The main goals of this research were to fabricate magnetic cobalt nanoparticles and study their structural, crystal structure, optical, and magnetic properties. Cobalt nanoparticles with average particle size 8.7 nm were fabricated by the method of high temperature reduction of cobalt salt utilizing trioctylphosphine as a surfactant, oleic acid as a stabilizer, and lithium triethylborohydride as a reducing reagent. Energy-dispersive X-ray spectroscopy (EDX) analysis confirmed the formation of cobalt nanoparticles. High resolution transmission electron microscopy images show that Co NPs form both HCP and FCC crystal structure. The blocking temperature of 7.6 nm Co NPs is 189 K. Above the blocking temperature, Co NPs are single domain and hence showed superparamagnetic behavior. Below the blocking temperature, Co NPs are ferromagnetic. Cobalt nanoparticles with a single-domain crystal structure support a sharp plasmon resonance at 280 nm. Iron nanoparticles with average particle size 4.8 nm were fabricated using chemical reduction method show plasmon resonance at 266 nm. Iron nanoparticles are ferromagnetic at 6 K and superparamagnetic at 300 K.

A nanociência e a nanotecnologia vêm abrindo inúmeros desenvolvimentos de dispositivos e sistemas em escala nanométrica, com novas organizações moleculares, propriedades e funções distintas. Nesse contexto, as nanopartículas magnéticas poliméricas são compósitos formados por materiais magnéticos com tamanhos de partículas entre 1 e 100 nm combinados com polímeros funcionais. São materiais bem conhecidos e têm sido amplamente estudados devido às suas aplicações em diversas áreas tecnológicas. Nas áreas biológica e médica, as aplicações incluem separação e imobilização de enzimas e proteínas, melhoria nas técnicas de imagem de ressonância magnética para diagnóstico e sistemas de liberação controlada de fármacos. Neste trabalho, proteínas foram imobilizadas na superfície de um biopolímero combinado com partículas superparamagnéticas de magnetita para formar o compósito magnético. Utilizou-se o biopolímero quitosana, reticulada e funcionalizada com glutaraldeído, aplicável em ensaios biológicos. Obtiveram-se 3 tipos de compósitos magnéticos, os quais foram nomeados QM1Glu, QM2NaGlu e QM3Glu. Foram caracterizados por difratometria de raios X, microscopia eletrônica de varredura, magnetometria de amostra vibrante, calorimetria exploratória diferencial, termogravimetria e espectroscopia por infravermelho. Foram avaliados quanto à imobilização das proteínas albumina de soro bovino (SAB), colágeno e tripsina. A imobilização das proteínas no biopolímero ocorreu em 30 min de incubação. O compósito magnético de quitosana não funcionalizada (QM3) também foi avaliado. Para a tripsina verificou-se que QM3 apresentou maior potencial de imobilização do que QM3Glu. Após 30 dias, QM3-Trip e QM3Glu-Trip ainda apresentavam a tripsina ativada. Foram demonstradas a atividade e a cinética enzimática da QM3Glu-trip com o substrato BApNA. / Nanoscience and nanotechnology have opened up numerous developments of devices and systems on the nanometer scale, with new molecular organization, properties and functions. In this context, the polymeric magnetic nanoparticles are composites formed by magnetic materials with a particle size between 1 and 100 nm combined with functional polymers. They are well-known and have been widely studied because of its applications in various technology areas. Applications on the biological and medical areas include separation and immobilization of enzymes and proteins, improved techniques of magnetic resonance imaging and diagnostic systems for controlled drug delivery. In this work, proteins were immobilized on the surface of a biopolymer combined with superparamagnetic particles of magnetite. The biopolymer chitosan was used, cross-linked and functionalized with glutaraldehyde, applicable to the biological assays. Three types of magnetic composites were obtained, which were called QM1Glu, QM2NaGlu and QM3Glu. They were characterized by X-ray diffraction, scanning electron microscopy, vibrating sample magnetometry, differential scanning calorimetry, thermogravimetry and infrared spectroscopy. They were evaluated concerning the immobilization of the proteins bovine serum albumin (BSA), collagen and trypsin. The study showed that the immobilization of proteins on the biopolymer occurred in 30 min of incubation. The magnetic composite of nonfunctionalized chitosan (QM3) was also evaluated. For trypsin, it was found that the immobilization potential of QM3 was higher than that observed for QM3Glu. After 30 days, the trypsin of the QM3-Trip and QM3Glu-Trip was still with activity. The activity and the enzyme kinetics of the QM3Glu-Trip with the substrate BApNA were demonstrated.

