Magnetic nanoparticles comprising magnetite (Fe3O4) were functionalized with 3-aminopropyl-triethoxysilane forming amino functionalized magnetite nanoparticles (AMNPs). The amino group allows for conjugation with zinc octacarboxyphthalocyanine (ZnOCPc) or zinc tetracarboxyphthalocyanine (ZnTCPc) via the carboxyl group to form an amide bond. A reduced aggregation of ZnTCPc is observed after conjugation with AMNPs. The thermal stability, conjugation, morphology and the sizes of the nanoparticles and their conjugates were confirmed using thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM) and Powder X-ray diffractometry (PXRD), respectively. The covalent linkage of AMNPs to ZnOCPc or ZnTCPc resulted in improvement in the photophysical behavior of the phthalocyanines. Improvement in the triplet quantum yield (ΦT), singlet oxygen quantum yield (ΦΔ), triplet lifetime (τT) and singlet oxygen lifetime (τΔ) of the ZnOCPc or ZnTCPc were observed, hence improving the photosensitizers efficiency. The conjugates comprising of zinc octacarboxyphthalocyanine (ZnOCPc) and AMNPs were electrospun into fibers using polyamide-6 (PA-6). This was used for the photodegradation of Orange-G and compared with ZnOCPc-AMNPs in suspension. For ZnOCPc-AMNPs in suspension, it is noteworthy that the catalyst can be easily recovered using an external magnetic field. The singlet oxygen generation increases as we increase the fiber diameter by increasing the ZnOCPc concentration. The singlet oxygen quantum yield is higher for PA-6/ZnOCPc-AMNPs nanofibers when compared to PA-6/ZnOCPc. The rate of degradation of Orange-G increased with an increase in the singlet oxygen quantum yield. Moreover, the kinetic analysis showed that the photodecomposition of Orange-G is a first-order reaction according to the Langmuir-Hinshelwood model.

Orientador: Débora de Barros Barbosa / Banca: Valentim Adelino Ricardo Barão / Banca: Emerson Rodrigues de Camargo / Banca: Sandra Helena Penha de Oliveira / Banca: Daniel Galera Bernabé / Resumo: O objetivo deste estudo foi investigar o efeito de diferentes soluções coloidais de nanopartículas de prata sobre a viabilidade celular de fibroblastos (linhagem L929) e sobre a resposta inflamatória de tecido subcutâneo de ratos. Nanopartículas de prata (SNP) com tamanho médio de 5 nm foram sintetizadas através da redução do nitrato de prata pelo citrato de sódio e estabilizadas com amônia (SNP-A) ou polivinilpirrolidona (SNP-P). Para avaliar a viabilidade celular, células L929 foram expostas SNP e agentes estabilizantes (amônia (NH3) e polivinilpirrolidona (PVP)) (0,1 - 100 μg/mL), e após 6, 24 e 48 h foi realizado o ensaio de citotoxicidade celular pelo método do MTT. A resposta tecidual foi realizada com tubos de polietileno contendo SNP (1.0 μg/mL; 540 μg/mL) e agentes estabilizantes (NH3 0.13 x 10-3 mol/L e PVP 0.19 g/L) implantados no tecido conjuntivo dorsal de ratos Wistar por 7, 15, 30, 60 e 90 dias. Os espécimes foram corados com hematoxilina e eosina e foram realizadas avaliações qualitativa e quantitativa. SNP inibiram a viabilidade celular no teste in vitro de maneira concentração-dependente. SNP-A foram mais tóxicas para L929 que as partículas estabilizadas com PVP. O exame histológico mostrou que SNP 540 μg/mL induziram reação tecidual significantemente mais intensa em 30 e 60 dias comparado aos grupos controles (solução fisiológica 0,9% e fibrina) nos mesmos períodos. As respostas inflamatórias causadas por SNP 1,0 μg/mL, NH3 0,13 x 10- 3 mol/L e PVP 0,19 g/L foram similares aos controles em todos os períodos experimentais. Foi possível concluir que a exposição à SNP reduziu a viabilidade de células L929 de maneira concentração-dependente. O tipo de agente estabilizante interferiu na citotoxicidade sendo SNP-A mais tóxica para L929. Ambos ... / Abstract: The aim of this study was to investigate the effect of different colloidal silver nanoparticles on cell viability of mouse fibroblasts (cell line L929) and on the subcutaneous connective tissue reaction of rats. Silver nanoparticles (SNP) of average size 5 nm were synthesized by the reduction of silver nitrate through sodium citrate and were stabilized with ammonia (SNP-A) or polyvinylpyrrolidone (SNP-P). To evaluate the cell viability, L929 cell were exposure to silver nanoparticles (0.1-100 μg/mL), and after 6, 24 and 48h MTT assay was performed. The tissue reaction was carried out with polyethylene tubes containing silver nanoparticles (1.0 μg/mL; 540 μg/mL) implanted in the dorsal connective tissue of Wistar rats for 7, 15, 30, 60, and 90 days. The specimens were stained with hematoxylin and eosin and qualitative and quantitative evaluations of the reaction were carried out. Silver nanoparticles inhibited the cell viability in the in vitro test in a concentration-dependent manner. SNP-A were more toxic to L929 than particles stabilized with polyvinylpyrrolidone (PVP). Histological examination showed that SNP at 540 μg/mL induced significant tissue reaction on 30 and 60 days after implantation compared to the controls groups (fibrin and saline 0.9%) at the same periods. The inflammatory responses caused by SNP at 1.0 μg/ml, NH3 at 0.13 x 10-3 mol/L and PVP at 0.19 g/L solutions were similar to the controls groups in all experimental periods. It was possible to conclude that SNP exposure decreased the viability of L929 cells in a concentration-dependent manner. The type of stabilizing agent interfered on the cytotoxicity of SNP being SNP-A more toxic to L929. Also, both colloidal silver nanoparticles (SNP-A and SNP-P) at 540 μg/mL induced significant inflammatory response in rat's subcutaneous tissue. / Doutor

Orientador: Devaney Ribeiro do Carmo / Banca: Mirian Cristina dos Santos / Banca: Magno Aparecido Gonçalves Trindade / Resumo: O presente trabalho descreve a preparação de nanopartículas de pentaciano metais de transição (Ni2+, Cu2+ e Ce3+) partindo do composto nitroprussiato de sódio. As nanopartículas foram caracterizadas por diferentes técnicas espectroscópicas: espectroscopia de difração de Raios-X (DRX), espectroscopia eletrônica na região do ultravioleta e visível (UV-Vis) e também através da técnica de voltametria cíclica (VC). As nanopartículas de pentaciano metais de transição foram preparadas em três proporções empregando os solventes Formamida/Água: 0:10, 10:0 e 6:4. Como etapa complementar, estes materiais foram testados para determinação eletrocatalítica de substâncias biologicamente importantes, tais como: dipirona, sulfito, dopamina, ácido L-ascórbico, L-cisteína, cistina, piridoxina, nitrito e outras substâncias, empregando a técnica de voltametria cíclica. A pasta de grafite modificada com NNiNP, exibiu um processo redox em cada um dos sistemas estudados (NNiNP6:4, NNiNPF e NNiNPA) com potencial médio (E θ'), iguais a 0,46; 0,32 e 0,32 V, respectivamente, atribuídos ao par redox [NiIIFeIII/II(CN)5NO]0/-1, (NaCl 1,0 mol L-1 ; v= 20 mV s-1). O eletrodo modificado com NNiNP6:4 foi sensível a concentrações milimolares de dipirona, e pode-se confeccionar uma curva analítica que apresentou uma resposta linear de 2,010-4 mol L-1 a 6,010-3 mol L-1 (r = 0,998), com limite de detecção e sensibilidade amperométrica de 4,01x10-4 mol L-1 e 21,63 A/mol L-1 respectivamente, e desvio padrão relativo de ± 2% (n=3). Os voltamogramas cíclicos, da pasta de grafite modificada com NCuNP, exibiram dois processos redox para cada sistema (NCuNPA, NCuNP6:4 e NCuNPF), onde os processos mais anódicos apresentaram potencial médio (E θ'), iguais a 0,78; 0,78 e 0,86 V atribuídos ao par redox Fe(II)(CN)5NO/Fe(III)(CN)5NO... