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1
Caserta, Laura. "Microencapsulation pour l'autoréparation". Thesis, Aix-Marseille 3, 2011. http://www.theses.fr/2011AIX30037.
Testo completoAbstract (sommario):
Un matériau qui se répare tout seul. Une fissure ou une rayure qui se rebouche elle-même après un impact, comme une blessure pour un être vivant. Le concept d’autoréparation ainsi décrit n’est plus une idée purement fantaisiste issue de l’imagination fertile des chercheurs. De récents travaux prouvent le contraire. Catalyse a choisi de mettre au point un processus d’autoréparation par l’intégration de microparticules contenant un principe actif liquide, libéré lors son l’éclatement. Ce liquide, un monomère, va alors polymériser, rebouchant ainsi la fissure et empêchant sa propagation.L’innovation de Catalyse a été d’imaginer une formulation autoréparante capable de polymériser directement au contact du milieu extérieur. Les éléments alors mis à disposition par l’environnement peuvent être la lumière (rayonnements UV ou visibles), l’oxygène, ou l’humidité. Les monomères envisagés pour l’encapsulation sont alors respectivement un acrylate, TMPTA, ou une époxy (mélangés avec un photoamorceur adapté), l’huile de lin (siccative) et un isocyanate trimère de l’hexamétylène diisocyanate. L’encapsulation des ces quatre composés est étudiée en parallèle et les travaux réalisés sont explicités dans les chapitres 2, 3 et 4 de ce document. Le TMPTA et l’huile de lin sont encapsulés par le procédé sol-gel, l’époxy et l’isocyanate, par polycondensation interfaciale. Les résultats obtenus sont variables d’un monomère à l’autre, mais dans l’ensemble, les résultats sont concluants et montrent d’une part, qu’il est possible d’obtenir des particules contenant un taux de principe actif intéressant et stables dans le temps, et d’autre part que suite à l’éclatement desdites capsules, le monomère polymérise, assurant ainsi le processus d’autoréparationA material that could repair itself, a crack that can heal itself after an impact, like a wound on the body. The concept of self-healing described is not science fiction created by the crazy imagination of researchers. Recent studies show otherwise. The French company CATALYSE has developed a process of self-healing through the integration of microparticles containing an active liquid ingredient that is released during a crack in the material. The liquid monomer fills the crack, polymerizes and prevents further spread. The innovation of CATALYSE was to imagine a self-repairing formula, which polymerizes when exposed to the outside of the self-contained environment. This includes light (UV or visible rays), oxygen or humidity. The corresponding monomers to be encapsulated are respectively an acrylate (for example TMPTA), an epoxy (mixed with an adapted photoinitiator), linseed oil or diisocyanate (for example an isocyanine trimer or hexamethylene diisocyanate). The encapsulations of these four compounds were studied in parallel and the results are explained in chapters 2, 3 and 4 of this document. The TMPTA and linseed oil are both encapsulated by the sol-gel process, the epoxy and isocyanate, by interfacial polycondensation. The results vary from one monomer to another but the overall results are conclusive. They show that it is possible to obtain a high percentage of the active ingredient and that the particles stay stable over time. Following the bursting of such capsules, the monomer polymerizes and ensures the self-healing process
2
Caserta, Laura. "Microencapsulation pour l'autoréparation". Electronic Thesis or Diss., Aix-Marseille 3, 2011. http://www.theses.fr/2011AIX30037.
Testo completoAbstract (sommario):
Un matériau qui se répare tout seul. Une fissure ou une rayure qui se rebouche elle-même après un impact, comme une blessure pour un être vivant. Le concept d’autoréparation ainsi décrit n’est plus une idée purement fantaisiste issue de l’imagination fertile des chercheurs. De récents travaux prouvent le contraire. Catalyse a choisi de mettre au point un processus d’autoréparation par l’intégration de microparticules contenant un principe actif liquide, libéré lors son l’éclatement. Ce liquide, un monomère, va alors polymériser, rebouchant ainsi la fissure et empêchant sa propagation.L’innovation de Catalyse a été d’imaginer une formulation autoréparante capable de polymériser directement au contact du milieu extérieur. Les éléments alors mis à disposition par l’environnement peuvent être la lumière (rayonnements UV ou visibles), l’oxygène, ou l’humidité. Les monomères envisagés pour l’encapsulation sont alors respectivement un acrylate, TMPTA, ou une époxy (mélangés avec un photoamorceur adapté), l’huile de lin (siccative) et un isocyanate trimère de l’hexamétylène diisocyanate. L’encapsulation des ces quatre composés est étudiée en parallèle et les travaux réalisés sont explicités dans les chapitres 2, 3 et 4 de ce document. Le TMPTA et l’huile de lin sont encapsulés par le procédé sol-gel, l’époxy et l’isocyanate, par polycondensation interfaciale. Les résultats obtenus sont variables d’un monomère à l’autre, mais dans l’ensemble, les résultats sont concluants et montrent d’une part, qu’il est possible d’obtenir des particules contenant un taux de principe actif intéressant et stables dans le temps, et d’autre part que suite à l’éclatement desdites capsules, le monomère polymérise, assurant ainsi le processus d’autoréparationA material that could repair itself, a crack that can heal itself after an impact, like a wound on the body. The concept of self-healing described is not science fiction created by the crazy imagination of researchers. Recent studies show otherwise. The French company CATALYSE has developed a process of self-healing through the integration of microparticles containing an active liquid ingredient that is released during a crack in the material. The liquid monomer fills the crack, polymerizes and prevents further spread. The innovation of CATALYSE was to imagine a self-repairing formula, which polymerizes when exposed to the outside of the self-contained environment. This includes light (UV or visible rays), oxygen or humidity. The corresponding monomers to be encapsulated are respectively an acrylate (for example TMPTA), an epoxy (mixed with an adapted photoinitiator), linseed oil or diisocyanate (for example an isocyanine trimer or hexamethylene diisocyanate). The encapsulations of these four compounds were studied in parallel and the results are explained in chapters 2, 3 and 4 of this document. The TMPTA and linseed oil are both encapsulated by the sol-gel process, the epoxy and isocyanate, by interfacial polycondensation. The results vary from one monomer to another but the overall results are conclusive. They show that it is possible to obtain a high percentage of the active ingredient and that the particles stay stable over time. Following the bursting of such capsules, the monomer polymerizes and ensures the self-healing process
3
Thomas, Julie Ann. "Microencapsulation Using Inorganic Wall Materials". Thesis, University of Manchester, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.503752.
Testo completo
4
Li, Ming. "Microencapsulation par évaporation de solvant". Nantes, 2009. http://www.theses.fr/2009NANT2020.
Testo completoAbstract (sommario):
The solvent evaporation encapsulation technique is widely used in the pharmaceutical applications for the controlled release of active principle (drug). The organic phase, which comprises solvent, polymer and active principle, is dispersed into an aqueous phase. The solvent diffuses into the latter one and then evaporates, leading consequently to the formation of solid polymer microspheres with active principle trapped inside. Contrary to most studies on the polymer choice and drug release, our study focused on the process-engineering aspects in the production of microspheres in order to optimize the process duration and analyze the influence the properties of obtained microspheres. The evaporation of solvent has been studies with different operating conditions (temperature, pressure, quantity of materials). The reduced pressure (60% of atmospheric pressure) has shown the most significant effect, which reduced the process duration to 1/3. The physical properties of the obtained microspheres (size, surface and inner structure) were examined. The investigation of the inner structure of microspheres by a novel technique X-ray tomography showed the size and location of pores. Microspheres produced under reduced pressure show smaller size, smoother surface and less porous structure. The study was then carried out at a microscopic scale on the solidification of one single drop of the dispersed phase. The mass transfer of the solvent at the interface of two phases was investigated with interferometer, which measured the variations of solvent concentration and the diffusion boundary layer with time. Our work enables to complete the knowledge of this process and propose the directions of future developments on the processLa technique d’encapsulation par évaporation de solvant est largement utilisée dans des applications pharmaceutiques pour la libération contrôlée du principe actif (médicament). La phase organique constituée de solvant, de polymère et de principe actif est dispersée dans une phase aqueuse. Le solvant diffuse dans cette dernière et puis il s'évapore, ce qui conduit à la formation des microsphères solides de polymère contenant du principe actif à l’intérieur. Contrairement à la plupart des études consacrées au choix des polymères et aux tests de libération, notre étude s’est intéressée aux aspects d'ingénierie afin d’optimiser la durée du procédé et d’analyser l'influence des conditions opératoires sur les propriétés des microsphères. L'évaporation du solvant a été étudiée pour de différentes conditions (température, pression, quantités des matériaux). La durée de procédé a été réduite à 1/3 en appliquant une faible pression (60% de la pression atmosphérique). Les propriétés des microsphères obtenues (taille, surface et structure interne) ont été examinées. L’analyse de la structure interne des microsphères par la nouvelle technique de tomographie à rayons X a montré la taille des pores et de l'emplacement des pores. L’étude a été effectuée ensuite à l’échelle microscopique sur la solidification d’une goutte de la phase dispersée. Le transfert de masse du solvant a été étudié avec l'interféromètre, permettant de mesurer la variation de concentration du solvant et l’épaisseur de la couche limite diffusive. Notre travail a permis de combler les lacunes dans la connaissance de ce procédé et il propose des pistes de développement du procédé
5
Ugazio, Stéphane. "Microencapsulation d'enzymes dans les sphérulites". Bordeaux 1, 1999. http://www.theses.fr/1999BOR10574.
Testo completoAbstract (sommario):
Les enzymes, du fait de leur specificite, de leur biodegradabilite et de leur efficacite, entrent dans de nombreux domaines d'applications. Leur encapsulation permet d'accroitre leur performance et d'etendre leur domaine d'action. En 1992 au laboratoire, un nouveau systeme d'encapsulation a ete decouvert les spherulites ou vesicules multilamellaires obtenues par le cisaillement d'une phase lamellaire de tensioactifs. Apres avoir montre que les spherulites peuvent encapsuler une enzyme efficacement, nous montrons que l'enzyme encapsulee est incapable d'agir sur un substrat place a l'exterieur des spherulites. A titre d'application nous avons encapsule une -galactosidase impliquee dans le soin de l'intolerance au lactose. Les enzymes peuvent perdre rapidement leur activite. Parmi les facteurs de denaturation on trouve l'autolyse c'est une caracteristique propre aux proteases : elles s'autodigerent. En utilisant la structure particuliere des spherulites on stoppe le phenomene en isolant une molecule enzymatique par feuillet lamellaire. Les spherulites bien qu'etant un systeme d'encapsulation efficace presentent quelques faiblesses notamment quant a l'encapsulation de molecules de petites tailles. Aussi avons-nous formule des spherulites ayant un cur aqueux mais dispersables dans l'huile. Cette dispersion peut etre ensuite mise en emulsion. La presence de la barriere huileuse permet de diminuer tous les phenomenes de diffusion comme la fuite d'un colorant et de maintenir une difference de ph entre l'interieur et l'exterieur des spherulites.
