Le développement de formes à libération prolongée destinées à ladministration pulmonaire est un domaine qui a, jusquà présent, été relativement peu étudié mais pour lequel il y a actuellement un intérêt croissant. Le but de notre travail est de développer une forme destinée à ladministration par inhalation qui libérerait de façon prolongée un agent bronchodilatateur. Dans le cadre de ce travail, les microparticules lipidiques solides (MLS) ont été choisies comme véhicule en vue de lobtention dune libération prolongée. Les MLS présentent en effet de nombreux avantages en termes de coûts de production, de stabilité et de biocompatibilité comparativement à dautres systèmes microparticulaires. Le salbutamol, principe actif ß2-mimétique choisi initialement pour cette étude, nétant pas suffisamment lipophile pour sincorporer de façon efficace dans les MLS, un dérivé plus lipophile du salbutamol, lacétonide de salbutamol (AS) a été synthétisé. Les caractéristiques physico-chimiques de lAS ont été déterminées, sa stabilité a été évaluée et des méthodes de dosage ont été mises au point. Des MLS vierges (non chargées en AS) ont tout dabord été produites après optimisation des paramètres de fabrication en vue dobtenir une taille adéquate pour ladministration par inhalation. Des études de tolérance au niveau pulmonaire effectuées in vivo sur des rats ont montré la biocompatibilité de ces MLS. Lactivité pharmacologique de lAS a été évaluée à la fois par des essais ex vivo de bronchodilatation sur organes isolés ainsi que par des essais daffinité (binding) envers les récepteurs ß1 et ß2-adrénergiques. Ces études nont malheureusement pas permis de conclure avec certitude quant à léventuel effet ß2-mimétique de lAS. Cependant, en raison de son caractère lipophile, lAS sera utilisé comme molécule modèle tout au long du processus de développement. LAS a donc été incorporé dans les MLS et les paramètres de production ont été étudiés et fixés par la méthodologie des plans dexpérience en vue doptimiser le pourcentage de particules possédant un diamètre géométrique convenant à ladministration par inhalation. La concentration en AS naffectant pas de façon significative la taille des MLS, celles-ci pourront être produites en utilisant la concentration en AS désirée. La caractérisation de ces MLS par microscopie électronique a montré que, lorsque la charge théorique initiale augmente, des cristaux dAS sont observés à lextérieur des MLS. Des essais de libération menés in vitro dans un premier temps puis ex vivo (en présence de fragments de poumons de porcs) ont permis de montrer une prolongation de la libération de lAS à partir des MLS comparativement à la libération à partir de mélanges physiques de MLS vierges et dAS. Ces résultats montrent la capacité des MLS possédant une taille pour administration pulmonaire, à libérer de façon prolongée la molécule qui y est incorporée. Cette libération est dautant plus prolongée que la charge en AS diminue. La présence denzymes pulmonaires na cependant pas modifié la cinétique de libération. Des poudres pour inhalation à base de MLS à 5% en AS ont été formulées en utilisant différents excipients porteurs et compétiteurs en différentes concentrations relatives. Les fractions respirables mesurées in vitro sont, dans le meilleur des cas, égales à 15%. Cependant, les MLS à 5% en AS administrées seules ont une fraction respirable proche de 25%. Leurs propriétés découlement savérant acceptables, il peut être envisagé dadministrer les MLS telles quelles en tant que poudre pour inhalation./ The sustained release of drugs for pulmonary delivery is a research field which has been so far rather unexploited but which is currently becoming increasingly attractive. The aim of this research work is to develop a pulmonary delivery system which will be able to sustain the release of a bronchodilator agent. Therefore, solid lipid microparticles (SLMs) were chosen in order to provide a sustained release to its incorporated substance. Indeed, this kind of drug carrier offers many advantages. In comparison with other microparticulate dosage forms, SLMs production costs are relatively low, they are physiologically compatible and their physical stability is well established. Salbutamol, a well-known short-acting ß2-adrenergic receptor agonist, was initially chosen for this study but this molecule proved to be not lipophilic enough to be efficiently incorporated into SLMs. Thats the reason why salbutamol acetonide (SA) was synthetized from salbutamol in order to get a more lipophilic molecule