Дисертації з теми "Drug delivery matrices"

Micro/macroporous matrices comprising a continuous phase of poly([epsilon]-caprolactone) . (PCL) and a dispersed phase of water soluble particles (lactose and gelatin) with defined size range (45-90, 90-125 and l25-250[mu]m) were produced by rapid cooling solutions of PCL in acetone followed by solvent extraction from the hardened material. This novel approach enables high loading (29-44% w/w) of particles (lactose and gelatin) to be achieved in PCL matrices by suspension of particulates in the PCL solution prior to casting. Highly efficient protein release (90%) was obtained over time periods of 3 days to 3 weeks by variation of particle loading and particle size range. The good particle distribution throughout the matrix and efficient extraction of the water-soluble phase allows formation of a macroporous structure with defined pore architecture by incorporation of particles of a specific shape and size range. SEM analysis revealed the porous surface morphology. Micro computed tomography (micro-CT) and image analysis enabled visualization of the internal 3-D pore structure, quantification of the frequency distribution of equivalent pore diameter and porosity (%) in peL matrices. Micro/macroporous PCL tubes exhibited a burst strength of 125 to l45MPa under hydrostatic loading at 37[degree]C and good recovery of tube diameter following short-duration flow rates of 1000 ml/min under continuous increasing and pulsatile conditions. Sustained release of incorporated enzymes (lysozyme, collagenase and catalase) occurred over 11 days from the PCL matrices, with retained activity dependent on the particular enzyme used (collagenase 100% at 11 days, lysozyme 75-80% at 11 days, catalase 10-20 % at 5 days). Swiss3T3 fibroblasts exhibited strong attachment and successful colonization of the surface. of PCL matrices over 8 to 15 days in cell culture. These findings demonstrate the potential of micro/macroporous PCL matrices for scaffold production in tissue engineering and for controlling drug delivery.

In this work. polymeric matrices comprising Eudragit" RL PO were manufactured using Hot Melt Extrusion (HME) technology. The thermal, physical and chemical characteristics of Eudragit'" RL PO were investigated and suitable processing parameters defined. Above 180°C, thermal decomposition proceeded by a mechanism which caused cleavage and subsequent loss of ammonio methacrylate functional groups. Acceptable processing limits for HME of Eudragit" RL PO were defined with an optimal temperature window between 120°C and 170°C and screw speed between 100 and 150rpm. Ingress of water as a liquid and vapour changed the physical and viscoelastic properties of the material. A model water soluble drug, metformin hydrochloride (MHCI), was formulated within the Eudragit'" RL PO carrier matrix using via HME. MHCI and Eudragit" RL PO exhibited a poor interaction and MHCI displayed a low solubility in the molten polymer matrix. PXRD showed that crystalline solid dispersions formed during HME at all concentrations. Addition of Eudragit" RS PO to the hot melt formulation also caused retardation of drug release from the matrix providing a mechanism through which release of MHCI could be sustained. The effect of drug salt form on the physiochemical and drug release properties was evaluated using quinine as the free base (QB), hydrochloride (QHCI) and sulphate (QS04) forms. A significant difference in solubility in the molten polymer matrix was observed for each of the quinine forms. QB, QHCI and QS04 acted as solid-state plasticizers for Eudragit" RL PO at concentrations below saturation solubility. Salt counter ion imparted a significant influence on the solubility of drug within the polymer matrix. FT-IR and Raman spectroscopy showed that quinine exhibited multiple sites of interaction and the formation of a salt occupied a key site of interaction which rendered the salt forms less soluble in the molten polymer matrix which in turn affected the physiochemical and drug release properties from hot melt extrudates. Rheological characteri ation using capillary rheometry showed that Eudragit" RL PO exhibited non ewtonian flow behaviour. Power law index and activation energy (Ea) were calculated for the pure polymer. Shear rate did not exert a significant influence on the Eudragit" RL PO microstructre post processing and the glass transition temperature and water uptake properties of the polymer remained unchanged. Significant die swell post processing was observed and was counteracted by increasing the length of extrusion die. Addition of QB to the formulation caused an improvement in the thermal processability of the material due to solid-state plasticization of the polymer. Application of a drawing force on the drug release properties from QB loaded Eudragit" RL PO extrudates were evaluated and no significant difference in the dissolution properties were observed at any of the applied drawing forces.

In the present work the application potential of injection molding (IM) and micromolding (µIM) for the manufacturing of drug products was investigated. These techniques are largely employed in the plastics industry to process thermoplastic polymers into objects with different size, shape and possibly many details, and they could offer several advantages in the pharmaceutical area, mainly related to versatility, patentability, scalability and production costs (continuous manufacturing). Processes and equipment generally employed as well as current pharmaceutical applications already proposed in the literature were preliminarily reviewed. Drug delivery systems (DDSs) in the form of gastro-resistant containers based on HPMCAS were afterwards designed and manufactured by µIM. Notably, such DDSs represent a step forward in the field as they may provide a ready-to-use alternative to enteric-coated dosage forms. Moreover, the feasibility by hot-processing techniques (hot melt extrusion and IM) of prolonged-release hydrophilic matrices and immediate release tablets was demonstrated, which could help promoting the use of continuous manufacturing in the pharmaceutical production areas.

The use of amorphous solid dispersions (ASDs) is an effective and increasingly widely adopted approach for solubility and bioavailability enhancement of hydrophobic drugs. Cellulose derivatives have strong potential as ASD polymers. We demonstrate herein design, synthesis and structure-property relationship characterization of a new series of organo-soluble cellulose omega-carboxyalkanoates for ASDs, by two different synthetic approaches. These carboxyl-containing cellulose mixed-esters possessed relatively high Tg values with sufficient differences versus ambient temperature, useful to prevent drug mobility and crystallization during storage or transport. Screening experiments were utilized to study the impact of ASD polymers including our new family of cellulose Ω-carboxyesters on both nucleation induction time and crystal growth rate of three poorly soluble model drugs from supersaturated solutions. Attributed to relatively rigid structures and bulky substituent groups, cellulose derivatives were more significant crystallization inhibitors compared to the synthetic polymers. The effective cellulose omega-carboxyesters were identified as possessing a similar hydrophobicity to the drug molecule and high number of ionization groups. Among them, cellulose acetate suberate prepared by us was an extraordinary solution crystal growth inhibitor for ritonavir and its formulated solid dispersions provided a substantial 15-fold enhancement of apparent solution concentration vs. the equilibrium solubility of the crystalline drug. To offset the issue of slow drug release from some cellulose omega-carboxyester based formulations, a new class of amphiphilic cellulosic polymers with hydrophilic oligo(ethylene oxide)-containing side chains was developed via versatile synthetic pathways, and the evaluation of these materials alone or by pairwise polymer blends will be performed as ASD matrices for the enhancement of drug solubility and stability.
Ph. D.

