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A Terapia Fotodinâmica (TFD) é uma técnica para tratamento de câncer que usa um fotossensibilizador (FS) na presença de luz e oxigênio molecular gerando espécies altamente reativas de oxigênio que levam as células tumorais à morte. Porém a hidrofobicidade de alguns FSs podem induzir a agregação em sistemas biológicos, com redução da sua atividade fotodinâmica. A incorporação de FSs em sistemas nanocarreadores pode ser uma alternativa para superar este problema. O objetivo deste trabalho foi preparar e caracterizar dois FSs hidrofóbicos (Hipericina e Tetra-carboxiftalocianinade zinco) encapsulados em nanopartículas lipídicas sólidas (NLS) para um potencial uso em terapia fotodinâmica. Os FSs incorporados em nanopartículas lipídicas sólidas foram preparados utilizando a técnica de ultra-sonicação e a caracterização físico-química foi realizada. O tamanho médio das nanopartículas de hipericina e tetra-carboxiftalocianinade zinco foram de 153 e 245 nm respectivamente, índice de polidispersão de 0,28 para Hy-NLS e 0,29 para FtZnT-NLS. Uma das vantagens dos sistemas de encapsulação utilizando NLS é o alto valor de eficiência de encapsulação (EE%) e neste estudo foram obtidos valores de eficiência de encapsulação superior a 80% para a Hy-NLS e FtZnT-NLS. De modo a obter a eficiência fotodinâmica da Hy e FtZnT antes e depois do encapsulamento em NLS, as constantes de velocidade de foto-decomposição utilizando dois agentes captadores de 1O2 (1,3 Difenilisobenzofurano e ácido úrico) foram determinadas. As constantes de velocidade de foto-decomposição tiveram aumento significativo após o encapsulamento que ocorreu provavelmente devido a um aumento no tempo de vida do estado triplete causado pelo aumento da solubilidade. Hy-NLS e FtZnT-NLS apresentaram um aumento acima de 30% e 60% respectivamente na acumulação intracelular e uma melhoria na fototoxicidade correlacionado com o aumento da acumulação intracelular. Todas essas vantagens sugerem que hipericina e a tetra-carboxiftalocianinade zincoencapsuladas em nanopartículas lipídicas sólidas tem potencial para serem utilizadas em terapia fotodinâmica. / Photodynamic therapy (PDT) is a technique for treating cancer using a photosensitizer (PS) in the presence of light and molecular oxygen generating highly reactive oxygen species that lead to tumor cell death. The hydrophobicity of some photosensitizers can induce aggregation in biological systems, reducing its photodynamic activity. The incorporation of PSs in nanocarriers can be an alternative to overcome this problem. The aim of this work was to prepare and characterize two hydrophobic photosensitizers (Hypericin and Zinc tetra-carboxylicphthalocyanine) encapsulated in solid lipid nanoparticles (SLN) for potential use in photodynamic therapy. The PSs incorporated into solid lipid nanoparticles were prepared using the ultrasonication technique, and physico-chemical characterization was performed. The average size of the nanoparticles with hypericin and zinc tetra-carboxylicphthalocyanine was 153 and 245 nm respectively, the polydispersivity index of 0.28 to Hy-SLN and 0.29 to FtZnT-SLN. One of the advantages of encapsulation systems using SLN is the high value of encapsulation efficiency (EE %). In this study were obtained values of encapsulation efficiency greater than 80% for the Hy-SLN and FtZnT-SLN. In order to obtain the photodynamic efficiency of Hy and FtZnT before and after encapsulation in SLN, rate constants using photo-decomposition of two scavengers of 1O2 agents (1,3-Diphenylisobenzofuran and uric acid) were determined. The rate constants of photo-decomposition had significant increase after encapsulation which occurred probably due to an increase in the lifetime of the triplet state caused by the increased solubility. Hy-SLN and FtZnT-SLN showed an increase above 30% and 60% respectively in the intracellular accumulation and an improvement in phototoxicity correlated with increased intracellular accumulation. So, all these advantages suggest that hypericin and zinc tetra-carboxylicphthalocyanine encapsulated in solid lipid nanoparticles have potential to be used in photodynamic therapy.