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: The present work describes the preparation of nanoparticles transition-metal pentacyano nitrosyl complexes (Ni2+, Cu2+ e Ce3+) starting from the compound sodium nitroprusside. The nanoparticles were characterized using different spectroscopic techniques: spectroscopy X- ray diffraction (XRD), electron spectroscopy in the ultraviolet and visible (UV-Vis) and the technique cyclic voltammetry (CV). The nanoparticles transition-metal pentacyano nitrosyl were prepared in three ratios, employing solvents formamide/water 00:10, 10:0 and 6:4. As a further step, these materials were tested to determine eletrocatalytic of biologically important such as dipyrone, sulfite, dopamine, L-ascorbic acid, L-cysteine, cystine, pyridoxine, nitrite and other substances, employing the technique of cyclic voltammetry. The modified graphite paste NNiNP, exhibited a redox process on each of studied the systems (NNiNP6:4, NNiNPF and NNiNPA) with formal potential (Eθ'), equal to 0,46; 0,32 and 0,32 V, respectively assigned to the redox couple [NiIIFeIII/II(CN)5NO]0/-1, (NaCl 1,0 mol L-1 ; v= 20 mV s-1). The modified electrode with NNiNP6:4 was sensitive to millimolar concentrations of dipyrone, and you can make an analytical curve which showed a linear response from 2,0x10-4 mol L-1 to 6,0x10-3 mol L -1 (r = 0,998), a detection limit and sensitivity amperometric 4,01x10-4 mol L-1 and 21,63 A/ mol L-1, respectively, and the relative standard deviation of ± 2% (n =3). The cyclic voltammograms of the modified graphite paste NCuNP exhibited two redox processes for each system (NCuNPA, NCuNP6:4 and NCuNPF) where more anodic processes presented formal potential (Eθ'), equal to 0,78; 0,78 and 0,86 V assigned to the redox couple Fe(II)(CN)5NO/Fe(III)(CN)5NO, respectively. The modified electrode with NCuNPF was sensitive to different... (Complete abstract click electronic access below) / Mestre

Orientador: Antonio Riul Júnior / Banca: Margarida Juri Saeki / Banca: Joelma Perez / Banca: Marystela Ferreira / Banca: Ana Flávia Nogueira / Resumo: As células a combustível de metanol direto (DMFCs) são promissoras devido à capacidade de geração de alta densidade de energia elétrica, no entanto, a alta permeabilidade da membrana de troca protônica ao combustível permite seu cruzamento do ânolo para o cátodo, que somado à lenta cinética de exidação do metanol, prejudicam a inserção destes dispositivos no mercado. Neste contexto, o presente trabalho tem como objetivo a melhoria do desempenho de DMFCs utilizando a técnica de automontagem LbL (layer-by-layer) na modificação da membrana trocadora de prótons e construção de eletrodos para oxidação de metanol. Para a nanoesetruturação dos filmes, nanofolhas de óxido de grafeno (GO) e óxido de grafeno reduzido estabilizados em PSS (poly(4styrenesulfonic acid) sodium salt), denominado GPSS, foram sintetizdos e aplicados como suspensões carregadaos negativamente na fabricação dos filmes LbL. Quando depositados sobre membranas comerciais de Nafion 212, apresentaram redução na permeabilidade ao metanol de até 80% e condutividade protônica superior a membrana pura. Os testes em DMFCs indicaram maior potencial de circuito aberto quando se empregou a membrana de Nafion revestida com os filmes LbL e densidade de potência de 83,5 mW.cm-2 (à 70ºC), superior ao resultado com a membrana pura (63,1 mW.com-2), devido à redução do cruzamento de metanol. Em relação a capacidade catalítica para oxidação de metanol, nanopartículas de platina foram sintetizadas por diferentes rotas e empregadas na fabricação de filmes LbL com polieletrólitos e/ou nanofolhas de grafeno sendo que os testes eletroquímicos indicaram correntes de oxidação superiores quando as nanopartículas foram depositadas sobre as nanofolhas de óxido de grafeno reduzidos. Sendo assim, filmes ultrafinos compostos por nanofolhas de grafeno podem contribuir significativamente para o desenvolvimento da tecnologia de DMFCs / Abstract: The Direct Methanol fuel Cel (DMFC) are promising to clean and high energy density generation, however, the fuel permeability from anode to the cathode and slow methanol oxidation kinetics hinder its rising in market. Within this context, the aim here is inhance the DMFCs