• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 209
  • 175
  • 39
  • 24
  • 23
  • 16
  • 12
  • 9
  • 4
  • 3
  • 3
  • 2
  • 2
  • 1
  • 1
  • Tagged with
  • 583
  • 128
  • 85
  • 82
  • 78
  • 63
  • 61
  • 59
  • 54
  • 50
  • 49
  • 48
  • 46
  • 46
  • 45
  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
381

SOUČASNÁ PRAXE V NAKLÁDÁNÍ S BIOLOGICKY ROZLOŽITELNÝMI ODPADY / CONTEMPORARY PRACTICE IN DISPOSE OF BIODEGRADABLE WASTE

Šmejkalová, Zuzana January 2008 (has links)
This diploma paper deals with contemporary practice in dispose of biodegradable waste, especially biodegradable communal waste (biowaste) in the Czech Republic. It explains fundamental terms, points out relevant legal rules and describes methods of biowaste handling. It evaluates collection and utilization systems in two cities in the way of comparison method. It compares them from cost and benefits (economic, environmental) points of view. The main purpose of the diploma paper is general introduction into the issue, pointing out negative effect of biowaste landfilling and presentation of actual systems of utilization. Also the work points out contemporary trend consisting in raising separation and reducing biodegradable communal waste landfilling.
382

Émulsions stabilisées par des particules polymériques biodégradables : études physico-chimiques et évaluation pour l'application cutanée / Pickering emulsions stabilization using biodegradable particles : physical chemistry studies and application to skin drug delivery

Laredj Bourezg, Faïza 08 July 2013 (has links)
La stabilisation dite de Pickering repose sur l'utilisation de particules solides au lieu des émulsifiants. Leur forte adsorption aux interfaces confère à celles-ci une rigidité les protégeant de la coalescence. Ce travail se partage en quatre grandes parties. Un premier volet traite de la fabrication de ces particules et de leur caractérisation physico-chimique. Une deuxième partie traite de la formulation d'émulsions H/E selon deux procédés différents et leur caractérisation. La troisième partie avait pour but l'investigation du comportement de ces particules à l'interface H/E par diffusion de neutrons. La dernière partie traite de l'évaluation de ces émulsions pour l'application cutanée. Ce travail a pour objectif de formuler des émulsions de Pickering en utilisant des particules polymériques biodégradables. Des particules individualisées formées à partir de copolymères di-blocs du type : PCL-b-PEG et PLA-b-PEG, ont été fabriquées selon un procédé de nanoprécipitation innovant. Elles ont été caractérisées en termes de taille et de stabilité. Leur structure interne a également été investiguée par RMN et cryo-MET. Leur aptitude à stabiliser des émulsions H/E très concentrées a été démontrée. L'impact du procédé d'emulsification sur les propriétés finales a été souligné et l'adsorption de particules en forme de chapelets serrés à l'interface a été visualisée par diffusion de neutrons et microscopie électronique après cryofracture. L'absorption du rétinol dans la peau à partir de ces émulsions innovantes, a montré une accumulation accrue de cet actif dans le stratum corneum comparée à celle d'une émulsion stabilisée par des tensioactifs classiques. Cette absorption cutanée a été montrée dépendre du procédé de fabrication des émulsions. Les particules en suspension aqueuse ont aussi été testées pour l'encapsulation et la libération cutanée du rétinol. Les résultats ont montré l'influence de la constitution interne des particules (PCL ou PLA) sur l'absorption du rétinol dans la peau. L'utilisation de polymères biodégradables apporte de nouvelles perspectives dans la formulation des émulsions de Pickering à usage cosmétique ou pharmaceutique, en s'affranchissant des effets jugées hasardeux pour la santé humaine des particules inorganiques / The so-called Pickering stabilization is based on the use of solid particles instead of emulsifiers. Their strong adsorption at interfaces confers rigidity preventing them from coalescence. This work is divided into four main parts. The first part deals with the manufacture of these particles and their physicochemical characterization. A second part deals with the O/W emulsions formulation according to two different methods and their characterization. The third part is an investigation into the behavior of these particles at the O/W interface by small angle neutron scattering. The last part deals with the evaluation of these emulsions for their application to skin delivery. This work aims at the preparation of Pickering emulsions using biodegradable polymeric particles. Individual particles formed from diblock copolymers such as: PCL-b-PEG and PLA-b-PEG, were made by an innovative nanoprecipitation process. They were characterized in terms of their size and stability. Their internal structure was also investigated by NMR and cryo-TEM. Their ability to stabilize highly concentrated O/W emulsions has been demonstrated. The impact of the emulsification process on the final properties was emphasized and the adsorption of particles as tight necklaces at the interface was visualized by neutron scattering and freeze-fracture electron microscopy. The skin absorption of retinol from these innovative emulsions showed enhanced accumulation of the asset in the stratum corneum compared to conventional surfactant-stabilized emulsions. Such skin absorption of retinol was shown to depend on the manufacturing method of the emulsions. Particles in aqueous suspension were also tested for encapsulation and delivery of retinol in skin. The results showed the influence of the internal structure of the particles (PCL or PLA) on the absorption of retinol in the skin. The use of biodegradable polymers brings new perspectives in the formulation of Pickering emulsions for cosmetic or pharmaceutical use, while avoiding the effects of inorganic particles considered hazardous to human health
383