A nanociência e a nanotecnologia vêm abrindo inúmeros desenvolvimentos de dispositivos e sistemas em escala nanométrica, com novas organizações moleculares, propriedades e funções distintas. Nesse contexto, as nanopartículas magnéticas poliméricas são compósitos formados por materiais magnéticos com tamanhos de partículas entre 1 e 100 nm combinados com polímeros funcionais. São materiais bem conhecidos e têm sido amplamente estudados devido às suas aplicações em diversas áreas tecnológicas. Nas áreas biológica e médica, as aplicações incluem separação e imobilização de enzimas e proteínas, melhoria nas técnicas de imagem de ressonância magnética para diagnóstico e sistemas de liberação controlada de fármacos. Neste trabalho, proteínas foram imobilizadas na superfície de um biopolímero combinado com partículas superparamagnéticas de magnetita para formar o compósito magnético. Utilizou-se o biopolímero quitosana, reticulada e funcionalizada com glutaraldeído, aplicável em ensaios biológicos. Obtiveram-se 3 tipos de compósitos magnéticos, os quais foram nomeados QM1Glu, QM2NaGlu e QM3Glu. Foram caracterizados por difratometria de raios X, microscopia eletrônica de varredura, magnetometria de amostra vibrante, calorimetria exploratória diferencial, termogravimetria e espectroscopia por infravermelho. Foram avaliados quanto à imobilização das proteínas albumina de soro bovino (SAB), colágeno e tripsina. A imobilização das proteínas no biopolímero ocorreu em 30 min de incubação. O compósito magnético de quitosana não funcionalizada (QM3) também foi avaliado. Para a tripsina verificou-se que QM3 apresentou maior potencial de imobilização do que QM3Glu. Após 30 dias, QM3-Trip e QM3Glu-Trip ainda apresentavam a tripsina ativada. Foram demonstradas a atividade e a cinética enzimática da QM3Glu-trip com o substrato BApNA. / Nanoscience and nanotechnology have opened up numerous developments of devices and systems on the nanometer scale, with new molecular organization, properties and functions. In this context, the polymeric magnetic nanoparticles are composites formed by magnetic materials with a particle size between 1 and 100 nm combined with functional polymers. They are well-known and have been widely studied because of its applications in various technology areas. Applications on the biological and medical areas include separation and immobilization of enzymes and proteins, improved techniques of magnetic resonance imaging and diagnostic systems for controlled drug delivery. In this work, proteins were immobilized on the surface of a biopolymer combined with superparamagnetic particles of magnetite. The biopolymer chitosan was used, cross-linked and functionalized with glutaraldehyde, applicable to the biological assays. Three types of magnetic composites were obtained, which were called QM1Glu, QM2NaGlu and QM3Glu. They were characterized by X-ray diffraction, scanning electron microscopy, vibrating sample magnetometry, differential scanning calorimetry, thermogravimetry and infrared spectroscopy. They were evaluated concerning the immobilization of the proteins bovine serum albumin (BSA), collagen and trypsin. The study showed that the immobilization of proteins on the biopolymer occurred in 30 min of incubation. The magnetic composite of nonfunctionalized chitosan (QM3) was also evaluated. For trypsin, it was found that the immobilization potential of QM3 was higher than that observed for QM3Glu. After 30 days, the trypsin of the QM3-Trip and QM3Glu-Trip was still with activity. The activity and the enzyme kinetics of the QM3Glu-Trip with the substrate BApNA were demonstrated.