performance using the Layer-by-Layer (LbL) technique to modify the polymer electrolyte membrane and build up of electrodes for methanol oxidation. Graphene oxide nanosheets and reduced graphene oxide nanosheets stabilized in PSS (poly(4-styrenesulfonic acid) sodium salt) were synthesized and used as negatively suspensions in the LbL film fabrication. When deposited onto commercial Nafion 212 membranes it was observed a reducition of ~80% in the methanol permeability, and also higher proton conductivity than that of pristine Nafion. DMFC tests indicated a high open circuit voltage with the LbL modified membranes due to a decrease in the methanol crossover, and a power density of 83,5 mW.com-2, superior to the pristine Nafion, at 70ºC (63,1 mW.com-2). Regarding to the catalytic capacity for methanol oxidation, platinum nanoparticles were synthesized from different ways and self-assembled with polyelectrolyte and/or graphene nanosheets and the electrochemical analysis indicated that when supported onto reduce graphene oxide nanosheets, it was produced higher oxidation peak currents. Consequently, composite ultrathin films of graphene nanosheets can contribute significantly to the development of DMFCs / Doutor

Thesis Submitted in Fulfilment of the Requirements for the Degree Master of Technology: Chemical Engineering in the Faculty of Engineering at the Cape Peninsula University of Technology 2014 / Iron oxide nanoparticles have recently become attractive for use in gas sensing, as catalysts and have also shown promise in other fields, such as biomedicine, for targeted drug delivery and cancer treatment. Despite these growing applications, the ability to produce iron oxide and one dimensional (1D) iron oxide nanoparticles on an industrial scale has proven to be a challenge. The continuous hydrothermal synthesis, (CHS), method has been proposed as the most promising method, yet the effect of the operating parameters on particle characteristics are still widely contested in the literature. One such parameter, temperature, is still widely contested on its effect on APS. To address this issue, a CHS pilot plant was constructed and commissioned. The inability to isolate certain parameters in CHS is a common shortcoming. Parameters such as temperature and flow rate are prime examples, as changing the temperature has several effects on the system resulting in a change in reaction rate, a change in density and a change in the reactor residence time while the flow rate is closely linked to the residence time and mixing conditions. A 3-level Box-Behnken factorial design method was used to statistically analyze the correlations and interactions between operating parameters (temperature, concentration and flow rate) in CHS and evaluate their resulting effect on particle characteristics, with focus on morphology. All particles were characterized by X-ray diffraction (XRD) and high resolution transmission electron microscopy (HRTEM). Reactions in the presence of solvents or surfactants proved incapable of modifying particle morphology, although significant particle size reduction revealed that they were actively involved in particle growth and may be used as a further tool for controlling particle characteristics. The concentration was found to have the greatest effect on particle characteristics including a slight alteration of particle shape and a massive influence on the average particle size. The interactions between operating parameters were significant, especially in the case of temperature and concentration. The temperature and concentration were found to interact revealing three different trends on APS, offering a solution to conflicting reports in the literature. The temperature was also observed to interact favourably with the flow rate, presenting a method of increasing the PY and RC, with little change in APS and PSD. This knowledge will prove invaluable for the design of future experiments in CHS.