A Terapia Fotodinâmica (TFD) é uma técnica para tratamento de câncer que usa um fotossensibilizador (FS) na presença de luz e oxigênio molecular gerando espécies altamente reativas de oxigênio que levam as células tumorais à morte. Porém a hidrofobicidade de alguns FSs podem induzir a agregação em sistemas biológicos, com redução da sua atividade fotodinâmica. A incorporação de FSs em sistemas nanocarreadores pode ser uma alternativa para superar este problema. O objetivo deste trabalho foi preparar e caracterizar dois FSs hidrofóbicos (Hipericina e Tetra-carboxiftalocianinade zinco) encapsulados em nanopartículas lipídicas sólidas (NLS) para um potencial uso em terapia fotodinâmica. Os FSs incorporados em nanopartículas lipídicas sólidas foram preparados utilizando a técnica de ultra-sonicação e a caracterização físico-química foi realizada. O tamanho médio das nanopartículas de hipericina e tetra-carboxiftalocianinade zinco foram de 153 e 245 nm respectivamente, índice de polidispersão de 0,28 para Hy-NLS e 0,29 para FtZnT-NLS. Uma das vantagens dos sistemas de encapsulação utilizando NLS é o alto valor de eficiência de encapsulação (EE%) e neste estudo foram obtidos valores de eficiência de encapsulação superior a 80% para a Hy-NLS e FtZnT-NLS. De modo a obter a eficiência fotodinâmica da Hy e FtZnT antes e depois do encapsulamento em NLS, as constantes de velocidade de foto-decomposição utilizando dois agentes captadores de 1O2 (1,3 Difenilisobenzofurano e ácido úrico) foram determinadas. As constantes de velocidade de foto-decomposição tiveram aumento significativo após o encapsulamento que ocorreu provavelmente devido a um aumento no tempo de vida do estado triplete causado pelo aumento da solubilidade. Hy-NLS e FtZnT-NLS apresentaram um aumento acima de 30% e 60% respectivamente na acumulação intracelular e uma melhoria na fototoxicidade correlacionado com o aumento da acumulação intracelular. Todas essas vantagens sugerem que hipericina e a tetra-carboxiftalocianinade zincoencapsuladas em nanopartículas lipídicas sólidas tem potencial para serem utilizadas em terapia fotodinâmica. / Photodynamic therapy (PDT) is a technique for treating cancer using a photosensitizer (PS) in the presence of light and molecular oxygen generating highly reactive oxygen species that lead to tumor cell death. The hydrophobicity of some photosensitizers can induce aggregation in biological systems, reducing its photodynamic activity. The incorporation of PSs in nanocarriers can be an alternative to overcome this problem. The aim of this work was to prepare and characterize two hydrophobic photosensitizers (Hypericin and Zinc tetra-carboxylicphthalocyanine) encapsulated in solid lipid nanoparticles (SLN) for potential use in photodynamic therapy. The PSs incorporated into solid lipid nanoparticles were prepared using the ultrasonication technique, and physico-chemical characterization was performed. The average size of the nanoparticles with hypericin and zinc tetra-carboxylicphthalocyanine was 153 and 245 nm respectively, the polydispersivity index of 0.28 to Hy-SLN and 0.29 to FtZnT-SLN. One of the advantages of encapsulation systems using SLN is the high value of encapsulation efficiency (EE %). In this study were obtained values of encapsulation efficiency greater than 80% for the Hy-SLN and FtZnT-SLN. In order to obtain the photodynamic efficiency of Hy and FtZnT before and after encapsulation in SLN, rate constants using photo-decomposition of two scavengers of 1O2 agents (1,3-Diphenylisobenzofuran and uric acid) were determined. The rate constants of photo-decomposition had significant increase after encapsulation which occurred probably due to an increase in the lifetime of the triplet state caused by the increased solubility. Hy-SLN and FtZnT-SLN showed an increase above 30% and 60% respectively in the intracellular accumulation and an improvement in phototoxicity correlated with increased intracellular accumulation. So, all these advantages suggest that hypericin and zinc tetra-carboxylicphthalocyanine encapsulated in solid lipid nanoparticles have potential to be used in photodynamic therapy.

Thesis (Ph.D. (Nutrition))--North-West University, Potchefstroom Campus, 2007.