The complete regeneration of damaged human tissues and organs is still a significant challenge. The integrative use of biomaterials, cells and bioactive factors in all-in-one devices exploits all current knowledge of materials science, nanotechnology and stem cell biology to best mimic the complex hierarchical architecture of native tissues. The artificial microenvironment design must be properly tuned to match the physicochemical features of the target, offering adequate nanoscale patterns and biological domains for cellular interactions. Scaffolds must promote and guide the regeneration route by mimicking host signalling pathways through the controlled release and retention of drugs or growth factors. For these purposes, polysaccharides have been often used and proposed to manufacture bioengineered scaffolds for regenerative medicine applications due to high biomimetic characteristics. The efforts made by researchers have highlighted how the cellular interactions with electrospun biomaterials offer excellent performances to achieve the desired differentiation and integration with the surrounding tissue. Alkyl derivatives of gellan gum (GG) and hyaluronic acid (HA) have been investigated as novel bioactive electrospun membranes for wound healing and periodontal regeneration. In this thesis, all the derivatives of these two polysaccharides have been produced via activation of the primary hydroxyl groups of β-glucose of gellan gum or N-acetyl-D-glucosamine of hyaluronic acid with bis(4-nitrophenyl) carbonate and the grafts of aliphatic chains at a different length. For hyaluronic derivatives, small moieties with free amino groups have been additionally inserted with the same chemistry. Membranes based on the octyl- and dodecyl-derivative of gellan gum (GG-C8 and GG-C12) have been produced by electrospinning and characterized in terms of fiber distribution and orientation verifying the improved processability of the polymers compared to native gellan gum. Rheological analyses have studied the influence of alkyl derivatization on the spinnability of blends. The feasibility of the process regarded the octyl-derivative one, so the swelling ability of such scaffold has been analyzed under physiological conditions after crosslinking with calcium chloride at different concentrations. To treat partial-thickness wounds, the membrane has been proposed to improve the cell homing at the damaged site, the adhesion of cells, and to encourage the regeneration of the extracellular matrix lost. Similar instrumental settings are used to incorporate the growth factor FGF-2 in the octyl-based membrane (GG-C8). The study has investigated physical interactions between the active and the polymer and how the ionotropic sensitivity of the GG-C8 could be exploited to assess a suitable FGF-2 releasing profile. The fabrication of the bilayer biodevice has involved a hydrophilic layer covered by a synthetic polyurethane layer loaded with ciprofloxacin. Considering the crosslinking degree of the membrane, the dissolution rate and the releases of FGF-2 and ciprofloxacin have been valued with Franz cells. The antibacterial effect of the bilayer has been investigated against the inhibition of units forming colonies of Staphylococcus aureus in the timeframe compatible with the complete regeneration of the tissue. The chemoattraction ability of the scaffold and the cytocompatibility have been tested using cultures of human fibroblasts (NIH3T3) by a specific migration assay. Electrospun membranes based on four chemical derivatives of hyaluronic acid at increasing hydrophobic character have been prepared and loaded with dexamethasone (a known osteoinductive drug) to induce osteogenic differentiation in pre-osteoblasts (MC3T3). The fibrillar supports have been characterized with a scanning electron microscope, and the hydrolytic and enzymatic degradation, as well as dexamethasone releases, have been tested after an autocrosslinking procedure. HA membranes have been designed as guided-bone regeneration barriers for periodontal regeneration; thus, wettability properties and biological performances have been investigated. The proliferation of cells above membranes is valued for up to seven days, and in vitro osteogenic induction is followed by quantifying the activity of alkaline phosphatases and evaluating the calcium content after one month of MC3T3 cultures. The final aim of the thesis is to fabricate a hyaluronan based membrane with high antibacterial properties for the healing of chronic wounds. The proposed membrane consists of incorporating graphene oxide in an electrospun membrane of a hydrophilic derivative of HA loaded with ciprofloxacin. According to an external laser stimulation in the near-infrared, the drug-releasing profile and hyperthermal features have been studied and related to the ability to eradicate bacterial infections and inhibit the generation of biofilm. The cytocompatibility has been valued culturing fibroblasts for up to three days, and the membrane was valued as a wound dressing system.

De acordo com o conceito de sistemas de liberação controlada, o presente estudo foi baseado na utilização de polímeros hidrofílicos biocompatíveis, formadores de hidrogéis, para o desenvolvimento de matrizes na forma de filmes finos. Os polímeros utilizados para a formação das matrizes foram a quitosana proveniente das cascas de camarão, o amido de milho modificado e a poli(N-vinil-2-pirrolidona) - PVP. As matrizes foram reticuladas utilizando glutaraldeído. O fármaco escolhido para testar a capacidade de liberação dos dispositivos foi o anti-inflamatório não esteroidal (AINE) diclofenaco sódico. Para obtenção das matrizes com propriedades adequadas para essa finalidade, foram testadas misturas de quitosana-amido e quitosana-PVP. Após a triagem qualitativa, os dispositivos foram avaliados quanto à citotoxidade, intumescimento máximo, fração gel, parâmetros cinéticos associados à absorção de vapor de água e à capacidade de liberação de diclofenaco sódico in vitro. As formulações de quitosana-PVP foram as que apresentaram melhores propriedades para a aplicação proposta nesse estudo, se destacando a formulação A3, com alto percentual de liberação, boas propriedades de manuseio, poucos componentes na formulação diminuindo o potencial alergênico e aprovação no teste de citotoxicidade em células de camundongo (NCTC) pelo método de incorporação do vermelho neutro.
According to the concept of drug delivery systems, this study has based on the use of biocompatible hydrophilic polymers hydrogels-forming for the development of matrices in the form of thin films. The polymers used for forming the matrices were chitosan from shrimp shells, modified maize starch and poly(N-vinyl-2-pyrrolidone) PVP. The matrices were cross-linked using glutaraldehyde. The drug chosen to test the ability of the devices release was the non-steroidal anti-inflammatory drug (NSAID) sodium diclofenac. Mixtures between chitosan-starch and chitosan-PVP tested to obtain the matrices with suitable properties for this purpose. The devices after qualitative screening had evaluated for cytotoxicity, maximum swelling, gel fraction, kinetic parameters associated with absorbing water vapor and the release of diclofenac sodium able to in vitro. The formulations based on chitosan-PVP were the presents the best properties, in evidence formulation A3, with high percentage of delivery, good handing properties, few compounds/components reducing the allergenic potential and successful in vitro cell viability red uptake cytotoxicity assay, using cell culture mouse cells (NCTC).