Design and Validation of an Automated Multiunit Composting System.

Pickens, Mark Everett 12 1900 (has links)
This thesis covers the design of an automated multiunit composting system (AMUCS) that was constructed to meet the experimental apparatus requirements of the ASTM D5338 standard. The design of the AMUCS is discussed in full detail and validated with two experiments. The first experiment was used to validate the operation of the AMUCS with a 15 day experiment. During this experiment visual observations were made to visually observe degradation. Thermal properties and stability tests were performed to quantify the effects of degradation on the polymer samples, and the carbon metabolized from the degradation of samples was measured. The second experiment used the AMUCS to determine the effect of synthetic clay nanofiller on the aerobic biodegradability behavior of poly (3-hydroxybutyrate-co-3-hydroxyvalerate).
384

Preparo, caracterização e avaliação do uso de nanoesferas de PLGA contendo doxiciclina associado ao debridamento periodontal no tratamento da periodontite crônica avançada = Preparation, characterization ans evaluation of the adjunctive use of PLGA nanospheres loading doxycycline to periodontal debridement on treatment of advanced chronic periodontitis / Preparation, characterization ans evaluation of the adjunctive use of PLGA nanospheres loading doxycycline to periodontal debridement on treatment of advanced chronic periodontitis

Moura, Lucas Alves, 1981- 02 April 2015 (has links)
Orientador: Antonio Wilson Sallum / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Odontologia de Piracicaba / Made available in DSpace on 2018-08-26T23:52:25Z (GMT). No. of bitstreams: 1 Moura_LucasAlves_D.pdf: 4231687 bytes, checksum: ec30a84348074c7f0f52d37535f57bbe (MD5) Previous issue date: 2015 / Resumo: O objetivo deste estudo foi avaliar o efeito da associação da administração local de nanoesferas contendo doxiciclina (DOX) com o debridamento periodontal no tratamento da periodontite crônica avançada. As nanoesferas foram preparadas pelo método da dupla emulsão (W/O/W), e caracterizadas quanto à morfologia através da microscopia eletrônica de varredura (MEV), e quanto à interação polímero (PLGA) e DOX através da espectroscopia infravermelha da transformada de Fourier (FTIR). A avaliação da liberação controlada de DOX foi feita através da cromatografia líquida de alta eficiência (HPLC), a partir do fluido gengival sulcular (GCF) coletado nos períodos: 2, 5, 7, 10, 15 e 20 dias após aplicação das nanoesferas. Foi realizado um ensaio clínico randomizado controlado duplo cego, incluindo 30 pacientes diagnosticados com periodontite crônica que apresentavam sete sítios com sangramento à sondagem e profundidade de sondagem (PS) ? 5 mm, sendo 2 dentes com PS ? 7 mm. Os pacientes foram aleatoriamente divididos em 2 grupos e receberam os seguintes tratamentos: debridamento periodontal por 45 minutos associado à administração local de nanoesferas contendo doxiciclina nos sítios com PS ? 5 mm (DB+DOX) ou debridamento periodontal por 45 minutos associado à aplicação de nanoesferas vazias (DB). Foram avaliados os seguintes parâmetros clínicos: Índice de Placa (IP), Sangramento à Sondagem (SS), Profundidade de Sondagem (PS) e Nível de Inserção Clínica (NIC), no baseline, 3 e 6 meses após a terapia. A avaliação microbiológica foi feita por meio da reação de cadeia de polimerase ¿ tempo real ("real time" - PCR) para detecção das bactérias: Porphyromonas gingivalis, Tannerella forsythia, Treponema denticola, Aggregatibacter actinomycetemcomitans e Prevotella intermedia, provenientes do biofilme subgengival coletado no baseline, 1, 3 e 6 meses após o tratamento. Os resultados foram comparados por meio do teste de análise de variância com medidas repetidas, com nível de significância de 