The role of a protein-repelling coating is to limit the interaction between a device and its physiological environment. Plasma-polymerized-PEG (pp-PEG) surfaces are of great interest since they are known to avoid protein adsorption. and cell attachment. However, in all the studies previously published in the literature, the PEG coatings have been prepared using low pressure processes. In this thesis, we synthesize biocompatible pp-PEG coatings using atmospheric pressure plasma. Two original methods are developed to obtain these pp-PEG films. 1. Atmospheric pressure plasma liquid deposition (APPLD) consists in the injection of the precursor, tetra(ethylene glycol)dimethylether (tetraglyme), by means of a liquid spray, directly in the post-discharge of an atmospheric argon plasma torch. 2. In atmospheric pressure plasma-enhanced chemical vapor deposition (APPECVD), tetraglyme vapors are brought in the post-discharge trough a heating sprinkler. The chemical composition, as well as the non-fouling properties of the APPLD and APPECVD films, are compared to those of PEG coatings synthesized by conventional low pressure plasma processes. In the first part of the study, the effect of the power on the chemical composition of the films has been investigated by infrared reflection absorption spectroscopy (IRRAS), X-ray photoelectron spectroscopy (XPS) and secondary ions mass spectroscopy (SIMS). The surface analysis reveals that for the APPECVD samples, the fragmentation of the precursor increases as the power of the treatment is increased. In other terms, the lower the plasma power is, the higher the “PEG character” of the resulting films is. Indeed, the C-O component (286.5 eV) of the XPS C 1s peak is decreasing while the hydrocarbon component (285 eV) is increasing as the power of the plasma is increased. The same conclusion can be drawn from the signature ToF-SIMS peaks (m/z = 45 (CH3OCH2+ and +CH2CH2OH), 59 (CH3OCH2CH2+), 103 (CH3(OCH2CH2)2+)) that are decreasing in the case of high power treatments. Accordingly, IRRAS measurements show that the C-O stretching band is decreasing for high power plasma deposition. This is in agreement with the observations made from the analysis of the LP PECVD coatings and from the literature. The films deposited by the APPLD process do not show the same behavior. Indeed, whatever the power injected into the discharge is, we are able to achieve films with a relatively high PEG character (83 %). The second part of this study is dedicated to the evaluation of the non-fouling properties of the coatings by exposing them to proteins (bovine serum albumin and human fibrinogen) and cells (mouse fibroblasts (L929 and MEF)) and controlling the adsorption with XPS (proteins) and SEM (cells). For the APPECVD samples, a low plasma power (30 W) leads to an important reduction of protein adsorption and cell adhesion (over 85%). However, higher-powered treatments tend to reduce the non-fouling ability of the surfaces (around 50% of reduction for a 80 W deposition). The same order of magnitude (over 90% reduction of the adsorption) is obtained for the APPLD surfaces, whatever is the power of the treatment. Those results show an important difference between the two processes in terms of power of the plasma treatment, and a strong relationship between the surface chemistry and the adsorption behavior: the more the PEG character is preserved, the more protein-repellent and cell-repellent is the surface. / Le rôle d’une couche empêchant l’adsorption de protéines est de limiter les interactions entre un implant et le milieu physiologique auquel il est exposé. Les films de poly(éthylène glycol) polymérisés par plasma (pp-PEG) sont d’intérêt majeur car ils sont connus pour empêcher l’adsorption de protéines ainsi que l’attachement cellulaire. Cependant, dans toutes les études publiées précédemment, les couches de type PEG ont été réalisées sous vide. Dans cette thèse de doctorat, nous synthétisons des couches de type pp-PEG biocompatibles par plasmas à pression atmosphérique. A cette fin, deux méthodes originales ont été développées. 1. La première méthode consiste en l’injection du précurseur, le tetra(éthylène glycol) diméthyl éther (tetraglyme), en phase liquide, en nébulisant ce dernier au moyen d’un spray, directement dans la post-décharge d’une torche à plasma atmosphérique fonctionnant à l’argon. En anglais, nous appelons ce procédé « Atmospheric pressure plasma liquid deposition (APPLD) ». 