Many scientists and engineers are turning to lab-on-a-chip systems for cheaper and high throughput analysis of chemical reactions and biomolecular interactions. In this work, we developed several lab-on-a-chip modules based on novel manipulations of individual microbeads inside microchannels. The first manipulation method employs arrays of soft ferromagnetic patterns fabricated inside a microfluidic channel and subjected to an external rotating magnetic field. We demonstrated that the system can be used to assemble individual beads (1-3µm) from a flow of suspended beads into a regular array on the chip, hence improving the integrated electrochemical detection of biomolecules bound to the bead surface. In addition, the microbeads can follow the external magnet rotating at very high speeds and simultaneously orbit around individual soft magnets on the chip. We employed this manipulation mode for efficient sample mixing in continuous microflow. Furthermore, we discovered a simple but effective way of transporting the microbeads on-chip in the rotating field. Selective transport of microbeads with different size was also realized, providing a platform for effective sample separation on a chip. The second manipulation method integrates magnetic and dielectrophoretic manipulations of the same microbeads. The device combines tapered conducting wires and fingered electrodes to generate desirable magnetic and electric fields, respectively. By externally programming the magnetic attraction and dielectrophoretic repulsion forces, out-of-plane oscillation of the microbeads across the channel height was realized. Furthermore, we demonstrated the tweezing of microbeads in liquid with high spatial resolutions by fine-tuning the net force from magnetic attraction and dielectrophoretic repulsion of the beads. The high-resolution control of the out-of-plane motion of the microbeads has led to the invention of massively parallel biomolecular tweezers.

Development of nanostructures as MR contrast agent will significantly improve the field of disease diagnostics. Contrast agents such as iron oxide nanoparticles are less toxic compared to more commonly used gadolinium based agents. A subclass of iron based nano particles are super paramagnetic iron oxide nano particles, (SPIOs) which are widely studied MR contrast agents useful in both imaging and drug delivery applications. In this work, SPIOs were synthesized and characterized and used for cellular tracking and multi modal labeling. A new solvent exchange method was utilized to coat different core size iron oxide nano particles. SPIOs were characterized for in-vivo imaging using MR and they had a very uniform size distribution which was determine using dynamic light scattering (DLS) and transmission electron microscopy. Furthermore, blood circulation half-life of 16nm SPIOs were determined through tail vein injection. SPIOs have many applications among which is the in vivo tracking of stem cells which is critical for determination of stem cells fate after injection. Magnetic Resonance (MR) as a non-invasive method can provide significant information about the fate of the cells as well as determination of the success rate of therapeutic cellular deliveries. Mesenchymal stem cells can be loaded with super paramagnetic iron oxide nano particles (SPIOs) and have their movements followed once planted in vivo. We present our findings on the effect of SPIO concentration and stem cell density on the MR signal and transverse relaxation time. Our preliminary results indicated that SPIOs do not cause mesenchymal stem cell cytotoxicity and do not affect proliferation ability up to 200 μg/ml concentration. The release of the nanoparticles was investigated 24 hours post internalization and the result showed that SPIOs will stay inside the cell. We also found that the contrast increases in a concentration dependent manner. Our results suggest that using MR with low concentration of SPIOs is a novel and promising method for tracking of mesenchymal stem cells. In this work SPIOs were also labeled with 64Cu to investigate their potential for multi modal positron emission tomography (PET) MR imaging. Dual modality PET MR SPIO contrast agent can be synthesized to image diseases such as cancer and atherosclerosis. The advantage is the non-invasive and early detection of disease at molecular lever before it has spread to late stages or in case of the atherosclerosis before the plaque has blocked the vessel. To develop a multi modal contrast agent, a positron emitter, 64Cu (half-life of 12.701 ± 0.002 hours), was used in labeling and synthesis was performed all in one step with the addition of 64Cu chelator, 14-PE DTPA followed by radiolabeling for both 6.5nm SPIO and 17nm SPIO. After labeling and purification with the desalting column, the amount of dissociated 64Cu in the solution was determined using radio thin layer chromotagraphy (TLC) and the particle was shown to have minimum amount of fee 64Cu. Serum stability of labeled SPIO was determined in vitro by incubating 64Cu-labeled SPIOs in mouse serum at 37 °C for 24 hr with constant shaking. Radio TLC result then revealed that 64Cu stays bounded to the SPIO after 24 hours in mouse serum. This means that 64Cu labeled SPIO has a great potential as a dual modality contrast agents and further in-vivo studies are required to verify the findings.

No description available.