5%. Foram obtidas nanoesferas variando de 700 nm a 4 um. Através do FTIR observou-se boa interação da DOX com o PLGA, sem alterações das propriedades químicas de nenhum dos compostos. Após a aplicação das nanoesferas observou-se uma liberação de DOX constante no GCF até o vigésimo dia pós-tratamento, acima da concentração inibitória mínima. No grupo DB+DOX houve redução significativa da PS e ganho de inserção clínica nas bolsas profundas e moderadas em relação ao baseline e entre grupos. Observou-se redução significativa dos níveis bacterianos pós-tratamento, sendo o grupo DB+DOX mais eficaz em manter os níveis mais baixos após 6 meses do tratamento. Dentro das limitações deste trabalho, os resultados sugerem que as nanoesferas de PLGA são efetivas como sistema de liberação controlada local de DOX e quando associadas ao debridamento periodontal podem promover resultados superiores em relação à terapia mecânica isoladamente / Abstract: The aim of this study was to assess the effect of the association of local administration of nanospheres loading doxycycline (DOX) with the periodontal debridement treating advanced chronic periodontitis. Nanospheres were made by double-emulsion method (W/O/W) and characterized regarding morphology, by scaning eléctron microscopy (SEM); and drug/polymer interaction, by Fourier transform infrared spectroscopy (FTIR). The DOX controlled release was assessed by high performance liquid chromatography (HPLC) of gingival crevicular fluid (GCF) samples collected 2, 5, 7, 10, 15 and 20 days after treatment. It was performed randomized double-blinded clinical trial, with thirty patients diagnosed with chronic periodontitis presenting at least seven sites with bleeding on probing and probing depth (PD) ? 5 mm, and 2 sites with PD ? 7 mm. The patients were randomly allocated in two groups receiving interventions as followed: 45 minutes periodontal debridement + subgengival nanospheres loading DOX (DB+DOX); and 45 minutes periodontal debridement + subgengival void nanospheres (DB). Plaque index (IP), bleeding on probing (BP), probing depth (PD) and clinical attachment level (CAL) were evaluated on baseline, 3, and 6 months after therapy. Real-time polymerase chain reaction (real-time PCR) was used to quantify Porphyromonas gingivalis, Tannerella forsythia, Treponema denticola, Aggregatibacter actinomycetemcomitans and Prevotella intermedia from subgingival biofilm samples collected on baseline, 1, 3 and 6 months after treatment. The results were compared by variance analyses test for repeated measures, with significance of 5%. Nanospheres varying from 700 nm to 4 um were obtained. There was a good interaction between DOX and PLGA, with no chemical properties alterations. After local administration of the nanospheres, it was observed constant DOX release in the GCF until 20th day post-treatment, with concentration above the minimum inhibitory concentration. DB+DOX group showed significant PD reduction and CAL gain in deep and moderates pockets comparing to baseline and between groups. It was observed significant reduction of bacteria levels along follow up period, and DB+DOX group was more eficiente in keeping lower levels of bacteria after 6 months from treatment. Within limitations of this study, the results can suggest that PLGA nanospheres are effective carriers for controlled release of DOX and when used adjunctively to periodontal debridement, improved results can be achieved compared to mechanical therapy alone / Doutorado / Periodontia / Doutor em Clínica Odontológica
385

Desenvolvimento de filmes à base de proteínas extraídas da torta de mamona (Ricinus communis L.) reticuladas com glutaraldeído e glioxal / Development of films based on proteins extracted from the castor bean cake (Ricinus communis L.) crosslinked with glutaraldehyde and glyoxal

