Due to the immuncompromised status of AIDS patients, secondary infections and malignancies are common. Conditions secondary to AIDS for which patients require treatment include Karposi's sarcoma (treated with methotrexate), varicella-zoster (treated with antivirals such as acyclovir) and herpes simplex (also treated with antivirals like acyclovir or idoxuridme). However the clinical efficacy of these drugs is limited by poor skin permeability. Few reports, however, have dealt with the delivery of low molecular weight hydrophilic drugs from these vesicles (El Maghraby et al, 2000). The aim of our study was to investigate in vitro permeation of methotrexate, acyclovir and idoxuridine across human epidermal membrane from elastic liposomes. The intent was to establish whether formulation of these hydrophilic drugs into elastic liposomes would enhance their skin permeation parameters. We developed and validated high-performance liquid chromatographic techniques for quantitative analysis of methotrexate, idoxuridine and acyclovir. Elastic liposomes were prepared from various phospholipids- phosphatidylcholine 78.6%; phosphatidylcholine 50%; hydrogenated phosphatidylcholine 90%; phosphatidylcholine 95% and surfactants - sodium cholate, sodium deoxycholate, Span 20, 40, 60, 80. These vesicles were characterised by transmission electron microscopy. The solubilities of methotrexate, acyclovir and idoxuridine were determined. Phospholipon G (95% phosphatidylcholine) was chosen for the preparation of the liposomes with different surfactants. Permeation of methotrexate, acyclovir and idoxuridme from these vesicles across human epidermal membrane was investigated. Flux values for methotrexate, acyclovir and idoxuridine values (J) obtained by curve-fitting of data using Easyplot were compared to those obtained by linear regression. We used Student's t-test to determine statistically significant differences in the flux values of the formulations. A computer program http://www.physics.csbsju.edu/stats/ttest- bulk-form.html was used for this purpose. Our results indicate that there are no statistically significant differences between flux values from elastic liposomes and saturated aqueous solutions. / Thesis (Ph.D. (Pharmaceutics))--North-West University, Potchefstroom Campus, 2004.

Due to the immuncompromised status of AIDS patients, secondary infections and malignancies are common. Conditions secondary to AIDS for which patients require treatment include Karposi's sarcoma (treated with methotrexate), varicella-zoster (treated with antivirals such as acyclovir) and herpes simplex (also treated with antivirals like acyclovir or idoxuridme). However the clinical efficacy of these drugs is limited by poor skin permeability. Few reports, however, have dealt with the delivery of low molecular weight hydrophilic drugs from these vesicles (El Maghraby et al, 2000). The aim of our study was to investigate in vitro permeation of methotrexate, acyclovir and idoxuridine across human epidermal membrane from elastic liposomes. The intent was to establish whether formulation of these hydrophilic drugs into elastic liposomes would enhance their skin permeation parameters. We developed and validated high-performance liquid chromatographic techniques for quantitative analysis of methotrexate, idoxuridine and acyclovir. Elastic liposomes were prepared from various phospholipids- phosphatidylcholine 78.6%; phosphatidylcholine 50%; hydrogenated phosphatidylcholine 90%; phosphatidylcholine 95% and surfactants - sodium cholate, sodium deoxycholate, Span 20, 40, 60, 80. These vesicles were characterised by transmission electron microscopy. The solubilities of methotrexate, acyclovir and idoxuridine were determined. Phospholipon G (95% phosphatidylcholine) was chosen for the preparation of the liposomes with different surfactants. Permeation of methotrexate, acyclovir and idoxuridme from these vesicles across human epidermal membrane was investigated. Flux values for methotrexate, acyclovir and idoxuridine values (J) obtained by curve-fitting of data using Easyplot were compared to those obtained by linear regression. We used Student's t-test to determine statistically significant differences in the flux values of the formulations. A computer program http://www.physics.csbsju.edu/stats/ttest- bulk-form.html was used for this purpose. Our results indicate that there are no statistically significant differences between flux values from elastic liposomes and saturated aqueous solutions. / Thesis (Ph.D. (Pharmaceutics))--North-West University, Potchefstroom Campus, 2004.