and thereby to increase the incorporation into SLMs. Then, the physico-chemical properties of SA were characterized, its stability was studied and chromatographic assays were developed. Drug free SLMs were produced using manufacturing parameters which were optimized in order to get particles with a suitable range of size for pulmonary administration. Tolerance studies were then carried out in vivo on rats to check SLMs biocompatibility in the respiratory tractus. Ex vivo tests using isolated organs were carried out in order to investigate the bronchodilating activity of SA. The obtained results were completed with a binding study to evaluate the affinity between SA on the one hand and ß1 and ß2-adrenergic receptors on the other hand. Unfortunately those studies didnt allow us to conclude about the possible ß2-mimetic activity of SA. Owing to its lipophilic character, SA will be used all along this research work as a model molecule for the development of SLMs as sustained release system for pulmonary delivery. SA was then incorporated into SLMs: the production parameters were studied using the methodology of experimental design in order to optimize the percentage of particles with a suitable diameter for pulmonary administration. It has been noticed that SA concentration does not affect significantly the particle size. So SLMs can be produced using the pre-established production parameters whatever the desired SA concentration. The characterization of the obtained SLMs-SA by scanning electron microscopy showed especially that SA crystals appear outside of the particles when the theoretical drug loading increases. Drug release studies were carried out both in vitro and ex vivo i.e. using fragments of porcine pulmonary tissues. These studies showed that SA release from SLMs is sustained in comparison with SA release from physical mixtures of drug free SLMs and SA. The obtained results tend to prove that produced SLMs are suitable carriers in order to get a sustained release of the incorporated substance. It has also been noticed that the release rate increases when the drug loading increases. Concerning the ex vivo studies, it may be concluded that the presence of pulmonary enzymes does not modify SA release profiles. Inhalation powders containing SLMs with 5% SA were finally developed using different carrier excipients and ternary agents at different relative concentrations. Respirable fractions were determined in vitro and proved to be at best equal to 15%. However, SLMs 5% SA have also been administered alone without any additional excipients. In this case, the obtained respirable fraction is close to 25%. Seeing that the flowability of SLMs 5% SA appeared to be acceptable, they could be administered just as they are as inhalation powder.

Au cours de ce travail de thèse nous avons proposé une stratégie de ciblage des macrophages alvéolaires afin d’y vectoriser des glucocorticoïdes. Une prodrogue de budésonide, le palmitate de budésonide (BP) a été synthétisée dans le but de prolonger sa demi-vie dans les poumons après inhalation. Des nanoparticules PEGylées de BP ont été développées et étudiées pour obtenir une formulation stable avec des caractéristiques physico-chimiques appropriées et un taux de charge élevé pour pénétrer dans les macrophages alvéolaires, cellules centrales dans l'inflammation pulmonaire. Des tests in vitro sur les macrophages RAW 264.7 ont confirmé l'activité anti-inflammatoire et l'absence de cytotoxicité des nanoparticules. Celles-ci ont ensuite été séchée au sein de microparticules Troyennes obtenues par atomisation-séchage afin de faciliter leur administration pulmonaire sous forme de poudres et libérer les nanoparticules à proximité des alvéoles pulmonaires. Les microparticulessphériques creuses contenant de 0 % à 20 % de nanoparticules de BP présentent des diamètres aérodynamiques et une fraction de particules fines appropriés pour la délivrance pulmonaire. Les études pharmacocinétiques in vivo montrent des concentrations élevées et prolongées de budésonide dans les poumons, avec de faibles concentrations plasmatiques. Dans la deuxième partie de cette thèse, une autre stratégie de ciblage des macrophages a été évaluée par la décoration de la surface des nanoparticules avec du mannose. Après la synthèse d'un lipide mannosylé, des nanoparticules ont été formulées et caractérisées, démontrant un taux de charge élevé et une bonne stabilité jusqu'à 30 jours. Des tests in vitro sur les macrophages RAW 264.7 ont montré que la présence du mannose à la surface