Gisele Lourenço da Aparecida Makishi 13 April 2012 (has links)
O processo de extração do óleo de mamona gera, como subproduto, uma torta rica em proteínas, que tem sido utilizada como adubo e contra fitonematóide, devido à sua toxicidade. Entretanto, as proteínas da torta de mamona são ricas em aminoácidos que permitem modificação química com aldeídos bifuncionais, como o glutaraldeído e o glioxal, o que pode ser interessante para a produção de filmes biodegradáveis com propriedades físicas adequadas ao emprego na agricultura. Assim, o objetivo geral deste trabalho foi a produção e caracterização de filmes à base de proteínas extraídas da torta de mamona e reticuladas com glioxal ou glutaraldeído e plastificados com glicerol. Especificamente, estudaram-se o efeito da concentração de proteína e do tipo de reticulante, e o efeito da concentração do reticulante sobre algumas propriedades dos filmes. Os filmes foram produzidos com uma técnica conhecida como tipo \"casting\", que consiste na desidratação de uma solução filmogênica (SF). Os filmes foram submetidos a testes para determinação da umidade, espessura, propriedades mecânicas (testes de tração e perfuração), permeabilidade ao vapor de água, solubilidade em água, cor, opacidade, brilho, além da microestrutura, por microscopia eletrônica de varredura. A concentração da proteína e o tipo de reticulante não influenciaram a umidade, espessura, microestrutura e propriedades óticas. Mas, de maneira geral, os filmes produzidos com o glioxal apresentaram melhores propriedades mecânicas e menor solubilidade em água que aqueles produzidos com glutaraldeído, sendo que a concentração de 6g de proteínas/100g de SF foi a formulação que apresentou os melhores resultados para os testes de tração e de solubilidade em água. Este resultado é muito importante para o emprego dos filmes na agricultura. Por outro lado, a concentração do glioxal não teve efeito sobre a umidade, espessura, propriedades óticas, microestrutura e nem sobre a permeabilidade ao vapor de água, influenciando apenas a solubilidade e as propriedades mecânicas. O teor de glioxal que proporcionou melhores propriedades mecânicas e baixa solubilidade em água foi de 5g/100g de proteínas. Filmes produzidos nessas melhores condições foram submetidos a análises complementares envolvendo testes de hidrofobicidade, propriedades térmicas, espectroscopia de infravermelho com transformada de Fourier, isoterma de sorção e biodegradabilidade. Finalmente, pode-se concluir que as proteínas da torta de mamona são capazes de formar uma matriz bem estruturada e que suas propriedades podem ser melhoradas com a adição de glioxal. / The extraction process of castor oil produces, as a co-product, a cake rich in proteins which has been used as a fertilizer and against plant parasitic nematode, because of its toxicity. However, the proteins of castor bean cake are rich in amino acids which allow chemical modification with bifunctional aldehydes such as glutaraldehyde and glioxal. This may be interesting for the production of biodegradable films with adequate physical properties to the use in agriculture. The objective of this work was the production and characterization of films based on proteins extracted from the castor bean cake and crosslinked with glyoxal or glutaraldehyde and plasticized with glycerol. Specifically, we studied the effect of protein concentration and type of crosslinker and the effect of the crosslinker concentration on some properties of the films. The films were produced with a technique known as \"casting\", which consists of drying a film solution (FS). The films were tested for determination of moisture content, thickness, mechanical properties (tensile and puncture tests), water vapor permeability, water solubility, color, opacity, gloss, and the microstructure by scanning electron microscopy. The protein concentration and type of crosslinking did not affect the moisture content, thickness, microstructure and optical properties. But, in general, films made with glyoxal showed improved mechanical properties and lower water solubility than those produced using glutaraldehyde. And, the concentration of 6g proteins/100 g of FS was the formulation that presented the best results for the tensile tests and water solubility. This result is very important for the use of films in agriculture. Moreover, the concentration of glyoxal had no effect on the moisture content, thickness, optical properties, or on the microstructure and permeability to water vapor, influencing only the solubility and mechanical properties. The concentration of glyoxal that provided the best mechanical properties and low water solubility of proteins was 5g/100g of gelatin. Films produced in the best conditions were subjected to further analyzes involving tests of hydrophobicity, thermal properties, spectroscopy, Fourier transform infrared spectroscopy, water vapor sorption isotherm and biodegradability. Finally, it can be concluded that the protein of castor bean cake are capable of forming a matrix structured and that their properties can be improved with the addition of glyoxal.
386

Estudo do metabolismo de ácidos graxos em Pseudomonas putida visando a modulação da composição monomérica de elastômero biodegradável. / Study of fatty acids metabolism in Pseudomonas putida aiming to modulate monomer composition of biodegradable elastomer.