No / This work evaluated the in vitro transdermal iontophoretic delivery of tritiated estradiol from ultradeformable liposomes compared with saturated aqueous solution (control). Effects of current density and application time on tritium exchange with water were also determined. Penetration studies used three Protocols. Protocol I involved occluded passive steady state estradiol penetration from ultradeformable liposomes and control. The effect of current densities on drug penetration rates was also assessed (Protocol II). In Protocol III, three consecutive stages of drug penetration (first passive, iontophoresis and second passive) through the same human epidermal membranes were monitored. Such an experimental design investigated the possible effect of high current density (0.8 mA/cm2) on skin integrity. The tritium exchange study showed that extent of exchange correlated well with current density and time of application, with some shielding of estradiol by the liposomal structure. Liposomes enhanced estradiol passive penetration after occlusion. Protocol II showed that estradiol flux increased linearly with current density, although being delivered against electroosmotic flow. In Protocol III, reduction in flux of the second passive stage to near that of the first reflected a reversibility of the structural changes induced in skin by current.

No description available.

Caffeine is frequently used in cosmetics due to its well-characterised skin permeation properties and is widely incorporated in cosmetic-related products intended for skin (Samah & Heard, 2013:631). Despite its polar characteristics (Dias et al., 1999:41), caffeine is an important biologically and cosmetically active compound (Herman & Herman, 2012:13). This active pharmaceutical ingredient (API) has a broad range of advantages in the world of cosmetics, including the improvement of microcirculation in the capillaries (Lupi et al., 2007:107), showing anti-cellulite activity in the fatty tissue (Velasco et al., 2008:24), anti-oxidation activity in sunscreens & anti-ageing products (Koo et al., 2007:964) and the stimulation of hair growth (Fisher et al., 2007:27). Caffeine has also shown significant decreases in UV-induced skin tumour multiplicity (Lu et al., 2001:5003, 5008) and has been proven to prevent photo-damaged skin, which includes the formation of wrinkles and histological alterations (Mitani et al., 2007:86). It is therefore clear that the challenge for the dermal delivery of the hydrophilic caffeine is for it to be retained in the specific skin layers (dermal delivery) where it can exert its action, rather than to permeate through the skin and into the hydrophilic systemic circulation (transdermal delivery) (Wiechers et al., 2008:10). In this study the calculated skin delivery gap (SDG) values, and the transdermal and dermal delivery of caffeine from three different semi-solid topical formulations were compared. The SDG theory was developed to evaluate the effectiveness of dermal delivery of API from topical formulations and is known as the ratio between the concentration required to achieve minimum effect relative to the concentration obtained at the target site (JW Solutions, 2011). During this study the principle of the SDG was investigated by using the formulating strategy, Formulating for Efficacy (FFE™), which aims to optimise skin delivery of APIs from different formulations. The SDG was therefore implemented and in vitro transdermal studies were utilised to ultimately prove or disprove the hypothesis of SDG on the prediction of the topical delivery of caffeine. The human skin consists of two distinctive layers namely the epidermis (including the stratum corneum (SC) and viable dermis) and the dermis (Menon, 2002:S3). The main barrier to dermal and transdermal permeation is the outermost layer of the skin, the SC (Fang et al., 2007:343). The difference between the target site for dermal and transdermal delivery of APIs is crucial to be mentioned. Dermal delivery includes the delivery of an API to the skin surface, SC, viable epidermis or dermis, whereas transdermal delivery requires the API to permeate all the way through the various skin layers and into the systemic circulation (Wiechers, 2000:42). Since this study involves the optimisation of the topical delivery of caffeine, the physicochemical properties of this API as well as those of the skin should be considered. As mentioned before, caffeine is a rather polar molecule (Dias et al., 1999:41), whereas the SC (lipophilic) provides the rate-limiting