden die Mikropartikel in dieser Region nur in Follikelkanälen, nicht aber im Bereich der lebenden Zellen nachgewiesen. Diese Ergebnisse belegen, dass Titandioxid nur in einzelne Follikelkanäle penetriert, eine Aussage, die im Rahmen der vorliegenden Untersuchungen erstmals beschrieben wurde. In Übereinstimmung mit der Zielsetzung der Arbeit konnte unter Einsatz unterschiedlicher Untersuchungsmethoden gezeigt werden, dass die beschichteten Titandioxid-Mikropartikel im oberen Bereich der Hornschicht lokalisiert sind und damit als hocheffiziente Lichtschutzfilter den Schutz der darunter liegenden lebenden Bereiche der Haut garantieren. Der sichere Nachweis der Titandioxid-Mikropartikel innerhalb einzelner Follikelkanäle besitzt grundsätzliche Bedeutung für das Verständnis von Penetrationswegen. / The objective of this work was to determine the behaviour of titanium dioxide microparticles, used in modern sunscreen agents, with quantitative methods in order to receive statements about their suitability. The focal point of the investigations was the question on the distribution of the substance within the stratum corneum. Because of the well-known photocatalytic activity of titanium dioxide, our aim was to clarify whether a contact with the living cells of the skin could be excluded. For these measurements, two commercial titanium dioxide micro particles were used, covered with different coating materials. The calculation of the stratum corneum profile was a substantial prerequisite for these investigations. This was done by application of the tape stripping method in combination with the spectroscopic determination of the absorption in the visible range. The concentration of the titanium dioxide particles on the tape strips was determined by X-ray fluorescence measurements. In this manner it was possible for the first time, to perform standardized and reproducible in vivo measurements to investigate the penetration behaviour of coated titanium dioxide micro particles into the horny layer of the human skin. Predications could be made about the penetration behaviour of the applied micro particles by observation of the titanium dioxide concentrations in the stratum corneum during several days after long-term application of the substances. It could be shown that the examined substances were localized mainly in the upper layers of the stratum corneum, independently of their structure, coating and the volunteers. After clarifying these basic questions, it was necessary to explain the occurrence of extremely small concentrations of titanium-dioxide on tape strips, which were taken from deeper layers of the stratum corneum. This observed phenomenon was investigated by combining tape stripping with a selective staining of the tapes and with laser scanning microscopy. Investigations of a biopsy with x ray fluorescence measurements showed that the micro particles penetrate into the hair follicles, and in this manner reached areas below the stratum corneum. In this region, the micro particles were found only in follicle channels, but not within the area of the living cells. These results prove that titanium dioxide micro particles only penetrate into single follicle channels, a statement, which has been described here for the first time. In agreement with the objective of this thesis, it was shown, that the coated titanium dioxide micro particles were localized within the upper area of the horny layer and as high efficient sunscreen filters consequently guarantee, the protection of the living areas of the skin below. The proof of the titanium dioxide micro particles within individual follicle channels has basic importance for the understanding of the penetration pathways.

Skin, more specifically the outermost skin layer, the stratum corneum (SC), forms an extremely effective barrier, preventing both the loss of heat and water, and the ingress of micro-organisms and chemicals. Assessing the rate and extent of drug permeation into or through the skin is important both to evaluate the usefulness of a drug for topical or transdermal delivery, and to compare different formulations to assess their bioequivalence. Prediction of drug permeation is logistically, ethically and economically preferable to in vivo measurements. The recent progress that has been made with empirical and mechanistic mathematical models, along with in vitro diffusion cell techniques has been reviewed. However, currently, in vivo measurements, in man, are still required. For new chemical entities, the need for clinical trials is clear. In the case of generic products, however, there is considerable effort currently being expended to replace expensive, subjective clinical trials with objective, validated measurements of drug permeation, in vivo, in particular to assess bioequivalence. The tape stripping technique has emerged as a promising technique to objectively measure drug permeation through skin, and is the focus of this thesis. After formulation application and removal, layers of SC are sequentially removed by adhesive tapes. As the SC performs the main barrier function of the skin, measuring the rate and extent of drug permeation through this layer is assumed to be related to overall topical bioavailability. The work in this thesis concentrates on performing tape stripping studies such that all tapes are analysed individually, and drug concentration as a function of SC depth is measured. The concentration depth profiles across the SC may be fitted to an appropriate solution of Fick's second law of diffusion to obtain estimates of the vehicle-SC partition coefficient and the drug's diffusivity in the membrane. These dermato-pharmacokinetic parameters may be compared for different formulations.