Thesis submitted in fulfilment of the requirements for the degree Doctor of Technology: Chemical Engineering in the Faculty of Engineering at the Cape Peninsula University of Technology 2014 / This study investigated water-in-oil (W/O) super-concentrated emulsions used as pumpable explosives. The aqueous phase of the emulsions is a supersaturated nitrate salt solution (at room temperature), with a volume fraction of approximately 0.9. Instability of such emulsions arises either from crystallization of the dispersed phase in the system during ageing or under high shear conditions. Here, we report an alternative approach to stabilize this highly concentrated W/O emulsion by adding colloidal particles in combination with short amphiphilic molecules. Thus, the primary goal of this research concerned a phenomenological study of the dependence of surfactant-to-particle ratio as well as the particle hydrophobicity index on stability under high shear in the emulsification process, rheological properties and stability against initiation of crystallization of an internal phase both with ageing and under high shear with a view to optimize the time to the start of crystallization of the emulsion both with ageing and under high shear; to elucidate the mechanism of initiation of crystallization of an internal phase (homogeneous or heterogeneous) and shed light in the stabilization mechanism of the emulsion; to determine how the emulsion formulation content affect pumping characteristics as measured by characteristic rheological parameters. A series of five fumed silica nanoparticles, each with a different hydrophobicity index (HI) in the range of 0.60 – 3, were used in the form of single types of particles as well as binary mixtures. These particles were combined with a low molecular weight conventional surfactant, Sorbitan MonoOleate (SMO), into the oil phase prior to emulsification. It has been found that regardless of the particle hydrophobicity, fumed nanosilica alone cannot form highly concentrated W/O emulsion up to 90 vol%. Moreover, Pickering emulsions are unstable under shear conditions and thus it is difficult to make highly concentrated W/O pumpable emulsion explosives using only fumed nanosilica. The correlation between the refinement time and SMO-to-particle ratio showed a deflection point/transitional point in the stabilization mechanism. Below the transitional point the silica content dominates over SMO. Conversely, above the transitional point the particles have little effect and the SMO dominates. A thermodynamic consideration revealed that in this region only SMO is likely to adsorb at the W/O interface and controls the emulsifying process. As with refinement time, the correlation between the shear modulus and SMO/particle ratio shows a deflection /transitional point which, as before, mark the transition point between regions of particle or SMO domination. Interestingly, it was found that for each HI, the initiation of crystallization is the most delayed, both on shelf life and under high shear, when the emulsion is prepared with an SMO-to-particle ratio equaling exactly the value at this transitional point. Moreover, the research demonstrated that a drastic change in mechanism of initiation of crystallization of the dispersed droplets occurs at the transitional point. Homogeneous nucleation within the droplets is the dominating mechanism of initiation of crystallization of an internal phase for SMO/particle ratios below and at the transitional point. In this case, the relationship between the zero modulus of particle dispersions in oil and the SMO-to-particle ratio demonstrated that the most stable emulsions are formed from the most unstable dispersions, indicating that less repulsion between particles is required to delay the onset of crystallization. This was further corroborated by the linear correlation between the time to the onset of crystallization and the shear modulus of the emulsion. On the contrary, it was found that for SMO/particle ratios above the critical point, heterogeneous nucleation catalyzed at the surface of droplets is the dominating mechanism of initiation of crystallization of nitrate salts in the super-cooled droplets This was found to be consistent with SMO-only system. That is the change in the mechanism of initiation of crystallization originates from a drastic change in the emulsion structure due to excess surfactant was highlighted by the drastic change in the linear correlation between the time to the start of crystallization and the strength of the emulsion structure as measured by the shear modulus. The optimum time to the start of crystallization (onset of crystallization associated with optimum SMO-to-particle ratio) is sensitive to the particle HI; increasing with increase of particle HI. A general correlation between the particle HI and optimum time to the onset of crystallization has been identified and formulated for the whole family of single types and mixtures of fumed nanosilica used in this study.