augmente l'internalisation des nanoparticules d’un facteur 2 après 48 h d'incubation, par rapport aux nanoparticules PEGylées. / This work focuses on strategies to target glucocorticoids to alveolar macrophages. We have synthesized a budesonide prodrug, budesonide palmitate (BP), increasing its lipophilicity to extend drug half-life in the lungs. BP PEGylated nanoparticles were developed and studied to obtain a stable formulation with suitable physicochemical characteristics and high drug loading to enter alveolar macrophages, key players in lung inflammation. In vitro tests on RAW 264.7 macrophages confirmed the anti-inflammatory activity and absence of cytotoxicity of nanoparticles. These were then encapsulated into Trojan microparticles obtained by spray-drying to facilitate their delivery to the lung as dry powders and release nanoparticles directly to the pulmonary alveoli. Spherical hollow microparticles containing from 0 % to 20 % of BP nanoparticles presented suitable aerodynamic diameters and fine particle fraction for lung delivery. In vivo pharmacokinetic studies demonstrated high and extended budesonide concentrations in the lungs, with low plasma concentrations. In the second part of this thesis, another macrophage targeting strategy was assessed by decoration of nanoparticle surface with mannose. After synthesis of a mannosylated lipid, nanoparticles were formulated and characterized, demonstrating high drug loading and stability up to 30 days. In vitro tests on RAW 264.7 macrophages showed that the presence of mannose on the surface increases nanoparticles internalization 2 fold after 48 h incubation, as compared with PEGylated nanoparticles.

La pyrazinamide est le seul anti-tuberculeux de première intention actif sur la formedormante de Mycobacterium tuberculosis. Sa prescription par voie orale permet de réduire la durée du traitement de 9 à 6 mois. Nous avons développé des formes galéniques de pyrazinamide administrables directement au niveau des poumons afin d'augmenter localement la concentration de pyrazinamide au site pathologique afin de réduire la durée du traitement. Deux formes galéniques de pyrazinamide ont été optimisées: une poudre sèche pour inhalation et des nanoparticules polymères administrables par nébulisation liquide ou sous forme de poudre sèche.La poudre sèche pour inhalation est composée de particules obtenues par atomisation-séchage. La pyrazinamide a été solubilisée dans un mélange 70/30 v/véthanol/eau. Après atomisation-séchage de cette solution, nous avons obtenu des particules cristallines instables et non adaptées à l'administration pulmonaire du fait de leur grande taille. Afin d'obtenir des poudres adaptées à une administration pulmonaire dans le poumon profond, et stables en termes de taille et de caractéristiques physico-chimiques, nous avons passé en revue toute une série d'excipients: phospholipides, bicarbonate d'ammonium, leucine, acide hyaluronique.Nous avons montré qu'en associant tous ces excipients au principe actif, on pouvait obtenir des particules d'environ 6 microns, de faible densité tassée et stables pendant 4 semaines dans des conditions de stockage classiques.L'évaluation aérodynamique in vitro de la poudre optimisée a révélé l'existence de deux populations de particules: de grosses particules pauvres en pyrazinamide et de petites particules riches en pyrazinamide. Ces deux populations proviennent d'une ségrégation des différents composants lors du processus de séchage. Pour remédier à ce phénomène et obtenir des particules de composition homogène, la vitesse de séchage a été diminuée. En conséquence, nous avons obtenu des poudres homogènes avec de bonnes propriétés aérodynamiques pour délivrance dans les poumons: fraction de particules fines de 40,1 ± 1,0% et fraction alvéolaire de 29,6 ±3,1%. Cette poudre a alors été évaluée in vivo chez le rat sain et nous avons mesuré les concentrations de pyrazinamide dans le plasma et le liquide de lavage bronchoalvéolaire après insufflation intratrachéale de la poudre, par comparaison avec une administration intraveineuse d'une solution de pyrazinamide. L'insufflation intratrachéale de poudre et l'administration intraveineuse conduisent à des paramètres pharmacocinétiques similaires prouvant que les particules se dissolvent rapidement lors du dépôt et que la molécule traverse efficacement la barrière pulmonaire pour atteindre la circulation systémique. De manière surprenante, la pyrazinamide est éliminée plus rapidement du liquide pulmonaire lorsqu'elle est administrée par