6
Mahmood, Arshad. "Microencapsulation strategies for islet transplantation". Thesis, Aston University, 1994. http://publications.aston.ac.uk/12597/.
Testo completoAbstract (sommario):
A variety of islet microencapsulation techniques have been investigated to establish which method provides the least occlusive barrier to net insulin release in vitro, and optimum biocompatibility for islet implantation in vivo. NMRI mouse islets have been microencapsulated with Na+ -alginate-poly-L-lysine (PLL)/poly-L-ornithine (PLO)-alginate, Na2+ -alginate and agarose gels. Both free and microencapsulated islets responded to glucose challenge in static incubation and perifusion by significantly increasing their rate of insulin release and theophylline significantly potentiated the insulin response to glucose. While little insulin was released from microencapsulated islets after short term (2 hours) static incubation, significantly greater amounts were released in response to glucose challenge after extended (8-24 hours) incubation. However, insulin release from all types of microencapsulated islets was significantly reduced compared with free islets. Na+ -alginate-PLO-alginate microencapsulated islets were significantly more responsive to elevated glucose than Na+ -alginate-PLL-alginate microencapsulated islets, due to the enhanced porosity of PLO membranes. The outer alginate layer created a significant barrier to glucose/insulin exchange and reduced the insulin responsiveness of microencapsulated islets to glucose. Ba2+ -alginate membrane coated islets, generated by the density gradient method, were the most responsive to glucose challenge. Low concentrations of NG-monomethyl L-arginine (L-NMMA) had no significant effect on glucose stimulated insulin release from either free or microencapsulated islets. However, 1.0 mmol/1 L-NMMA significantly inhibited the insulin response of both free and microencapsulated islets to glucose challenge. In vivo work designed to evaluate the extent of pericapsular fibrosis after 28 days ip. and sc. implantation of microencapsulated islets into STZ-diabetic recipients, revealed that the inclusion of islets within microcapsules increased their immunogenicity and markedly increased the extent of pericapsular fibrosis.
7
Mitchell, Karen Claire. "Microencapsulation for next generation lubricants". Thesis, University of Leeds, 2014. http://etheses.whiterose.ac.uk/8758/.
Testo completoAbstract (sommario):
Lubricants within an engine perform the important tasks of increasing engine efficiency and lifetime of parts, dissipating heat and decreasing fuel consumption. To help lubricating engine oils perform to the best of their ability different chemical additives are blended into the oil; the amount of additives added is dictated by the respective solubilities and the nature of any interactions between different additives. Using a technology already utilised in the pharmaceutical, food and dye industries this work presented in this thesis aims to increase the concentration of one particular additive, a friction modifier (FM), within a model oil. Monodisperse poly(methyl methacrylate) (PMMA) particles have been efficiently produced via dispersion polymerisation in a non-aqueous continuous phase and, through the incorporation of a co-solvent within the particle core, the encapsulation of FM inside these particles has been demonstrated. Work has been carried out to determine the factors which can be used to reproducibly synthesise particles to a desirable size and degree of polydispersity. The storage and release of FM from the particle core when it is required is an important consideration in the action of these particles. The rate of release from the core of particles has been studied to demonstrate the ability of these particles to act as a FM reservoir, replenishing the additive as it is consumed. An investigation of the action of particles produced, with and without FM encapsulated, on the tribological behaviour of dodecane has been carried out using a TE77 Cameron Plint tribometer. Analysis of the friction and wear results is presented here and a possible mechanism for the action of the particles in the tribological testing has also been suggested.
8
Mitchell, Claire Elizabeth Teall. "Microencapsulation and organocatalysis in organic synthesis". Thesis, University of Cambridge, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.613750.
Testo completo
9
Abderrahmen, Robin. "Conception d'étiquettes autoadhésives par microencapsulation d'adhésif". Thesis, Grenoble, 2012. http://www.theses.fr/2012GRENI051/document.
Testo completoAbstract (sommario):
Le but de ce projet est de concevoir un nouveau type d'étiquette ‘écologique', n'utilisant pas de dorsale siliconé. Ainsi, la couche d'adhésif est remplacée par une couche de microcapsules d'adhésif. Ces microcapsules doivent avoir une paroi suffisamment étanche et résistante pour envelopper l'adhésif et ne pas se rompre lors des étapes de fabrication du produit. Par contre, elles doivent céder sous l'effet d'une pression et libérer l'adhésif au moment de leur utilisation. Dans un premier temps, 3 adhésifs en émulsion aqueuse ont été caractérisés en vue de leur microencapsulation. Par la suite, un adhésif a été sélectionné et encapsulé par coacervation (avec des biomatériaux comme carapace) et par polymérisation in situ aminoplaste. Ensuite, 2 autres procédés d'encapsulation d'adhésif réalisés au LAGEP (le spray-drying et le spray-cooling) ont été comparés avec les 2 techniques précédentes. Les capsules produites par spray-cooling, les plus adhésives, ont permis la formulation d'un bain d'enduction en vue d'un couchage des capsules à l'aide d'une barre de Meyer, et par procédé sérigraphique. La compatibilité de ces microcapsules avec le procédé de fabrication d'une étiquette autoadhésive classique, sur une rotative d'impression flexographique, a été montrée. Les caractéristiques finales du produit ainsi fabriqué (adhésion, pression d'application) ont été comparées avec celles de différents produits autoadhésifs industriels (étiquette, enveloppe et timbre)The main objective of this investigation is to prepare innovative silicone liner-free labels. It can be achieved by the adhesive ‘self protection', thanks to its incorporation into microcapsules. This allows the preparation of ‘dry labels' gluing under the application of a pressure, which induces the rupture of the microcapsules, thus releasing the core material, a pressure sensitive adhesive. The first step was to analyse 3 water-based PSA in view of their encapsulation. Then, the most suitable adhesive was microencapsulated by coacervation (using biopolymer as shell) and by in situ polymerisation. Two other encapsulation processes (spray-cooling and spray-drying), were also carried out at the LAGEP and were compared with the 2 former processes. Coating colour formulations were prepared with spray-cooling microcapsules (the most adhesive ones). Coating trials were carried out with a Meyer rod, and by screen printing. Compatibility between microcapsules and the label making process, using a flexographic printing press, was determined. Finally, the mains characteristics of the prepared innovative products (adhesion, application pressure) were compared to industrial self-adhesive homologues, and found that they could be suitable for the preparation of silicon liner-free envelops and stamps
10
Mhlana, Kanyisile. "Microencapsulation of anti-tuberculosis drugs using sporopollenin". Thesis, Nelson Mandela University, 2017. http://hdl.handle.net/10948/13912.
Testo completoAbstract (sommario):
In this thesis, we explore the benefits of microencapsulating isoniazid and pyrazinamide within sporopollenin exine capsules derived from Lycopodium clavatum. Sporopollenin is a natural biopolymer, which is extracted from the outer shell of pollen grains. These hollow microcapsules can encapsulate and release drug actives in a controlled manner and possess many other advantages such as homogeneity in morphology and size, resilience to both strong acids and bases, they have antioxidant properties as well as UV protection to protect the material inside the microcapsule. Compared to artificial microcapsules, sporopollenin’s muco-adhesion to intestinal tissues contributes greatly to the extended contact of the sporopollenin with the intestines leading to an increased efficiency of delivery of drugs. The hollow microcapsules can be easily filled with a solution of the active or active in a liquid form by simply mixing both together. The drug actives are released in the human body depending on pH factors. Active release can otherwise have controlled by adding a coating on the shell, or co-encapsulation with the active inside the shell so that high drug concentrations are delivered to the site of infection. Encapsulation of the drug active will possibly improve therapeutic abilities of the drugs; simplify the treatment of TB-HIV coinfections by eliminating troublesome drug-drug interactions and drastically reduce or eliminates side effects. The SECs were loaded using a passive filling method. The drug active (0.1 g) was dissolved in a solvent and mixed with the SECs (0.1 g) for 10 minutes. After mixing for 10 minutes, the solvent was removed by a rotary evaporator and dried to a constant mass. The surface of the sporopollenin exines were analysed on a FTIR to observe if there are any drug deposits on the surface of the SECs. The loading efficiency and drug release percentage was determined by using calibrations curves and analysed on a UV-vis spectrophotometer. Further work has been proposed in which to characterize the SECs further and producing coated tablets from loaded SECs.
11
Carvallo, Raquel. "Supercritical Fluid Aided Microencapsulation of Dry Powders". Scholar Commons, 2011. http://scholarcommons.usf.edu/etd/3035.
Testo completoAbstract (sommario):
Coating of fine pthesiss to produce tailored surface properties is currently a key development for supercritical fluids applications, in different areas such as: pharmaceutical, nutraceutical, cosmetic, agrochemical, electronic and specialty chemistry industries. During the encapsulation process the pthesis surface can be designed with specific properties by spreading a thin film coating material over the surface of the pthesiss.
Chitosan, a natural polymer, was used in this work as the encapsulant material. Chitosan is biocompatible, biodegradable to normal body constituents, safe, non-toxic, bacteriostatic, anticancerogen, and versatile polymer. These attributes are among the properties that make Chitosan an attractive component of pharmaceutical products.
The main objective of this research was to encapsulate solid pthesiss under 5fÝm with a biopolymer, Chitosan, using supercritical CO2 as one of the solvents. In order to reach this goal, some the following initial tasks were completed: the cloud point for the system DMSO-CO2 was determined and compared with published data to validate the experimental system. Subsequently the cloud point experiments were extended to include the ternary system Chitosan-DMSO-CO2, and a dynamic solubility experimental set-up was constructed and used to obtain solubility data for the same ternary system.