The world-wide transdermal drug delivery market is quite large, but only a small number of agents have FDA approval. The primary reason for such limited development is the difficulty in permeating the stratum corneum layer of human skin. In our study, we developed a novel percutaneous delivery enhancing approach. Magainin peptide was previously shown to disrupt vesicles from stratum corneum lipid components and this ability of magainin allows us to propose that magainin can increase skin permeability. Therefore, we tested the hypothesis that magainin, a pore-forming peptide, can increase skin permeability by disrupting stratum corneum lipid structure and that magainin¡¯s enhancement requires co-administration of a surfactant chemical enhancer to increase magainin penetration into the skin. In support of these hypotheses, synergistic enhancement of transdermal permeation can be observed with magainin peptide in combination of N-lauroyl sarcosine (NLS) in 50% ethanol-PBS solution. The exposure to NLS in 50% ethanol solution increased in vitro skin permeability to fluorescein 15 fold and the addition of magainin synergistically increased skin permeability 47 fold. In contrast, skin permeability was unaffected by exposure to magainin without co-enhancement by NLS-ethanol. To elucidate the mechanism of this synergistic effect, several characterization methods such as differential scanning calorimetry, Fourier transform infrared spectroscopy, and X-ray diffraction were applied. These analyses showed that NLS-ethanol disrupted stratum corneum lipid structure and that the combination of magainin and NLS-ethanol disrupted stratum corneum lipids even further. Furthermore, confocal microscopy showed that magainin in the presence of NLS-ethanol penetrated deeply and extensively into stratum corneum, whereas magainin alone penetrated poorly into the skin. Together, these data suggest that NLS-ethanol increased magainin penetration into stratum corneum, which further increased stratum corneum lipid disruption and skin permeability. Finally, skin permeability was enhanced by changing the charge of magainin peptide via pH change. We modulated pH from 5 to 11 to change the magainin charge from positive to neutral, which decreased skin permeability to a negatively charged fluorescein and increased skin permeability to a positively charged granisetron. This suggests that an attractive interaction between the drug and magainin peptide improves transdermal flux.

Hypertrophic scarring is a common occurrence for severe burn victims leading to major functional, physiological, and aesthetic effects to the patients. Limiting the hypertrophic scarring of the patients alleviates the functional, physiological, and aesthetic effects. Silicone gels, over the past decade, have been widely used to remediate and limit hypertrophic scarring but the mechanism of action is yet to be determined. One explanation has been that hydration of the outermost area of the burn is induced by the silicone gel . However, non-silicone polymers which increase hydration could not mimic the effect. An alternative interpretation is that there may be silicone species that migrate from the silicone gel into the viable tissue to mediate reactions in the extra-cellular matrix that result in a decreased deposition of excessive amounts of collagen - a central feature of the hypertrophic scar. A novel and informative technique to study these species is MALDI-TOF/MS (Matrix Assisted Laser Desorption Ionisation-Time of Flight Mass Spectrometry) in conjunction with gel permeation chromatography. MALDI-TOF/MS, which has allowed the detection of intact molecular species that were not possible with more established mass spectrometric techniques. The mobile species that may migrate from polydimethylsiloxane medical gel sheeting into skin have been identified by MALDI-MS. The bulk gel contains predominantly cyclic oligomers with a mass distribution peaking at n = 19 (number of repeating siloxane units), but in an aqueous environment the species at the surface of the silicone medical gel are predominantly methyl/methylol-terminated linear siloxanes. By using a gelatine matrix as a model substrate, the distribution of silicon after application of the silicone gel for 16 weeks was determined by Energy-dispersive X-Ray mapping of the sectioned gelatine. The association of the linear and cyclic oligomers with proteins relevant in hypertrophic scarring are considered. The mobility of silicone species across stratum corneum was confirmed by Attenuated Total Reflectance Fourier Transform Infrared spectroscopy (ATR-FT/IR). This method confirms our hypothesis that not only are the low molecular weight silicone species mobile, but also that they do traverse the natural barrier, the stratum corneum, to levels that are detectable by ATR after a continuous application over approximately 11 days. Invitro studies of the effects of LMWS on primary line fibroblast cells indicate a response that down regulates the proliferation of fibroblast cells and protein production. Preliminary results indicate that a family of pendant functional LMWS are effective in down regulating hypertrophic-derived fibroblast primary cells. Studies on hypertrophic scar tissue treated with silicone medical gel indicate that LMWS permeate across the stratum corneum into viable scar tissue. In some areas, the LMWS tend to pool as detected by SEM/EDX elemental silicon analysis. These areas of LMWS pooling tend to be composed of highly disorganised collagen nodules.