This thesis mainly consists of three parts. This first part is the synthesis of ultrasmall (< 2.0 nm) thiolated α-cyclodextrin-capped gold nanoparticles (α-CD-S-AuNPs). Per-6-thio-α-cyclodextrins were firstly synthesized and were employed to protect gold nanoparticles (AuNPs) from aggregation. These α-CD-S-AuNPs (core size < 2.0 nm) display remarkably strong blue emissions at 478 nm when excited at 400 nm. The 1.4 nm-sized α-CD-S-AuNP shows photoluminescence enhancement in the presence of tetraalkylammonium ions but is strongly quenched by Hg(II). We found that the α-CD-S-AuNP possesses ultrahigh sensitivity and good selectivity for the determination of Hg (II) with the limit of detection at 49 pM (9.7 ppt). In the second part of this work, two liquid chromatographic methods have been developed and their efficiencies in separating samples of polydisperse gold nanoparticles protected with N-acetyl-L-cysteine ligand (NAC-AuNPs) and other ultrasmall ligand-protected gold NPs are compared. The total elution time for analysing a NAC-AuNPs sample by ultra high-performance liquid chromatography (UHPLC) is ten times shorter than that of high-performance liquid chromatography. The major attributes of UHPLC are smaller sample volume (12 L) and better separation efficiency. More importantly, our proposed UHPLC method has been successfully applied to evaluate and compare polydisperse NAC-AuNPs products synthesised with the one-phase and two-phase Brust-Schiffrin methods. The results indicate that the two-phase method would harvest AuNPs product with smaller core size and less dispersity. The third part of this work is to describe a novel and effective capillary electrophoretic method to study positively charged, sub-nanometer-sized, water-soluble gold nanoclusters protected by N,N'-dimethylformamide (DMF-AuNC). The effects of buffer concentration, pH, and % ethanol (EtOH) on the electrophoretic mobility of the cationic DMF-AuNC are investigated. The optimum CE conditions are found to be 30 mM phosphate run buffer in 20 v/v % EtOH (pH 7.0) and an applied voltage of 15 kV. We find that the addition of SDS to the run buffer can enhanced the separation of cationic DMF-AuNC, attributing to the attachment of the charged SDS to the AuNC surface with a concomitant effect on changing the charge-to-size ratio of the cationic DMF-AuNC.

No description available.

Orientador: Nelson Eduardo Durán Caballero / Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Química / Made available in DSpace on 2018-08-25T19:26:39Z (GMT). No. of bitstreams: 1 Silva_JeaniferCaverzan_M.pdf: 3206387 bytes, checksum: 2e1b76efef3afb5141bea5a703a092d6 (MD5) Previous issue date: 2014 / Resumo: A alopecia é uma doença caracterizada pela diminuição ou ausência de cabelos e/ou pelos, que gera estresse emocional para milhões de homens e mulheres no mundo. O tratamento da alopecia é realizado, em geral, com aplicação tópica de medicamentos como o 17-alfa-estradiol, que é um estereoisômero do hormônio sexual 17-beta-estradiol. Entretanto este fármaco, assim como outros utilizados no tratamento de alopecia, apresentam baixa eficácia. Para tentar reverter essa situação, a associação deste fármaco com sistemas de liberação sustentada pode aumentar a sua eficácia e reduzir os efeitos colaterais. Desta forma, o objetivo deste trabalho foi o desenvolvimento e a caracterização físico-química e biológica de carreadores lipídicos nanoestruturados (CLN) no encapsulamento de estradiol visando aumentar a eficácia deste fármaco no tratamento de alopecia. Os CLN foram preparados pelo método de microemulsão à quente/sonicação, e foram caracterizados quanto ao diâmetro e potencial Zeta, utilizando-se as técnicas de espectroscopia de correlação de fótons e mobilidade eletroforética respectivamente, sendo o diâmetro médio obtido no valor de 96 ± 15 nm e o potencial zeta médio foi de -16 ± 6 mV. A eficiência de encapsulamento (EE) do 17-alfa-estradiol avaliada por cromatografia líquida/fluorescência foi de 99,6 ± 0,3%. No estudo de estabilidade física dos CLN armazenados em temperatura ambiente foi observado que após dois meses os parâmetros de diâmetro, potencial Zeta, pH, EE e índice de recristalização (IR) não sofreram alterações significativas, demonstrando que a formulação de CLN desenvolvida neste projeto tem grande potencial como sistema de liberação do 17-alfa-estradiol. O poder de penetração cutânea dos CLN foi avaliado em célula de difusão de Franz e microscopia confocal, sendo que os resultados indicam que há acumulo dos CLN nas porções mais externas da epiderme, o que sugere que esta formulação está dentro dos padrões de biossegurança, principalmente no folículo piloso, sítio de ação do fármaco. Além disso, as avaliações de internalização dos CLN em células de queratinócitos demonstraram que os nanocarreadores foram internalizados e