insufflation intratrachéale que par voie intraveineuse. La délivrance pulmonaire de pyrazinamide apparaît comme une alternative intéressante à l'administration orale de la molécule et doit maintenant être testée dans un modèle d'animal infecté pour évaluer son efficacité contre Mycobacterium tuberculosis.En parallèle, nous avons optimisé l'encapsulation de pyrazinamide dans des nanoparticules polymères de poly(lactide-co-glycolide) PLGA monodisperses de taille inférieure à 200nm, grâce un plan d'expériences. Les nanoparticules de PLGA chargées en pyrazinamide ont été préparées par la méthode d'émulsion double. La méthode de Taguchi a été utilisée pour optimiser les paramètres de formulation. Le type de solvant, le rapport en poids pyrazinamide/ PLGA et le rapport des volumes des phases aqueuse et organique étaient les paramètres pertinents. La méthode de Taguchi s'est avérée efficace pour optimiser les nanoparticules d'environ 170nm avec un indice de polydispersité ˂ 0,1, un potentiel zêta d'environ -1mV et une efficacité d'encapsulation de 7-8% soit 3% de taux de charge de la pyrazinamide. / Pyrazinamide is the only first intention anti-TB drug active on the dormant form ofMycobacterium tuberculosis. Its oral prescription reduces treatment duration from 9to 6 months. We have developed dosage forms of pyrazinamide to administer directlyto the lungs to locally increase the concentration of pyrazinamide at the diseased siteand further reduce the duration of treatment. Two dosage forms of pyrazinamidewere optimized: a dry powder for inhalation and polymer nanoparticles administrableeither by liquid nebulization or as a dry powder.The dry powder for inhalation is composed of particles obtained by spray-drying.Pyrazinamide was dissolved in a mixture 70/30 v/v ethanol/water. After spray-dryingthe solution, we obtained large crystalline particles that were unstable and notsuitable for pulmonary administration because of their large sizes. To obtain powderssuitable for pulmonary delivery to the deep lungs, and stable in terms of size andphysico-chemical characteristics, we reviewed a variety of excipients: phospholipids,ammonium bicarbonate, leucine, hyaluronic acid. We have shown that by combiningall these excipients with the drug, one could obtain particles of about 6 microns, witha low tapped density and stable for 4 weeks under conditions of conventionalstorage.The in vitro aerodynamic evaluation of the optimized powder showed the existence oftwo populations of particles: large particles with a low content of pyrazinamide andsmall particles with high pyrazinamide content. These two populations derived fromthe segregation of different components during the drying process. To obtainparticles of uniform composition, the drying rate was decreased. As a result, weobtained homogeneous powders with good aerodynamic properties for delivery intothe lungs: fine particle fraction of 40.1 ± 1.0% and alveolar fraction of 29.6 ± 3.1%.This powder was then evaluated in vivo in healthy rats and we measured theconcentrations of pyrazinamide in plasma and bronchoalveolar lavage fluid afterintratracheal insufflation of the powder in comparison with intravenous administrationof a solution of pyrazinamide. The intratracheal insufflation of the powder and theintravenous injection lead to similar pharmacokinetic parameters proving that theparticles dissolve rapidly after deposition and pyrazinamide crosses efficiently thelung barrier to reach the systemic circulation. Surprisingly, pyrazinamide disappears4faster form lung lining fluid when administered by pulmonary insufflation than afterintravenous administration. Pulmonary delivery of pyrazinamide appears as anattractive alternative to oral administration of the drug and must now be tested in ananimal model of infection to assess its efficacy against Mycobacterium tuberculosis.In parallel, we have optimized the encapsulation of pyrazinamide in polymericnanoparticles of poly (lactide-co-glycolide) PLGA lower than 200 nm andmonodisperse, using experimental design. The pyrazinamide-loaded PLGAnanoparticles were prepared by the double emulsion method. The Taguchi methodwas used to optimize the formulation parameters. The type of solvent, thepyrazinamide / PLGA weight ratio and aqueous to organic phases volume ratio wererelevant parameters. The Taguchi method has proven effective to optimizenanoparticles of about 170nm with a polydispersity index < 0.1, a zeta potential ofapproximately -1mV and an encapsulation efficiency of 7-8% or 3% pyrazinamide drugloading.