Sonia Regina da Silva Queiroz 30 April 2008 (has links)
Neste trabalho, foram desenvolvidas estratégias para modular a composição de elastômeros biodegradáveis da família dos polihidroxialcanoatos (PHA), produzidos por Pseudomonas, a partir de ácidos graxos ou óleos vegetais, para diversificar suas aplicações, sobretudo pela inserção de monômeros insaturados. A composição do PHA produzido variou com o tipo de ácido graxo fornecido e com sua proporção em misturas. Em genomas seqüenciados, detectaram-se dois genes fadH (codificador de 2,4-dienoilCoA hidratase) em P. aeruginosa e apenas um em outras Pseudomonas. Observou-se uma correlação entre o número de cópias de fadH no genoma e maior eficiência na oxidação de ácidos graxos insaturados. Mutantes afetados no metabolismo de ácidos graxos insaturados foram obtidos utilizando-se transposon, alguns destes mutantes apresentaram maior eficiência na incorporação de monômeros insaturados ao PHA. A clonagem e seqüenciamento de fragmentos de DNA interrompidos pelo transposon permitiram a identificação dos genes afetados nesses mutantes. / Different strategies were applied to modulate the composition of biodegradable elastomeric polyhydroxyalkanoates (PHA) accumulated by Pseudomonas from fatty acids and plant oils, in order to improve the applications of this material, mainly by unsaturated monomer insertion. PHA composition varied both with fatty acid type and fatty acids ratio in mixtures supplied. Analysis of genome sequences revealed two fadH (encoding 2,4-dienoyl-CoA hydratase) copies in Pseudomonas aeruginosa and only one in other Pseudomonas species. The number of fadH copies in the genome was related to the higher oxidation of unsaturated fatty acids. Transposon-induced mutants affected on unsaturated fatty acids metabolism were obtained, some of them showing higher efficiency to incorporate unsaturated monomers do the PHA. Cloning and sequencing of transposon-disrupted DNA regions allowed to identify the genes affected in those mutants.
387

Reologické vlastnosti biodegradabilních termocitlivých kopolymerů / Rheological properties of biodegradable thermosensitive copolymers

