The Electrospray (ES) technique is a promising particle generation method for drug delivery due to its capabilities of producing monodisperse PLGA composite particles with unique configurations and high drug encapsulation efficiency. In the dissertation work, the coaxial dual capillary ES was used to generate drug-loaded core-shell PLGA particles to study the effects of particle filling materials, drug loading locations and particle shell thicknesses on the resultant in vitro release behaviors of the hydrophilic and/ or hydrophobic model drugs. Through release profile characterization of drug-loaded PLGA particles (particle size: 400 nm and 1 μm), it was confirmed that the co-encapsulation of Budesonide (BUD, the hydrophobic small-molecule model drug) and Theophylline (THY, the hydrophilic small-molecule model drug) in the particle cores is the most effective drug loading strategy for extended release of the fixed combined BUD and THY. Particles composed of PLGA fillers with lower molecular weights and with greater shell layer thicknesses could release THY in a well controlled fashion. On the other hand, a slower release rate of Bovine Serum Albumin (BSA, the protein model drug) from PLGA particles with greater shell thickness was also observed. Sequential release of BSA and Paclitaxel (PTX, the hydrophobic small-molecule anti-cancer model drug) was achieved by the 400-nm PLGA (Mw: 7,000-17,000 g/mol, LA/GA: 50/50) particles with potential biopharmaceutical applications in cancer therapy.

Les catalyseurs bifonctionnels pour l’hydrocraquage nécessitent à la fois des sites acides de Brønsted et des sites métalliques. L’intimité entre sites acides et sites métalliques peut donc influer sur l’activité et la sélectivité de la réaction. Nous nous sommes proposés d’explorer l’effet de la distance sites métalliques-sites acides sur la conversion du n-heptane en concevant des catalyseurs à base de platine supportés sur des nanostructures alumine-zéolithe. Pour cela, nous avons étudié la synthèse de suspensions colloïdales nanométriques de zéolithes NaY (20 nm) beta (30 nm), ZSM-5 (50 nm). Des matériaux composites ont ensuite été préparés, soit par synthèse directe en présence d’un support, soit par mise en contact de ces suspensions colloïdales (dans les conditions appropriés de pH) avec des suspensions de boehmite (se transformant en γ-alumina par calcination). Des composites cœur-zéolithe@couronne(alumine) ont ainsi été obtenus. Les particules de platine ont été par la suite sélectivement formées sur les domaines alumine ou zéolithe de ces composites en utilisant le précurseur approprié de platine dans un domaine de pH adapté (pH=5-8). Les catalyseurs ainsi préparés ont été comparés à d’autres catalyseurs pour lesquels la distance entre sites acides et sites métalliques varie entre le nm et le μm, pour former une série de catalyseurs avec des distances métal-acide et des accessibilités aux sites différentes. L’étude catalytique a permis de conclure que l’amélioration de l’accessibilité aux sites actifs (Pt0/Alumine-nanozéolithe) améliore la sélectivité a vers les produits d’isomérisation, alors que la distance ne joue un rôle inhibiteur que quand elle atteint une échelle de plusieurs μm. / Bifunctional hydrocracking catalysts require both Brønsted acid sites and metal sites. Hence, the intimacy between acid sites and metal sites can influence the activity and selectivity of the reaction. We intended to explore the effect of metal sites-acid sites distance on the conversion of n-heptane by designing platinum catalysts supported on alumina-zeolite nanostructures. For this, we studied the synthesis of nanoscale colloidal suspensions of zeolite NaY (20 nm) beta (30 nm), ZSM-5 (50 nm). Composite materials were then prepared either by direct synthesis in the presence of a support, or by contacting these colloidal suspensions (at appropriate pH conditions) with suspensions of boehmite (turning into γ-alumina by calcination). Zeolite-core@alumina-crown composite crown) were thus obtained. The platinum particles were thereafter selectively formed on the alumina or zeolite domains of these composites using the appropriate precursor of platinum in a suitable pH range (pH = 5-8). The thus-prepared catalysts were compared with other catalysts, for which the distance between the acid sites and the metal sites varies between nm and μm scales, to form a series of catalysts with variable acid-metal distances and accessibilities. Catalytic study concluded that improving accessibility to the active sites (Pt0 / Alumina-nanozéolithe) improves the selectivity to isomerization, while the distance plays an inhibitory role only when it reaches a scale of several microns.