Un polymère à empreintes moléculaires (MIP) est un récepteur synthétique supramoléculaire, un matériau possédant des cavités pouvant reconnaître spécifiquement une molécule cible. Il est synthétisé en mettant en contact la molécule cible, avec un mélange de monomères fonctionnels et réticulants qui permettent d'obtenir un réseau polymérique tridimensionnel rigide. L'élimination de la molécule empreinte laissera des sites vides complémentaires de cette dernière. Ces cavités sont maintenant capables de la recapturer spécifiquement. Ces polymères sont utilisés dans les domaines tels que l’extraction en phase solide, la chromatographie d’affinité, la catalyse enzymatique, les biocapteurs et la vectorisation des médicaments. Bien que le concept des MIPs a pour origine les travaux réalisés sur des matériaux sol-gel imprimés dans les années 1930, ces derniers sont restés dans l’ombre jusqu’à l'introduction de polymères organiques imprimés plus versatiles. Par rapport aux MIPs organiques, les MIPs sol-gel présentent quelques avantages comme une plus grande stabilité thermique, une meilleure compatibilité avec l'eau et une plus grande porosité. Dans cette thèse, nous avons développé des MIPs organiques et des MIPs sol-gel pour leur application en cosmétologie et pour la vectorisation de médicaments. Dans la première partie, nous présentons des MIPs pouvant adsorber d’une façon spécifique l’acide oléique (OA), un biomarqueur de l’état pelliculaire sur le cuir chevelu. Pour la préparation des MIPs organiques, nous avons employé plusieurs monomères basiques dont l’acryloylaminobenzamidine (AB), que nous avons tout spécialement synthétisé. Tous les MIPs pouvaient lier l’OA mais beaucoup d’interaction non-spécifique était observé. D’autre part, les MIPs sol-gel présentaient une bonne reconnaissance spécifique et une capacité élevée pour OA; par exemple, un MIP de composition OA:APTES:TEOS = 1:1.6:1.7 pouvait adsorber 625 μmol.g-1 de OA dans le sébum artificiel. Des tests pour capturer l’OA sur le stratum corneum et la peau reconstruite (Episkin) ont également été effectués. La pénétration de l’OA sur les deux types de peau était plus faible en présence de MIP que de NIP. Les MIPs comme matériaux désodorisants font l’objet de la deuxième partie de cette thèse. Des MIPs pouvant adsorber les précurseurs de molécules malodorantes comme les conjugués glutamine des acides (E)-3-méthyl-2-hexénoïque (3M2H) et 3-hydroxy-3-méthyl-hexanoïque (3H3MH) ont été préparés. Le N-hexanoyl glutamine et le N-hexanoyl glutamate ont été utilisés comme template. Nous observons que le MIP synthétisé avec AB comme monomère fonctionnel possède la plus grande capacité d'adsorption pour le N-hexanoyl glutamine, ainsi que pour les précurseurs glutamines des molécules malodorantes. Des résultats préliminaires et très prometteurs ont également été obtenus dans la sueur. La dernière partie de cette thèse concerne des MIPs pour la vectorisation de médicaments. L'acide salicylique (SA) est un médicament efficace utilisé dans le traitement de l’acné. Des MIPs organiques et sol-gel contre SA ont été synthétisés. Les MIPs sol-gel ont une plus grande capacité d’adsorption, 180 μmol.g-1, que les MIPs organiques et ils lient le SA sept fois plus que le NIP. Les tests de relargage du SA ont été effectués dans plusieurs milieux, avec la plus grande efficacité dans l’eau pure. En conclusion, les applications de MIPs en cosmétologie et en vectorisation de médicaments ont étés étudiés. Nos résultats montrent que les MIPs sol-gel sont les plus appropriés pour ce type de travail
Molecularly imprinted polymers (MIPs) are tailor-made synthetic receptors possessing specific cavities for a given target molecule. They are produced by introducing, into the polymer precursors, guest molecules that act as templates at the molecular level. Interacting and cross-linking monomers are then copolymerized to form a cast-like shell. After removal of the template, cavities complementary to the template in size, shape and position of functional groups are revealed in the polymer, which can now specifically bind the template. Thanks to these specific molecular recognition properties, MIPs have found applications in areas like bio sensors, solid phase extraction, affinity chromatography, catalysis, and drug delivery. Although the MIP concept originated from imprinted silica in the 1930s, imprinted sol-gel materials received little attention afterwards due to the introduction of the more versatile organic polymers as imprinting matrix. However, compared to organic polymers, sol-gels possess higher thermal stability, better water compatibility and larger inner surface area. There have been many applications to biomolecules in aqueous conditions with sol-gel imprinting materials. In this thesis, we have developed organic and silica sol-gel MIPs for applications in cosmetics and drug delivery. MIPs able to adsorb the dandruff-inducing molecule oleic acid (OA) were produced via both the organic and inorganic routes. In the organic MIPs synthesis, different positively charged monomers were used, one of which, acryloyl aminobenzamidine, was specifically synthesized. Although some binding of oleic acid was obtained, specificity and capacity of these polymers were not satisfying. Sol-gel MIPs, on the other hand, exhibited good specific recognition and high binding capacity for OA. A MIP of the composition OA:APTES:TEOS= 1:1.6:1.7 yielded a capacity of 625 μmol.g-1 in artificial sebum. Furthermore, tests were carried out to capture OA on stratum corneum and reconstructed skin (Episkin). Less penetration of OA was observed in the presence of a MIP than with a non-imprinted control polymer. Deodorant materials are another topic of this thesis. MIPs that are able to adsorb certain precursors of odorant molecules, the glutamine conjugates of (E)-3-methyl-2-hexenoic acid (3M2H) and 3-hydroxy-3-methyl-hexanoic acid (3H3MH) were prepared. N-hexanoyl glutamine and N-hexanoyl glutamate were used as templates. After optimization of the MIP composition, we found that MIPs synthesized with acryloyl aminobenzamidine as functional monomer had the highest adsorption capacity for N-hexanoyl glutamine, and also recognised the glutamine targets of 3M2H and 3H3MH. Some preliminary promising binding results were obtained in artificial sweat. The third part of this work concerns a drug delivery MIP. Salicylic acid (SA) is a drug used to treat acne. SA-imprinted polymers were prepared via both organic imprinting and the sol-gel process.Compared to organic MIPs, sol-gel MIPs have a higher capacity, 180 μmol.g-1, and 7 times higher binding than to a non-imprinted control polymer was observed. Release tests were carried out in different aqueous media, the most efficient drug release was observed in pure water. In conclusion, applications of molecularly imprinted polymers for cosmetics and drug delivery have been investigated. Our results demonstrate the great potential of in particular sol-gel MIPs for these purposes