Chamradová, Ivana January 2012 (has links)
Hlavním cílem předložené diplomové práce byla příprava, charakterizace a reologická studie "inteligentních" injektovatelných hydrogelů, které jsou biodegradovatelné, biokompatibilní a s řízenou životností sestávajících se z hydrofilního polyethylenglykolu (PEG) a hydrofobního kopolymeru kyseliny polymléčné a polyglykolové (PLA/PGA). Výsledný termosenzitivní PLGA–PEG–PLGA kopolymer, který geluje při teplotě lidského těla, byl dále funkcionalizován anhydridem kyseliny itakonové získané z obnovitelných zdrojů, přinášející jak reaktivní dvojné vazby tak i funkční –COOH skupiny na konce kopolymeru. Navíc byl PLGA–PEG–PLGA kopolymer modifikován bioaktivním anorganickým hydroxyapatitem pro použití jako injektovatelné kostní adhezivum. Oba modifikované kopolymery jak ITA/PLGA–PEG–PLGA/ITA tak i PLGA–PEG–PLGA/HAp ovlivňují reologické vlastnosti původního PLGA—PEG—PLGA kopolymeru rozhodující o tom, zda by mohly být nové polymerní materiály vhodné jako injektovatelné nosiče léčiv nebo kostní lepidla v lékařských aplikacích. Experimentální část této práce je zaměřena především na charakterizaci viskoelastických vlastností jak nemodifikovaného PLGA—PEG—PLGA kopolymeru tak i s přidáním ITA nebo HAp metodou obrácených testovacích vialek (TTIM) a dynamickou reologickou analýzou. Výhodou TTIM je vizualizace přechodu sol-gel, určení kritické gelační teploty a kritické gelační koncentrace. Reologická měření poskytují informace o viskozitě a vizkoelasticitě gelu změnou elastického (G´) a ztrátového (G´´) modulu. Připravené kopolymery byly také charakterizovány 1H NMR a GPC. Povrch a velikost částic HAp byl popsán pomocí SEM a laserového analyzátoru částic. Původní PLGA—PEG—PLGA kopolymer i kopolymer modifikovaný ITA a HAp vykazovaly sol-gel přechod vyvolaný zvýšením teploty. Reologické vlastnosti kopolymerů v koncentračním rozmezí 6 až 24 hm. % ve vodě byly studovány buď TTIM nebo užitím reometru a získané výsledky spolu velmi dobře korespondovaly. Reologické vyhodnocení prokázalo dvě „překřížení“, kde G´ =G´´. První překřížení velmi dobře korespondovalo s prvním sol-gel přechodem nalezeným prostřednictvím TTIM. Maximální hodnota G´ odpovídající nejvyšší tuhosti polymerního gelu byla situována v bílém gelu. Druhý fázový přechod představuje přechod mezi gelem a suspenzí, kdy je bílý polymer oddělen od vody. Tuhost gelu roste s rostoucí koncentrací polymeru ve vodě. Pro srovnání, kopolymer modifikován jak ITA, tak i přidáním HAp (0, 10, 20, 30, 40, 50 hm %) vykázal zvýšení tuhosti gelu oproti původnímu kopolymeru PLGA–PEG–PLGA a přiblížení teploty maximální hodnoty G´ tělesné teplotě (37 °C). Bylo prokázáno, že jak ITA/PLGA–PEG–PLGA/ITA kopolymer tak i PLGA—PEG—PLGA/HAp kompozit jsou vhodnými kandidáty na injekovatelné systémy pro řízené uvolňování léčiv či kostní adhezivum pro ortopedii nebo zubní aplikace.
388

Návrh fermentoru pro domácnost / Household fermentor design

Švec, Jan January 2012 (has links)
The aim of this thesis is to design a fermentation unit specially adjusted for household operating. Unit processes kitchen and garden biodegradable waste with requirements of low acquisition costs, operating costs and demands of service. Benefits of this unit are production of biogas, which will be utilized in household, and processed of biodegradable waste to nutritious manure. The first part of the work is aimed on description of anaerobic fermentation process and summary of operating conditions. The main part deals with potential of household and garden biodegradable waste for production of biogas and design of fermentation unit. Proposals for biogas utilization and economy of whole project are mentioned.
389

Utilisations originales d'un liquide ionique : catalyseur et support pour la préparation de polymères biodégradables et composant d'une phase stationnaire séparative à base d'une beta-cyclodextrine et d'un polymère ionique / Original uses of a ionic liquid : as a catalyst and support for the preparation of biodegradable polymers and as a component of a stationary separative phase based on a beta-cyclodextrin and a ionic polymer

Bouyahya, Asmaa 27 June 2018 (has links)
Les liquides ioniques, unions de cations organiques et d’anions, sont des milieux structurés sur plusieurs nanomètres et présentent des propriétés très intéressantes et modulables. Grâce à ces propriétés, les liquides ioniques ont retrouvé une place dans d’abondantes applications, particulièrement en synthèse organique. Dans le cadre de cette thèse nous avons présenté trois utilisations différentes : i) La première utilisation est basée sur l’emploi des LIs comme catalyseur de polymérisation par ouverture de cycle (POC) contrôlée de l’-caprolactone dans des conditions douces. ii) La deuxième utilisation des liquides ioniques repose sur la synthèse d’un nouveau catalyseur/initiateur organostannique supporté sur un liquide ionique pour la préparation d’un polymère biodégradable. La présence du LI devrait permettre d’éliminer le catalyseur par simple filtration. iii) La troisième et la dernière application repose sur la réalisation d’un assemblage original composé de -cyclodextrines native et perméthylée, d’un liquide ionique et d’un polymère chargé. Cette assemblage est totalement nouveau et pourrait donner accès à des matériaux hydrosolubles avec de nouvelles applications séparatives. / Ionic liquids, combinations of organic cations and anions, are structured media of several nanometers and have very interesting and flexible properties. Thanks to these properties, ionic liquids have found a place in abundant applications, particularly in organic synthesis. In this thesis we have presented three different uses: i) The first use is based on the use of ILs as a controlled ring-opening polymerization (POC) catalyst for -caprolactone under mild condition. ii) The second use of ionic liquids is based on the synthesis of an innovative organotin catalyst / initiator supported on an ionic liquid for the preparation of a biodegradable polymer. The presence of the IL should make possible the elimination of the catalyst by simple filtration. The biological tests must agree our theory. iii) The third and last application is based on the creation of an original assembly composed of native and permethylated -cyclodextrins, an ionic liquid and a charged polymer. This new association could give access to water-soluble materials with new separation applications.
390