<p>U ovom radu sintetisani su kompozitni nanoprahovi i nanoprahovi tipa jezgro&ndash; omotač sa dielektričnom i magnetnom fazom, kao pogodan polazni materijal za procesiranje kompozitne keramike za primenu u mikroelektronici. Osnovni cilj ove doktorske disertacije je bio utvrđivanje veza između uslova sinteze, morfologije čestica, uslova procesiranja i mikrostrukture kompozitne keramike. Nanoprahovi su sintetisani hemijskim metodama sinteze u tečnoj fazi (sol-gel i koprecipitacija) i gasnoj fazi (CVS), pri čemu je vr&scaron;ena optimizacija procesnih uslova u cilju sinteze čestica željene strukture i hemijskog sastava. Istraživanja su vr&scaron;ena na nekoliko modelnih sistema sa feritima kao magnetnom fazom i titanatima ili silikom kao dielektričnom fazom: NiFe2O4SiO2, Fe3O4SiO2, SrTiO3NiFe2O4, BaTiO3NiFe2O4 i BaTiO3Fe3O4. Hemijska sinteza u tečnoj fazi se pokazala pogodnom zato &scaron;to pruža mogućnost kontrolisanja morfologije kompozitnih čestica ne samo pode&scaron;avanjem procesnih parametara sinteze već i funkcionalizacijom faza kojom se uzrokuje njihovo elektrostatičko privlačenje i formiranje strukture jezgro&ndash;omotač. Ipak, zbog velikog stepena aglomeracije prisutnog tokom sinteze u tečnoj fazi, dobijanje omotača uniformne debljine i izbegavanje homogene nukleacije faza se pokazalo te&scaron;ko. Hemijskom sintezom u gasnoj fazi (CVS) je po prvi put sintetisan kompozitni nanoprah na bazi kompleksnih oksida titanata i ferita.<br />Utvrđeno je da i pored velikog potencijala CVS metode u smislu sinteze ultrafinih prahova na bazi titanata i ferita u jednom koraku, ova metoda nudi relativno slabu kontrolu morfologije kompozitnih čestica pri visokim procesnim temperaturama koje su neophodne za kristalizaciju dve faze. Sintetisani nanoprahovi na bazi titanata i ferita (SrTiO3NiFe2O4 i BaTiO3NiFe2O4) procesirani su u gustu kompozitnu keramiku visokotemperaturnim sinterovanjem, u cilju ispitivanja veze morfologije čestica i mikrostrukture kompozita, optimizacije režima sinterovanja i funkcionalne karakterizacije dobijene keramike sa različitim masenim odnosom faza. Prahovi su sinterovani putem konvencionalnog sinterovanja u atmosferi vazduha, spark plazma sinterovanja (SPS) ili kombinacijom ove dve metode. Utvrđeno je da prahovi strukture jezgro&ndash;omotač densifikuju u značajno gu&scaron;ću i homogeniju keramiku u odnosu na kompozitne prahove istog sastava na istim procesnim temperaturama. Pored toga, pH vrednost sinteze čestica i atmosfera visokotemperaturnog sinterovanja su se pokazali veoma značajnim u smislu održavanja željenog faznog sastava dobijenih kompozita. U pogledu režima sinterovanja dobijenih prahova, kombinacija niskotemperaturnog konvencionalnog i SPS sinterovanja (1000 &deg;C) je dala najbolje rezultate u smislu postizanja zadovoljavajuće gustine kompozita (&gt;95% teorijske gustine), održavanja željenog faznog sastava i homogene distribucije faza. Funkcionalna karakterizacija sinterovane keramike sa različitim masenim odnosom faza (BaTiO3 : NiFe2O4 = 1,2,8) potvrdila je očekivano dielektrično, feroelektrično i ferimagnetno pona&scaron;anje dobijenih kompozita.</p> / <p>Composite and core&ndash;shell nanopowders with dielectric and magnetic phase have been synthesized in this work, as a suitable starting material for processing of composite ceramics for microelectronic application. The main goal of this doctoral dissertation was the determination of the link between synthesis conditions, particle morphology, processing conditions and microstructure of composite ceramics. Nanopowders have been synthesized by chemical synthesis methods in wet phase (sol&ndash;gel and coprecipitation) and gas phase (CVS), whereas the optimization of processing parameters was conducted with the goal to synthesize particles of desired structure and chemical composition. Studies were conducted on the few model systems with ferrites as a magnetic and titanates as a dielectric phase: NiFe2O4SiO2, Fe3O4SiO2, SrTiO3NiFe2O4, BaTiO3NiFe2O4 and BaTiO3Fe3O4. Chemical wet synthesis has proven suitable because it offers composite particle morphology control not only by adjustment of synthesis parameters but also by phase functionalization causing their mutual electrostatic attraction and thus core&ndash;shell structure formation. However, due to the high degree of agglomeration present during the wet phase synthesis, formation of the shell with uniform thickness and avoidance of homogeneous nucleation has proven difficult. For the first time, composite ferrite and titanate-based nanopowder has been synthesized by means of Chemical Vapor Synthesis (CVS). It has been found that beside high potential of CVS method for one-step synthesis of ultrafine titanate and ferrite-based nanopowders, this method offers relatively low control of composite particle morphology at high processing temperatures which are necessary for crystallization of both phases. Synthesized titanate and ferrite-based nanopowders (SrTiO3NiFe2O4 and BaTiO3NiFe2O4) were processed into dense ceramics by high-temperature sintering, in order to find the link between particle morphology and composite microstructure, optimize the sintering regime and conduct the functional characterization of obtained ceramics with different phase mass ratio.<br />The powders were sintered by conventional sintering in air, spark plasma sintering<br />(SPS) or combination of these two methods. It was found that core&ndash;shell powders densify in ceramics with considerably higher density and homogeneity at the same processing temperature, than the composite powders with the same composition. Moreover, synthesis pH value and sintering temperature was found to be very important in terms of phase composition preservation of obtained composites. Regarding the sintering regime of obtained powders, combination of low-temperature conventional and SPS sintering (1000 &deg;C) has given the best results in terms of achieving adequate composite density (&gt;95% theoretical density), phase preservation and homogeneous phase distribution. Functional characterization of sintered ceramics with different phase mass ratio (BaTiO3 : NiFe2O4 = 1,2,8) confirmed the expected dielectric, ferroelectric and ferromagnetic behaviour of obtained composites.</p>