2. Dans la deuxième méthode, appelée en anglais « Atmospheric pressure plasma-enhanced chemical vapor deposition (APPECVD)», le tetraglyme est amené en phase vapeur dans la post-décharge, au moyen d’un diffuseur chauffant. La composition chimique des dépôts de type APPLD et APPECVD, ainsi que leurs propriétés d’anti-adsorption sont évaluées, et comparées aux dépôts pp-PEG obtenus par les méthodes à basse pression conventionnelles. Dans la première partie de cette étude, nous nous focalisons sur la composition chimique des films déposés, et plus particulièrement sur l’influence de la puissance injectée dans le plasma sur cette composition chimique. A cette fin, nous avons fait appel à des techniques d’analyse telles que la spectroscopie de réflexion-absorption infrarouge (IRRAS), la spectroscopie des photoélectrons X (XPS) et la spectrométrie de masse des ions secondaires (SIMS). Il en ressort que les films de type APPECVD perdent progressivement leur « caractère PEG » à mesure que la puissance de la décharge plasma est élevée. Cela serait dû à une plus grande fragmentation du précurseur dans la post-décharge d’un plasma plus énergétique. Cette tendance est cohérente avec ce que nous avons observé pour les dépôts à basse pression ainsi que dans la littérature. Dans le cas des films de type APPLD, un tel comportement n’a pas été mis en évidence : quelle que soit la puissance dissipée dans le plasma, les films présentent un « caractère PEG » relativement élevé. La deuxième partie de cette thèse est dédiée à l’évaluation des propriétés d’anti-adsorption des films synthétisés, en les exposant à des protéines (albumine de sérum bovin et fibrinogène humain) et des cellules (fibroblastes de souris, L929 et MEF). L’adsorption de protéines est contrôlée par XPS tandis que l’attachement cellulaire est contrôlé par imagerie SEM. Pour les échantillons de type APPECVD, un dépôt à faible puissance (30 W) mène à une importante réduction de l’adsorption de protéines et de cellules (> 85%) tandis qu’à de plus hautes puissances (80 W), l’anti-adsorption est sensiblement diminuée (50% de réduction). Dans le cas des dépôts de type APPLD, quelle que soit la puissance du plasma, une forte diminution de l’adsorption de protéines et de cellules est observée (> 90 %). Ces résultats montrent une différence majeure entre les deux procédés quant à l’influence de la puissance du plasma ainsi qu’une forte relation entre la composition chimique de la surface synthétisée et son pouvoir d’anti-adsorption : plus le « caractère PEG » du dépôt est conservé, plus la surface empêchera l’interaction avec les protéines et les cellules.

Esta tesis tiene como objetivo final la propuesta de un protocolo de acceso al medio imbricado con los parámetros de nivel físico que dan soporte a dicho protocolo. Puesto que la propuesta se basa en un esquema TDMA, se eligen como base del análisis los sistemas de segunda generación GSM, TETRA y DECT, a partir de los cuales se extrapolan determinados parámetros a fin de sintonizarlos con los sistemas de tercera generación en su especificación TDMA. Se evalúan dichos sistemas a nivel físico sobre diferentes modelos de canal de propagación y distintas técnicas de compensación implementadas en el receptor: ecualizadores implementados sobre filtros transversales y antenas adaptativas. Además, se implementan y evalúan algoritmos de ecualización sencillos como LMS o RLS y más complejos como algoritmos bidireccionales sobre ecualizadores DFE. La elección de una u otra opción condicionará fuertemente el diseño del protocolo de acceso propuesto en el subnivel MAC. / This thesis has as final aim the proposal of a medium access protocol (MAC) closely related to the physical layer parameters that support such protocol. As the proposal is based on a TDMA scheme, three representative systems belonging to the second generation of mobile communication systems have been chosen: GSM, TETRA and DECT, which are employed to extract some parameters in order to tune them with the third generation systems in its TDMA specification. Such systems are evaluated at physical layer over different propagation channel models with several compensation techniques implemented on the receiver. As well, equalizers based on digital filters and adaptive antennas are utilized. The equalization algorithms evaluated include from the simplest ones like LMS or RLS to bidirectional algorithms over DFE structure. Choosing one or another option will strongly condition the design of the proposed access protocol within the MAC sublayer.