A novel SCF fluidized bed was used to micro encapsulate porous (TiO2) and non-porous pthesiss (CaO) through a temperature swing with a Chitosan thin layer. DMSO was used as an entrainer to enable solubilization of Chitosan and removed within the supercritical carbon dioxide.
Several analytical methods were used to characterize these pthesiss; SEM-EDS analysis was used to evaluate a group of pthesiss, determining composition and pthesis diameter on samples up to 900 pthesiss. TEM and AFM confirmed pthesiss of one micron or less were encapsulated with a thickness of less than 5 nm. AFM shows pthesis roughness on the nanometer range, 46 nm or more for uncoated pthesiss and 2-4 nm for the encapsulated ones.
FTIR, NMR and DSC-TGA analysis confirmed that the chemical structure of Chitosan remained constant before and after processing, and the changes observed were attributed to some DMSO and moisture adsorbed during the encapsulation process.
12
Hamad, Shwan Abdullah. "Novel techniques for microencapsulation of probiotic bacteria". Thesis, University of Hull, 2012. http://hydra.hull.ac.uk/resources/hull:6873.
Testo completoAbstract (sommario):
Microencapsulation of living cells such as probiotic bacteria can be used for the protection of the cells from harsh conditions such as low pH and mechanical stress in the digestive system. In this thesis we demonstrate various novel strategies to microencapsulate living yeast cells as a model for probiotic bacteria. We prepared and used sporopollenin microcapsules to encapsulate yeast cells by compressing the sporopollenin particles into a pellet which was exposed to an aqueous suspension of yeast cells in the presence of a biocompatible surface active agent. We also demonstrate that the viability of the cells is preserved after the microencapsulation. We fabricated novel shellac-yeast cells composite microcapsules programmed to release the cells upon change of pH in a narrow range. This was achieved by either spray drying or sprays co-precipitating dispersion of yeast cells in aqueous solution of ammonium shellac doped with a pH-sensitive polyelectrolyte. We also demonstrate that yeast cells retain their viability even when treated with aqueous solutions of low pH. In addition, the pH-triggered release of yeast cells from these composite microcapsules and their disintegration rates were investigated. We developed a theoretical model for the kinetics of yeast cells release from the microcapsules triggered by (i) pH change and (ii) the growth of the cells in a culture media. In a separate strategy of microencapsulation of living cells, we used templates of Pickering emulsions stabilised with latex nanoparticles to fabricate colloidosomes loaded with viable probiotics. Depending on the method of transfer, we have shown that magnetic colloidosomes containing pH-sensitive polyelectrolyte loaded with living cells can be prepared using Pickering emulsion templates. In addition, we demonstrate two strategies to strengthen the stability of water-in-oil Pickering emulsion droplets by interlocking the adsorbed latex particle monolayer: by (i) using oppositely charged polyelectrolyte adsorption or (ii) using polyelectrolyte pre-coated yeast cells which act as cross-linkers inside the water-in-oil droplets. Furthermore, we report the fabrication of 3 D multicellular cellosomes of living cells by using water-in-oil emulsion templates as intermediate. We have used two strategies to assemble yeast cells pre-coated with polyelectrolytes in water-in-oil emulsion droplets stabilised with either surfactant or solid particles. The emulsion droplets containing oppositely charged yeast cells linked together by electrostatical interactions were shrunken to compact structures upon addition of dry octanol and subsequently transferred into water to fabricate cellosomes. In summary, this thesis contributes an arsenal of new methods for microencapsulation of living cells for the purpose of their protection and triggered release. The results of this thesis can be used in the formulation of better probiotic products, protection and release of cells implants, tissue engineering and development of live vaccines.
13
Anozie, Uchechukwu Chamberlin. "Microencapsulation of Soluble Sulfur by Calcium Alginate". University of Akron / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=akron1353388178.
Testo completo
14
Embleton, Jonathan K. "Microencapsulation studies with P(HB-HV) polymers". Thesis, Aston University, 1991. http://publications.aston.ac.uk/9742/.
Testo completoAbstract (sommario):
Microencapsulation processes, based upon the concept of solvent evaporation, have been employed within these studies to prepare microparticles from poly--hydroxybutyrate homopolymers and copolymers thereof with 3-hydroxyvalerate [P(HB-HV) polymers]. Variations in the preparative technique have facilitated the manufacture of two structurally distinct forms of microparticle. Thus, monolithic microspheres and reservoir-type microcapsules have been respectively fabricated by single and double emulsion-solvent evaporation processes. The objective of the studies reported in chapter three is to asses how a range of preparative variables affect the yield, shape and surface morphology of P(HB-HV) microcapsules. The following chapter then describes how microcapsule morphology in general, and microcapsule porosity in particular, can be regulated by blending the fabricating P(HB-HV) polymer with poly--caprolactone [PCL]. One revelation of these studies is the ability to generate uniformly microporous microcapsules from blends of various high molecular weight P(HB-HV) polymers with a low molecular weight form of PCL. These microcapsules are of particular interest because they may have the potential to facilitate the release of an encapsulated macromolecule via an aqueous diffusion mechanism which is not reliant on polymer degradation. In order to investigate this possibility, one such formulation is used in chapter five to encapsulate a wide range of different macromolecules, whose in vitro release behaviour is subsequently evaluated. The studies reported in chapter six centre on the preparation and characterization of hydrocortisone-loaded microspheres, prepared from a range of P(HB-HV) polymers, using a single emulsion-solvent evaporation process. In this chapter, the influence of the organic phase viscosity on the efficiency of drug encapsulation is the focus of initial investigations. Thereafter, it is shown how the strategies previously adopted for the regulation of microcapsule morphology can also be applied to single emulsion systems, with profound implications for the rate of drug release.
15
Ciamponi, Federica. "Characterisation of microencapsulation process in Saccharomyces cerevisiae". Thesis, University of Manchester, 2011. https://www.research.manchester.ac.uk/portal/en/theses/characterisation-of-microencapsulation-process-in-saccharomyces-cerevisiae(1450cb31-7ae8-49b5-a6e3-56803f826a19).html.
Testo completoAbstract (sommario):
Since the 1970's there has been industrial interest in using microorganisms as microcapsules. The encapsulation of actives (e.g. flavours, drugs, perfumes) is a necessary process for pharmaceutical and food companies because the precious and often expensive ingredients must be protected from degradation and also released in a specific site or under a specific stimulus. Saccharomyces cerevisiae, baker's yeast, represents a first choice microorganism for the encapsulation of active ingredients. It is biodegradable and biocompatible with human digestion and skin, and can be produced in an easy and cheap way. A major part of this project has been dedicated to the development of robust methods of extraction and quantification of hydrophobic substances loaded inside yeast cells, which have been subsequently combined with an indirect, fluorescence-based method for the evaluation of the rate of loading of hydrophobic substances in the same cells. In particular, it has been found that this process reaches a limit in the maximal loading capacity of intact yeast cells, most likely reflecting the maximal volume of the lipid droplet organelles in which loaded hydrophobes accumulate. With the new on-line (fluorescence-based) and off-line (chromatography-based) methods developed here it has been established that the loading process fundamentally follows a diffusion model, in which the solubility in water determines the permeation of substances through the cell wall and ultimately their uptake by yeast cells. However, treating yeast cells with organic solvents like DMSO - a new approach introduced in Prof. Tirelli's lab to enhance the encapsulation of hydrophobes - completely changes the chemical-physical parameters of the encapsulation process. In DMSO-treated cells, substances are loaded fundamentally in response to their hydrophobicity. Conversely, once loaded, the same substances are released with a rate that is inversely proportional to their hydrophobicity, as observed by applying a novel approach to measure the release of hydrophobes encapsulated in yeast cells, either in the absence of presence of DMSO-treatment. In conclusion, the new evidence reported here clarifies basic aspects of hydrophobe encapsulation in intact yeast cells and will thus help improving future applications of these microcapsules as a valid, inexpensive and biocompatible drug delivery system.
16
Giraud, Stéphane Bourbigot Serge Tighzert Lan. "Microencapsulation d'un diisocyanate et d'un phosphate d'ammonium". [S.l.] : [s.n.], 2002. http://www.univ-lille1.fr/bustl-grisemine/pdf/extheses/50376-2002-311-312.pdf.
Testo completo
17
SCHMITT, BENOIT. "La microencapsulation par la methode d'emulsion/evaporation". Strasbourg 1, 1993. http://www.theses.fr/1993STR15035.
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18
Soto-Portas, Maria-Lidicé. "Élaboration et caractérisation des microcapsules en polyamide par polycondensation interfaciale". Lyon 1, 2003. http://www.theses.fr/2003LYO10070.
Testo completoAbstract (sommario):
Les objectifs de ce travail concernent la synthèse et l'étude des propriétés de microcapsules en polyamide, obtenues à partir d'une diamine du type oligomère (polyoxypropylène diamine). L'encapsulation de principes actifs hydrophiles et lipophiles a été étudiée. Dans un premier temps l'étude des paramètres ayant une influence sur l'obtention de microcapsules à cœur aqueux a été réalisée. La deuxième partie porte sur la synthèse de microcapsules à cœur huileux. L'influence de la fonctionnalité des amines sur les propriétés macroscopiques des microcapsules, telles que la tenue mécanique, l'aspect après séchage et la diffusion de la paraffine, a été étudiée. La libération de la phase interne sous différentes conditions, sous forme de poudre ou en dispersion dans l'eau ou dans le cyclohexane, a été également étudiée mettant en évidence la possibilité de formuler des microcapsules imperméables sur une durée de quelques mois.
19
Alexakis, Theodora. "Microencapsulation of DNA within cross-linked chitosan membranes". Thesis, McGill University, 1992. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=61068.
Testo completoAbstract (sommario):
DNA was microencapsulated by emulsification/interfacial polymerization within semi-permeable cross-linked chitosan membranes. Polar solvents and pH extremes were avoided during microencapsulation by using vegetable or mineral oil as the continuous phase and chitosan as the polymeric backbone. The membrane was cross-linked with glutaraldehyde or hexamethylene diisocyanate and microcapsules varied in diameter from 95 to 325 $ mu$m. DNA was visualized within the microcapsules with ethidium bromide stain. Binding of ($ sp{14}$C) methyl iodide and ($ sp{14}$C) benzo (a) pyrene by microcapsules was demonstrated in vitro and in vivo, respectively, although binding was mostly evident in the chitosan membranes. Magnetic recovery of the microcapsules from rat faeces following GI transit was facilitated by co-encapsulating magnetite. The microcapsule diameter decreased by 60-70% during GI transit due to dehydration in the colon and the recovery was approximately 10%.