Local delivery of medication to the lung is highly desirable as the principal advantages include reduced systemic side effects and higher dose levels of the applicable medication at the site of drug action. This administration could be particularly useful for patients with specifically chronic pulmonary infections or pulmonary diseases, such as cystic fibrosis, asthma or lung cancer. In order to deliver a high dose range of medication for highly-dosed drugs such as antibiotics, “carrier-free” DPI formulations of tobramycin were developed with the aim of minimizing the use of excipients. Briefly, dry powders were prepared by spray drying various suspensions of tobramycin in isopropanol. First, as particle size is a key parameter in defining drug deposition in the lungs, the new Spraytec® laser diffraction method specifically modified for measuring the PSD of aerosolized drug was evaluated. The dispersion properties of various dry powder formulations were investigated using different laser diffraction and impaction apparatuses at different flow rates and using different inhalator devices. Different correlations between geometric and aerodynamic size data were demonstrated in this study. As a potential application, for the flow rate, the different inhalation devices and the drug formulations examined, the tobramycin fine particle fraction could be predicted from measurements obtained from the Spraytec® using linear relationships. Correlations (R² > 0.9) between the MMAD and the percentage of particles with a diameter below 5 µm could be demonstrated between the results obtained from the laser diffraction technique and the impaction method. Consequently, the Spraytec® laser diffraction technique was proved to be an important tool for initial formulation and process screening during formulation development of DPIs. In order to modify the surface properties of the raw tobramycin powder, different powder compositions were formulated with the aim of studying the influence of the concentration of tobramycin in drug suspensions used for spray-drying, the lipid film composition (cholesterol:Phospholipon ratio) and the coating level (in percentage) on the physicochemical and aerodynamic characteristics of the antibiotic. The results indicated that the application of a lipid coating around the active particles allowed an improvement in particle dispersion from the inhalator, decreasing raw powder agglomeration and thus enhancing drug deposition deep in the lungs. Moreover, these results seemed to be influenced by the amount and composition of the lipids in the formulations. The evaluation of the influence of the coating level showed that the deposition of only 5% w/w lipids (on a dry basis) was sufficient to improve particle dispersion properties during inhalation. The FPF, which is around 36% for the uncoated micronized tobramycin, was increased to up to about 68% for the most effective lipid-coated formulation. Of particular importance, these results revealed the need to add sufficient amounts of covering material in order to significantly modify the particle surface properties and reduce their tendency to agglomeration, while limiting the lipid level in the formulations in order to avoid any undesirable sticking and to allow the delivery of more of the active drug to the deep lung. Another approach used to modify the surface properties of raw tobramycin was to coat the micronized particles with nanoparticles of the drug, produced by high pressure homogenization. The evaluation of the influence of the level of nanoparticle coating of the micronized particles showed that the presence of nanoparticles in the formulations improved the particle dispersion properties during inhalation. One microparticle was completely covered with a single layer or several layers of nanoparticles, in function of the percentage of nanoparticles in the mixture. Coating the fine drug particles with particles in the nanometer range was believed to reduce Van Der Waals forces and powder agglomeration. These various layers of nanoparticles also allowed a decrease in the cohesion of the powder by improving the slip between the particles. On the other hand, suspensions containing solely nanoparticles were spray dried with various concentrations of surfactant in order to produce easily dispersible and reproducible micron-size agglomerates of nanoparticles during inhalation. The evaluation of the influence of the concentration of surfactant showed that deposition of only 2% w/w (on a dry basis) of Na glycocholate is sufficient to improve particle dispersion properties during inhalation. Consequently, the use of nanoparticles in dry powder formulations increased the FPF from 36% for the uncoated micronized tobramycin to about 61% for this latter formulation. To modify the balance between the different forces of interactions without the need for any excipient, the influence of formulation components on the aerosolization characteristics of spray-dried tobramycin through the use of various proportions of water in the solvent used to prepare initial suspensions was investigated. These results showed that it is possible to modify the surface properties of the particles by