Abstract Protecting human skin against harmful UV radiation from the sun is an acute problem nowadays. Due to decreased thickness of the ozone layer, more UV light reaches the ground surface. This is one of the reasons of increased frequency of skin diseases. Titanium dioxide (TiO2) nanoparticles are embedded with sunscreens into the skin to attenuate UV radiation through absorption and scattering. The effectiveness of the interaction between particles and UV light depends on nanoparticle sizes. The aim of the study is to predict how the optical properties of the superficial layer of the human skin (stratum corneum) can be modified by means of nanoparticles, assuming that these particles are spheres and do not aggregate (this is achieved by application of some modern treatment techniques). In-depth distribution of TiO2 particles embedded into the skin after multiple applications of sunscreens was determined experimentally using the tape-stripping technique. A computer code implementing the Monte Carlo method was developed to simulate photon migration within the 20-μm thick horny layer partially filled with nano-sized TiO2 spheres, 35–200 nm in diameter. Dependencies of UV radiation of two wavelengths (310 and 400 nm) absorbed by and totally reflected from, as well as transmitted through the horny layer on the size of TiO2 particles were obtained and analyzed. Silicon nanoparticles of the same diameters were considered for comparison. The most attenuating particles were found for both cases. The harmful side-effect of UV light absorption by TiO2 particles is the generation of free radicals. Study of this phenomenon, using an electron paramagnetic resonance technique, was also carried out in this thesis. Comparison of the strength of the effect was done for two particle sizes administered onto either glass slides or porcine ear skin.

La peau est une interface essentielle entre le corps humain et son environnement externe. Au-delà du rôle de couche protectrice contre les agressions externes (mécaniques, thermiques, chimiques…), elle dispose de multiples fonctions de régulation comme l’absorption, la thermorégulation ou la synthèse d’hormones. L’étude de cette interface cutanée est importante, non seulement pour les spécialistes cliniques, mais également pour les chercheurs travaillant dans la compréhension des mécanismes des processus de transfert transcutanés. Longtemps considéré comme une simple couche de cellules mortes, le stratum corneum (SC, couche de la peau la plus externe) était considéré alors comme un acteur secondaire dans ces processus. Des études récentes montrent au contraire que cette couche cutanée, d’une épaisseur pouvant aller de 10 à 40 µm, joue un rôle primordial et déterminant. Ces études révèlent une architecture complexe, qui peut être représentée schématiquement par un empilement de cellules protéiniques (les cornéocytes) situées dans une matrice extracellulaire riche en lipides. Cette couche compacte est loin d’être complètement imperméable aux substances chimiques directement appliquées sur la peau. Nous proposons ici une approche physico-chimique visant à mettre en évidence les mécanismes d’interactions acide-base agissant à l’extrême surface du SC (i.e. une dizaine d’Angströms). En utilisant : i) les réactions de transfert de protons comme “sonde” et ii) une démarche multi-échelles basée sur des titrations de surface par angles de contact et par forces chimiques, nous déterminons quantitativement le rôle de chacune des composantes du SC (i.e. cornéocytes et lipides) dans ce type d’interactions. / Stratum corneum (SC) is a heterogeneous tissue composed of lipid-depleted corneocytes embedded in a lipid-enriched extracellular matrix. It comes from the epidermal differentiation of