Les hydrogels sont des réseaux 3D retenant de grandes quantités d'eau. Biocompatibles, ils sont utilisés pour la délivrance de médicaments. Dans le but de développer des hydrogels antibactériens, cette thèse présente deux études basées sur l'utilisation d'un tripeptide phosphorylé protégé par un fluorénylméthoxycarbonyle (Fmoc), qui peut s'auto-assembler en hydrogel. Dans la première étude, différentes conditions de préparation (pH, sel, présence de polysaccharide) ont été étudiées pour former un hydrogel autocicatrisant et antibactérien libérant un antibiotique, le florfénicol. Dans la seconde étude, des stratégies de synthèse peptidiques et de phosphoramidites en phase solide ont été combinées pour ajouter le florfénicol au phosphate de tyrosine protégé par le Fmoc via un phosphodiester, clivable par des nucléases produites par des bactéries. Des résultats encourageants ont montré la formation du composé ciblé, ouvrant la voie au design d'un peptide antibactérien auto-défensif
Hydrogels are 3D networks of fibers that retain large amounts of water when swollen. Due to their biocompatibility, they are increasingly used for drug delivery. To develop antibacterial peptide-based hydrogels, this dissertation presents two studies based on the use of a fluorenylmethoxycarbonyl (Fmoc)-protected phosphorylated tripeptide that can self-assemble into a hydrogel. In the first study, different preparation conditions (pH, salt, presence of polysaccharide) were investigated to obtain a self-healing and antibacterial hydrogel capable of releasing an antibiotic, florfenicol. In the second study, a solid-phase peptide and phosphoramidite synthesis strategies were combined to add florfenicol to the Fmoc-protected tyrosine phosphate via a phosphodiester, which can be cleaved by nucleases produced by bacteria. Encouraging results showed the formation of the targeted compound, paving the way for the design of a self-defensive antibacterial peptide

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Résume: La capacité d'assemblage de composants organique, inorganique, et même bioactifs dans un matériel unique représente une orientation intéressante pour développer des nouveau matériaux multifonctionnels hybride. Dans ces hybrides, l'association des caractéristiques des composés organiques et inorganiques permet à de nouveaux matériaux présentant des propriétés uniques telles que la résistance mécanique élevée, la transparence et de souplesse, étant adaptée à une application dans plusieurs domaines scientifiques et technologiques, y compris ceux de santé humaine. Cette these se concentre sur la relation entre la structure et les propriétés de libération des molécules anti-inflammatoire (diclofenac sodium) et à base de platine antitumorale (cisplatine) incorporées dans des matériaux siloxane polyéther. Pour parvenir à un contrôle précis du taux de libération du médicament, différentes proportions de polymères hydrophilic (PEO)/hydrophobic (PPO) ont été combinés. Ces matrices ont été préparées par mélange de différentes fractions de précurseurs hybrides siloxane-poly (oxyde d'éthylène) (PEO) et siloxane-poly (oxyde de propylène) (PPO). Molécules de médicaments ont été incorporée lors des étapes de l’hydrolyse et polycondensation. La structure nanoscopique de xérogel a été analysée par difusion de la lumiere à petites angles (SAXS) et les propriétés de libération du médicament par les UVvis spectroscopie. En plus la structure de le médicament cisplatine incorporés dans les matrices hybrides a été étudiée atravers de la couplage de Raman-UVvis et EXAFS spectroscopies. Les résultats (SAXS) montrent que la structure nanoscopie de tous les hybrides siloxane polyéther peut être décrite par un modèle de deux densités életroniques. La distance régulière entre les domaines inorganiques imposées... (Résume complet accès électronique ci-dessous)
A capacidade de moldar materiais a partir de componentes orgânicos, inorgânicos, e mesmo bioativos em uma única direção é interessante para desenvolver novos materiais híbridos multifuncionais. Nesses híbridos, a associação das características dos compostos orgânicos e inorgânicos permite obter novos materiais com propriedades únicas como alta resistência mecânica, transparência e flexibilidade, sendo adequado para aplicação em vários campos da ciência e tecnologia, incluindo as da saúde humana. Esta tese foca a relação entre estrutura e propriedades de liberação de moléculas antiinflamatórias (diclofenaco de sódio DCFNa) e antitumoral a base de platina (cisplatina CisPt) incorporada em materiais siloxano-poliéter. Para conseguir um controle preciso da taxa de liberação dos fármacos, diferentes proporções de polímeros hidrofílicos (PEO)/hidrofóbicas (PPO) foram combinados. Essas matrizes foram preparadas pela mistura de diferentes proporções de precursor híbrido de siloxano-poli (óxido de etileno) (PEO) e siloxano-poli (óxido de propileno) (PPO). Moléculas do fármaco foram incorporadas durante as etapas de hidrólise e policondensação. A estrutura nanoscopica dos xerogéis foi analisada por espalhamento de raios X a baixos ângulos (SAXS) e as propriedades de liberação do fármaco por espectroscopia UV-vis. Além disso, a estrutura do fármaco cisplatina incorporado nas matrizes híbridas foi estudada através de medidas simmultaneas UV-vis-Raman e espectroscopia EXAFS. Os resultados (SAXS) mostram que a estrutura nanoscopia de todos os híbridos siloxano-poliéter pode ser descrita por um modelo de duas densidades eletrônicas. A distância medias de correlação entre os domínios inorgânicos impostas pelo tamanho das cadeias poliméricas foi confirmada pelo pico de correlação observada nas curvas de SAXS. Isto foi confirmado pela...

