Silica (inorganic)-g-polymer (organic) hybrid materials with a large variety of functionality have been studied intensively because of the improvement in their physical and chemical properties (e.g., thermal, mechanical, electrical, magnetic properties, etc.) with respect to conventional organic and inorganic materials. 1–3 This research work introduces a new strategy based on in situ formation of poly(methyl methacrylate) block copolymer grafted silica nanoparticles. The thesis is divided into two major parts. In the first part, the atom transfer radical polymerization (ATRP) method was used to synthesize poly(methyl methacrylate-b-trimethoxysilyl propyl methacrylate) (PMMA-b-PTMSPMA); and poly(methyl methacrylate-b-trimethoxysilyl propyl acrylate) (PMMA-b-PTMSPA) block copolymers. Gel permeation chromatography (GPC) was performed to determine the number-average molecular weight (Mn) and polydispersity index (Đ) of PMMA-b PTMSPMA and PMMA-b-PTMSPA. In addition, proton nuclear magnetic resonance spectroscopy (1H NMR) was used to confirm the successful synthesis of the above copolymers. In the second part, the copolymers were used to form silica nanoparticles grafted with poly(propyl methacrylate-b-methyl methacrylate) [silica-g-(PPMA-b PMMA)] and silica nanoparticles grafted with poly(propyl acrylate-b-methyl methacrylate) [silica-g-(PPA-b-PMMA)]. Fourier transform infrared spectroscopy (FT-IR) and 29Si solid-state NMR were performed to confirm the formation of silica-g-(PPMA-b PMMA) and silica-g-(PPA-b-PMMA). Additionally, thermogravimetric analysis (TGA) was performed to assess the thermal decomposition of silica-g-(PPMA-b-PMMA) and silica-g-(PPA-b-PMMA). Multiple microscopic techniques such as TEM, cryo-TEM, SEM, and AFM were used to study micellization of the silica-g-(PPMA-b-PMMA) and silica-g-(PPA-b-PMMA) in tetrahydrofuran (THF) and chloroform

Thesis (Ph.D.)--University of Delaware, 2006. / Principal faculty advisors: Dionisios G. Vlachos and Raul F. Lobo, Dept. of Chemical Engineering Includes bibliographical references.

De part leurs propriétés physiques et chimiques, les nanoparticules de silice mésoporeuses (MSNs) sont de bonnes candidates pour la délivrance de principes actifs. Cependant, leurs toxicités et leurs devenirs intracellulaires sont largement méconnus. Au cours de ces travaux, nous avons étudié la cytotoxicité et l’endocytose de MSNs. Nous avons montré que les MSNs peuvent être endocytées par une variété de lignées cellulaires et par des astrocytes de rat en culture sans signe apparent de cytotoxicité importante. Ces nanoparticules ne présentent pas une toxicité observable in vivo chez des souris. Après avoir montré que l’endocytose des MSNs s’effectue par la voie des puits de clathrines, nous avons procédé à la délivrance intracellulaire d’une protéine. Nous avons montré un échappement des lysosomes de cette protéine grâce aux MSNs. En couplant l’acide folique aux MSNs, les cellules tumorales ont été ciblées. Lors de ces études, nous avons également montré que l’un des tests les plus utilisés en toxicologie surestime la cytotoxicité des MSNs. Cette surestimation est due à une modification du trafic intracellulaire. Nos travaux ont montré que les MSNs sont endocytés sans nuire à la viabilité cellulaire, ce qui nous a permis de réaliser les premiers essais de délivrances de principes actifs avec nos nanoparticules. / Due to their physical and chemical properties, the mesoporous silica nanoparticles (MSNs) are good candidates for drug delivery applications. However, their toxicity and their intracellular trafficking remain unclear. During these works, we studied the cytotoxicity and the endocytosis of MSNs. We showed that the MSNs can be internalised by a variety of cell lines and rat astrocytes in culture without visible sign of important cytotoxicity. These nanoparticles did not present an observable in vivo toxicity in mice. Then we showed that the endocytosis of the MSNs was made by the clathrines coated pits and we proceeded to the intracellular delivery of a protein. We showed an escape of the lysosomes of this protein due to MSNs. Such an internalised protein escaped from lysosomes under the effect of MSNs. After linking folic acid to MSNs, we are able to target tumoral cells with these nanoparticles. During the preceding studies we observed that one of the most used tests in toxicology overestimated the cytotoxicity of MSNs because the latter nanoparticles modified intracellular traffic. Our works showed that the MSNs are internalized without damaging the cellular viability and we made the first experiments of drug delivery using our nanoparticles.