acumularam-se principalmente em seu citoplasma / Abstract: Alopecia is a disease characterized by decreased or absent hair, which creates emotional stress for millions of men and women worldwide. The treatment of alopecia is carried out usually with topical application of drugs such as, sex hormone. However, this drug as well as others used in the treatment of alopecia have low efficacy. In this way the association of this drug with sustained delivery systems may increase the efficacy and reduce side effects. Thus, the aim of this work is the development and physico-chemical characterization of nanostructured lipid carriers (NLC) in the encapsulation of a steroid, aiming to increase the effectiveness of this drug in the treatment of alopecia. NLCs were prepared by the microemulsion of hot sonication method. The diameter and zeta potential were characterized , by using the technique of photon correlation spectroscopy and the average diameter obtained was 96 ± 15 nm while the average zeta potential was -16 ± 6mV. The encapsulation efficiency (EE) of the steroid measured by liquid chromatography with fluorescence detection was 99.6 ± 0.3%. In the study of physical stability of CLN stored at room temperature was observed that after two months the parameters diameter , zeta potential , pH , EE and recrystallization index (RI ) did not change significantly , demonstrating that this project has developed CLN great potential as a delivery system of 17-alpha- estradiol. The power dermal penetration of CLN was evaluated in Franz diffusion cell and confocal microscopy, and the results indicate that there is accumulation of CLN in the outer portions of the epidermis, especially the hair follicle, suggesting that this formulation is within the standards of biosecurity. Furthermore, evaluations of internalization of CLN on keratinocytes cells demonstrated that nanocarriers were internalized and accumulated mainly in the cytoplasm / Mestrado / Físico-Química / Mestra em Química

Manufactured nanoparticles can be toxic to living organisms. This work aims to study the interaction of nanoparticles with bacteria as a model organism. The first objective was, to determine the mechanistic pathways of nanotoxicity with an emphasis on ions and oxidative stress as two key contributors and the second objective, was to investigate what mechanisms bacteria have developed as a strategy to protect themselves against nanotoxicity. The thesis further explores the role of environmental variables such as water chemistry, organic matter and other microorganisms, all of which can potentially change speciation of nanoparticles through their transformation into less toxic species. KEIO deletion mutants lacking genes encoding proteins which mediate resistance to oxidative stress and ionic toxicity were screened and found to be sensitive to both ionic silver and silver nanoparticles. A bioreporter to detect silver ions was constructed. This was found not to be induced by silver nanoparticles, yet showed reduced viability; this observation also indicates that besides ionic silver there are other toxicity pathways. E. coli strains capable of mediating resistance to oxidative stress by overexpression of certain proteins and bio reporters that could detect oxidative stress were constructed. The biosensor cells provide some but not too significant signals. Overexpression of proteins like superoxide dismutase and catalase reduces cell growth, hence, cell viability assays do not provide a realistic measure of protective impact, and thus this strategy is not suited to detect the nature of nanotoxicity. The protective role of extracellular polymeric substances (EPS) was studied by developing an engineered strain of E. coli that overproduces the EPS colanic acid, and use of mutant strains of Sinorhizobium meliloti, a free-living N2 fixing bacterium. Nanoparticle exposure studies reveal that overproduction of EPS mitigates silver nanotoxicity. EPS encapsulates the cells and leads to aggregation of nanoparticles, as shown by microscopy and dynamic light scattering. Furthermore, addition of xanthan, an EPS analogue also produces a similar effect. Lastly, x-ray absorption spectroscopy (XAS) of microcosms amended with silver and zinc oxide nanoparticles show rapid transformation of nanoparticles into corresponding oxides and sulphides. The microcosms show a significant presence of dissimilatory sulphate reducing bacteria (DSRB), and display only marginal change in bacterial community composition on exposure to nanoparticles. These findings suggest that nanomaterials will undergo changes in speciation dependent on the sediment chemistry and the metabolic activities of bacteria in the environment. This process will influence the impact of nanoparticles and the outcomes could be quite different from controlled in vitro exposure studies.