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Hydrotalcite (HTC) was intercalated with different aromatic carboxylic acids via two synthesis methods: reconstruction and co-precipitation. The reconstruction method involves the rehydration of the products of LDH calcination. The co-precipitation method involves the addition of a base to solutions containing a mixture of the MII and MIII ions found in the metallic layers of an LDH. The intercalated compounds were then compounded with flexible grade PVC to see if these compounds had any effect on the heat stability of the PVC. Complete intercalation of these stabilisers did not occur; however layered double hydroxides did form for almost every synthesis. The organic acids that were to be intercalated were also present in every synthesised stabiliser. Neat hydrotalcite was the best overall stabiliser with an early stability time of 32.40 min and a final or long term stability time of 106.51 min. The best modified layered double hydroxide (LDH) in terms of early stability was 4-hydroxybenzoic acid + HTC synthesised with the reconstruction method. This stabiliser had an early stability time of 25.40 min. The best performing modified stabiliser in terms of late stability was salicylic acid + HTC synthesised with the co-precipitation method. This stabiliser had a late stability time of 71.32 min. The highly activating nature of the hydroxyl substituent group should make hydrotalcites intercalated with hydroxybenzoic acids good free radical scavengers. The substituent group positions that give the best PVC heat stability are the ortho and para positions. The pKa 2 value for an organic acid may be used as a selection parameter for intercalation into hydrotalcite. If a high pKa 2 value organic acid is intercalated into hydrotalcite, the resulting compound will have good PVC heat stabilisation properties. / Dissertation (MEng)--University of Pretoria, 2017. / Chemical Engineering / MEng / Unrestricted

Norint diagnozuoti kepenų funkcijos pažeidimus yra atliekami biocheminiai kraujo tyrimai. Net mažiausius paktimus kepenyse parodo kepenų fermentų padidėjimas, arba sumažėjimas kraujo serume. Mūsų tikslas buvo įvertinti 3 fermentų kitimo dinamiką (laktatdehydrogenazę (LDH), šarminę fosfatazę (ALPL) , aspartatamino transferazę (AST)) ganykliniu ir tvartiniu laikotarpiais. Rezultatai parodė, kad šarminės fosfatazės rodikliai buvo didžiausi tvartiniu laikotarpiu, o ganykliniame laikotarpyje ženkliai krito. Tačiau aspartatamino transferazės ir laktatdehydrogenazės aktyvumas svyravo nepriklausomai nuo laikotarpio. / In order to diagnose a hepatic disorder a biochemical blood test was carried out. Even slight changes in hepatic function show a decrease or an increase in the concentration of hepatic enzymes. Our aim was to monitor 3 enzymes: alkaline phosphatase (ALP), lactate dehydrogenase (LDH) and aminotransferase (AST). From the results of the blood test we deduced hepatic enzyme funcionality of local Lithuanian cow breed („ Lietuvos šėmųjų“). The experiment was carried out during indoor and pasture periods. The greatest activity of alkaline phosphatase was observed during the pasture period and during the indoor period its activity was greatly reduced. The activity of aminotransferase and lactate dehydrogenase was independent on the season.