barrier to the percutaneous absorption of polar (hydrophilic) molecules, such as caffeine (Barry, 1983:105). Caffeine was incorporated into three different formulations: a gel and two creams (differing only in the ratio of the primary and secondary emollient). The three topical formulations each had different polarities, where the Gel represented the hydrophilic formulation (more polar than the skin), whereas the first cream, Cream 1 (containing 5% DMI and 9% glycerine), served as the intermediate formulation (similar polarity as the SC), and the second cream, Cream 2 (10% DMI and 4% glycerine), was the formulation less polar (therefore more lipophilic) than the SC. Franz cell type transdermal diffusion studies were performed on the three semi-solid formulations (Gel, Cream 1 and Cream 2). The diffusion studies were conducted over a period of 12 h, followed by the tape stripping of the skin directly after each diffusion study. Caucasian female abdominal skin was obtained with consent from willing donors. Ethical approval for the acquisition and use of the donated skin was granted under reference number NWU-00114-11-A5. The formulations each contained 1% of caffeine as API. The skin used for the diffusion studies was prepared with the use of a Zimmer Dermatome®. The receptor phase of each Franz cell was withdrawn at predetermined time intervals and subsequently analysed with high performance liquid chromatography (HPLC) in order to determine the concentration of caffeine that permeated through the skin. Stratum corneum-epidermis (SCE) and epidermis-dermis (ED) samples were prepared and left overnight at a temperature of 4 °C, and they were analysed the following day with the use of HPLC in order to determine the concentration of caffeine that had accumulated in the particular skin layers. The SDG value for each caffeine formulation was calculated and it was compared to the flux and tape stripping results obtained from the diffusion studies. To ultimately prove or disprove the SDG theory, the skin diffusion studies and tape stripping results were used to determine whether any difference occurred in the absorption or penetration of the API from the different formulations into the skin. The formulation with the intermediate polarity (Cream 1) produced the highest transdermal flux of caffeine due to the hydrophilic and lipophilic nature of caffeine and the formulation, respectively. Cream 1 is sufficiently lipophilic to transport caffeine into the SC and at the same time sufficiently hydrophilic (more polar than Cream 2) to cause a greater driving force of caffeine through to the more hydrophilic epidermis, dermis and systemic circulation. The results from the tape stripping yielded that Cream 2 (the more lipophilic formulation) produced the highest concentration of caffeine into the SCE due to the hydrophilic and lipophilic nature of caffeine and the formulation, respectively. The difference in polarity between the formulation and the API in Cream 2 was the greatest compared to the other formulations, which significantly increased the driving force of caffeine to partition into the SC (Wiechers et al., 2004:177). The hydrophilic gel showed the highest concentration of caffeine in the ED layer of the skin due to the hydrophilic compounds formulated in the Gel, which showed greater ability to partition into the aqueous dermis and viable epidermis (Imai et al., 2013:372). Cream 2 had the lowest calculated SDG value compared to that of the Gel and Cream 1. The smaller the delivery gap, the greater the delivery of the API should be into the skin (Wiechers, 2010). Considering this, it was expected that Cream 2 would deliver greater amounts of caffeine into the skin than the more hydrophilic formulations. Cream 2, which showed the lowest calculated SDG value delivered the highest amount of caffeine into the SCE during the diffusion studies. The calculated SDG values therefore are consistent with the concentration of caffeine in the SCE (the lowest SDG value produced the highest concentration of API in the SCE). However, no correlations were found between the calculated SDG values and ED delivery or the flux of caffeine. The final conclusion for this study is that the SDG theory proved to be effective and trustworthy regarding the delivery of caffeine into the SC. / MSc (Pharmaceutics), North-West University, Potchefstroom Campus, 2014