Foi estudado o comportamento fotofísico da 9-aminoacridina (9AA) e derivados, safranina O, auramina e 9-vinilantraceno, em partículas de sílica. Inicialmente, partículas de sílica obtidas comercialmente foram modificadas e marcadas com corantes acridínicos, porém sua morfologia tornou inviável o estudo fotofísico, devido à sua irregularidade. Foram preparadas nanoesferas de sílica, pelo método de Stöber, com diâmetro médio de 50 nm, que apresentaram altos sinais de fluorescência. Além disso, para evitar a dessorção dos marcadores nas nanopartículas em suspensão, foram preparadas nanopartículas do tipo cascacaroço, contendo um núcleo rico em marcador, protegido por uma casca de sílica. Estas nanopartículas, com diâmetro médio de 125 nm, mostraram-se excelentes matrizes para o estudo dos corantes, retardando sua difusão para o solvente. Foram ainda preparadas nanopartículas contendo poli(metacrilato de metila) marcado com derivado acridínico. A interação entre grupos silanol na superfície e o grupo N-H do marcador bloqueou o processo de transferência de carga intramolecular, característico do corante. Por fim, foram preparadas nanopartículas marcadas com 9-aminoacridina e safranina O. Na presença de safranina O, o tempo de vida de fluorescência referente à desativação do cromóforo acridina passou de 12,2 ns para 9,71 ns, indicando processos de transferência de energia e supressão de fluorescência, no interior das partículas. / Photophysical behavior of 9-aminoacridine (9AA) and derivatives, safranine O, auramine and 9-vinylanthracene was investigated, in silica particles. Firstly, commercial silica was modified and grafted with acridinic dyes; however, photophysical studies became unviable, due to its morphology. Silica nanospheres were prepared by Stöber method, with mean diameter of 50 nm, presenting high fluorescence emission. Moreover, in order to avoid de desorption of dyes from particles in suspension, systems containing a dye reach nucleus protected by silica shells were prepared (core-shell nanoparticles). The core-shell nanospheres, with mean diameter of 125 nm, are excellent matrixes for fluorescence studies, since it retards dye diffusion to the solvent. It was also prepared nanoparticles containing poly(methylmethacrylate) grafted with 9AA derivative. Interaction between silica silanol groups and dye N-H groups broke the intramolecular charge transfer, a characteristic process occurring in this dye. Finally, nanoparticles grafted with 9AA and safranine O were prepared. In the presence of safranine, fluorescence lifetime related to the deactivation of the chromophore acridine reduced from 12.2 ns to 9.71 ns, suggesting energy transfer and fluorescence quenching processes within the particles.

Foi estudado o comportamento fotofísico da 9-aminoacridina (9AA) e derivados, safranina O, auramina e 9-vinilantraceno, em partículas de sílica. Inicialmente, partículas de sílica obtidas comercialmente foram modificadas e marcadas com corantes acridínicos, porém sua morfologia tornou inviável o estudo fotofísico, devido à sua irregularidade. Foram preparadas nanoesferas de sílica, pelo método de Stöber, com diâmetro médio de 50 nm, que apresentaram altos sinais de fluorescência. Além disso, para evitar a dessorção dos marcadores nas nanopartículas em suspensão, foram preparadas nanopartículas do tipo cascacaroço, contendo um núcleo rico em marcador, protegido por uma casca de sílica. Estas nanopartículas, com diâmetro médio de 125 nm, mostraram-se excelentes matrizes para o estudo dos corantes, retardando sua difusão para o solvente. Foram ainda preparadas nanopartículas contendo poli(metacrilato de metila) marcado com derivado acridínico. A interação entre grupos silanol na superfície e o grupo N-H do marcador bloqueou o processo de transferência de carga intramolecular, característico do corante. Por fim, foram preparadas nanopartículas marcadas com 9-aminoacridina e safranina O. Na presença de safranina O, o tempo de vida de fluorescência referente à desativação do cromóforo acridina passou de 12,2 ns para 9,71 ns, indicando processos de transferência de energia e supressão de fluorescência, no interior das partículas. / Photophysical behavior of 9-aminoacridine (9AA) and derivatives, safranine O, auramine and 9-vinylanthracene was investigated, in silica particles. Firstly, commercial silica was modified and grafted with acridinic dyes; however, photophysical studies became unviable, due to its morphology. Silica nanospheres were prepared by Stöber method, with mean diameter of 50 nm, presenting high fluorescence emission. Moreover, in order to avoid de desorption of dyes from particles in suspension, systems containing a dye reach nucleus protected by silica shells were prepared (core-shell nanoparticles). The core-shell nanospheres, with mean diameter of 125 nm, are excellent matrixes for fluorescence studies, since it retards dye diffusion to the solvent. It was also prepared nanoparticles containing poly(methylmethacrylate) grafted with 9AA derivative. Interaction between silica silanol groups and dye N-H groups broke the intramolecular charge transfer, a characteristic process occurring in this dye. Finally, nanoparticles grafted with 9AA and safranine O were prepared. In the presence of safranine, fluorescence lifetime related to the deactivation of the chromophore acridine reduced from 12.2 ns to 9.71 ns, suggesting energy transfer and fluorescence quenching processes within the particles.