20
Amer, Laila I. "Interfacial cationic polymerization and its application in microencapsulation". Thesis, University of Strathclyde, 1990. http://oleg.lib.strath.ac.uk:80/R/?func=dbin-jump-full&object_id=21162.
Testo completoAbstract (sommario):
Direct polymerization on the solid surfaces of three crystalline biologically active drugs has been carried out in this study to provide a thin polymer film (capsule wall) around the crystals. This polymer film would act as a release controlling layer of the encapsulated crystals into a surrounding fluid. To date there has not been to our knowledge, any study of release control by the encapsulation of solids by direct polymerization. This thesis describes a new technique based on solid/liquid interfacial cationic polymerization which was carried out in an entirely non-aqueous medium to encapsulate solid crystals of almost any size. The first step of the proposed technique involved the adsorption of a surface active agent (α-monoolein) from n-heptane solution onto the surface of the three drug crystals used in this study (KCI, β-estradiol and 5-aminosalicylic acid) to form a hydroxylated (polar) surface which was able to complex an appropriate cationic catalyst, BF₃ (C₂ H₅)₂O from solution to form a highly concentrated layer. This layer was in turn capable of polymerising the appropriate monomers used in this study namely, styrene, 3,4-dihydro-2H-pyran-2-methyl-(3,4-dihydro-2H-pyran-2- carboxylate) (abbreviated to "Cl monomer), 2,3-epoxypropylmethacrylate (GMA) and bisphenol-A diglycidylether (Epikote 828) present in the solution phase to produce the rate controlling polymer layer. Encapsulation processes were also carried out without first adsorbing a surfactant layer onto the crystal surface to investigate whether the surfactant is essential to conduct polymerization and encapsulation of the crystals by a polymer layer. Experiments proved that the encapsulation process took place on the surfaces of the three drugs used in this study even without first adsorbing a surfactant layer on their surfaces. The studies involved measurements of the area per molecule of α-monoolein which recorded an average of 46.1 A/M at air/water interface using the automated Lauda Surface Balance. The specific surface area of each drug powder was measured by nitrogen gas adsorption at low temperature using BET method. Values of 0.074, 3.14 and 1.69 m 2/g were obtained for KC1, β-estradiol and 5-aminosalicylic acid, respectively. The adsorption of α-monoolein on the three drug powders was analyzed using the Lauda Surface Balance, which indicated that KCI had higher affinity towards surfactant adsorption than either β-estradiol or 5-aminosalicylic acid. Encapsulations of the three different drugs by the polymers formed from the four previously mentioned monomers were achieved. Characterization of the polymers, their topographies and permeabilities were carried out using GPC, NMR, FTIR, IR, DSC, SEM, TEM, optical microscopy techniques. From the polymers' analyses and their release profiles, it was found that the C1 and Epikote polymers provided a continuous glassy thin layer which showed potential for release control. Polystyrene provided a microporous brittle layer which did not look practically promising, but interesting signs of tacticity were observed. GMA polymer provided a rubbery porous layer for which further investigation is warranted. The permeability of C1 ploymer layer (0.8% wlw of the total formulation and thickness of 0.11µm) to KCI (very water soluble drug) was found to be 2.5 x 10-¹' cm ²/sec.
21
El, Abbouni Sarah. "Microencapsulation of LL-37 Antimicrobial Peptide in PLGA". Digital WPI, 2016. https://digitalcommons.wpi.edu/etd-theses/235.
Testo completoAbstract (sommario):
Antimicrobial peptides are key actors in organisms€™ immune systems. They play an important role in phagocytosis, breaking bacteria membranes. They destroy the microbes, keeping them from repairing themselves, and therefore do not promote antimicrobial resistance. LL37 is a peptide produced by the human body. It is a short amino acid chain that is particularly active on the skin and mucous membranes. It has antimicrobial and fungal activity as well as wound healing properties, which makes it a very interesting active substance in wound treatment. However, its fragile and sensitive structure is a challenge to its use. Nowadays, encapsulation in a biocompatible polymer system is a promising technique in drug delivery, and presents a solution to LL37 administration and delivery. LL37 is a hydrophilic active substance, it will be trapped in PLGA (poly (lactic-co-glycolic acid)) by double emulsion and the microspheres will be shaped and stabilized by solvent evaporation. The capsules will be characterized by Dynamic Light Scattering (DLS) and Scanning Electron Microscopy. Their main features, drug loading, encapsulation efficiency and release profile, are determined using the Bradford assay. Since the peptide is expensive and delicate, it is important to optimize its encapsulation. For that reason, we will adapt the process to have the best drug loading as possible using water in oil in oil emulsions. For an external use, the capsules would be used over a few days, so having a fast release is very relevant. The larger the specific surface area, the faster the diffusion. For that reason, we will also study the impact of porosity on the release profile. As a result, different types of capsules will be synthesized, with higher porosity and by two processes: aqueous double emulsion and oil double emulsion. Their characteristic features and impact on bacterial pathogens will be determined and compared in order to determine their optimal synthesis process and formulation in given conditions of use.
22
Fernandez-Gonzalez, Angel. "Stabilization of functional ingredients by microencapsulation : interfacial polymerisation". Thesis, University of Birmingham, 2012. http://etheses.bham.ac.uk//id/eprint/3577/.
Testo completoAbstract (sommario):
Perfume is an expensive ingredient for most laundry detergents. To target its delivery to the fabric fibres at the right moment after the wash, improve its performance and reduce costs, using perfume microcapsules is one of the technologies that have been developed. Old technology based on melamine-formaldehyde resins presents some safety and environmental issues and current microcapsules made by interfacial polymerisation techniques do not provide the desired performance. In this work it has been done a deep study of the interfacial polymerisation process focusing on the effect that the formulation and process conditions have on the final properties of the microcapsules produced. The microcapsule walls have been characterized by SEM, TEM and FTIR. The encapsulation efficiency, release profile of the perfume from the microcapsules and their mechanical properties have also been measured. Microcapsules prepared at low temperature with a mix of trimesoyl and terephthaloyl chloride as organic monomers and diethylenetriamine, hexamethylenediamine and ethylenediamine as aqueous monomers showed good mechanical strength and low permeability which make them of industrial interest. Microencapsulation of glycerol for its potential use in lipsticks and other cosmetic products has also been achieved. The use of a salt (magnesium sulphate) greatly stabilized the emulsion and permitted to form small and uniform microcapsules. The process conditions selected may also be applied to encapsulate other oil-based or water soluble active ingredients for various industrial applications.
23
Farook, U. "Microbubbling and microencapsulation by co-axial electrohydrodynamic atomization". Thesis, University College London (University of London), 2009. http://discovery.ucl.ac.uk/18525/.
Testo completoAbstract (sommario):
Microbubbles coated with polymers or surfactants have been used in medical imaging for several years as ultrasound contrast agent particles and are now being investigated by researchers as drug and gene delivery vehicles and blood substitutes. Current methods available for the preparation of microbubbles are insufficient as they result in microbubbles with a wide size distribution and as such filtration is necessary before their use. With a view to fill the above demand, a detailed investigation has been carried out in this research to learn the viability of co-axial electrohydrodynamic atomization (CEHDA) technique to prepare microbubbles. The research also focuses on the effects of the process parameters such as flow rates, applied voltage and material parameters such as electrical conductivity, surface tension and viscosity with the objective of preparing polymer or surfactant coated stabilized microbubbles with diameters < 8 μm and with a narrow size distribution. A model glycerol-air system was used so that the CEHDA technique was modified to generate suspensions of microbubbles to a diameter < 8 μm with a narrow size distribution and then to characterise the CEHDA microbubbling process in terms of size and stability with varying process parameters and material parameters. Construction of a parametric plot between the air flow rate and the liquid flow rate was extremely useful in identifying the flow rate regime of air and liquid or suspension or solution for the continuous microbubbling of the system used. With further investigations into the CEHDA microbubbling technique, it was possible to develop strategies, first, to prepare suspensions of stabilized phospholipids-coated microbubbles with a mean diameter of ~ 5 μm and a polydispersivity index of 9%, and second, polymeric microspheres with a mean diameter of 400 nm and a polydispersivity index of 8% using a biocompatible polymer.
24
Pandolfi, Vittoria. "Microencapsulation of hepatic cells for extracorporeal liver supply". Thesis, Compiègne, 2016. http://www.theses.fr/2016COMP2262/document.