the skin. The wetting properties of this upper layer are of major interest in the understanding of interfacial phenomena, such as adhesion of microorganisms or proliferation of resident flora. Until now, the wettability behaviour has been characterized through different parameters such as surface energy, critical surface tension, or hydrophilia, via macroscopic contact angle measurements. But this method does not allow to discriminate the effect of the corneocytes with the one of the extracellular matrix on the final surface properties, because of the size of the liquid drop. This work, performed in vitro on human skin explants provided by Pierre Fabre Dermo-Cosmetics, consists in understanding the wetting properties of the SC from macroscopic and nanoscopic points of view. Initially, it is compulsory to thoroughly describe at different scales the physical chemistry of our material, i.e. in vitro SC. Then, knowing that macroscopic contact angles are sensitive to the pH of the liquid probe, the first aim of this work is to determine the “macroscopic pKa values” of the SC, both in vitro and in vivo. Consequently, dynamic contact angles are measured between test-liquid drops (aqueous solutions ranging from pH 1 to pH 13) and the SC in order to obtain the contact angle titration curve of the SC. The same procedure is applied in vivo on SC suffering from skin dryness (xerosis), the results being compared to those obtained previously on safe skin. The second purpose of this study is to reach the pKa values of the different functional groups located on the complex-cornified envelope. This consists in measuring adhesion forces between an AFM (Atomic Force Microscopy) tip (functionalized with specific groups, such as amine, carboxylic acid, hydroxyl, methyl or amide groups) and single-isolated corneocytes through buffered liquid media (ranging from pH 1 to pH 13). As previously, such titration curves are realised on corneocytes coming from safe skin, but also from dry skin. The variations observed in the contact angle titration and chemical force titration curves will be discussed in terms of acid-base, electrostatic interactions and hydrogen bondings. The comprehension of the pH-dependent properties of the SC shall provide a better understanding of the role of individual corneocytes in the final surface properties of the SC.

Erhöhte Hautoberflächen-pH-Werte werden bei atopischer Dermatitis beobachtet.Störungen der pH-Regulation, insbesondere eine unzureichende Azidifizierug des Stratum corneum, werden mit der Störung der epidermalen Barrierefunktion bei atopischer Dermatitis als pathogenetischer Faktor diskutiert.Zielsetzung der vorliegenden Arbeit war die Klärung der Frage, ob Störungen der pH-Regulation schon unmittelbar im Verlauf der postpartalen Phase bei Neugeborenen nachweisbar sind. Ferner sollte geklärt werden, ob der Hautoberflächen-pH-Wert als Prädiktor der atopischen Dermatitis herangezogen werden kann.Es wurden 108 Säuglinge der Entbindungsstation des Städtischen Klinikums Gütersloh im postpartalen Verlauf (4 bis 7 Tage,sowie 6, 12 und 24 Wochen nach der Geburt) mittels Hautoberflächen-pH-Messung und Corneometrie (24 Woche postpartum) untersucht. Es wird gezeigt, dass der Hautoberflächen-pH-Wert atopisch disponierter Säuglinge und von Säuglingen ohne atopische Disposition keinen signifikanten Unterschied im postpartalen Verlauf aufweist.Dagegen zeigten atopisch disponierte Säuglinge einen deutlich niedrigeren Wert der Stratum-corneum-Hydratation (Corneometrie). Die Ergebnise lassen den Schluß zu, dass der Barrierefunktionsstörung der atopischen Dermatitis keine primäre pH-Regulationsstörung zugrunde liegt. Die Messung der Hautoberflächen-pH eignet sich nicht zur Früherkennung der atopischen Dermatitis.