Highly repellent surfaces are constantly being sought in a number of industrial sectors, where accumulation of unwanted material (ice, debris, insects etc…) can cause seriously detrimental effects on these function. The chemistry and physics of such surfaces is relatively well-understood, yet their industrial adoption is still very limited, due to their poor durability. Emerging technologies for nanostructured coatings have significant potential for the development of advanced surfaces, where high repellency can be combined with mechanical robustness. However, lack of understanding of the wear mechanism in such coatings and lack of recognised test methodologies to enable comparison of various approaches hinders effective progress in advanced surfaces development. Furthermore, there is no comprehensive classification system that allows categorization of highly repellent surfaces. New multi-variable analysis methodology for the evaluation of durability in highly repellent coatings was developed in this study. Key coating parameters were identified, including initial wettability, abrasive wear, adhesive wear and ability to retain repellency. Coating characteristics were examined with FTIR, SEM, AFM, DSA, Taber Abrader, roughness profilometer and goniometer. Furthermore, these characteristics were presented in a form of spider diagrams and performance indices and are used to generate plot of performance indices. In this study, six types of TWI coating anti-soiling materials (based on patented TWI’s Vitolane® technology, containing silsesqioxanes and functionalized silica nanoparticles) and two commercial easy clean products were prepared and subjected to new assessment methodology. It has been found that this novel methodology for evaluation of highly repellent surfaces allows comparison and categorizing different families of coatings. The data obtained from plot of performance indices supports the statement that there is an inverse relation between repellency and durability of hydrophobic surfaces. It has been found that coatings with low Ra value (no more than 10nm) and symmetric distribution of peaks and valleys are the most durable, yet their WCA value doesn’t exceed more than 105°. It has been also found that some nanostructured coatings behave beyond this inverse relationship. Addition of novel inorganic building blocks with controlled size (Ra in a range of 200nm and symmetric distribution in roughness profile) and functionalities (3-(trimethoxysilyl)propyl methacrylate and 1H 1H 2H 2H-perfluorooctyltriethoxysilane) improves overall coating performance by linking mechanical robustness with desired wetting characteristics (WCA reaches 112°C). The progress in testing and classification criteria of repellent coatings enables further development of next generation of materials. This novel knowledge-based approach for highly repellent coatings validation has the potential to accelerate uptake. The findings open a promising new direction in materials development, where advanced coatings and surface treatments can be developed by design, reducing the number of development iterations, ultimately leading to reduced cost and development time.

DNA and interfering RNA (RNAi) – short interfering RNA (siRNA) and micro RNA (miRNA) – are promising new cancer therapies, especially for drug resistant lines. However, they require a delivery system in vivo to prevent degradation and off target effects. Silica based nanoparticles, both solid and mesoporous, are a promising option due to their biocompatibility, ease of preparation and morphology control, reproducibility, and facile addition of functional groups including targeting ligands. After a brief introduction to cancer treatment and review of the current nanoparticle treatments undergoing clinical trials, this thesis details the many methods explored over the past ten years to fine-tune particle preparation, pore size, functionalization, and delivery strategies. The majority of both solid and mesoporous silica nanoparticles are synthesized using the sol-gel method and then various functionalization techniques are employed to load and protect the oligonucleotides. Externally loaded systems generally use a combination of polyethylenimine (PEI) and polyethylene glycol (PEG). Mesoporous silica nanoparticles internally load the DNA or RNAi, resulting in the added variable of pore size. Several groups have investigated how pore size alters loading and release kinetics to perfect this variable. Many groups have also tested ligands targeting for over expressed proteins on the intended cancer, triggered release techniques, cell-penetrating peptides in order to create a viable in vivo delivery system. By compiling the techniques employed by researchers over the past ten years, this thesis will elucidate which approaches are most promising for future research. Furthermore, overall strategies within the field are suggested to more easily compare studies and evaluate methods.

No description available.

Silica nanoparticles (SiO2 NPs) were prepared and functionalized with polyethylene (PE@SiO2 NPs) using the surface-initiated polyhomologation (SI polyhomologation) technique. Polyolefin nanocomposites were fabricated later by melt mixing of different ratios of the as-prepared SiO2 NPs and PE@SiO2 NPs with linear low-density polyethylene (LLDPE) and low-density polyethylene (LDPE) matrices. Firstly, SiO2 NPs were modified with different alkoxysilane ligands, dichloro(divinyl)silane (DCDVS), allyl trimethoxysilane (ATMS), and vinyl triethoxylsilane (VTES). Subsequently, thexylborane, an initiator for SI polyhomologation, was immobilized to the modified surface of SiO2 NPs through hydroboration reactions. Polyhomologation was then allowed to proceed by adding monomer solution to form polyethylene brushes covalently bonded to the surface of the NPs. Physicochemical characterization had confirmed the morphology, chemical structure, and thermal stability for each step of modification reactions. LLDPE and LDPE nanocomposites were prepared by extrusion with SiO2 NPs and PE@SiO2 NPs as nanofillers. Finally, tensile tests and morphological SEM-based analyses are presented to discuss the influence of the grafted PE on both the dispersion of the fillers and the mechanical properties of the filler/matrix interphase.

No description available.