Ce travail décrit la synthèse et le comportement de nouveaux photocatalyseurs à base de dioxyde de titane utilisés pour des applications environnementales. Dans la première partie, la pertinence des composés modèles testés, le colorant acide orange 7 (AO7) et le 4-Chlorophénol (4-CP), pour des traitements photocatalytiques à base de TiO2 a été étudiée et validée. Cette étude a été centrée sur l’effet de la concentration initiale en composé et sur la vitesse d’agitation pendant la réaction photocatalytique. La deuxième partie est consacrée principalement à la synthèse et la caractérisation des suspensions de particules colloïdales de TiO2. Leur séparation puis leur récupération après le traitement étant pratiquement impossible l’immobilisation de ces particules sur des supports de type hydroxydes doubles lamellaires (HDL) a été étudiée afin de préparer un matériau composite TiO2/HDL présentant une activité photocatalytique comparable à celle du dioxyde de titane pur. Un deuxième type de composite basé sur des mélanges de TiO2/SiO2 a également été envisagé et utilisé dans la préparation de fines couches efficaces pour la photodégradation de l’hexane. Enfin, le comportement photocatalytique d’HDL pur à base de zinc et de chrome, sans addition de TiO2, a également été étudié et est présenté dans la partie finale de cette thèse. Les matériaux préparés ont été caractérisés par différentes analyses chimiques, diffraction et fluorescence des rayons X, microscopie électronique à transmission et à balayage, spectroscopie IR à transformé de Fourier, analyse thermogravimétrique, mesure du potentiel Zeta, diffusion de la lumière, mesure d’adsorption N2. Les différents matériaux ont été testés photocatalytiquement via la photo-Oxydation en solution aqueuse de l’acide orange 7 (AO7), du 4-Chlorophénol (4-CP) ou du bleu de méthylène à différents pH. L’activité photocatalytique du matériau composite à base de TiO2/SiO2 sous forme de film fin a été évaluée en phase gaz en présence d’hexane. / This work describes the behaviour and fabrication of new photocatalysts based on titaniumdioxide for the purpose of environmental applications. It consists of five closely connectedparts. In the first part the suitability of chosen model compounds, azo dye Acid Orange 7(AO7) and 4-Chlorophenol (4-CP), for photocatalytic activity assessment of TiO2 was studied.This study was focused on the effect of different initial concentrations of model compoundand different rates of stirring during photocatalytic reaction. The second part then focusedmainly on the synthesis and characterization of aqueous colloidal suspensions of TiO2. Theseparation of TiO2 particles in the form of colloidal suspensions and their regeneration afterthe reaction, while keeping the same photocatalytic properties, is almost not possible.Therefore, it was necessary to find an appropriate method how to immobilize these particleson the support or in the form of composite. The layered double hydroxides (LDH) werechosen as one of suitable supports for TiO2 photocatalyst. The focus was kept on thepreparation of TiO2/LDH composites with the same or higher photocatalytic activity as purecolloidal titanium dioxide. The second chosen type of composite was based on twocomponentTiO2/SiO2 material and these composites were used for the preparation of thinlayers. Photocatalytic behaviour of pure LDHs and their possible use as photocatalyst withoutTiO2 addition was also studied and described in a final part of this work. Prepared materials were characterized by chemical analysis, X-Ray diffraction andflorescence, transmition electron microscopy, scanning electron microscopy, Fouriertransform infrared spectroscopy, thermogravimetric analysis, dynamic light scattering, zetapotential measurement and N2 adsorption. As another step, materials were tested asphotocatalyst by the photooxidation of Acid Orange 7, 4-Chlorophenol and Methylene Blue indifferent pH in aqueous medium. Photocatalytic activity of TiO2/SiO2 composites in the formof thin films was tested in gaseous phase using hexane as a model pollutant. It was found that quantum yields of 4-CP degradation for all prepared alkaline colloidalsuspensions of TiO2 were lower than those obtained for acidic TiO2 colloidal suspensions. Inthe contrary to the quantum yield of acidic TiO2, the quantum yield of alkaline suspensionsdecreased during the aging. Prepared TiO2/Mg2Al1.5 nanocomposites exhibited higherphotocatalytic activity than the original TiO2 in basic conditions and also it was much easierto recover the photocatalyst after reaction by simple sedimentation. In the case of TiO2/SiO2composites, it was found that composite prepared with TiO2:SiO2 ratio 1:1 has higherphotocatalytic activity in aqueous media than starting pure TiO2 but with increasing SiO2content reaction rate of AO7 degradation decreases. Thin layers of TiO2:SiO2 compositeprepared from simultaneously co-Precipitated particles (they have improved crystallinity inrelation to pure TiO2) are able to photocatalyticaly degrade hexane. In the case of pure LDH,it was proved that even noncalcined Zn2CrCO3 LDH can produce HO• radicals. However,mixed oxides (containing ZnO) prepared by LDH calcination at temperatures higher than500°C, showed higher efficiency.

abstract: In recent years, the field of nanomedicine has progressed at an astonishing rate, particularly with respect to applications in cancer treatment and molecular imaging. Although organic systems have been the frontrunners, inorganic systems have also begun to show promise, especially those based upon silica and magnetic nanoparticles (NPs). Many of these systems are being designed for simultaneous therapeutic and diagnostic capabilities, thus coining the term, theranostics. A unique class of inorganic systems that shows great promise as theranostics is that of layered double hydroxides (LDH). By synthesis of a core/shell structures, e.g. a gold nanoparticle (NP) core and LDH shell, the multifunctional theranostic may be developed without a drastic increase in the structural complexity. To demonstrate initial proof-of-concept of a potential (inorganic) theranostic platform, a Au-core/LDH-shell nanovector has been synthesized and characterized. The LDH shell was heterogeneously nucleated and grown on the surface of silica coated gold NPs via a coprecipitation method. Polyethylene glycol (PEG) was introduced in the initial synthesis steps to improve crystallinity and colloidal stability. Additionally, during synthesis, fluorescein isothiocyanate (FITC) was intercalated into the interlayer spacing of the LDH. In contrast to the PEG stabilization, a post synthesis citric acid treatment was used as a method to control the size and short-term stability. The heterogeneous core-shell system was characterized with scanning electron microscopy (SEM), energy dispersive x-ray spectroscopy (EDX), dynamic light scattering (DLS), and powder x-ray diffraction (PXRD). A preliminary in vitro study carried out with the assistance of Dr. Kaushal Rege's group at Arizona State University was to demonstrate the endocytosis capability of homogeneously-grown LDH NPs. The DLS measurements of the core-shell NPs indicated an average particle size of 212nm. The PXRD analysis showed that PEG greatly improved the crystallinity of the system while simultaneously preventing aggregation of the NPs. The preliminary in vitro fluorescence microscopy revealed a moderate uptake of homogeneous LDH NPs into the cells. / Dissertation/Thesis / M.S. Materials Science and Engineering 2011