[pt] As nanopartículas magnéticas (NPMs) apresentam grande potencial em diversas aplicações tecnológicas e vem ganhando destaque na área da biomedicina devido suas propriedades superparamagnéticas. Para este trabalho foram sintetizadas nanopartículas de óxido de ferro (Fe3O4) pelo método de coprecipitação e recobertas com Pluronic F-127 (PL F-127), o qual se demonstrou, a partir de estudos anteriores, um surfactante com ótima estabilidade coloidal e alto grau de biocompatibilidade, sendo tais características relevantes para as aplicações na área da biomedicina. O método de produção se mostrou eficiente para produção de uma grande quantidade de amostra e baixo grau de oxidação, o que mantém a integridade dos resultados e do material para diversas análises no decorrer de longos períodos. A espectroscopia Raman e a difração de elétrons apontam para a composição majoritária de magnetita cristalina das amostras. As imagens obtidas através de microscopia de transmissão (MET) mostraram que o diâmetro médio das NPMs não é afetado pela concentração PL F-127 e está de acordo com os tamanhos obtidos pelas técnicas magnéticas. O MET também mostrou partículas monodispersas com formato esféricas. As técnicas de microscopia magnética de varredura (MMV), magnetômetro de amostra vibrante e de efeito Hall revelaram que o comportamento das NPMs é superparamagnético em temperatura ambiente e que a funcionalização não interferiu significativamente na magnetização de saturação. / [en] Magnetic nanoparticles (MNPs) have great potential in several technological applications and are gaining prominence in the biomedical area due to their superparamagnetic properties. For this work, iron oxide (Fe3O4) nanoparticles were synthesized by the coprecipitation method and coated with Pluronic F-127 (PL F127), which was demonstrated, from previus studies, a surfactante with excellent coloidal stability and high degree of biocompatibility, such characteristics being relevant for applications in the área of biomedicine. The production method proved to be efficient for producing a large amount of sample and a low degree of oxidation, which maintains the integrity of the results and material for several analyzes over long periods. Raman spectroscopy and eléctron diffraction indicate the samples are pure and crystalline magnetite. The images obtained through transmission eléctron microscopy (TEM) showed that the mean diameter of MNPs is not affected by the PL F-127 concentration and is in agreement with the sizes obtained by magnetic techniques. TEM also showed monodisperse particles with a spherical shape. Scanning magnetic microscopy (MMV), vibrating sample magnetometer and Hall effect techniques revealed that the behavior of NPMs is superparamagnetic at ambient temperature and that the functionalization did not significantly interfere in the saturation magnetization.

Ziel der Untersuchungen war es, neue Strategien zu entwickeln, die zu einer Verbesserung der MR-Diagnostik von Gliomen führen. Im Vordergrund des Interesses stand dabei die MR-Charakterisierung von experimentellen Gliomen mittels superparamagnetischer Eisenoxide, wobei MION ("Monocrystalline-Iron-Oxide-Nanopartikel") als Modellsubstanz für einen Großteil der Untersuchungen benutzt wurde. In Experimenten zur Blut-Hirn-Schranke (BHS) wurde gezeigt, dass normales Hirngewebe jenseits der BHS mit Eisenoxiden erreicht werden kann, wenn artifiziell die BHS zuvor hyperosmotisch durch Mannitol-Infusion temporär geöffnet wurde. Neben der intrazellulären Aufnahme in Astrozyten werden Eisenoxide nach erfolgter BHS-Öffnung in signifikant höherem Maße von aktivierter Mikroglia phagozytiert. Nach selektiver Öffnung der BHS durch Bradykinin-Injektion in die A. carotis interna lässt sich selektiv der Transport von Eisenoxiden in das Gliomzentrum vergrößern. Am experimentellen Gliommodell ließ sich zeigen, dass intravenöse MION-Gabe zu einem