Resumo: A capacidade de moldar materiais a partir de componentes orgânicos, inorgânicos, e mesmo bioativos em uma única direção é interessante para desenvolver novos materiais híbridos multifuncionais. Nesses híbridos, a associação das características dos compostos orgânicos e inorgânicos permite obter novos materiais com propriedades únicas como alta resistência mecânica, transparência e flexibilidade, sendo adequado para aplicação em vários campos da ciência e tecnologia, incluindo as da saúde humana. Esta tese foca a relação entre estrutura e propriedades de liberação de moléculas antiinflamatórias (diclofenaco de sódio DCFNa) e antitumoral a base de platina (cisplatina CisPt) incorporada em materiais siloxano-poliéter. Para conseguir um controle preciso da taxa de liberação dos fármacos, diferentes proporções de polímeros hidrofílicos (PEO)/hidrofóbicas (PPO) foram combinados. Essas matrizes foram preparadas pela mistura de diferentes proporções de precursor híbrido de siloxano-poli (óxido de etileno) (PEO) e siloxano-poli (óxido de propileno) (PPO). Moléculas do fármaco foram incorporadas durante as etapas de hidrólise e policondensação. A estrutura nanoscopica dos xerogéis foi analisada por espalhamento de raios X a baixos ângulos (SAXS) e as propriedades de liberação do fármaco por espectroscopia UV-vis. Além disso, a estrutura do fármaco cisplatina incorporado nas matrizes híbridas foi estudada através de medidas simmultaneas UV-vis-Raman e espectroscopia EXAFS. Os resultados (SAXS) mostram que a estrutura nanoscopia de todos os híbridos siloxano-poliéter pode ser descrita por um modelo de duas densidades eletrônicas. A distância medias de correlação entre os domínios inorgânicos impostas pelo tamanho das cadeias poliméricas foi confirmada pelo pico de correlação observada nas curvas de SAXS. Isto foi confirmado pela... (Resumo completo, clicar acesso eletrônico abaixo)
Résume: La capacité d'assemblage de composants organique, inorganique, et même bioactifs dans un matériel unique représente une orientation intéressante pour développer des nouveau matériaux multifonctionnels hybride. Dans ces hybrides, l'association des caractéristiques des composés organiques et inorganiques permet à de nouveaux matériaux présentant des propriétés uniques telles que la résistance mécanique élevée, la transparence et de souplesse, étant adaptée à une application dans plusieurs domaines scientifiques et technologiques, y compris ceux de santé humaine. Cette these se concentre sur la relation entre la structure et les propriétés de libération des molécules anti-inflammatoire (diclofenac sodium) et à base de platine antitumorale (cisplatine) incorporées dans des matériaux siloxane polyéther. Pour parvenir à un contrôle précis du taux de libération du médicament, différentes proportions de polymères hydrophilic (PEO)/hydrophobic (PPO) ont été combinés. Ces matrices ont été préparées par mélange de différentes fractions de précurseurs hybrides siloxane-poly (oxyde d'éthylène) (PEO) et siloxane-poly (oxyde de propylène) (PPO). Molécules de médicaments ont été incorporée lors des étapes de l'hydrolyse et polycondensation. La structure nanoscopique de xérogel a été analysée par difusion de la lumiere à petites angles (SAXS) et les propriétés de libération du médicament par les UVvis spectroscopie. En plus la structure de le médicament cisplatine incorporés dans les matrices hybrides a été étudiée atravers de la couplage de Raman-UVvis et EXAFS spectroscopies. Les résultats (SAXS) montrent que la structure nanoscopie de tous les hybrides siloxane polyéther peut être décrite par un modèle de deux densités életroniques. La distance régulière entre les domaines inorganiques imposées... (Résume complet accès électronique ci-dessous)
Orientador: Celso Valentim Santilli
Coorientador: Valérie Briois
Banca: Marian Rosaly Davolos
Banca: Pedro de Oliveira
Banca: Maria Palmira Daflon Gremião
Banca: Jean-Louis Bantignies
Doutor

Solid dispersion technology represents a well-established approach for enhancing dissolution and oral bioavailability of BCS Class II drugs. This work explores the use of a solvent-free temperature-controlled centrifugal spinning process as an alternative technique for producing amorphous solid dispersions in the form of drugloaded sucrose microfibres. This technique has promising large scale production capability and microfibres can be prepared with significant dissolution improvements for three BCS Class II model drugs olanzapine, piroxicam and itraconazole, assessed in both sink and non-sink conditions. This was attributed to the amorphous nature, the solubilising capacity of sucrose and the high surface area of the microfibres formed. However, because of the hygroscopic nature of amorphous sucrose, such microfibres were found to rapidly recrystallise when exposed to high moisture environment. Drugloaded microfibres were observed to collapse into a fine powder and a detrimental effect on the dissolution performance was expected as a result of the moistureinduced recrystallisation. Unexpectedly, the solubility advantage was instead fairly preserved if not enhanced in the case of itraconazole, leaving a product with higher physical stability and morphological properties that is less difficult to handle and process into a conventional dosage form compared to the original product. In fact, moisture-treated itraconazole-loaded microfibres were successfully incorporated into tablets and the influence of several tableting process variables on the tablet characteristics were also evaluated. For instance, by increasing the compression force, tablets with different disintegration times and drug potency could be produced and the latter factor was found to significantly affect the drug dissolution performance, especially in terms of degree and extent of drug supersaturation. Overall, these findings suggest that is not only possible to produce a product with high yield, enhanced dissolution performance and physical stability, but also the final product can be easily incorporated into conventional tablets, while preserving the solubility advantage.

Thesis (Ph.D.)--University of Mississippi, 2008.
Typescript. Vita. "March 2008." Major professor: Dr. Michael Repka Includes bibliographical references (leaves 306-326). Also available online via ProQuest to authorized users.

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Dissertação (Mestrado)
IPEN/D
Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP

Chaque année, environ 1,5 million de patients requièrent un remplacement vasculaire en réponse à une athérosclérose avancée, causant le rétrécissement interne des vaisseaux sanguins. Malheureusement, encore aujourd'hui les matériaux synthétiques utilisés pour remplacer les artères de petits diamètres (inférieurs à 6 mm) restent associés à un haut taux d'échecs, démontrant ainsi un manque de biocompatibilité certain. L'une des principales complications observées est l'hyperplasie néointimale artérielle caractérisée par l'obstruction du vaisseau sanguin due à la prolifération tridimensionnelle de cellules sur la paroi interne de la prothèse. Différentes stratégies visant à limiter cette réaction naturelle sont aujourd'hui envisagées, notamment l'utilisation d'un système à libération contrôlée de médicament intégré localement aux prothèses vasculaires. En parallèle, l'essor des technologies plasma a permis de montrer qu'il était possible de revêtir la surface de matériel biomédical pour améliorer son interaction avec un environnement biologique. La stratégie consiste à utiliser l'énergie et la réactivité d'un plasma pour polymériser un précurseur gazeux. En sélectionnant la structure moléculaire du précurseur et les conditions expérimentales du plasma appropriées, il est possible de déposer un polymère plasma à la surface du matériel sélectionné pour lui conférer des propriétés sur mesure. C'est dans ce contexte que cette thèse a consisté à synthétiser, à l'aide d'un plasma, une matrice polymère plasma biodégradable pour revêtir la paroi interne d'une prothèse vasculaire, dans le but d'y incorporer un médicament choisi de façon à limiter l'hyperplasie néointimale. Ce projet a permis d'une part de réaliser une preuve de concept en déposant un revêtement polymère plasma dégradable par décharge à barrière diélectrique en configuration planaire. En utilisant le lactate d'éthyle en tant que précurseur et après de nombreuses analyses, des conditions de dépôt optimales ont pu être élues pour leur potentiel dans le cadre d'applications vasculaires. D'autre part, grâce à une caractérisation approfondie de la décharge, une corrélation étroite entre la physico-chimie du plasma et les dépôts dégradables obtenus a pu être établie. Afin d'élargir les possibilités de vitesse de dégradation, l'influence d'une alimentation impulsionnelle sur la décharge et sur le dépôt a de plus été étudiée. Si la manière d'apporter l'énergie a eu une forte influence sur la décharge, aucune influence majeure n'a été notée sur la chimie et la morphologie des dépôts faits à partir de lactate d'éthyle. Enfin, la construction d'un réacteur plasma tubulaire permettant de déposer la matrice développée à l'intérieur de prothèses artérielles a permis de s'étendre aux conditions réelles de dépôt. Dans l'ensemble, ce projet de recherche a mis en évidence le potentiel des procédés plasma pour le développement de matrices polymères plasma dégradables, notamment dans le cadre de systèmes à libération contrôlée et locale de médicaments pour des applications en chirurgie vasculaire. D'un point de vue de la physique des plasmas, ce travail a de plus souligné l'importance de l'étude de la décharge dans de véritables conditions de dépôt de couches minces
Every year, about 1.5 million patients need a vascular replacement due to advanced arteriosclerosis, which causes the internal narrowing of blood vessels. Unfortunately, even today the synthetic materials used to replace small diameter arteries (below 6 mm) remain associated with low patency rate, which demonstrates an evident lack of biocompatibility. One of the main observed complications is arterial neointimal hyperplasia, which is characterized by the blood vessel obstruction due to the tridimensional proliferation of cells on the graft internal wall. Different strategies aiming at limiting this body reaction are currently considered, in particular the use of a drug delivery system locally integrated to the vascular grafts. Concurrently, the rise of plasma technologies enabled to demonstrate the possibility to coat the surface of biomedical devices to improve their interaction with a biological environment. The strategy consists in using the plasma energy and reactivity to polymerize a gaseous precursor. By selecting the appropriate precursor molecular structure and plasma experimental conditions, one can build up a plasma polymer with tailored properties. It is in this context that this thesis consisted in synthesizing, using plasma, a biodegradable polymeric plasma polymer matrix to coat the internal wall of a vascular graft, with the goal to incorporate a drug chosen to limit neointimal hyperplasia. On one hand, this project acted as proof of concept by developing a degradable plasma polymer coating using a planar dielectric barrier discharge. After extensive studies using ethyl lactate as precursor, optimal chemical vapor deposition conditions were elected for their potential in terms of vascular applications. On the other hand, thanks to an extended discharge characterization, a strong correlation was established between the plasma physico-chemistry and the properties of the degradable coatings synthesized. In addition, to broaden possibilities in terms of degradation rate, the influence of a squared pulse power supply on the discharge and the coating was studied. If changing the way to bring the energy had a strong influence on the discharge, no major influence was noticed on the ethyl lactate-based coatings' chemistry and morphology. Finally, a tubular plasma reactor was build up to empower the internal wall of vascular prosthesis to be coated, which enabled to extend this project to the deposition conditions of its final application. Overall, this research project highlighted the potential of plasma processes for the development of degradable plasma polymer matrices, particularly for local drug delivery systems for vascular applications. On a physics perspective, this work emphasized the importance of studying the discharge under actual thin layer deposition conditions