Testo completoAbstract (sommario):
Aujourd’hui, la transplantation est le seul traitement efficace proposé aux patients souffrant d’une insuffisance hépatique fulminante. La nécessité de disposer d’un système de suppléance hépatique transitoire apparaît donc indispensable. C’est dans cet axe que se sont développés les systèmes qualifiés de foies bio artificiels (BAL). Leur principale caractéristique est d’incorporer un bioréacteur hébergeant des cellules pouvant restaurer l’activité hépatiques dans son ensemble. A l’heure actuelle, les hépatocytes primaire humains (HEP) issus de foies de donneurs non transplantables sont considérées comme le meilleur choix. Cependant, leur utilisation reste limitée par leur faible disponibilité et la difficulté à les maintenir différenciés en culture in vitro. Pour remédier à ce dernier point, l’approche la plus prometteuse semble être une co-culture des hépatocytes avec les cellules non parenchymateuses afin de recréer un environnement proche des sinusoïdes hépatiques. Ce travail de thèse repose sur la mise en place d’une nouvelle approche de co-culture tridimensionnelle sous la forme de sphéroïdes, d’HEP primaires avec les principaux types de cellules non-parenchymateuses (les cellules de Kupffer, les cellules endothéliales et les cellules étoilées) selon des proportions spécifiques. Puis de leurs encapsulations dans des billes d’alginate et leurs cultures au sein d’un bioréacteur à lit fluidisé. Ce modèle s’est révélé pertinent et approprié à maintenir les fonctions hépatiques dans le temps. Bien que beaucoup d’optimisation reste à définir, ce travail exploratoire témoigne de l’intérêt de cette approche intéressante pour le progrès des systèmes BALLiver shortage makes transplantation inapplicable to all acute liver failure patients. Bioartificial Iiver (BAL) devices represent a temporary solution for these patients which are thereby bridged tilt Iiver transplantation or regeneration BAL treatment offers blood purification and substitution of metabolic functions through the activity of hepatocytes (HEPs), which are integrated in the device within acclimating containers, so-called bioreactors. Primary human hepatocytes are the ideal cell type to use in BAL, but they are scarcely available and difficult to maintain in vitro. Co-culture of HEPs with supporting cells has been proposed as the most promising strategy for preserving HEP behaviors in in vitro conditions. In fact, assisting cells types hold their ability to influence functional responses of the HEPs by providing them with cues of the native organ.This PhD work proposed a novel approach of co-culture for the functional sustain and preservation of the HEPs in the environment of the fluidized bed bioreactor (designed in our Iaboratory). Definition of this model took inspiration from the cellular organization in the organ; therefore, it employed three major sinusoidal non-parenchymal cell populations (liver sinusoidal, Kupffer, and hepatic stellate cells) which, together with HEPs, were cultured with three-dimensional arrangement (spheroids) and according to specific proportions. The resulting model was characterized in terms of functional benefits for the HEPs, and then applied in the microenvironment of alginate beads, which provide cells with immunological and mechanical protection in the fluidized bed bioreactor. This spheroidal multi-cultured model revealed its potentiality in sustaining in vitro HEP behaviors over time. Although much remains to be refined, this model may represent an interesting approach for the progress of BAL
25
AMIET, CHARPENTIER CAROLINE. "Microencapsulation de bacteries du groupe pseudomonas fluorescens-putida en vue de la bacterisation directe de semences". Angers, 1996. http://www.theses.fr/1996ANGE0510.
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26
Lassiaz, Guillemette. "Microencapsulation de l'acide amino-5 salicylique suivant une méthode de coacervation par évaporation de solvant". Paris 5, 1995. http://www.theses.fr/1995PA05P189.
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27
Keen, Polly Helena Ruth. "Encapsulation of biological material in colloidosomes". Thesis, University of Cambridge, 2014. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.648725.
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28
Tran, My-Kien. "Microencapsulation de protéines dans des systèmes polymériques par des procédés sans solvants toxiques, en particulier la technologie des fluides supercritiques". Angers, 2013. http://tel.archives-ouvertes.fr/tel-00952800.
Testo completoAbstract (sommario):
Aujourd'hui, l'encapsulation de protéines dans le but de chercher une action prolongée reste un défi dans le domaine de microencapsulation. Ce sujet de recherche attire beaucoup l'attention des chercheurs depuis des décennies en raison des avantages que l'encapsulation de protéines pourrait apporter au confort du patient et à l'efficacité du traitement thérapeutique. L'encapsulation de protéines dans des systèmes polymériques comme par exemple des microparticules de PLGA (polylactique- glycolique-acide) est une des approches permettant d'atteindre ce objectif. Nombreuses méthodes d'encapsulation ont été décrites mais le point négative généralement observé dans ces méthodes est l'utilisation des solvants organiques volatiles, considérés toxiques pour la santé humaine et l'environnement. Le but de ce travail était d'élaborer de nouveaux procédés de préparation de particules de PLGA en vue de l'encapsulation de protéine. Des solvants miscibles avec l'eau, non-volatiles et peu-toxiques (glycofurol, ,isosorbide dimethyl ether) ont été choisis pour l'utilisation dans des procédés présentés dans ce travail. Le CO2 pressurisé, possédant des propriétés physicochimiques fortement modulables, a été utilisé pour le développement de ces nouveaux procédés. Différents procédés ont été développés en basant soit sur le phénomène de séparation de phase, soit sur la méthode d'émulsification/extraction. Des particules sphériques de taille variant de 0. 3 à 30 μm ont été générés avec le rendement d'encapsulation satisfaisant (65-80%). Les détails de la formulation sont présentés et le mécanisme de formation de particules est discuté. La méthodologie de plan d'expérience a été utilisée pour évaluer l'influence des paramètres opératoires et pour prédire le rendement d'encapsulation dans le domaine expérimental choisiTo date, protein encapsulation for sustained-release purpose remains a challenge in the field of microencapsulation. Owing to many benefits that it can offer to patient comfort and therapeutic efficiency, protein encapsulation in drug delivery systems has been drawing the attention of researchers since decades. Protein encapsulation in polymeric systems such as PLGA (poly-lactic-glycolic-acid) particles has been proven to be an useful approach to attain this objective. Many protein encapsulation methods have been developed; however, the main drawback in these methods lies in the use of volatile toxic solvents, which are considered toxic for the body and the environment. The goal of this work was then to elaborate formulation strategies to find ways of avoiding the use of volatile toxic solvents. Water-miscible non-volatile low-toxic solvents such as glycofurol, isosorbide dimethyl ether were chosen to be used in this work. Pressurized CO2, with its highly flexible properties in fuction of pressure and temperature, was made use of for the development of these new processes. Two formulation methods have been used: the phenomenon of phase separation and the emulsification/extraction method. Different processes for protein encapsulation were developed during this work. Spherical polymeric PLGA particles were successfully generated with satisfactory encapsulation yield of protein (65-80%). Depending on the chosen process, particle size can range from 0. 3 to 30 μm. Details in the formulation of PLGA particles for protein encapsulation are presented and the mechanism of particle formation is discussed. Experimental design was used to ascertain the influence of operating factors on the encapsulation yield and to better predict the output in the chosen experimental space
29
El, Mafadi Samira. "Maîtrise d'un procédé d'enrobage en lit fluidisé en mode Wurster". Nantes, 2004. http://www.theses.fr/2004NANT2029.
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30
Mathieu, Éric. "Étude de la microencapsulation par coacervation complexe utilisant des dérivés acryliques". Nantes, 2003. http://www.theses.fr/2003NANT2115.
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31
Bohman, Sara. "Microencapsulation of Pancreatic Islets : A Non-Vascularised Transplantation Model". Doctoral thesis, Uppsala universitet, Institutionen för medicinsk cellbiologi, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-9369.
Testo completoAbstract (sommario):
Transplantation of pancreatic islets is a potential treatment of type 1 diabetes that aims to restore normal blood glucose control. By encapsulating the islets in alginate, they can be protected from rejection. The aim of this thesis was to study the biology of encapsulated islets and to use the technique of microencapsulation to study the effect of transplantation in a system that is separated from direct contact with the vascular system and the host tissue at the transplantation site. Encapsulated islets can effectively reverse hyperglycaemia after transplantation into the peritoneal cavity of diabetic mice. A period of culture before encapsulation and transplantation did not affect their insulin release or curative capability. Pre-culture with exendin-4 improved insulin secretion, but not to the extent that the long term outcome in our transplantation model was improved. Despite being able to reach and retain normoglycaemia, microencapsulated islets transplanted intraperitoneally decreased in size. More specifically the number of beta cells in each individual islet was decreased. However, in contrast to previous studies using non-encapsulated islets, the alpha cell number was maintained, and thus the capsule seems to protect these peripherally located and otherwise exposed cells. As the capsule also prevents revascularisation of the islets, the model was used to study the importance of vascular supply for islet amyloid formation. Islet amyloid is a possible reason for the long-term failure of transplanted islets. It is likely that their low vascular density causes a disturbed local clearance of IAPP and insulin that starts the aggregation of IAPP. Indeed, encapsulated islets had an accelerated amyloid formation compared to normal islets, and might serve as a model for further studies of this process. In conclusion, although revascularisation is not a prerequisite for islet graft function, it plays an important role for islet transplantation outcome.
32
Kaur, Harkirat, e h_harkiratkaur@student rmit edu au. "Baking enzymes and microencapsulation strategies for retardation of staling". RMIT University. Applied Sciences, 2008. http://adt.lib.rmit.edu.au/adt/public/adt-VIT20081203.133339.
Testo completoAbstract (sommario):
The staling of baked products remains a significant cause of economic loss due to the loss of enjoyment seen as crumb firming occurs. The aims of the current project have been to investigate the stability of amylases in bakery formulations. In addition, the impact of partial hydrolysis products of starch on staling is investigated. Specific assays were used to measure Ñ-amylase and Ò-amylase, in the presence of the other potentially interfering activity. Ñ-Amylase activity levels appeared to gradually increase during the proofing stages and then to decline upon heating of the dough. However, the activity remaining in the final baked loaf was readily measurable indicating that not all of the enzyme had been inactivated. Free and total Ò-amylase activities were also measured and most was found to be in the free form. Ò-Amylase was unstable with only relatively low activities remaining in the final baked loaf. It appears that of the two amylolytic enzymes, Ñ-a mylase is sufficiently stable that it may exert some impact on the crumb characteristics in the freshly baked product and during subsequent storage. In order to assess the likelihood that amylolysis is of significance to crumb characteristics, HPLC was used to analyse aqueous extracts for sugars. Commercial flours were found to contain low levels of sugars with maltose being the predominant sugar present. A number of commercial breads were also analysed and the composition found to vary between the different samples. Typically maltose was present at higher levels than the other sugars. When experimental loaves were analysed, the patterns showed that other sugars declined during proofing whereas maltose remained at readily measurable levels. Upon baking and subsequent storage the amounts of maltose increased. These results are consistent with the findings that some amylolytic activity remains in the baked product. In the third phase of this study, a potential means of investigating the role of particular carb ohydrates in product textures and staling rates was examined. The approach of spray drying was used to prepare microencapsulated maltodextrin. The encapsulating agents used were based upon rice starch and guar galactomannan. When these microcapsules were incorporated into the breadmaking formulation and baked, it appeared that softer crumb characteristics were achieved. The data also indicates an effect of delay in the staling rates. In a preliminary evaluation of the potential of two X-ray scattering methods, it was found that both techniques appear useful. The differences seen for samples of bread crumb analysed at various stages of storage did not show large differences in the intensity patterns. Of the two approaches, small angle analysis (SAXS) appears to show greater potential for application in ongoing studies of staling. In conclusion, cereal grain Ñ-amylase may be more stable during breadmaking than previously thought. There appears to be an increase in the level of some low molecular weight sugars in the final, baked product. Microencapsulation may offer a useful technique for the study of the role of specific carbohydrates during baking and storage of breads.