Caffeine is frequently used in cosmetics due to its well-characterised skin permeation properties and is widely incorporated in cosmetic-related products intended for skin (Samah & Heard, 2013:631). Despite its polar characteristics (Dias et al., 1999:41), caffeine is an important biologically and cosmetically active compound (Herman & Herman, 2012:13). This active pharmaceutical ingredient (API) has a broad range of advantages in the world of cosmetics, including the improvement of microcirculation in the capillaries (Lupi et al., 2007:107), showing anti-cellulite activity in the fatty tissue (Velasco et al., 2008:24), anti-oxidation activity in sunscreens & anti-ageing products (Koo et al., 2007:964) and the stimulation of hair growth (Fisher et al., 2007:27). Caffeine has also shown significant decreases in UV-induced skin tumour multiplicity (Lu et al., 2001:5003, 5008) and has been proven to prevent photo-damaged skin, which includes the formation of wrinkles and histological alterations (Mitani et al., 2007:86). It is therefore clear that the challenge for the dermal delivery of the hydrophilic caffeine is for it to be retained in the specific skin layers (dermal delivery) where it can exert its action, rather than to permeate through the skin and into the hydrophilic systemic circulation (transdermal delivery) (Wiechers et al., 2008:10). In this study the calculated skin delivery gap (SDG) values, and the transdermal and dermal delivery of caffeine from three different semi-solid topical formulations were compared. The SDG theory was developed to evaluate the effectiveness of dermal delivery of API from topical formulations and is known as the ratio between the concentration required to achieve minimum effect relative to the concentration obtained at the target site (JW Solutions, 2011). During this study the principle of the SDG was investigated by using the formulating strategy, Formulating for Efficacy (FFE™), which aims to optimise skin delivery of APIs from different formulations. The SDG was therefore implemented and in vitro transdermal studies were utilised to ultimately prove or disprove the hypothesis of SDG on the prediction of the topical delivery of caffeine. The human skin consists of two distinctive layers namely the epidermis (including the stratum corneum (SC) and viable dermis) and the dermis (Menon, 2002:S3). The main barrier to dermal and transdermal permeation is the outermost layer of the skin, the SC (Fang et al., 2007:343). The difference between the target site for dermal and transdermal delivery of APIs is crucial to be mentioned. Dermal delivery includes the delivery of an API to the skin surface, SC, viable epidermis or dermis, whereas transdermal delivery requires the API to permeate all the way through the various skin layers and into the systemic circulation (Wiechers, 2000:42). Since this study involves the optimisation of the topical delivery of caffeine, the physicochemical properties of this API as well as those of the skin should be considered. As mentioned before, caffeine is a rather polar molecule (Dias et al., 1999:41), whereas the SC (lipophilic) provides the rate-limiting barrier to the percutaneous absorption of polar (hydrophilic) molecules, such as caffeine (Barry, 1983:105). Caffeine was incorporated into three different formulations: a gel and two creams (differing only in the ratio of the primary and secondary emollient). The three topical formulations each had different polarities, where the Gel represented the hydrophilic formulation (more polar than the skin), whereas the first cream, Cream 1 (containing 5% DMI and 9% glycerine), served as the intermediate formulation (similar polarity as the SC), and the second cream, Cream 2 (10% DMI and 4% glycerine), was the formulation less polar (therefore more lipophilic) than the SC. Franz cell type transdermal diffusion studies were performed on the three semi-solid formulations (Gel, Cream 1 and Cream 2). The diffusion studies were conducted over a period of 12 h, followed by the tape stripping of the skin directly after each diffusion study. Caucasian female abdominal skin was obtained with consent from willing donors. Ethical approval for the acquisition and use of the donated skin was granted under reference number NWU-00114-11-A5. The formulations each contained 1% of caffeine as API. The skin used for the diffusion studies was prepared with the use of a Zimmer Dermatome®. The receptor phase of each Franz cell was withdrawn at predetermined time intervals and subsequently analysed with high performance liquid chromatography (HPLC) in order to determine the concentration of caffeine that permeated through the skin. Stratum corneum-epidermis (SCE) and epidermis-dermis (ED) samples were prepared and left overnight at a temperature of 4 °C, and they were analysed the following day with the use of HPLC in order to determine the concentration of caffeine that had accumulated in the particular skin layers. The SDG value for each caffeine formulation was calculated and it was compared to the flux and tape stripping results obtained from the diffusion studies. To ultimately prove or disprove the SDG theory, the skin diffusion studies and tape stripping results were used to determine whether any difference occurred in the absorption or penetration of the API from the different formulations into the skin. The formulation with the intermediate polarity (Cream 1) produced the highest transdermal flux of caffeine due to the hydrophilic and lipophilic nature of caffeine and the formulation, respectively. Cream 1 is sufficiently lipophilic to transport caffeine into the SC and at the same time sufficiently hydrophilic (more polar than Cream 2) to cause a greater driving force of caffeine through to the more hydrophilic epidermis, dermis and systemic circulation. The results from the tape stripping yielded that Cream 2 (the more lipophilic formulation) produced the highest concentration of caffeine into the SCE due to the hydrophilic and lipophilic nature of caffeine and the formulation, respectively. The difference in polarity between the formulation and the API in Cream 2 was the greatest compared to the other formulations, which significantly increased the driving force of caffeine to partition into the SC (Wiechers et al., 2004:177). The hydrophilic gel showed the highest concentration of caffeine in the ED layer of the skin due to the hydrophilic compounds formulated in the Gel, which showed greater ability to partition into the aqueous dermis and viable epidermis (Imai et al., 2013:372). Cream 2 had the lowest calculated SDG value compared to that of the Gel and Cream 1. The smaller the delivery gap, the greater the delivery of the API should be into the skin (Wiechers, 2010). Considering this, it was expected that Cream 2 would deliver greater amounts of caffeine into the skin than the more hydrophilic formulations. Cream 2, which showed the lowest calculated SDG value delivered the highest amount of caffeine into the SCE during the diffusion studies. The calculated SDG values therefore are consistent with the concentration of caffeine in the SCE (the lowest SDG value produced the highest concentration of API in the SCE). However, no correlations were found between the calculated SDG values and ED delivery or the flux of caffeine. The final conclusion for this study is that the SDG theory proved to be effective and trustworthy regarding the delivery of caffeine into the SC. / MSc (Pharmaceutics), North-West University, Potchefstroom Campus, 2014

Vesicular delivery systems, like liposomes, represent an attractive approach to improving skin delivery of drugs. Liposomes are composed of one or several lipid bilayers surrounding an aqueous compartment. They are able to encapsulate hydrophilic compounds into their inner compartment and lipophilic compounds into their lipid bilayers. In the first part of this thesis, we developed a new dermal delivery system combining the advantages of cyclodextrin inclusion complexes and those of deformable liposomes. This system was called drugs-in-cyclodextrin-in-deformable liposome. Betamethasone was chosen as the model drug. These systems were successfully developed and characterised. In vitro diffusion studies using Franz diffusion cells and polycarbonate membranes gave promising results. In order to better mimic the in vivo conditions, ex vivo penetration studies using pig ear skin and Franz diffusion cells were developed. The tape stripping method was used to determine the amount of drug in the stratum corneum. The amount of drug in the epidermis, dermis and receptor medium was also assayed. These methods were successfully validated. Unfortunately, ex vivo penetration studies of the developed skin delivery system could not confirm the promising in vitro results. Our research was then directed towards studies allowing a better understanding of liposome skin penetration mechanisms. In the second part of this thesis, the influence of several parameters on the skin penetration behaviour of liposomes was investigated. The formulation importance on skin penetration efficiency was highlighted by the comparison of two liposomal systems. In the first system, betamethasone is encapsulated by the help of cyclodextrin inclusion complexes