Il sistema nervoso centrale svolge un ruolo chiave nella raccolta, integrazione ed elaborazione delle informazioni provenienti dagli organi di senso e dall’ambiente interno dell’organismo. La sua struttura, formata da una complessa rete neurale finemente organizzata può essere soggetta a danni di vario tipo, che ne minano le funzionalità. Per far fronte a tale evenienza, negli ultimi anni, sta emergendo una nuova scienza dal carattere fortemente multidisciplinare, ovvero la medicina neurorigenerativa. Essa comprende l’ingegneria tissutale, che mira all’ingegnerizzazione dei materiali per la produzione di supporti per la rigenerazione (scaffold), la neurologia, e l’ingegneria biomedica. Scopo di questa tesi è stato quello di passare in rassegna le ricerche più recenti sui materiali impiegati per la medicina neurorigenerativa, così come le tecniche e le tecnologie emergenti per il loro processo. In particolare, i polimeri naturali e di sintesi rappresentano una reale potenzialità per possibili interventi terapeutici. D’altra parte, tecnologie di processo quali l’electrospinning e la stampa tridimensionale (3D BIOPRINTING) hanno consentito di progredire notevolmente nella fabbricazione di supporti finalizzati allo sviluppo di impianti neurorigenerativi eterologhi o coadiuvanti l’impianto autologo. In particolare, il 3D Bioprinting è una tecnologia che ha la potenzialità di consentire, in un prossimo futuro, di riprodurre con precisione sempre maggiore la delicata organizzazione spaziale e strutturale gerarchica della matrice extracellulare neuronale. I vantaggi e le applicazioni del Bioprinting sono potenzialmente vastissimi e ancora in fase di esplorazione. L’impatto di nuove tecnologie, nuovi materiali e tecniche bioigegneristiche d’avanguardia potrebbero rappresentare non solo un passo avanti nel campo della rigenerazione neurale, ma anche per la comprensione di processi fisiologici ed ancor di più patofisiologici del Sistema Nervoso Centrale.

The oral delivery of drugs has several disadvantages, particularly in pediatrics, geriatrics and other patients experiencing difficulty in swallowing tablets or capsules. A frequent approach to this problem is the use of liquid formulations or buccal drug delivery systems. However, with liquid formulations, many drugs have an undesirable solubility or stability in appropriate solvents and dosing accuracy is compromised due to the patient being required to measure doses. Current rapidly disintegrating buccal drug delivery systems, such as buccal tablets, are able to dissolve rapidly within the oral cavity; however the short residence time at the absorption surface is a limiting factor in the effectiveness of these delivery systems. Furthermore, buccal tablet and wafer systems tend to be brittle and fragile and hence require special protective packaging. A rapidly disintegrating, flexible, mucoadhesive fibrous matrix system (FMS) with drug-loaded electrospun fibers incorporated onto a polymeric backing film may be capable of overcoming some of the innate disadvantages of the non-invasive delivery of various drugs, especially those requiring a rapid onset of action. Various electrospinnable polymers were investigated for suitability in the development of the electrospun fibrous layer of the FMS, and it was determined that polyvinylalcohol (PVA) produced drug-loaded fibers with the most acceptable morphology and a desirable disintegration time. An ideal drug-loaded fiber formulation was obtained by design of experiments and employed in further investigations. The original model drug, zidovudine (AZT), exhibited less than 1% permeation after 90 minutes. Permeation was not adequately increased by penetration enhancers, and AZT was therefore tested against diphenhydramine (DPH), which exhibited 42-82% permeation after 5 minutes. The polymeric backing film layer was developed by investigating various film-forming polymers and methods of film or membrane preparation. Acceptable films were produced by film-casting of solutions containing combinations of PVA and hydroxypropylmethylcellulose (HPMC), and variables for an Experimental Design were obtained. The variables were fill volume (40-100mL), HPMC concentration (0-0.5%w/v) and concentration of glycerol (10-15%w/w of total polymer mass). The film layer was optimized according to a Box-Behnken experimental design, employing the responses disintegration time, work of adhesion, maximum detachment force, dissolution and ex vivo permeation. In vitro physicochemical and physicomechanical characterization, as well as ex vivo analysis, was performed on the optimized FMS in order to assess the suitability of the system for rapid oramucosal drug delivery. The FMS was deemed to be suitable for buccal drug delivery and able to overcome some of the inherent limitations of current drug delivery systems.