33
Al, Kindi Adil Hashim 1976. "Cellular cardiomyoplasty : optimizing cellular dosage and retention by microencapsulation". Thesis, McGill University, 2008. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=111585.
Testo completoAbstract (sommario):
Cellular Cardiomyoplasty (cell therapy for myocardial regeneration) targets the basic pathophysiology of heart failure and represents a novel technique for augmenting the function of the failing heart. Previous studies have demonstrated massive mechanical losses in the first few minutes. Thus, efforts to reduce mechanical losses may prove more beneficial than those directed against biological losses alone. We believe that "Wash-out" into the disrupted blood vessels is responsible for these early losses.In the first part of this study we hypothesized that by increasing the size of the injectate, the amount of immediate losses can be reduced achieving better retention. Using Alginate-poly-L-lysine-Alginate (APA) miscrocapsules of two different sizes (200mum&400mum) and comparing retention with bare microspheres (10mum) of similar size to MSCs, we demonstrated that immediate retention rate increased by four folds. The retention rate for group 1 (microspheres only) was 4.28+/-3.46% which was significantly lower than that for groups 2 (microspheres in 200mum microcapsules) at 16.45+/-12.66% and group 3 (microspheres in 400mum microcapsules) at 12.93+/-6.28% for Group (p<0.05). There was no difference between group 2 and 3.
In the second part, we investigated the potential of gradually increasing the cell load on functional improvement and engraftment using conventional intramuscular delivery. Five groups of rats received escalating doses of MSCs after surgically induced ischemia (gp1 no cells, gp2 0.5x 10 6, gp3 1.5x106, gp4 3x106,gp5 5x106 MSCs). At 7 weeks, we observed significant improvement in cardiac function in groups 3 to 5 compared to post-infarction baseline. This was not observed in groups 1 & 2. However, in groups 3 to 5, we observed no functional advantage for increasing the cell load beyond a minimal therapeutic dose. This is consistent with our hypothesis that small cells are washed out into the circulation.
We also showed the ability of Alginate-Poly-l-lysine-Alginate (APA) microcapsules to sustain the viability of encapsulated MSCs in-vitro. Finally, the ability of encapsulated MSCs to improve the function of the heart in-vivo was tested.
34
Tagalakis, Aristides Dimitrios. "Microencapsulation technology and chimeraplasty to counteract apolipoprotein E deficiency". Thesis, Royal Holloway, University of London, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.397981.
Testo completo
35
Bedie, Kouadio Gérard. "Microencapsulation de composés nutraceutiques dans des complexes protéines-polysaccharides". Thesis, Université Laval, 2008. http://www.theses.ulaval.ca/2008/25147/25147.pdf.
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36
Bedie, Kouadio Gerard. "Microencapsulation de composés nutraceutiques dans des complexes protéines-polysaccharides". Doctoral thesis, Université Laval, 2008. http://hdl.handle.net/20.500.11794/19823.
Testo completo
37
Tran, Nhu Mai. "Microencapsulation de cellules hépatiques pour des études de virologie". Compiègne, 2012. http://www.theses.fr/2012COMP2023.
Testo completoAbstract (sommario):
La culture de cellules hépatiques en trois dimensions (3D), ainsi que l’ingénierie tissulaire, trouvent à l’heure actuelle de nouvelles applications en bioingénierie, et notamment en virologie pour l’étude de l’hépatite C. En effet, la mise en place de nouvelles stratégies antivirales nécessite la maîtrise de la culture du virus de l’hépatite C (VHC) dans des conditions mimant la physiologie de l’infection naturelle. L’accès à de nouveaux modèles de culture cellulaire permissifs au VHC représenterait donc une innovation importante pour les études sur le VHC et la production massive du virus. Les travaux de ce doctorat s’inscrivent dans cette optique et portent sur la mise au point d’un modèle de culture 3D de cellules hépatiques humaines. Celui-ci repose sur la microencapsulation d’une lignée de cellules hépatiques (Huh-7) permissives au VHC au sein de billes poreuses d’alginate-calcium. Notre démarche expérimentale repose sur la caractérisation physique et biologique de ce modèle, en modulant la composition du biomatériau (modification de la viscosité, de la concentration de l’alginate-sodium ou greffage de polyéthylène glycol (PEG)). Les résultats de ces travaux ont permis de déterminer une condition d’encapsulation qui allie une porosité de la matrice d’alginate compatible avec l’infection virale à un comportement cellulaire adéquat du fait de l’organisation tridimensionnelle des cellules et l’expression de récepteurs membranaires au VHC. Ce modèle de culture cellulaire a ensuite été soumis à différents tests d’infection par le VHC et d’autres types de virus hépatotropiques. A l’encontre des hypothèses ayant permis de définir les conditions d’encapsulation optimales, nous montrons que les cellules hépatiques encapsulées ne sont pas infectées ou ne produisent pas de particules virales, quels que soient le type de virus et les conditions d’infection utilisés. Ces résultats inattendus ouvrent des perspectives novatrices dans le cadre de la transplantation de cellules encapsuléesThree dimensional (3D) hepatocyte cell culture and tissue engineering nowadays finds new applications in bioengineering, and more specifically in virologyand for hepatitis C studies. Indeed, the establishment of new antiviral strategies requires culture model for hepatitis C virus (HCV) that mimics the physiology of natural infection. New culture models permissive to HCV would thus appear as a promising innovation for HCV studies and mass production of virus. This PhD thesis is part of this perspective and focuses on the development of a 3D culture model of human hepatic cells. It is based on the microencapsulation of a hepatic cell line (Huh-7), permissive to HCV in calcium alginate porous beads. Our experimental approach is based on the physical and biological characterization of this model, after changes in the composition of the material (viscosity and concentration of sodium alginate, or polyethylene glycol (PEG) grafting). The results of these studies permitted to identify a condition for encapsulation which combines a matrix porosity compatible with viral infection with an adequate cell behavior due to a 3D cell organization and the expression of HCV membrane receptors. This culture model was submitted to various infection tests with HCV and others hepatotropic viruses. In contrast with the hypothesis leading to optimal encapsulation conditions, we showed that hepatic cells were not infected or did not produce viral particles, regardless of the virus and infection conditions used. These unexpected results open up innovative prospects in the context of cell transplantation
38
Casas, ferrer Laura. "Microfluidic flow of biomimetic tissues". Thesis, Université de Montpellier (2022-….), 2022. http://www.theses.fr/2022UMONS001.
Testo completoAbstract (sommario):
Nous avons conçu un prototissu biomimétique comme modèle de tissus cellulaires qui permet d'identifier le rôle individuel des différents constituants cellulaires qui jouent un rôle dans le comportement rhéologique des tissus. L'objectif final est de caractériser le comportement d'écoulement de ce prototissu sous confinement microfluidique. La première partie de la thèse se concentre sur la conception et la synthèse du prototissu à partir de l'assemblage de Vésicules Unilamellaires Géantes (GUVs). Le système ligand-récepteur que nous avons utilisé pour l'assemblage est la paire streptavidine-biotine. Nous avons démontré qu'en modifiant le rapport streptavidine-biotine, le nombre de vésicules en solution et la concentration de biotine dans la membrane des vésicules, il est possible de contrôler la taille des agrégats et la compacité du tissu. Nous avons également modifié la morphologie du tissu biomimétique en changeant la méthode d'incubation, passant ainsi de formes 3D à une structure monocouche 2D. Un autre système d'adhésion basé sur des complémentarités de séquences d’ADN a également été évalué. Il s'est avéré efficace pour contrôler l'adhésion entre les vésicules, et a permis de concevoir des prototissus avec un niveau élevé de compaction. Dans la deuxième partie de la thèse, la rhéologie de ce tissu biomimétique a été testée au moyen d'une configuration microfluidique. Plus précisément, une pression contrôlée a été appliquée et la déformation de l'agrégat lors de son écoulement à travers une constriction a été suivie. Le changement de taille et de forme de l'agrégat a été calculé pour les petits agrégats, ce qui a contribué à élucider la nature de leur comportement élastique. Pour les agrégats plus grands, le mouvement vers l'avant du front de l'agrégat dans une constriction microfluidique en fonction du temps a été mesuré. Il a été possible d'observer un comportement viscoélastique, que nous avons comparé à celui observé dans les tissus épithéliaux. Le modèle de prototissu et les outils que nous avons développés pour caractériser sa rhéologie peuvent être mis en oeuvre à présent pour étudier les propriétés mécaniques des tissus cellulaires en faisant varier ses propriétés clés : l'adhésion entre les cellules individuelles, les propriétés mécaniques du cytosquelette et l'activité cellulaireWe designed a biomimetic prototissue as a model for cellular tissues that allows to identify the individual role of the different cellular constituents that play a role in the rheological behavior of tissues. The final goal is to characterize the flow behavior of this prototissue under microfluidic confinement. The first part of the Thesis focuses on the design and synthesis of the prototissue from the assembly of Giant Unilamellar Vesicles (GUVs). The ligand-receptor system that we used to drive the assembly was provided by the streptavidin-biotin pair. We have demonstrated that by changing the streptavidin-to-biotin ratio, the number of vesicles in solution and the biotin concentration in the vesicle membrane it is possible to tune the size of the aggregates and the compactness of the tissue. We have also been capable of changing the morphology of the biomimetic tissue from 3D-shapes to a 2D-monolayer structure by changing the incubation method. An alternative adhesion system based on DNA tethers was also evaluated. It proved to be effective in tuning the adhesion between vesicles, and was found to allow the design of prototissue with a high level of compaction. In the second part of the Thesis, the rheology of this biomimetic tissue was tested by means of a microfluidic setup. Specifically, a controlled pressure was applied and the deformation of the aggregate as it flowed through a constriction was tracked. The change in the aggregate size and shape was calculated for small aggregates, which contributed to elucidate the nature of their elastic behavior. For larger aggregates, the forward motion of the aggregate front in a microfluidic constriction as a function of time was measured. It was possible to observe a viscoelastic behavior, that we compared to the one observed in soft epithelial tissues. Both the prototissue model and the tools we developed to characterize its rheology can be implemented in the future to investigate cellular tissues mechanical properties varying its key properties: the adhesion between individual cells, the mechanical properties of the cytoskeleton and the cellular activity
39
Arenas, Gamboa Angela Maria. "Evaluation of microencapsulation as an improved vaccination strategy against brucellosis". [College Station, Tex. : Texas A&M University, 2007. http://hdl.handle.net/1969.1/ETD-TAMU-1384.