The major hurdle in the development of transdermal route as a versatile drug delivery method is the formidable transport barrier provided by the stratum corneum. Despite decades of research to overcome the stratum corneum barrier, limited success has been achieved. The objectives of this research were to develop and characterize two different strategies to overcome the stratum corneum barrier for transdermal delivery of biopharmaceuticals and vaccines. In the first strategy, coated microneedles (sharp-tipped, micron-sized structures) were developed to enable delivery of drugs directly into the skin by bypassing the stratum corneum barrier. In the second strategy, instead of bypassing the barrier, microdermabrasion was used to selectively abrade stratum corneum with sharp microparticles for topical drug application. Coated microneedles For developing painless microneedles, the first detailed study was performed to characterize the effect of microneedle geometry on pain caused by microneedle insertions in human volunteers. This study demonstrated that microneedles are significantly less painful than a 26-gage hypodermic needle and that decreasing microneedle length and numbers reduces pain. Next, the first in-depth study of microneedle coating methods and formulations was performed to (i) develop a novel micron-scale dip-coating process, (ii) test the breadth of compounds that can be coated onto microneedles, and (iii) develop a rational basis to design novel coating formulations based on the physics of dip-coating. Finally, a plasmid DNA-vaccine was coated onto microneedles to immunize mice, to provide the first evidence that microneedle-based skin immunization can generate a robust in vivo antigen-specific cytotoxic-T-lymphocyte response using similar, or lower, DNA doses on microneedles as when using the gene gun or intramuscular injection. Microdermabrasion We demonstrated for the first time that microdermabrasion in monkeys and humans can selectively, yet completely remove the stratum corneum layer. Using a mobile mode of microdermabrasion, an increase in the number of treatment passes led to greater tissue removal. Furthermore, topical application of Modified Vaccinia Ankara virus after microdermabrasion induced virus-specific antibodies in monkeys. In conclusion, both coated microneedles and microdermabrasion were developed to enable delivery of biomolecules into the skin, indicating their potential for transdermal delivery of a wide range of biopharmaceuticals and vaccines.

Microemulsions (MEs) are dispersed systems, thermodynamically stable, isotropic, transparent, and stabilized by an interfacial film of surfactant compounds. In this study were obtained MEs from differents co - surfactant (ethanol - ET, isopropanol-ISO and propylene glycol - PG), Citrus sinensis (L.) Osbeck essential oil (CSEO), Tween 80 ® and phosphate buffer (pH 5.0). The co - surfactants were selected because they are tolerated by the skin. Therefore, the aim of the study was to evaluate the influence of co - surfactants in the formation of MEs containing Tween 80, CSEO and evaluate the influence of nifedipine (NFD) in the structure of systems formed. The MEs were obtained by constructing diagrams of pseudo-ternary phase in order to evaluate the influence of co-surfactant in the formation of MEs. The structural characterization of these systems was obtained by Polarized Light Microscopy (MLP), test electrical conductivity and Small angle X-ray scattering (SAXS). In each diagram, two formulations were selected, which was the criterion sense phase, in the O / A and bicontinuous, in which the NFD is incorporated. The formulations were evaluated by the techniques mentioned, to observe the influence of NFD and characterized by pH, droplet size, polydispersity index (PDI), surface tension and rheology. Interaction studies with model stratum corneum (SC) were performed using the techniques of differential scanning calorimetry (DSC) and Fourier transform infrared spectroscopy (FTIR). In the diagrams showed the greatest formation region of the MEs to the ISO (above 40 % T / Cot) instead of the co- surfactants ET and PG. When assessing the electrical conductivity has been observed that increasing the aqueous fraction resulted in an increase in conductivity. The SAXS curves demonstrated that all systems are characteristic of micellar structures and as the water content was added, it was observed the formation of larger structures. Therefore, from the results