Nanostructured drug delivery systems (DDS) have drawn great attention in these last years due to the improvement of the efficacy of therapeutic principle, by enhancing their biocompatibility, bioavailability and targeting. Particular interest was focused on the design and development of multifunctional architectures for the delivery of different therapeutics and diagnostic agents and their spatially and temporally controlled release. In this study we report the design, synthesis and characterization of two main categories of nanostructured functional materials for drug delivery: simple DDS based on inorganic and magnetic nanoparticles (MNPs) and more complex hybrid responsive platforms based on lipids and MNPs. Calcium Phosphate NPs decorated with oligonucleotide single and double strands as nanocarriers for gene delivery endowed of high biodegradability and biocompatibility, were synthesized and characterized by DLS and Atomic Force Microscopy. Moreover, magnetic core-shell hydrophobic and hydrophilic nanoparticles of magnetite (Au@Fe3O4) were prepared and characterized through DLS and SAXS. These MNPs, having suitable sizes to be incorporated in the lipid bilayers and in the aqueous core of liposomes (magnetoliposomes), were used as actuators for the magnetic triggered release of Carboxyfluorescein from the core of liposomes dispersed in biological fluids (serum 10% and 55% in protein concentration), in order to study the effects of the serum proteins on the release behavior. The design, preparation and characterization of another hybrid lipid/MNPs DDS, where hydrophobic Fe3O4 NPs are embedded in the bilayer of bicontinuous cubic lipid phase of Glyceryl Monooleate (GMO), either in bulk phase and in dispersed cubic lipid nanoparticles (magnetocubosomes), were performed. Furthermore, for the first time Fluorescence Correlation Spectroscopy was employed to investigate the magnetoliposomes’ ability to encapsulate simultaneously both hydrophilic and hydrophobic drugs and also to study their diffusion inside the bicontinuous cubic phase domains. Finally, with the same technique a magnetically triggered release of a hydrophilic model drug toward an aqueous environment from aqueous channels of both bulk cubic phase, doped with MNPs, and magnetoliposomes was monitored highlighting that a low-frequency alternating magnetic field (LF-AMF) can act as an external trigger to boost the release of a model drugs confined in the cubic phase.

The aim of the present study was to formulate oral modified release matrices of diclofenac sodium, using the Eudragit® polymers. In addition to the formulation processes, numerous variables had to be investigated, which included dissolution variables, formulation variables, and processing variables. The application of the tabletting technique as well as the use of Eudragit® polymers to modify the release of diclofenac sodium is motivated at the outset. A comprehensive review of modified drug release, the use of the tabletting methodologies and the application of Eudragit® polymers are presented. In-process quality control tests as well as the mechanisms and interpretation of the dissolution process are outlined. Diclofenac sodium, a potent nonsteroidal anti-inflammatory drug, was used in the present study, hence a brief review of this drug is also presented. The direct compression as well as the wet granulation tabletting methods were investigated. The major limitation of the direct compression method was found to be the lack of suitable flow properties of the powder blend. The wet granulation technique however, was successfully employed to prepare various diclofenac sodium Eudragit® matrix tablets. All tablets were prepared to contain 100 mg diclofenac sodium. The optimisation process was shown to be an integral procedure in influencing the matrix characteristics. In addition, it was shown that drug release was significantly influenced by different types and concentrations of Eudragit® polymers. A specific formulation was selected to investigate the integrity of the matrices produced by the wet granulation technique. The drug release profile of a commercially available modified release preparation containing diclofenac sodium viz. Veltex® 100 CR (reference standard) was also obtained. A comparison of the drug release profiles of Veltex® 100 CR capsules and the selected formulation showed them to be markedly dissimilar. Hence, a strong motivation is provided for rationalising the selection of the particular formulation in the present study, that was shown to release diclofenac sodium optimally. The selected formulation was prepared using a combination of the Eudragit® RL and Eudragit® RS polymers. In vitro dissolution studies on the selected as well as various other formulations demonstrated the wet granulation method to be both predictable and reproducible. However, absolute drug release independency of dissolution methods, media and agitation rates was unattainable. Furthermore, drug release was shown to be pH dependent. The selected formula was subjected to certain formulation and processing variables. An increase in the concentrations of lactose and starch was shown to increase drug release. Different types of diluents were also shown to influence drug release from the tablets. The method of incorporation of the lubricant, magnesium stearate, was investigated. Compression studies demonstrated the susceptibility of the tablets to changes in drug release behaviour and morphological characteristics as the hardness was varied. X-ray diffraction studies demonstrated that the processes of granulation and compression did not promote any atomic rearrangement of the drug and Eudragit® polymers. Scanning electron microscopy was useful in investigating the integrity and surface morphology of newly formulated as well as stored samples, while energy dispersive x-ray microprobe analysis adequately revealed the elemental composition of the tablets. The selected formulation was shown to be stable at room temperature (21 ±1°C) and low temperature (5± 1°C), while storage at 37°C with 80% relative humidity and 40°C demonstrated significantly decreased drug release behaviour during short term (3 months) stability testing. Tablet hardness evaluated during the stability testing showed that there were virtually no differences in tablet hardness between the room temperature and low temperature samples, while tablets stored at 37°C with 80% relative humidity and 40°C hardened considerably. However, tablet potencies and the moisture content of the samples were not significantly influenced during the storage period. In addition to usual observations and mathematical manipulation, some of the data generated from this study were also evaluated statistically.
Thesis (M.Sc.)-University of Durban-Westville, 1998.