in the aqueous compartment. In the second system, betamethasone is encapsulated alone in the lipid bilayer. The second system shows high membrane permeability of the encapsulated betamethasone. Despite this decreased drug retention, the second system enhances the skin penetration of betamethasone. This high membrane permeability and the better penetration of the second formulation support the mechanism of penetration as a free drug substance. In addition, no difference in penetration is observed between liposomes containing betamethasone alone and a non liposomal dispersion. Several surfactants or edge activators were incorporated in the lipid bilayer of liposomes in order to obtain deformable liposomes. Unfortunately, these deformable liposomes are unable to enhance skin penetration compared to classical non deformable liposomes. The addition of charged lipids in the lipid bilayer of liposomes encapsulating either betamethasone or betamethasone dipropionate was investigated. The addition of negatively charged lipids enhances the penetration of the encapsulated drug. The use of negatively charged liposomes enhanced the epidermis accumulation of betamethasone 9.3 times compared with the ethanolic solution. This improvement is not observed with the corresponding non liposomal dispersion, indicating that the vesicle form is of high importance. In the case of the ester, the use of negatively charged liposomes enhances the epidermis accumulation 5.5 times compared with the Diprosone® lotion and only 1.6 times compared with the ethanolic solution. The penetration of a more lipophilic drug, with a high intrinsic penetration, is less enhanceable when incorporated in liposomes. Confocal microscopy was performed to visualise skin penetration of fluorescently labelled liposomes. The lipophilic dye rhodamine B encapsulated in the lipid bilayer as betamethasone penetrates the epidermis at the same level as NBD-phosphatidylcholine. On the other hand, the hydrophilic dye calcein encapsulated in the aqueous compartment as betamethasone-cyclodextrin complexes does not penetrate the epidermis. These observations seem to confirm the ex vivo results. In addition, the skin penetration of rhodamine B seems to be improved by the incorporation in negatively charged liposomes compared with classical ones. Finally, the efficiency of the negatively charged vesicles was evaluated in vivo on volunteers by the skin blanching assay. Carbomer gel containing the negatively charged vesicles seems to enhance the blanching response of encapsulated betamethasone in comparison with the ethanolic hydroxypropylcellulose gel. However, results are not significantly different. This could be explained by the small number of volunteers. On the other hand, in the case of formulations containing betamethasone dipropionate, no tendency could be highlighted. These results seem to confirm that the use of negatively charged liposomes is more attractive for improving the efficiency of a lesser lipophilic drug, betamethasone, in comparison with the more lipophilic ester, betamethasone dipropionate. These results need to be confirmed using a higher number of volunteers./ Les systèmes vésiculaires, comme les liposomes, représentent une approche intéressante pour améliorer ladministration cutanée de médicaments. Les liposomes sont des vésicules sphériques composées dune ou plusieurs bicouches lipidiques entourant une cavité aqueuse. Ils sont capables dencapsuler des molécules hydrophiles dans leur cavité aqueuse, ainsi que de retenir des molécules hydrophobes dans leur bicouche lipidique. Dans la première partie de la thèse, nous nous sommes intéressés au développement dun nouveau système dadministration cutanée combinant les avantages des complexes dinclusion dans les cyclodextrines et ceux des liposomes déformables, aboutissant à un nouveau concept appelé : « drugs-in-cyclodextrin-in-deformable liposome». La bétaméthasone a été utilisée comme molécule modèle. Ces nouveaux systèmes ont été mis au point et caractérisés avec succès. Les premières études de diffusion réalisées in vitro, à travers des membranes synthétiques et au moyen des cellules de diffusion de Franz, étaient prometteuses. Afin de se rapprocher des conditions in vivo, des études de pénétration des liposomes ont alors été mises au point, ex-vivo, au moyen de cellules de diffusion et à travers des peaux doreilles de cochons. La méthode du « tape stripping » a permis de déterminer la quantité de bétaméthasone dans le stratum corneum. La quantité de substance active dans lépiderme, le