charakteristischen ringförmigen Erscheinungsbild in der MRT der großen Tumoren führt: Die histologischen Untersuchungen bei mehreren Gliomarten (C6 und 9L) zeigen eindeutig die Phagozytose von Eisenpartikeln durch Gliomzellen selbst. Verglichen mit der Eisenoxid-Aufnahme in die Gliomzelle ist die Phagozytose der Eisenpartikel durch ortsständige Mikrogliazellen und Blutmakrophagen jedoch signifikant größer. Die intrazelluläre Aufnahme von MION durch Tumorzellen lies sich in Zellkulturexperimenten an verschiedenen Gliom- (C6, 9L) und Karzinom-Zelllinien (LX-1) bestätigen. In vitro konnte gezeigt werden dass die Konjugation von Transferrin (Tf) an eine Eisenoxidverbindung zu einer verstärkten intrazelluläre Aufnahme verglichen mit unkonjugiertem Verbindungen führt. Die Untersuchungen zur Bildgebung der Tumorvaskularisation von experimentellen Gliomen ergaben, dass durch die kombinatorische Anwendung eines kleinmolekularen und eines großmolekularen Markers mit anschließender einfacher Bildsubtraktion die vaskulären und interstitiellen Volumenfraktionen (VVF, IVF) ermittelt werden können. Auch die alleinige Injektion der noch experimentellen Blut-Pool-Marker MPEG-Pl-GdDTPA und Gadomer-17 ermöglicht im Tiermodell die quantitative Bestimmung sowohl des vaskulären Volumens (CBV) als auch der Permeabilität (P). Bei den Eisenoxiden verfälschen deren starke Suszeptibilitätseffekte die quantitative Bestimmung von Blutflussdaten, auch die Quantifizierung der Gefäßpermeabilität ist mit diesen Verbindungen mittels dynanischer MRT nicht möglich. / The aim of the studies was to develop new strategies for improving magnetic resonance imaging (MRI) of gliomas. In the majority of experiments the focus was on the characterization of experimental gliomas after administration of superparamagnetic iron oxides using MION (Monocrystalline Iron Oxide Nanoparticles) as a model compound. Experiments on the blood-brain barrier (BBB) demonstrated that iron oxides reach normal brain tissue beyond the BBB after their artificial, transient hyperosmotic opening by mannitol infusion. Upon opening of the BBB, iron oxides not only show intracellular uptake by astrocytes but are also phagocytosed in significantly higher amounts by activated microglia. Selective opening of the BBB by bradykinin injection into the internal carotid artery specifically increases the transport of iron oxides into the center of gliomas. Using an experimental glioma model, it was shown that intravenous administration of MION produces a characteristic ring enhancement of large tumors on MR images. Histologic studies of different types of gliomas (C6 and 9L) unequivocally demonstrated that iron oxide particles were phagocytosed by the glioma cells themselves. However, iron oxide uptake by glioma cells is significantly less pronounced compared to the phagocytosis of iron oxide particles by local microglial cells and blood macrophages. The incorporation of MION by tumor cells was confirmed in cell culture experiments using different glioma (C6, 9L) and carcinoma cell lines (LX-1). In vitro studies showed that conjugation of transferrin to an iron oxide compound enhanced intracellular uptake compared to unconjugated compounds. The imaging studies investigating tumor vascularization in experimental gliomas demonstrated that the combined use of a small-molecular and a large-molecular marker and simple image subtraction allow for determining vascular and interstitial volume fractions (VVF, IVF). Furthermore, injection of the blood pool markers MPEG-P1-Gd-DTPA and gadomer-17 alone likewise enables quantitative determination of both vascular volume (CBV) and permeability (P) in the animal model. Iron oxide particles, on the other hand, have pronounced susceptibility effects, which impair the quantitative determination of blood flow data. Nor do the particles allow for quantifying vascular permeability by dynamic MR imaging.