Les amidons non modifiées et modifiés représentent un groupe d’excipients biodégradables et abondants particulièrement intéressant. Ils ont été largement utilisés en tant qu’excipients à des fins diverses dans des formulations de comprimés, tels que liants et/ou agents de délitement. Le carboxyméthylamidon sodique à haute teneur en amylose atomisé (SD HASCA) a été récemment proposé comme un excipient hydrophile à libération prolongée innovant dans les formes posologiques orales solides. Le carboxyméthylamidon sodique à haute teneur en amylose amorphe (HASCA) a d'abord été produit par l'éthérification de l'amidon de maïs à haute teneur en amylose avec le chloroacétate. HASCA a été par la suite séché par atomisation pour obtenir le SD HASCA. Ce nouvel excipient a montré des propriétés présentant certains avantages dans la production de formes galéniques à libération prolongée. Les comprimés matriciels produits à partir de SD HASCA sont peu coûteux, simples à formuler et faciles à produire par compression directe. Le principal objectif de cette recherche était de poursuivre le développement et l'optimisation des comprimés matriciels utilisant SD HASCA comme excipient pour des formulations orales à libération prolongée. A cet effet, des tests de dissolution simulant les conditions physiologiques du tractus gastro-intestinal les plus pertinentes, en tenant compte de la nature du polymère à l’étude, ont été utilisés pour évaluer les caractéristiques à libération prolongée et démontrer la performance des formulations SD HASCA. Une étude clinique exploratoire a également été réalisée pour évaluer les propriétés de libération prolongée de cette nouvelle forme galénique dans le tractus gastro-intestinal. Le premier article présenté dans cette thèse a évalué les propriétés de libération prolongée et l'intégrité physique de formulations contenant un mélange comprimé de principe actif, de chlorure de sodium et de SD HASCA, dans des milieux de dissolution biologiquement pertinentes. L'influence de différentes valeurs de pH acide et de temps de séjour dans le milieu acide a été étudiée. Le profil de libération prolongée du principe actif à partir d'une formulation de SD HASCA optimisée n'a pas été significativement affecté ni par la valeur de pH acide ni par le temps de séjour dans le milieu acide. Ces résultats suggèrent une influence limitée de la variabilité intra et interindividuelle du pH gastrique sur la cinétique de libération à partir de matrices de SD HASCA. De plus, la formulation optimisée a gardé son intégrité pendant toute la durée des tests de dissolution. L’étude in vivo exploratoire a démontré une absorption prolongée du principe actif après administration orale des comprimés matriciels de SD HASCA et a montré que les comprimés ne se sont pas désintégrés en passant par l'estomac et qu’ils ont résisté à l’hydrolyse par les α-amylases dans l'intestin. Le deuxième article présente le développement de comprimés SD HASCA pour une administration orale une fois par jour et deux fois par jour contenant du chlorhydrate de tramadol (100 mg et 200 mg). Ces formulations à libération prolongée ont présenté des valeurs de dureté élevées sans nécessiter l'ajout de liants, ce qui facilite la production et la manipulation des comprimés au niveau industriel. La force de compression appliquée pour produire les comprimés n'a pas d'incidence significative sur les profils de libération du principe actif. Le temps de libération totale à partir de comprimés SD HASCA a augmenté de manière significative avec le poids du comprimé et peut, de ce fait, être utilisé pour moduler le temps de libération à partir de ces formulations. Lorsque les comprimés ont été exposés à un gradient de pH et à un milieu à 40% d'éthanol, un gel très rigide s’est formé progressivement sur leur surface amenant à la libération prolongée du principe actif. Ces propriétés ont indiqué que SD HASCA est un excipient robuste pour la production de formes galéniques orales à libération prolongée, pouvant réduire la probabilité d’une libération massive de principe actif et, en conséquence, des effets secondaires, même dans le cas de co-administration avec une forte dose d'alcool. Le troisième article a étudié l'effet de α-amylase sur la libération de principe actif à partir de comprimés SD HASCA contenant de l’acétaminophène et du chlorhydrate de tramadol qui ont été développés dans les premières étapes de cette recherche (Acetaminophen SR et Tramadol SR). La modélisation mathématique a montré qu'une augmentation de la concentration d’α-amylase a entraîné une augmentation de l'érosion de polymère par rapport à la diffusion de principe actif comme étant le principal mécanisme contrôlant la libération de principe actif, pour les deux formulations et les deux temps de résidence en milieu acide. Cependant, même si le mécanisme de libération peut être affecté, des concentrations d’α-amylase allant de 0 UI/L à 20000 UI/L n'ont pas eu d'incidence significative sur les profils de libération prolongée à partir de comprimés SD HASCA, indépendamment de la durée de séjour en milieu acide, le principe actif utilisé, la teneur en polymère et la différente composition de chaque formulation. Le travail présenté dans cette thèse démontre clairement l'utilité de SD HASCA en tant qu'un excipient à libération prolongée efficace.
Unmodified and modified starches represent a particularly interesting group of biodegradable and abundant excipients. They have been widely used as excipients for various purposes in tablet formulations, such as binders and/or disintegrants. Spray-dried high-amylose sodium carboxymethyl starch (SD HASCA) was recently proposed as an innovating hydrophilic excipient for sustained-release (SR) in solid oral dosage forms. Amorphous high-amylose sodium carboxymethyl starch (HASCA) was first produced by the etherification of high-amylose corn starch with chloroacetate. HASCA was then spray dried to obtain SD HASCA. This new excipient has shown advantageous and effective properties in the production of SR delivery systems. SR matrix tablets prepared from SD HASCA are inexpensive, simple to formulate and easy to produce by direct compression. The main objective of the present research was to continue the development and optimization of matrix tablets using SD HASCA as the retarding excipient in view of their ultimate application as sustained drug-release delivery systems for oral administration. For this purpose, dissolution tests simulating some of the most relevant physiological conditions of the gastrointestinal tract, taking into account the nature of the polymer under investigation, were employed to evaluate the drug-release characteristics and demonstrate the performance of SD HASCA SR formulations. An exploratory clinical study was also carried out to evaluate the SR properties of this new drug delivery system in the gastrointestinal tract. The first article presented in this thesis evaluated the drug-release characteristics and the physical integrity of formulations containing a compressed blend of drug, sodium chloride and SD HASCA in biorelevant media. The influence of different acidic pH values and residence times was investigated. The SR profile from an optimized SD HASCA formulation was not significantly affected by both the acidic pH value and the residence time in the acidic medium. These results suggest a limited influence of intra- and inter-subject variability of gastric pH on the release kinetics from SD HASCA matrices. In addition, the optimized formulation maintained its integrity throughout the duration of the dissolution tests. The exploratory in vivo study demonstrated extended drug absorption after oral administration of SD HASCA matrix tablets and that the matrix tablets did not disintegrate while passing through the stomach and resisted hydrolysis by α-amylase in the intestine. The second article reports the development of once-daily and twice-daily SD HASCA tablets containing tramadol hydrochloride (100 mg and 200 mg). These SR formulations presented high crushing strengths without requiring the addition of binders, which facilitates tablet processing and handling. The compression force (CF) applied to produce the tablets did not significantly affect the drug-release profiles. The total release time from SD HASCA tablets increased significantly in function of the tablet weight and can be used to modulate the total release time from theses formulations. When exposed to a pH gradient and to a 40% ethanol medium, a very rigid gel formed progressively on the surface of the tablets providing controlled drug-release properties. These properties indicated that SD HASCA is a robust excipient for oral, sustained drug-release, likely to minimize the possibility of dose dumping and consequent adverse effects, even when co-administered with high doses of alcohol. The third article investigated the effect of α-amylase on drug-release from previously developed SD HASCA tablets containing acetaminophen and tramadol hydrochloride (Acetaminophen SR and Tramadol SR). Mathematical modeling showed that an increase in α-amylase concentration resulted in an increase of polymer erosion over drug diffusion as the main mechanism controlling drug-release, for both formulations and both residence times in acidic medium. However, even if the mechanism of release was affected, α-amylase concentrations ranging from 0 IU/L to 20000 IU/L did not significantly affect the drug-release profiles from SD HASCA SR tablets, regardless of the residence time in acidic medium, the drug used, the polymer content and the different composition of each formulation. The work presented in this thesis clearly demonstrates the value of SD HASCA as an efficient SR excipient.