Development and advanced characterisation of antibiotic-loaded nanoparticles to fight intracellular bacteria / Mise au point et caractérisation avancé de nanoparticules chargées en antibiotique dirigées contre des bactéries intracellulaires

Pancani, Elisabetta 15 December 2017 (has links)
Le traitement des infections intracellulaires est compliqué par la capacité des bactéries à «se cacher» à l’intérieur des cellules de l’hôte, en particulier celles du système immunitaire, entravant ainsi l’action de nombreux agents antimicrobiens. La diffusion croissante de souches résistantes est très inquiétante. Dans ce cadre, les nanoparticules (NPs) constituent une stratégie prometteuse pour administrer de manière optimisée des agents antimicrobiens.Ce travail de thèse, réalisé dans le cadre du projet européen ITN Cyclon Hit, visait à développer et caractériser des NPs biodégradables et biocompatibles chargées en antibiotiques, composés d’acide polylactique (PLA), d’acide poly (lactique-co-glycolique) (PLGA) et de polycaprolactone (PCL) ou de cyclodextrines polymérisées (pCD).Les deux premiers chapitres sont consacrés aux verrous technologiques liés à l'encapsulation de certains médicaments puissants dans les NPs polymériques. Tout d'abord, ces vecteurs ont été utilisés pour la délivrance simultanée d'une combinaison de molécules actives récemment découverte, l'éthionamide (ETH) et son Booster, pour le traitement de la tuberculose. Deuxièmement, ils ont été employés pour relever les défis liés à l'incorporation d'une quinolone de première génération, l'acide pipémidique (PIP), dans le but d'optimiser sa distribution intracellulaire dans des infections telles que la salmonellose.La co-incorporation efficace de l'ETH et du booster a dû surmonter de nombreuses difficultés liées à des problèmes de solubilité, de cristallisation et de biodisponibilité. Nos NPs en PLA et en pCD ont montré leur capacité de co-encapsuler efficacement les deux molécules et tout particulièrement celles en pCD. Elles incorporent les médicaments à la fois dans les cavités des CD et dans des microdomaines hydrophobes. Les NPs en pCD, non toxiques après administration pulmonaire répétée de fortes doses, ont été administrés in vivo par voie endotrachéale directement au site d'infection. Elles ont permis une diminution de 3-log de la charge bactérienne pulmonaire des animaux infectés après seulement 6 administrations. De même, l'incorporation de PIP a été confrontée à des défis liés à la cristallisation de PIP et à sa libération incontrôlée. Malheureusement, le PIP présentait une faible affinité pour tous les matériaux polymériques étudiés et son encapsulation physique était infructueuse. Ainsi, une approche alternative a été développée en couplant le PIP au PCL via une réaction sans catalyseur initiée par le médicament. Le conjugué PCL-PIP se auto-assemble en forme de NPs avec une charge en PIP de 27%. Cependant, le PCL-PIP n'a pas pu être dégradé in vitro, mais l’approche de synthèse de conjugués est séduisante pour obtenir de particules stables et avec un contenu important en PIP.La compréhension approfondie de la structure et de la composition du noyau et de la couronne des nanostructures contenant une ou deux molécules actives est cruciale pour leur optimisation. Les deux derniers chapitres sont donc consacrés à l'application innovante de l'AFM-IR, une méthode nanospectroscopique originale combinant la microscopie à force atomique (AFM) avec la spectroscopie infrarouge (IR), à l'analyse chimique des NPs en PLGA ou à leur détection sans marquage après internalisation dans les cellules.L’AFM-IR est capable de fournir une caractérisation chimique à l'échelle nanométrique (résolution ~10 nm). Une avancée majeure du travail est l'application du mode tapping permettant l'investigation individuelle de chaque NP. Le signal IR spécifique des composants des NPs a été utilisé pour appréhender la composition chimique de leur cœur et couronne ainsi que pour localiser précisément le médicament. De plus, l'AFM-IR en mode contact a permis pour la première fois la localisation sans marquage et l'identification chimique des NP à