coating the particles of drug with a homogeneously distributed film of the active compound dissolved in a solvent system containing a mixture of different solvents such as isopropanol and water. During nebulization of the suspension, droplets are composed of one or more particles in solid state surrounded with solvent containing the dissolved drug. It is hypothesized that during the drying step, dissolved tobramycin forms a coating of the amorphous drug around particles in suspension. The coating of drug particles can thus be used as an alternative approach that permits the modification of the surface properties of the particles, increasing the flowability, the desagglomeration tendency and the fine particle fraction deposited in the deep lung. So, the evaluation of the influence of the water content of the suspensions and the effect of the inlet temperature during spray-drying showed that the addition of 2% water v/v is sufficient to improve particle dispersion during inhalation. Of particular interest, as tobramycin is a very hygroscopic drug, the addition of water turned out to be a critical step. It was thus important to add a small amount of water to the solvent system and to process the drying step at a high temperature to produce formulations containing solely the active drug and showing a FPF of up to 50%. Moreover, stability studies demonstrated that these optimized formulations (lipid-coated formulation, nanoparticle formulation and amorphous drug-coated formulation) were stable over a long time period at various ICH temperature and relative humidity storage conditions (25°C/60% RH, 30°C/65% RH and 40°C/75% RH). The formulations were shown to keep their crystalline state, initial PSD, redispersion characteristics and deposition results for more than twelve months. In order to confirm these encouraging results, two optimized formulations (one with a lipid coating and another with amorphous drug coating) were selected and compared to the only commercially available tobramycin formulation for inhalation, Tobi® (nebulizer solution), by performing a combined in vivo scintigraphic and pharmacokinetic evaluation of tobramycin DPIs in nine CF patients. In comparison with Tobi®, it was estimated that lung deposition, expressed as a percentage of the nominal dose, was 7.0 and 4.5 times higher for the lipid-coated and amorphous tobramycin-coated formulations, respectively. Moreover, the pharmacokinetic data, adjusted to the same drug dose as that of the Tobi® deposited in the lungs, showed that the AUC values were found to be 1.6 times higher for Tobi® than for DPI formulations. So this evaluation confirmed the superiority of dry powder formulations in terms of drug deposition and reduced systemic exposure in comparison with the conventional comparator product, Tobi®. Thus, these new and orginal tobramycin DPI formulations based on the use of very low excipient levels and presenting very high lung deposition properties, were shown to offer very good prospects for improving the delivery of drugs to the pulmonary tract and to the widest possible patient population.

L'objectif de ce travail est de développer des vecteurs pharmaceutiques, encapsulant la vitamine E, adaptés à l'administration pulmonaire par aérosolisation. La vitamine E, antioxydant physiologique, peut être utilisée pour lutter contre les phénomènes du stress oxydatif en particulier ceux observés au niveau pulmonaire. L'encapsulation de la vitamine E dans des vecteurs inhalables a été envisagée afin d'optimiser son efficacité thérapeutique en améliorant la concentration du principe actif pouvant atteindre son site d'action, les alvéoles pulmonaires. Les différents systèmes d'encapsulation de la vitamine E ont été préparés par des méthodes utilisant des contacteurs à membrane. Le principe de préparation se résume au passage de la phase dispersée, à travers les pores d'une membrane microporeuse, au sein de la phase continue. Les avantages de cette technique sont en particulier une bonne reproductibilité et un faible apport d'énergie et par conséquent un coût d'exploitation modéré. De plus, les procédés à base de contacteurs à membrane se prêtent aisément au passage à l'échelle de production industrielle. Au cours de ce travail, les paramètres influençant le procédé de fabrication par contacteur à membrane ont été étudiés ; principalement la pression transmembranaire de passage de la phase discontinue, la force de cisaillement de la phase continue et la microstructure de la membrane utilisée. Différentes configurations membranaires ont été testées telles que (i) les modules membranaires tubulaires avec écoulement tangentiel de la phase continue, (ii) les membranes planes montées dans des cellules d'agitation et (iii) les membranes dotées d'un mouvement d'oscillation à l'intérieur de la phase continue. En cas d'émulsification directe, diverses membranes ont été utilisées : des membranes SPG, des membranes microsieves et des membranes en céramique. Pour la « premix emulsification » des membranes dites dynamiques, constituées par un lit de billes en verre, ont été étudiées / The present study investigated the preparation of pharmaceutical drug carriers encapsulating the