obtained, the NFD has been incorporated in the formulations selected. The MEs presented as stable systems, isotropic, translucent droplet size between 16 and 34 nm, PDI below 0.5 and pH in the range of 5.64 to 6.7, compatible with the skin and pH stability of the NFD. In conductivity tests for each co - surfactant, the MEs were classified as bicontinuous and O / A. The MEs exhibited reduced surface tension and the formulations containing ISO submitted a surface tension value (24,764 mN / m) lower than the other co - surfactants (ET - 29.512 mN/m PG - 31.784 mN/m), confirmed by the evaluation of the droplet diameter and obtaining the phase diagram. The MEs exhibited Newtonian behavior, with consistency indices (k) higher in formulations with higher proportions of T / Cot, result corroborated the structures observed by SAXS. The DSC and FTIR techniques have demonstrated the use of the MEs as permeation promoters, provided from interactions with SC model. Therefore, the diagrams have elucidated the effect of co- surfactant in the formation of MEs and the same interference suffered no NFD, suggesting their use as permeation enhancers on the skin on application. / As microemulsões (MEs) são sistemas dispersos, termodinamicamente estáveis, isotrópicos, transparentes, estabilizados por um filme interfacial de compostos tensoativos. Neste trabalho foram obtidas MEs a partir de diferentes co-tensoativos (etanol-ET, isopropanol-ISO e propilenoglicol-PG), óleo essencial de Citrus sinensis (L.) Osbeck (OECS), Tween 80® e tampão fosfato (pH 5.0). Os co-tensoativos foram selecionados por serem toleráveis pela pele. Assim, o objetivo deste trabalho foi avaliar a influência dos co-tensoativos na formação de MEs contendo Tween 80, OECS bem como avaliar a influência da nifedipina (NFD) na estrutura dos sistemas formados. As MEs foram obtidas pela construção de diagramas de fase pseudoternário com o propósito de avaliar a influência do co-tensoativo na zona de formação das MEs. A caracterização estrutural desses sistemas foi realizada por Microscopia de Luz Polarizada (MLP), ensaios de condutividade elétrica e espalhamento de raios-X a baixo ângulo (SAXS). De cada diagrama, foram selecionadas duas formulações, cujo critério foi o sentido de fases, na região de óleo-água (O/A) e bicontínuas, nas quais a NFD foi incorporada. As formulações foram reavaliadas pelas técnicas citadas, a fim de observar a influência da NFD, além de caracterizadas por pH, tamanho de gotícula, índice de polidispersividade (IPD), tensão superficial e reologia. Estudos de interação com modelo de estrato córneo (EC) foram realizados através das técnicas de Calorimetria exploratória diferencial (DSC) e Espectroscopia na região de infravermelho com transformada de Fourier (FTIR). Nos diagramas foi observada uma maior região de formação das MEs para o ISO (acima de 40% de T/Cot) ao contrário dos co-tensoativos ET e PG. Ao avaliar a condutividade elétrica foi observado que o aumento da fração aquosa proporcionou um aumento na condutividade. As curvas de SAXS demonstraram que todos os sistemas foram característicos de estruturas micelares e à medida que o conteúdo aquoso foi adicionado, observou-se a formação de estruturas com maiores dimensões. Logo, a partir dos resultados obtidos, a NFD foi incorporada nas formulações selecionadas. As MEs apresentaram-se como sistemas estáveis, isotrópicos, translúcidos, tamanho de gotículas entre 16 e 34 nm, IPD abaixo de 0,5 e pH na faixa de 5,64 a 6,07, compatíveis com a pele e pH de estabilidade da NFD. Nos ensaios de condutividade para cada co-tensoativo, as MEs foram classificadas como bicontínuas e O/A. As MEs apresentaram redução da tensão superficial, sendo que as formulações contendo ISO apresentaram um valor de tensão (24,764 mN/m) inferior aos demais co-tensoativos (ET- 29,512 mN/m e PG- 31,784 mN/m), confirmado pela avaliação do diâmetro de gotas e obtenção do diagrama de fases. As MEs apresentaram comportamento newtoniano, com os índices de consistência (k) maiores nas formulações com proporções mais elevadas de T/Cot, resultado que corroborou com as estruturas observadas por SAXS. As técnicas de DSC e FTIR demonstraram a utilização das MEs como promotores de permeação, a partir das interações proporcionadas com modelo de EC. Logo, os diagramas elucidaram a influência do co-tensoativo na área de formação de MEs e os mesmos não sofreram interferência da NFD, sugerindo a sua utilização como promotores de permeação em aplicação sobre a pele.