derme et le mileu récepteur des cellules de Franz a également été déterminée. Ces méthodes ont été validées avec succés. Malheureusement, les études sur peaux doreilles de cochons nont pas permis de confirmer nos premières conclusions. Les recherches ont alors été orientées vers des études permettant de mieux comprendre les mécanismes de pénétration cutanée des liposomes. Dans la seconde partie de la thèse, linfluence de différents paramètres sur la pénétration cutanée a été étudiée. La comparaison de la pénétration cutanée de deux systèmes liposomiaux différents a mis en évidence limportance de la formulation des liposomes sur leur efficacité. Dans le premier, la bétaméthasone est encapsulée comme précédemment à laide de cyclodextrines dans la cavité aqueuse des liposomes déformables. Dans le second système, la bétaméthasone est encapsulée seule au niveau de la bicouche lipidique des liposomes. Ce second système a montré une plus grande perméabilité de la molécule modèle encapsulée. Malgré cette plus faible rétention, le deuxième système a permis daugmenter la pénétration de la molécule modèle. La plus grande perméabilité et la meilleure pénétration du deuxième système permettent de conclure que la bétaméthasone pénétrerait sous une forme non encapsulée dans les liposomes. De plus, aucune différence na été observée entre la pénétration cutanée des liposomes encapsulant la bétaméthasone dans leur bicouche et une dispersion non liposomale. Plusieurs tensio-actifs ont également été incorporés au niveau de la bicouche des liposomes afin dobtenir des liposomes déformables. Malheureusement, la faible augmentation de pénétration observée par rapport aux liposomes classiques non déformables nest pas significative. Lajout de lipides chargés au niveau de la bicouche lipidique de liposomes encapsulant soit la bétaméthasone soit le dipropionate de bétaméthasone a été investigué. Laddition de lipides chargés négativement a permis daugmenter la pénétration de la molécule encapsulée. Lutilisation de liposomes chargés négativement a permis daugmenter la quantité de bétaméthasone au niveau de lépiderme dun facteur 9,3 par rapport à une solution éthanolique de bétaméthasone. Cette augmentation na pas été observée avec la dispersion non liposomale correspondante, indiquant que la formulation sous forme de vésicules est très importante. En ce qui concerne le dipropionate de bétaméthasone, lencapsulation dans les liposomes chargés négativement a augmenté la quantité dester dans lépiderme dun facteur 5,5 par rapport à la spécialité Diprosone® lotion et seulement dun facteur 1,6 par rapport à la solution éthanolique. Lencapsulation dans les liposomes chargés négativement semble donc moins avantageuse dans le cas dune molécule plus lipophile, comme le dipropionate de bétaméthasone et qui possède déjà une bonne pénétration cutanée intrinsèque par rapport à une molécule plus hydrophile comme la bétamethasone. La pénétration de liposomes rendus fluorescents a été visualisée grâce à la microscopie confocale. Un marqueur lipophile, la rhodamine B, encapsulé dans la bicouche comme la bétaméthasone, pénètre bien dans la peau de la même façon que la phosphatidylcholine fluorescente. Par contre, un marqueur hydrophile, la calcéine, encapsulé dans la cavité des liposomes comme les complexes bétaméthasone-cyclodextrines, ne pénètre pas dans lépiderme. Ces observations confirment les résultats de dosage ex vivo au moyen des cellules de Franz. De plus, la pénétration dans la peau de la rhodamine B semble être plus importante lorsquelle est encapsulée dans les liposomes chargés négativement par rapport aux liposomes non chargés. Enfin, lefficacité des liposomes négatifs a été évaluée in vivo sur des volontaires grâce à lévaluation du pouvoir de blanchiement des corticostéroïdes. Le gel de carbomère contenant les liposomes chargés négativement semble augmenter la réponse de la bétaméthasone par rapport au gel éthanolique dhydroxypropylcellulose. Cependant, les résultats ne sont pas significatifs. Une explication pourrait être le faible nombre de volontaires. Par contre, dans le cas des liposomes contenant le dipropionate de bétaméthasone, il a été plus difficile de dégager une tendance. Ces résultats semblent confirmer que lutilisation des liposomes chargés négativement est plus intéressante dans le cas dune molécule moins lipophile comme la bétamethasone par rapport à une molécule plus lipophile comme le dipropionate de bétaméthasone. Ces résultats nécessitent cependant dêtre confirmés sur un plus grand nombre de volontaires.