vitamin E and intended for pulmonary administration after nebulisation. Vitamin E, a physiological antioxidant, could be used to prevent cigarette smoke toxicity since several pulmonary disorders are mainly caused by oxidative stress phenomena. The methods used for the drug carriers’ preparation were based on the membrane emulsification principle. In these methods, the to-be-dispersed phase was injected in the continuous phase through the pores of a microporous membrane. The advantages of this method are: a better control over the diffusive mixing at the liquid / membrane interface and thus a fine control of droplets size distribution, a less energy consumption and an easy extrapolation of the obtained results for an industrial large scale-up. In order to investigate the preparation processes, key parameters influence on particles characteristics was investigated. Different experimental set-ups were used: (i) tubular membranes with a cross flow circulation of the continuous phase, (ii) stirred cell device with a flat micro-engineered membrane, (iii) oscillating membrane module in a stationary continuous phase. For direct emulsification, various membranes were used such as : SPG membranes, micro-engineered membranes and ceramic membranes. For premix emulsification, a packed bed of glass beads, called dynamic membrane, was studied. Four different drug carriers were developed during this study: liposomes, micelles, nano-emulsion and solid-lipid particles. The different encapsulating systems were characterized in terms of size distribution, zeta potential, microscopic morphology, encapsulation efficiency and stability. Results showed that the obtained drug carriers presented convenient properties. After nebulization of vitamin E encapsulating systems, the obtained aerosols presented satisfying aerodynamic characteristics which allowed the prediction (using a mathematical model) of a high level of vitamin E deposit on its action site

Local delivery of medication to the lung is highly desirable as the principal advantages include reduced systemic side effects and higher dose levels of the applicable medication at the site of drug action. This administration could be particularly useful for patients with specifically chronic pulmonary infections or pulmonary diseases, such as cystic fibrosis, asthma or lung cancer.<p>In order to deliver a high dose range of medication for highly-dosed drugs such as antibiotics, “carrier-free” DPI formulations of tobramycin were developed with the aim of minimizing the use of excipients. Briefly, dry powders were prepared by spray drying various suspensions of tobramycin in isopropanol.<p><p>First, as particle size is a key parameter in defining drug deposition in the lungs, the new Spraytec® laser diffraction method specifically modified for measuring the PSD of aerosolized drug was evaluated. The dispersion properties of various dry powder formulations were investigated using different laser diffraction and impaction apparatuses at different flow rates and using different inhalator devices. Different correlations between geometric and aerodynamic size data were demonstrated in this study. As a potential application, for the flow rate, the different inhalation devices and the drug formulations examined, the tobramycin fine particle fraction could be predicted from measurements obtained from the Spraytec® using linear relationships. Correlations (R² > 0.9) between the MMAD and the percentage of particles with a diameter below 5 µm could be demonstrated between the results obtained from the laser diffraction technique and the impaction method. Consequently, the Spraytec® laser diffraction technique was proved to be an important tool for initial formulation and process screening during formulation development of DPIs.<p><p>In order to modify the surface properties of the raw tobramycin powder, different powder compositions were formulated with the aim of studying the influence of the concentration of tobramycin in drug suspensions used for spray-drying, the lipid film composition (cholesterol:Phospholipon ratio) and the coating level (in percentage) on the physicochemical and aerodynamic characteristics of the antibiotic.<p>The results indicated that the application of a lipid coating around the active particles allowed an improvement in particle dispersion from the inhalator, decreasing raw powder agglomeration and thus enhancing drug deposition deep in the lungs. Moreover, these results seemed to be influenced by the amount and composition of the lipids in the formulations. The evaluation of the influence of the coating level showed that the deposition of only 5% w/w lipids (on a dry basis) was sufficient to improve particle dispersion properties during inhalation. The FPF, which is around 36% for the uncoated micronized tobramycin, was increased to up to about 68% for the most effective lipid-coated formulation. Of particular importance, these results revealed the need to add sufficient amounts of covering material in order to significantly modify the particle surface properties and reduce their tendency to agglomeration, while limiting the lipid level in the formulations in order to avoid any