O carbono, em suas muitas formas distintas, tem sido largamente empregado como material adsorvente, do tratamento de água à tecnologia industrial em virtude de sua boa performance, baixo custo e compatibilidades biológica e ambiental. Nesta tese foi verificada a associação sinérgica entre carvão ativo e nanopartículas superparamagnéticas de óxido de ferro ensejando a exploração entre a capacidade adsortiva e o magnetismo para o desenvolvimento de processos de remoção de contaminantes de meios aquosos e melhorando sua análise por meio de concentração magnética. Para este propósito, nanopartículas magnéticas recobertas com ácidos oleico ou esteárico foram especialmente preparadas e combinadas com carvão ativo em proporções variadas (1, 5, 10, 20, 25, 50 % m/m), seguindo rigoroso controle químico. Os materiais de carbono magnetizáveis mantém suas afinidades química e característica porosa do material precursor com alguma diminuição de sua área superficial, embora exibindo uma forte atração por campos magnéticos externos, permitindo sua fácil concentração e remoção. Estes materiais foram extensivamente caracterizados por técnicas como BET, FTIR, XRD, DLS, SEM, TG/DTA, VSM e SQUID. Por conveniência, o compósito a 10 % de nanopartículas de magnetita foi escolhido como o principal a ser utilizado na maioria das aplicações exibindo ampla área superficial (700 m2.g-1), volume e diâmetro médio de poro (0,487 cc.g-1 e 8,5 nm, respectivamente) e uma magnetização de saturação de 5 emu.g-1, com histerese desprezível à temperatura ambiente. Suas características adsorventes foram exploradas com sucesso na captura de corantes orgânicos (pararosanilina e azul de metileno), nitrobenzeno, bisfenol-A e BTEX (benzeno, tolueno, etilbenzeno e o,m,p-xilenos), bem como para íons de metais pesados como Hg(II), Pb(II) e Ag(I) em solução aquosa. Estudos eletroanalíticos foram feitos explorando o efeito de pré-concentração magnética na superfície do eletrodo após realizar estudos de adsorção envolvendo o levantamento de isotermas afim de investigar parâmetros como capacidade adsortiva e constantes de adsorção. Em todos os casos, um elevado aumento de aumento na sensibilidade foi obtido através do confinamento magnético em relação aos métodos convencionais. Desta forma, o emprego do compósito de carbono com nanopartículas de óxido de ferro superparamagnéticas demonstrou ser uma ferramenta poderosa a ser explorada em Química Analítica e Ambiental. / Carbon in many distinct forms has been widely employed as absorbing material in industrial and water technology because of its good performance, low cost and bio/environmental compatibility. In this doctoral thesis, a synergistic association of activated carbon with superparamagnetic Fe3O4 nanoparticles was carried out, aiming the exploitation of their combined absorption capability and magnetism, for developing new processes of removing contaminants from water and improving their analysis by means of magnetic concentration effect. For this purpose, magnetite nanoparticles coated with stearic or oleic acids were specially prepared and combined with activated carbon, at several proportions (1, 5, 10, 20, 25, 50 % m/m), following a rigorous chemical and analytical control. The magnetized carbon materials kept the original porous characteristics and molecular affinity of the original absorber, with some decrease of the active surface area, but exhibiting a strong attraction by the magnetic field, allowing their easy concentration and removal. Such materials were extensively characterized by BET, FTIR, XRD, DLS, SEM, TG/DTA, VSM and SQUID techniques. For convenience, the carbon material containing 10 % of magnetite was elected as principal, exhibiting a surface area of 700 m2 g-1, average volume and porous diameter of 0,487 cm3 g-1 and 8,5 nm, respectively, and a saturation magnetization of 5 emu g-1, with null hysteresis at room temperature. Its absorbing characteristics were successfully explored for the capture of organic dyes (pararosaniline, and methylene blue), bisphenol-A, and BTEX (benzene, toluene, ethylbenzene, and o,m,p-xilene), as well as hazardous, heavy metal ions, such as Hg(II), Pb(II) and Ag(I) in aqueous solution. Electroanalytical studies were carried out by exploring the magnetic pre-concentration effect on the electrodes, after performing a detailed adsorption study involving the construction of isotherms, in order to evaluate the equilibrium and mass capacity parameters. In all the cases, a great increase of sensitivity was attained by the magnetic confined method, in relation to the conventional methods. In this way, the use of carbon with superparamagnetic nanoparticles demonstrated a powerful strategy to be explored in environmental and analytical chemistry.