Les nanoparticules (NPs) organiques représentent un outil majeur d'innovation en dermatologie. L'objectif de cette thèse a été de développer et d'optimiser des procédés d'encapsulation d'un mélange de molécules odorantes appelé fragrance mix I (FMI) dans des nanoparticules (NPs) de différentes natures: NPs polymères (poly-ε-caprolactone, PCL), ou NPs lipidiques solides (SLNs) (à base de vaseline, beurre de karité, cire de candelilla, triglycérides C10-18, ou palmitate de cétyle). Ces nouveaux systèmes ont alors été évalués pour la vectorisation de ce mélange à travers un explant de peau de porc, afin de modéliser la distribution des molécules composant le FMI dans les différentes assises cutanées. En parallèle, elles ont également été appliquées en tant que promoteurs de solubilisation du FMI pour le développement d'un nouveau test de diagnostic in vitro de l'allergie aux parfums. Nos résultats montrent que: (i) les NPs polymères, principalement anioniques, sont les plus adaptées pour promouvoir la pénétration transépidermique du FMI. Au contraire, les SLNs s'agglomèrent dans le stratum corneum, conduisant à une accumulation du FMI dans cette assise ; (ii) qu'au-delà du type de vecteur utilisé, la pénétration des molécules du FMI dans les couches les plus profondes de la peau dépend de leur coefficient de partage intrinsèque ; (iii) que les nanoparticules de PCL augmentent significativement la solubilisation du FMI dans les milieux de culture conventionnels et permettent ainsi une réactivation robuste des lymphocytes T spécifiques circulant chez des patients présentant une allergie au parfums. L'ensemble de ces résultats confirme donc tout le potentiel des NPs organiques pour le développement de futures stratégies de délivrance ciblée de plusieurs actifs dans les différents compartiments cutanés. Ces nouveaux vecteurs offrent en outre une alternative prometteuse pour améliorer le diagnostic de l'eczéma de contact induit par les parfums et plus généralement par des allergènes hydrophobes / The aim of this work was to develop and optimize methods for fragrance mix I (FMI) encapsulation into nanoparticles (NPs) of two types of nanoparticles (NPs) : polymeric NPs (poly-ε-caprolactone, PCL) and solid lipid NPs (SLNs) (prepared with petrolatum, shea butter, candelilla wax, C10-18 triglycerides, or cetyl palmitate). Then, these new NPss were evaluated as vectors through a pig skin to analyze the distribution of the FMI molecules in the different skin layers. In parallel, NPs have also been applied as solubilizers for the development of a new in vitro test for the diagnosis of fragrance allergy. Our results show that (i) NPs polymers, mainly anionic NPs, are the most suitable vectors to promote trans-epidermal penetration of fragrance. On the contrary, SLNs were found in the stratum corneum, leading to an accumulation of fragrance in this layer; (ii) whatever the type of NPs, the penetration of the FMI molecules in the deeper layers of the skin depends on their intrinsic partition coefficient; (iii) PCL-NPs significantly increase the FMI solubilization in conventional culture media and, allowing a robust reactivation of circulating specific T cells in patients with allergy to fragrances. All of these results confirm the potential of organic NPs for the development of future strategies (for the skin delivery of several actives in the different skin layers). These new vectors further offer a promising alternative to improve the diagnosis of contact dermatitis induced by fragrances and more generally by hydrophobic allergens