l'intérieur des cellules. Ce travail ouvre la voie à d'innombrables applications de cette technique dans le domaine de la nanomedecine. / The treatment of intracellular infections is very challenging given the ability of bacteria to “hide” inside the cells of the host, especially the ones of the immune system, thus hampering the action of many antimicrobial agents. The battle against these bacteria has been further exacerbated by the increasing diffusion of antimicrobial resistant strains. In this frame, nanoparticles (NPs) are a very promising strategy to overcome the limitations of free antimicrobial agents by administering them in an optimized manner.This PhD work, performed as part of the European Project ITN Cyclon Hit, aimed at the development and advanced characterisation of antibiotic-loaded biodegradable and biocompatible NPs made of poly (lactic acid) (PLA), poly (lactic-co-glycolic) (PLGA) and polycaprolactone (PCL) or of polymerised cyclodextrins (pCDs).The first two chapters are dedicated to the encapsulation of powerful but challenging drugs in polymeric NPs. Firstly, these carriers were employed for the simultaneous delivery of a potent drug combination recently discovered, ethionamide (ETH) and its booster, for tuberculosis therapy. Secondly, they were used to address the challenges related to the incorporation of a first-generation quinolone, pipemidic acid (PIP), with the aim of optimising its intracellular delivery in infections such as salmonellosis.The efficient co-incorporation of ETH and booster had to overcome several technological barriers. These drugs presented solubility, crystallisation and bioavailability-related problems which were overcome thanks to the developed NPs. Our engineered PLA and pCD NPs were both able to efficiently co-encapsulate the two molecules. Among the in depth-characterised formulations, pCDs NPs displayed the best physico-chemical properties and were shown to host the drugs both in the CD cavities and in confined spaces inside NPs crosslinked polymer. The pCD NPs were administered in vivo by endotracheal route directly to the infection site. Empty NPs were shown non-toxic after repeated pulmonary administration of high doses. Moreover, loaded pCD NPs led to a 3-log decrease in the pulmonary bacterial load of infected animals after only 6 administrations. Similarly, the incorporation of PIP faced challenges mainly related to PIP crystallization and burst release. Unfortunately, PIP displayed poor affinity for all the studied polymeric materials and its physical encapsulation was unsuccessful. Thus, an alternative approach was developed by coupling PIP to PCL by using an original catalyst-free drug-initiated reaction. The PCL-PIP conjugate self-assembled in NPs with up to 27 wt% PIP which were thoroughly characterised. However, the conjugate couldn’t be enzymatically degraded. With the design of novel PCL-PIP conjugates, this self-assembly approach could represent a promising strategy.The deep understanding of the structure and composition of complex core-corona nanocarriers containing one or two active molecules is crucial for their optimisation. The last two chapters are devoted to the innovative application of AFM-IR, an original nanospectroscopic method combining atomic force microscopy (AFM) with infrared (IR) spectroscopy, to the chemical analysis of PLGA NPs or to their label-free detection after cell internalisation.AFM-IR is able to provide chemical characterisation at the nanometer scale (resolution ~10nm). One main breakthrough here is the application of the recently developed tapping mode allowing the investigation of single polymeric NPs. The specific IR signal of NPs constituents was used to unravel the chemical composition of their core and corona as well as to precisely locate the drug. Moreover, the AFM-IR in contact mode enabled for the first time the label-free localisation and unambiguous chemical identification of NPs inside cells using the polymer IR specific response as a fingerprint. This work paves the way for countless application of this technique in the field of drug delivery.

Page generated in 0.0876 seconds