Testo completo
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Begum, Syeda Nargis. "Microencapsulation of lemon oil by precipitation method using sodium caseinate /". [St. Lucia, Qld.], 2005. http://www.library.uq.edu.au/pdfserve.php?image=thesisabs/absthe18497.pdf.
Testo completo
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Zhao, D. "Novel processing and microencapsulation of Ganoderma lucidum spores for healthcare". Thesis, University College London (University of London), 2014. http://discovery.ucl.ac.uk/1416860/.
Testo completoAbstract (sommario):
Ganoderma lucidum spores (GLS) have attracted increasing attention for its versatile biological activities, particularly in cancer therapy. The resilient chitin bilayer of sporoderm is conventionally regarded as an obstacle in the exploitation of bioactive ingredients. Present study found that ethanol extract of broken GLS was able to inhibit cancer cells, however, water extract, especially medium extract (containing serum protein) from unprocessed GLS have also demonstrated anti-proliferative effects on cancer cells. The effectiveness of GLS extract on the inhibition of a series of human cancer cells, namely, osteosarcoma, neuroblastoma, myeloid leukaemia and breast cancer, has been compared, and DNA assays showed that the GLS extract is more efficient in inhibiting neuroblastoma but has less effect on osteosarcoma cell line. To overcome the limitations of the existing processing methods of GLS, the feasibility of sonication as a new way to break GLS has been tested. A series of processing parameters, such as sonication power and duration, have been compared to maximise the breaking efficiency. The preservation of bioactive components of GLS (e.g. polysaccharides and ganoderic acids) from sonication processing was revealed by Fourier Transform Infrared Spectroscopy (FTIR) and High Performance Liquid Chromatography (HPLC) analyses. In vitro study showed that sonication processed GLS were able to inhibit breast cancer cells, at dose and time dependent manner, particularly at low pH (6.5), favourable for cancerous cell growth. The inhibitory efficiency of sonication processed GLS on the growth of breast cancer cells was ranked the highest, compared with that of unprocessed GLS and commercially broken GLS. To preserve further the bioactive ingredients of GLS, broken GLS have been encapsulated with alginate by electrospraying (ES). The size of GLS encapsulated alginate (GLS/A) beads was found to affect the in vitro release profiles of bioactive ingredients of GLS, and can be controlled by varying the processing parameters (e.g. crosslinking time, infuse rates and applied voltage). A series of GLS/A beads with mean sizes ranging from 500 to 2500 µm have been produced by ES and the in vitro release profiles of GLS/A beads in simulated gastrointestinal mediums were found to be related to the pH, bead size and drying methods. In summary, an advanced method combining a customised sonication with ES has been developed by setting up a lab-scale production line from processing to encapsulation of GLS. This may pave the way to produce effective GLS products with desirable natural bioactive components for healthcare.
42
Kopp, Victoria V., C. B. Agustini, Santos J. H. Z. dos e M. Gutterres. "Microencapsulation of clove essential oil with gelatin and alginate - 164". Verein für Gerberei-Chemie und -Technik e. V, 2019. https://slub.qucosa.de/id/qucosa%3A34186.
Testo completoAbstract (sommario):
Content:
Essential oils are of commercial interest primarily because of their potential antimicrobial, antifungal and antioxidant properties and for being of natural origin, which generally represents lower risk to the
environment and human health. Clove essential oil not only contains many kinds of biological active compositions but also has highly effective and comprehensive antibacterial functions. Remarkably, clove
has strong antimicrobial activities against a wide range of pathogenic microorganisms. To prevent chemical changes the oil is microencapsulated. The aim of this study is to develop essential oil
microcapsules with gelatin and alginate. Various solutions were prepared for the capsule wall material at different concentrations. The encapsulation efficiency (%) was accessed and the microcapsules were
characterized by oil content (%), oil charge (%), morphology, functional groups present, thermogravimetric analysis and by Fourier transform - infrared spectral analysis. FT-IR spectra of the clove oil shows some special peaks at 1148,01 and 1033,33 cm-1. The spectra of the capsule showed peaks 1148.34 and 1033.29 cm -1, the same peaks present in clove oil, showing that the encapsulation did not alter the
structure of the oil's main assets. In case of the gelatin and alginate microcapsules containing clove oil, most of the characteristic peaks of clove oil remained unchanged, indicating the successful incorporation
of clove oil into the microcapsules and the chemical stability of the clove oil after encapsulation. In otherwords, there was no significant chemical interaction between the oil and the wall of the microcapsule.
Take-Away:
The clove oil was microencapsulated according the FTIR spectra.
43
Pensé-Lhéritier, Anne-Marie. "Microencapsulation de composés amphiphiles antiseptiques par polycondensation interfaciale des isocyanates". Paris 11, 1991. http://www.theses.fr/1991PA114808.
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CAUMARTIN, DHIEUX CLAUDIA. "Etude de la microencapsulation de vaccins destines a la pisciculture". Le Mans, 1995. http://www.theses.fr/1995LEMA1021.
Testo completoAbstract (sommario):
Des pathologies bacteriennes et virales se sont developpees avec l'intensification de la pisciculture traditionnelle continentale et marine causant d'importantes pertes de poissons. Les moyens therapeutiques existant posant de nombreux problemes (resistance aux antibiotiques, problemes ecologiques), la vaccination s'est averee necessaire pour l'eradication de ces maladies. La voie la plus efficace et la plus adaptee a la vaccination en masse semble etre la vaccination par voie orale en incorporant le vaccin a l'aliment. Cependant, d'importantes quantites de vaccin sont necessaires pour induire une bonne reponse immunitaire du fait d'une degradation ou d'une desactivation digestive de l'antigene limitant ainsi l'emploi courant de ce mode de vaccination. La microencapsulation de l'antigene est une voie potentielle pour minimiser ce phenomene. Le systeme microparticulaire doit proteger l'antigene du milieu environnant (acidite du milieu gastrique et aliment) et aussi permettre sa vectorisation et sa liberation au niveau de l'intestin posterieur du poisson. Ce travail presente la mise au point et l'evaluation in vitro et in vivo chez la truite et la carpe d'un systeme matriciel vecteur et gastroprotecteur pour une vaccination par voie orale contre la vibriose et contre la septicemie hemorragique virale. Le systeme matriciel a ete realise a partir d'un polymere polysaccharidique, l'alginate, qui en presence d'ions divalents, forme un reseau tridimensionnel
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Rabeau, Sophie. "Étude d'un procédé continu de microencapsulation basé sur un micromélangeur". Thesis, Vandoeuvre-les-Nancy, INPL, 2009. http://www.theses.fr/2009INPL096N/document.
Testo completoAbstract (sommario):
Cette étude se concentre sur l'influence des conditions hydrodynamiques et de mélange sur les caractéristiques de microcapsules obtenues par inversion/précipitation. Ce processus est classiquement exécuté dans une cuve agitée alors qu'il a été montré que l'exécution de procédés de fabrication de produits chimiques peut être améliorée en utilisant des microtechnologies en raison du meilleur contrôle hydrodynamique et de l'intensification des échanges de chaleur et de matières. Donc, afin d'évaluer l'avantage potentiel de ces nouvelles technologies, des microcapsules de parfum enrobé dans du PMMA ont été fabriquées par inversion de phase/précipitation (système THF/Eau) dans une cuve semi-fermé agitée standard, dans un mélangeur structuré et dans un micromélangeur de type V (FZK). Les trois procédés sont évalués en terme de propriétés de capsules (la distribution de taille, l'épaisseur de membrane, l'efficacité d'encapsulation et la cinétique de libération). Il a été montré que le micromélangeur offre une vaste gamme de conditions de fonctionnementThis study focuses on the influence of the hydrodynamic and mixing conditions on the characteristics of microcapsules obtained by inversion/precipitation. This process is classically run in semi-batch stirred tank while it has been shown that the performance of chemical product manufacturing processes can be improved by using microtechnologies due to better hydrodynamic control and intensification of mass and heat exchanges. Therefore, in order to evaluate the potential benefit of these new technologies, microcapsules of perfume in PMMA have been manufactured by phase inversion/precipitation (system THF/Water) in a classical semi-batch stirred tank, in a structured mixer and in a V-Type micromixer (FZK). The three process is evaluated in term of capsules properties (size distribution, membrane thickness, encapsulation efficiency and release rate). It is shown that micromixer offers a wide range of operating conditions
46
Bile, Jessica. "Microencapsulation d’agent antimicrobien pour le développement de conditionnements primaires fonctionnalisés". Thesis, Lyon 1, 2015. http://www.theses.fr/2015LYO10182/document.