undesirable sticking and to allow the delivery of more of the active drug to the deep lung. <p><p>Another approach used to modify the surface properties of raw tobramycin was to coat the micronized particles with nanoparticles of the drug, produced by high pressure homogenization. The evaluation of the influence of the level of nanoparticle coating of the micronized particles showed that the presence of nanoparticles in the formulations improved the particle dispersion properties during inhalation. One microparticle was completely covered with a single layer or several layers of nanoparticles, in function of the percentage of nanoparticles in the mixture. Coating the fine drug particles with particles in the nanometer range was believed to reduce Van Der Waals forces and powder agglomeration. These various layers of nanoparticles also allowed a decrease in the cohesion of the powder by improving the slip between the particles.<p>On the other hand, suspensions containing solely nanoparticles were spray dried with various concentrations of surfactant in order to produce easily dispersible and reproducible micron-size agglomerates of nanoparticles during inhalation. The evaluation of the influence of the concentration of surfactant showed that deposition of only 2% w/w (on a dry basis) of Na glycocholate is sufficient to improve particle dispersion properties during inhalation. Consequently, the use of nanoparticles in dry powder formulations increased the FPF from 36% for the uncoated micronized tobramycin to about 61% for this latter formulation.<p>To modify the balance between the different forces of interactions without the need for any excipient, the influence of formulation components on the aerosolization characteristics of spray-dried tobramycin through the use of various proportions of water in the solvent used to prepare initial suspensions was investigated. These results showed that it is possible to modify the surface properties of the particles by coating the particles of drug with a homogeneously distributed film of the active compound dissolved in a solvent system containing a mixture of different solvents such as isopropanol and water. During nebulization of the suspension, droplets are composed of one or more particles in solid state surrounded with solvent containing the dissolved drug. It is hypothesized that during the drying step, dissolved tobramycin forms a coating of the amorphous drug around particles in suspension. The coating of drug particles can thus be used as an alternative approach that permits the modification of the surface properties of the particles, increasing the flowability, the desagglomeration tendency and the fine particle fraction deposited in the deep lung. So, the evaluation of the influence of the water content of the suspensions and the effect of the inlet temperature during spray-drying showed that the addition of 2% water v/v is sufficient to improve particle dispersion during inhalation. Of particular interest, as tobramycin is a very hygroscopic drug, the addition of water turned out to be a critical step. It was thus important to add a small amount of water to the solvent system and to process the drying step at a high temperature to produce formulations containing solely the active drug and showing a FPF of up to 50%.<p><p>Moreover, stability studies demonstrated that these optimized formulations (lipid-coated formulation, nanoparticle formulation and amorphous drug-coated formulation) were stable over a long time period at various ICH temperature and relative humidity storage conditions (25°C/60% RH, 30°C/65% RH and 40°C/75% RH). The formulations were shown to keep their crystalline state, initial PSD, redispersion characteristics and deposition results for more than twelve months.<p><p>In order to confirm these encouraging results, two optimized formulations (one with a lipid coating and another with amorphous drug coating) were selected and compared to the only commercially available tobramycin formulation for inhalation, Tobi® (nebulizer solution), by performing a combined in vivo scintigraphic and pharmacokinetic evaluation of tobramycin DPIs in nine CF patients.<p>In comparison with Tobi®, it was estimated that lung deposition, expressed as a percentage of the nominal dose, was 7.0 and 4.5 times higher for the lipid-coated and amorphous tobramycin-coated formulations, respectively. Moreover, the pharmacokinetic data, adjusted to the same drug dose as that of the Tobi® deposited in the lungs, showed that the AUC values were found to be 1.6 times higher for Tobi® than for DPI formulations. So this evaluation confirmed the superiority of dry powder formulations in terms of drug deposition and reduced systemic exposure in comparison with the conventional comparator product, Tobi®.<p><p>Thus, these new and orginal tobramycin DPI formulations based on the use of very low excipient levels and presenting very high lung deposition properties, were shown to offer very good prospects for improving the delivery of drugs to the pulmonary tract and to the widest possible patient population. <p><p> / Doctorat en Sciences biomédicales et pharmaceutiques / info:eu-repo/semantics/nonPublished