Polymerverkapselte magnetische Nanopartikel versprechen, in der Zukunft sehr erfolgreich bei Anwendungen in der Biologie und der Medizin eingesetzt werden zu können z. B. in der Krebstherapie und als Kontrastmittel bei der magnetischen Kernspinresonanztomographie. Diese Arbeit zeigt, dass durch die interdisziplinäre Kombination verschiedener Techniken Herstellungsverfahren und Eigenschaften solcher Partikel verbessert werden können. <br /> <br /> Unter Miniemulsionen versteht man wässrige Dispersionen relativ stabiler Öltröpfchen, zwischen 30 und 50 nm Größe. Ein Nanometer (nm) ist der 1.000.000.000ste Teil eines Meters. Ein Haar ist ungefähr 60.000 Nanometer breit.<br /> <br /> Hergestellt werden Miniemulsionen durch Scherung eines Systems bestehend aus Öl, Wasser, Tensid (Seife) und einer weiteren Komponente, dem Hydrophob, das die Tröpfchen stabilisieren soll. Die Polymerisation von Miniemulsionen ermöglicht die Verkapselung anorganischer Materialen z. B. magnetischer Teilchen oder Gadolinium-haltiger Komponenten. Zu Optimierung des Verkapselung, ist es notwendig, die richtige Menge eines geeigneten Tensids zu finden. <br /> <br /> Die magnetischen polymerverkapselten Nanopartikel, die in einer wässrigen Trägerflüssigkeit dispergiert sind, zeigen in Abhängigkeit von Partikelgröße, Zusammensetzung, elektronischer Beschaffenheit, etc. ein sogenanntes superpara- oder paramagnetisches Verhalten. Superpara- oder paramagnetisches Verhalten bedeutet, dass die Flüssigkeiten in Anwesenheit äußerer Magnetfeldern ihre Fließfähigkeit beibehalten. Wenn das Magnetfeld entfernt wird, haben sie keine Erinnerung mehr daran, unter dem Einfluss eines Magnetfeldes gestanden zu haben, d. h., dass sie nach Abschalten des Magnetfeldes selbst nicht mehr magnetisch sind. <br /> <br /> Die Vorteile des Miniemulsionsverfahrens sind der hohe Gehalt und die homogene Verteilung magnetischer Teilchen in den einzelnen Nanopartikeln. Außerdem ermöglicht dieses Verfahren nanostrukturierte Kompositpartikel herzustellen, wie z. B polymerverkapselte Nanopartikel mit Nanoschichten bestehend aus magnetischen Molekülen. / Combining the magnetic properties of a given material with the tremendous advantages of colloids can exponentially increase the advantages of both systems. This thesis deals with the field of magnetic nanotechnology. Thus, the design and characterization of new magnetic colloids with fascinating properties compared with the bulk materials is presented. <br /> <br /> Ferrofluids are referred to either as water or organic stable dispersions of superparamagnetic nanoparticles which respond to the application of an external magnetic field but lose their magnetization in the absence of a magnetic field. <br /> <br /> In the first part of this thesis, a three-step synthesis for the fabrication of a novel water-based ferrofluid is presented. The encapsulation of high amounts of magnetite into polystyrene particles can efficiently be achieved by a new process including two miniemulsion processes. The ferrofluids consist of novel magnetite polystyrene nanoparticles dispersed in water which are obtained by three-step process including coprecipitation of magnetite, its hydrophobization and further surfactant coating to enable the redispersion in water and the posterior encapsulation into polystyrene by miniemulsion polymerization. It is a desire to take advantage of a potential thermodynamic control for the design of nanoparticles, and the concept of &quot;nanoreactors&quot; where the essential ingredients for the formation of the nanoparticles are already in the beginning. The formulation and application of polymer particles and hybrid particles composed of polymeric and magnetic material is of high interest for biomedical applications. Ferrofluids can for instance be used in medicine for cancer therapy and magnetic resonance imaging.<br /> <br /> Superparamagnetic or paramagnetic colloids containing iron or gadolinium are also used as magnetic resonance imaging contrast agent, for example as a important tool in the diagnosis of cancer, since they enhance the relaxation of the water of the neighbouring zones. New nanostructured composites by the thermal decomposition of iron pentacarbonyl in the monomer phase and thereafter the formation of paramagnetic nanocomposites by miniemulsion polymerization are discussed in the second part of this thesis. In order to obtain the confined paramagnetic nanocomposites a two-step process was used. In the first step, the thermal decomposition of the iron pentacarbonyl was obtained in the monomer phase using oleic acid as stabilizer. In the second step, this iron-containing monomer dispersion was used for making a miniemulsion polymerization thereof. <br /> <br /> The addition of lanthanide complexes to ester-containing monomers such as butyl acrylate and subsequent polymerization leading to the spontaneous formation of highly organized layered nanocomposites is presented in the final part of this thesis. By an one-step miniemulsion process, the formation of a lamellar structure within the polymer nanoparticles is achieved. The magnetization and the NMR relaxation measurements have shown these new layered nanocomposites to be very apt for application as contrast agent in magnetic resonance imaging.