Testo completoAbstract (sommario):
Dans un premier temps, ce travail a concerné la réalisation de microparticules chargées en agent antimicrobien suivant la technique de microencapsulation par évaporation de solvant en émulsion simple. Différentes morphologies ont été obtenues avec des microparticules éloignées du standard lisse, démontrant des cicatrices et des défauts, de la rugosité ou encore des trous. Les paramètres ainsi que les mécanismes physico-chimiques responsables des dégradations morphologiques ont été identifiés et discutés. Il a été démontré que les paramètres de formulation tels que la masse et masse molaire du polymère ou encore la présence de tensioactifs ainsi que les paramètres du procédé tels que la force et la vitesse de cisaillement modifient l'état de surface finale des microparticules. Ce travail a notamment prouvé qu'il existe une compétition entre la cinétique d'évaporation du solvant et la vitesse de coalescence des gouttelettes d'émulsion qui est à l'origine des dégradations morphologiques. Suite à cette étude, les microsphères résultantes contenant de l'alcool phényléthylique ont été enduites à la surface du conditionnement primaire polyoléfine sous forme de films minces de différentes épaisseurs grâce à la technique de revêtement par immersion. L'introduction de microparticules au sein du liant ralentit la diffusion de l'agent antimicrobien en augmentant le nombre de matrices polymériques à traverser pour atteindre le milieu extérieur. La réalisation de telles couches a permis d'obtenir des libérations sur des périodes supérieures à au moins trois mois ce qui est 15 fois plus important que celles obtenues pour l'agent antimicrobien non encapsulé. Ce travail de thèse a également étudié l'activité antimicrobienne de l'alcool phényléthylique au sein d'une émulsion. Il a été mesuré le partage de l'alcool phényléthylique entre les phases aqueuse, huileuse et micellaire de l'émulsion. Les résultats obtenus ont permis de développer un modèle mathématique calculant la fraction en agent antimicrobien libre présent en solution aqueuse. Ce dernier a été corrélé à des dosages de l'émulsion et des mesures microbiologiques utilisant les cinq souches microbiennes du challenge test sur 14 jours. Ainsi, il a été démontré que les calculs permettent de prédire la concentration en conservateur nécessaire afin d'assurer la protection antimicrobienne des formulations. Cette étude a notamment prouvé que la quantité d'alcool phényléthylique nécessaire à la conservation des formulations est respectivement 1,6 et 4,3 fois plus importante dans une solution micellaire et une émulsion par rapport à une solution aqueuseFirst, this work focused on the formulation of microparticles loaded with antimicrobial agent using the emulsion/solvent evaporation method. Several morphologies have been obtained with nonsmooth microparticles characterized by scars and defects, roughness and holes. The parameters and the physico-chemical mechanisms involved in these morphological deteriorations have been identified and discussed. It has been shown that the formulation and processing parameters as the polymer mass and molar mass, the surfactant as well as the speed and shear rate of the propeller play a key role in the final microparticles surface states. This study proved that there is a competition between solvent evaporation and the coalescence of emulsion droplets which is responsible for the morphological degradations. Following this study, the resulting microspheres loaded with phenylethyl alcohol were dispersed in a binder and coated as thin films of various thicknesses by the dip-coating method at the polyolefin surface. It has been measured that the use of microparticles slows the antimicrobial agent diffusion by increasing the number of polymeric matrices that have to be crossed in order to reach the external medium. Such thin films resulted in an antimicrobial agent delivery up to 3 months which is 15 times higher than the delivery obtained for the non-encapsulated antimicrobial agent. The antimicrobial activity of the phenylethyl alcohol in an emulsion has also been investigated. The phenylethyl alcohol partition between the water phase, the oil phase and the micellar phase of an emulsion has been measured. These results led to the development of a mathematical model calculating the fraction of free antimicrobial agent present in the aqueous phase. It has been correlated with emulsion dosages and microbiological measurements using the five microorganisms of the challenge test during 14 days. It has been demonstrated that calculations enable the prediction of the antimicrobial agent concentration needed to ensure the antimicrobial protection. In particular, this work proved that the phenylethyl alcohol quantity necessary for antimicrobial protection is respectively 1.6 and 4.3 times higher for a micellar solution and an emulsion compared to an aqueous solution
47
Argin, Sanem. "Microencapsulation of probiotic bacteria in xanthan-chitosan polyelectrolyte complex gels". College Park, Md.: University of Maryland, 2007. http://hdl.handle.net/1903/7826.
Testo completoAbstract (sommario):
Thesis (Ph. D.) -- University of Maryland, College Park, 2007.Thesis research directed by: Dept. of Nutrition and Food Science. Title from t.p. of PDF. Includes bibliographical references. Published by UMI Dissertation Services, Ann Arbor, Mich. Also available in paper.
48
Williams, Mark. "Polymer-modified inorganic particles : versatile Pickering emulsifiers for microencapsulation applications". Thesis, University of Sheffield, 2013. http://etheses.whiterose.ac.uk/6633/.
Testo completo
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Seidel, Julia [Verfasser]. "Container crystals for microencapsulation : manufacturing and application potential / Julia Seidel". Halle, 2017. http://d-nb.info/1143595874/34.
Testo completo
50
Loughrill, Emma Sarah. "A nutritional evaluation and optimisation of infant foods using microencapsulation". Thesis, University of Greenwich, 2015. http://gala.gre.ac.uk/18148/.
Testo completoAbstract (sommario):
Over recent decades the modern lifestyle dynamic has led to an increased parental reliance on commercially marketed complementary infant foods in the UK, which has been highlighted by the Diet and Nutrition Survey of Infants and Young Children. The current nutritional labelling formats for ready-to-eat complementary infant foods are a duplicate of the legislative requirements for manufacturing of ready meals, intended for the general population, the implication of this is that a number of important nutrients maybe limiting or excessive, which will affect their nutritional quality and suitability as an infant food. Furthermore nutritional databases, such as McCance and Widdowson provide limited data on the composition of these types of food products. The European Food Safety Authority has highlighted that nutrient intake data after six months of life is currently inadequate as well as insufficient and urgently needs to be addressed. Therefore the nutritional content of these food products needs to be assessed to ascertain whether or not infants are meeting dietary requirements when consuming such products. The aims of this study were to evaluate the nutritional suitability of infant food products currently available on the UK market, according to the most up to date recommendations and recent relevant legislation and to explore the microencapsulation of docasahexaenoic acid (DHA) to optimise the nutrient content of infant food products. New protocols were developed for the quantitative analysis of certain key nutrients including High Pressure Liquid Chromatography (HPLC) – Charged Aerosol Detection for essential fatty acids, HPLC and UV spectrophotometry for fat soluble vitamins A and E, competitive enzyme immunoassay (Vitakit D™) for vitamin D and Inductively Coupled Plasma Optical Emission Spectroscopy for essential elements (Ca, Cu, Fe, K, Mg, Na, P and Zn) in commercial infant foods in the UK. The estimated daily intakes of these products were compared against current dietary recommendations for infants. In addition the Ca:P ratio was also determined in a range of commercial infant foods and compared with recommendations in relation to bone health. Furthermore, the effects of commonly practiced re-heating treatments used by parents were examined to establish whether different preparation methods affected the fatty acid content of manufactured infant formula milks. Finally, through the nutritional evaluation of these infant food products, the infant’s diet was found to be low in DHA, which provided opportunities for scope and product optimisation to improve the nutritive value of infant food products. Therefore microencapsulation of DHA was explored as a potential way to improve the nutritional quality of infant food products. The nutritional evaluation of the essential fatty acid content of a 6-9 month old infant’s diet highlighted that pre-formed long chain polyunsaturated fatty acids (LCPUFA) DHA and arachidonic acid (AA) intakes (at 23.3 mg/day and 36.7 mg/day, respectively) were below recommendations set by the US, at 103.3 mg/day and 147.5 mg/day, respectively. This provides scope for product optimization to improve the nutritive value of commercial infant food products. With respect to the precursor essential fatty acids, the dietary intake of the n-6 fatty acid linoleic acid (LA) was found to be above recommendations at 3147.9 mg/day, whereas the n-3 fatty acid α-linolenic acid (ALA) was found to be below recommendations at 296.4 mg/day, which increases the LA:ALA ratio of the diet; this may have implications for allergy. As the fortified infant formula was identified as the major dietary contributor and due to the fact that unsaturated fatty acids are prone to oxidation, the impact of re-heating treatments used by parents on the fatty acid content of formula milk was investigated and a degree of statistically significant changes were observed. In relation to the transparency of the nutritional information declared on the labels by the manufacturers, infant formula milks were all within the limits of EU regulations although there was a degree of significant variation between the quantitative values analyzed in this study and the declared values on the labels. With regards to the vitamin A and E analysis, normal phase HPLC was employed for the simultaneous quantification of retinyl acetate, retinyl palmitate, α-tocopherol and γ-tocopherol; reverse phase HPLC was used for the quantification of β-carotene and UV spectrophotometry for the quantification of carotenoids from selected meat and vegetable ‘ready-to-feed’ commercial infant meals. Based on the results of the study, the estimated total daily intake for a 6-9 month old infant of vitamin A (retinol equivalents, RE) and vitamin E (α-tocopherol equivalents, ATE) from both infant food and formula milk were 1.74 mg RE/day and 10.4 mg ATE/day, respectively. These intakes exceed the recommendations set by the Department of Health (1991). The main dietary contributor was highlighted as being the fortified infant formula which highlights the importance of nutrient dense foods in situations where infant formula is reduced or compromised. The study into the essential elemental content of dairy based commercial infant food products found that the Ca:P ratio of a 7-12 month old infant’s diet was 1.49:1, which was within the recommended range of 1-2:1. However, the level of intake for each of the elements analyzed, with the exception of sodium, were found to be above the Recommended Nutrient Intake (RNI) set by the Department of Health (1991), which warrants further investigation in relation to both micronutrient interactions, and in situations where the intake of fortified infant formula milk is compromised. In addition, as this study was the first to include consumption of infant snack products, the level of total calorie intake was also assessed, which indicated that energy intakes exceed recommendations set by the Scientific Advisory Committee of Nutrition (2011) by 42%, which may have implications for obesity. This highlights that parents need to select appropriate snack products. In relation to bone health, vitamin D was also quantified in a range of commercial infant meals. The total dietary intake of vitamin D3 was determined to be 9.61 μg/day, which is 137% higher than the RNI set by the Department of Health (1991) for 7-12 month old infants. However 120% is contributed from fortified infant formula, which may raise a cause for concern over deficiency issues, in situations where infant formula is reduced or compromised or the infant is breastfed. Furthermore the National Diet and Nutrition Survey have shown evidence for an increased risk of vitamin D deficiency in all age and sex groups in the UK. Consequently, following the nutritional evaluation of commercial infant food products, an infant’s diet is not meeting recommendations for the pre-formed long chain polyunsaturated fatty acids, DHA and AA. DHA may be of more significance due to endogenous production. Therefore, two approaches have been explored for the encapsulation of DHA in the pH dependent polymer hydroxypropyl methylcellulose acetate succinate (HPMCAS). In the first approach direct spray drying was implemented for the microencapsulation of DHA/HPMCAS organic solutions, while in the second approach solid lipid nano-emulsions of DHA, produced by high pressure homogenization, were subsequently spray dried in HPMCAS aqueous solutions. The direct spray drying approach resulted in significantly higher quantities of DHA being encapsulated, at 2.09 g/100 g compared to 0.60 g/100 in the spray dried solid lipid nano-emulsions. DHA stability was increased by the direct spray drying approach and the release of DHA was analysed by a dissolution methodology.The encapsulated powders produced by the desired method offer a source of DHA that has the potential to be incorporated into infant foods to increase their dietary DHA consumption.