Background: The high prevalence of iron deficiency and anaemia among South African children highlights the need for iron fortification, especially with a highly bioavailable iron compound. Fortification of staple foods is an adequate strategy to provide additional iron to populations at risk. In South Africa it is mandatory to fortify maize meal and wheat flour with iron, as well as other micronutrients. Elemental iron, specifically electrolytic iron, is currently the preferred choice but other compounds that might be more effective in alleviating iron deficiency are under consideration. Objectives: The objective of this study was to provide information about the bioavailability of ferrous fumarate and NaFeEDTA from maize meal porridge in young children, which would assist in selecting a bioavailable alternative to electrolytic iron in the South African National Food Fortification Programme, Methods: A randomized parallel study design was used, with each of the 2 groups further randomised to receive either one of two test regimens in a crossover design in which each child acted as his/her own control. Iron bioavailability was measured with a stable-isotope technique based on erythrocyte incorporation 15 days after intake. Results: The mean absorption of iron from NaFeEDTA and ferrous fumarate from the maize porridge meal was 11.5% and 9.29% respectively. NaFeEDTA and ferrous fumarate are both sufficiently bioavailable from a maize based meal rich in phytates. Conclusion: Both NaFeEDTA and ferrous fumarate would provide a physiologically important amount of iron should they replace electrolytic iron as fortificant in maize flour fortification. The final choice between ferrous fumarate and NaFeEDTA as when it comes to finding the alternative iron fortificant will depend on factors such as technical compatibility, bioavailability, relative cost and organoleptic characteristics. / Thesis (Ph.D. (Nutrition))--North-West University, Potchefstroom Campus, 2007

Tetra-n-Butyl Ammonium Bromide (TBAB) forms semi-clathrate hydrates which can incorporate small gas molecules, such as methane and nitrogen at ambient temperatures and atmospheric pressure. Such favourable stability conditions, combined with ease of formation could make semi-clathrates particularly attractive for a large variety of applications. These hydrates have recently been investigated for their use in the separation of gases, and it is proposed that the same technology could potentially be used for storage and transportation of gases. To evaluate the feasibility of using TBAB hydrates for separation and storage purposes, an extensive test programme was conducted to determine: phase stability of the semi-clathrates, gas storage capacity, and composition of the stored gas. The results show that TBAB semi-clathrates have very favourable stability conditions. They can store considerable quantities of gas, and favour small molecules in their structures. These experiments suggest that semi-clathrate hydrates, such as TBAB, could have a significant potential as an alternative for industrial separation, storage, and transportation of natural gas.

Background: The high prevalence of iron deficiency and anaemia among South African children highlights the need for iron fortification, especially with a highly bioavailable iron compound. Fortification of staple foods is an adequate strategy to provide additional iron to populations at risk. In South Africa it is mandatory to fortify maize meal and wheat flour with iron, as well as other micronutrients. Elemental iron, specifically electrolytic iron, is currently the preferred choice but other compounds that might be more effective in alleviating iron deficiency are under consideration. Objectives: The objective of this study was to provide information about the bioavailability of ferrous fumarate and NaFeEDTA from maize meal porridge in young children, which would assist in selecting a bioavailable alternative to electrolytic iron in the South African National Food Fortification Programme, Methods: A randomized parallel study design was used, with each of the 2 groups further randomised to receive either one of two test regimens in a crossover design in which each child acted as his/her own control. Iron bioavailability was measured with a stable-isotope technique based on erythrocyte incorporation 15 days after intake. Results: The mean absorption of iron from NaFeEDTA and ferrous fumarate from the maize porridge meal was 11.5% and 9.29% respectively. NaFeEDTA and ferrous fumarate are both sufficiently bioavailable from a maize based meal rich in phytates. Conclusion: Both NaFeEDTA and ferrous fumarate would provide a physiologically important amount of iron should they replace electrolytic iron as fortificant in maize flour fortification. The final choice between ferrous fumarate and NaFeEDTA as when it comes to finding the alternative iron fortificant will depend on factors such as technical compatibility, bioavailability, relative cost and organoleptic characteristics. / Thesis (Ph.D. (Nutrition))--North-West University, Potchefstroom Campus, 2007

Zugl.: Mainz, Univ., Diss., 2005