Made available in DSpace on 2014-07-29T15:07:11Z (GMT). No. of bitstreams: 1 dissertacao Heverton.pdf: 3726246 bytes, checksum: d1604716538cf27f6497805271c49501 (MD5) Previous issue date: 2009-03-31 / Terpenes are a very promising class of skin penetration enhancers especially due to their low potential of irritation in the skin. In this work, we have used the electron paramagnetic resonance (EPR) spectroscopy of the small spin label di-tert-butyl nitroxide (DTBN), which partitions the aqueous and hydrocarbon phases, to study the interaction of the terpenes ®-terpineol, 1,8-cineole, L(-)-carvone and (+)-limonene with the uppermost skin layer, the stratum corneum, and the membrane models of 1,2-dipalmitoyl-sn-glycero- 3-phosphatidylcholine (DPPC) and 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC). The EPR spectra indicated that the terpenes increase both the partition coe±cient and the rotational di®usion rate of the spin labels in the stratum corneum membranes whereas for DMPC and DPPC bilayers were observed similar e®ects only at temperatures below the liquid-crystalline phase. The EPR parameter associated to probe polarity inside the membranes showed thermotropic induced changes, suggesting relocations of spin probe, which were dependent of the membrane phases. While DMPC and DPPC bilayers showed abrupt changes in the partitioning and rotational correlation time parameters at the phase transitions, the SC membranes were characterized by slights changes in whole interval of measured temperatures, presenting the greatest changes or membranes reorganizations in the temperature range of v50 to v74±C. The results suggest that the terpenes act as spacers that weaken the hydrogen-bonded network at the polar interface thus °uidizing the stratum corneum lipids and, in consequence, increase the permeation of small polar molecules across the membranes. 2 / Os terpenos são uma classe muito promissora de facilitadores de permeação da pele devido aos seus baixos potenciais de irritação na pele. Neste trabalho utilizamos a espectroscopia de ressonância paramagnética eletrônica (RPE) do pequeno marcador de spin di-terc-butil nitróxido (DTBN) que particiona na fase aquosa e hidrocarbônica, para estudar a interação dos terpenos ®-terpineol, 1,8-cineol, L(-)-carvona e (+)-limoneno com a camada superior da pele, o estrato córneo, e membranas modelos de 1,2-dimiristoil-sn- glicero-3-fosfocolina (DMPC) e 1,2-dipalmitoil-sn-glicero-3-fosfocolina (DPPC). Os espectros de RPE indicaram que os terpenos aumentam o coeficiente de partição e a taxa de difusão rotacional do marcador de spin nas membranas de estrato córneo, enquanto que para as bicamadas de DMPC e DPPC o efeito foi semelhante somente nas temperaturas abaixo da fase líquido-cristalina. O parâmetro de EPR associado µa polaridade do marcador de spin no interior das membranas mostrou mudanças induzidas termotropicamente, sugerindo que a posição média da molécula marcada muda com a temperatura e fases das membranas. Enquanto as bicamadas de DMPC e DPPC mostraram abruptas mudanças nos parâmetros da partição e do tempo de correlação rotacional com as transições de fase, as membranas de EC forão caracterizadas por suaves mudanças em todo o intervalo de temperatura medido, apresentando as maiores mudanças ou reorganizações das membranas na faixa de temperatura de ~50 a ~74°C. Os resultados sugerem que a terpenos atuando como espaçadores dos lipídios que compõem as membranas, enfraquecem as redes de ligações de hidrogênio na interface polar, e isto leva a um aumento da °uidez dos lipídios do estrato córneo e, em consequência, a uma maior permeação de moléculas polares através das membranas.