Layered Double Hydroxide (LDH) belongs to a class of ceramic materials that present structure formed by stacked layers of double metals hydroxides and an anion into the lamellar space. They present a large variety of applications possibilities, as industrial, environment, medicine, among others. Non-calcined Mg-Al layered double hydroxide (LDH) with molar ratio, x = Al / (Mg + Al), 0.20, 0.25 and 0.30 were synthesized using co-precipitation method, followed by hydrothermal treatment at a fixed temperature 80ÂC and different aging from 2 to 35 days. The material obtained was characterized by XRD, IR, TG, SEM and EDS. The samples crystallinity was evaluated and particle size was calculated using Scherrer equation. Sorption of anionic acid blue 25 and reactive blue 4 dyes from aqueous solution was investigated for some of the 0.25 molar ratio samples. The purpose of this research was to study the effect of hydrothermal treatment aging conditions on textural properties of synthetic hydrotalcite with different molar ratios and propose a mathematical function to predict crystallite size and crystallinity. This function takes just two of many parameters in consideration: hydrothermal treatment aging time and molar ratio. The obtained as-synthesized samples with a molar ratio 0.20 and 0.25 showed good crystallinity for all the samples. On the other hand the third samples with molar ratio 0.30 showed poor crystallinity, a pronounced shift in the correspondent basal planes peaks 003 and 006, and a broadening in all peaks. The shift in the basal planes was shown to be statistically significant to the others. A non-expected result was found in disagreement with literature: a new crystalline phase was observed in two 0.20 molar ratio samples. MEV and EDS results indicate the existence of a probable amorphous phase in the 0.30 molar ratio samples. The amorphous phase would explain the reduction in crystallinity of this series samples. Just the function to predict the crystallinity was obtained and showed in a 3D and hypsometric graphics. This function may be used to predict a characteristic of a synthesized LDH for an industrial application, like adsorption. / HidrÃxidos Duplos Lamelares (HDL) pertencem a uma classe de materiais cerÃmicos formados por camadas empilhadas de hidrÃxidos metÃlicos com um Ãnion entre os espaÃos lamelares. Apresentam uma grande variedade de possÃveis aplicaÃÃes, na Ãrea industrial, ambiental, medicinal, entre outras. HidrÃxidos Duplos Lamelares (HDL) nÃo calcinados de MagnÃsio e AlumÃnio com razÃo molar x = Al / (Mg + Al), 0,20, 0,25 e 0,30 foram sintetizados utilizando o mÃtodo de co-precipitaÃÃo, seguido por tratamento hidrotÃrmico em temperatura fixa de 80  C e diferente tempos de maturaÃÃo de 2 a 35 dias. O material obtido foi caracterizado por DRX, IV, TG, MEV e EDS. A cristalinidade das amostras foi avaliada e tamanho de partÃcula foi calculado usando a equaÃÃo Scherrer. Foram investigadas adsorÃÃo de corantes Ãcido azul 25 e azul reativo 4 para algumas amostras de razÃo molar 0,25. O objetivo deste trabalho foi estudar o efeito do tratamento hidrotÃrmico e condiÃÃes de tempo de maturaÃÃo nas propriedades texturais de hidrotalcita sintetizada com diferentes razÃes molares e propor uma funÃÃo matemÃtica para prever o tamanho de cristalito e cristalinidade. Esta funÃÃo leva apenas dois de muitos parÃmetros em consideraÃÃo: tempo de tratamento hidrotÃrmico e razÃo molar. As amostras obtidas com uma razÃo molar 0,20 e 0,25 apresentaram boa cristalinidade para todas as amostras. Por outro lado, as amostras com razÃo molar 0,30 apresentaram baixa cristalinidade, um pronunciado deslocamento nos picos basais 003 e 006, e um alargamento em todos os picos. O deslocamento desses picos para essa Ãltima amostra foi mostrado ser estatisticamente significativo em relaÃÃo Ãs outras duas. Um resultado nÃo esperado foi encontrado em desacordo com a literatura: uma nova fase cristalina foi observada em duas amostras de razÃo molar 0,20. Os resultados do MEV e EDS indicam que hà uma provÃvel fase amorfa nas amostras de razÃo molar 0,30. A fase amorfa explicaria a reduÃÃo da cristalinidade das amostras dessa sÃrie. Apenas a funÃÃo para prever a cristalinidade foi obtida e mostrada em grÃficos 3D e hipsomÃtricos. Esta funÃÃo pode ser usada para prever caracterÃsticas de um HDL sintetizado para uma aplicaÃÃo industrial, tal como a adsorÃÃo.

Fatty acid intercalated layered double hydroxides were used as additives for Jojoba oil and polymer matrices. The first phase of the study was to intercalate carboxylic acids (C14 to C22). These were successfully intercalated into layered double hydroxides (LDHs), with the formula [Mg0.7Al0.3 (OH) 2](CO3)0. 15•0.5H2O. The one-pot synthesis consistently yielded a bilayer intercalated product for the range of acids employed. The intercalated anions had an orientation tilt angle of 55–63°, depending on the length of the fatty acid chain. However, there is an indication that the anion exchange process employed in this study is accompanied by probable dissolution and recrystallisation of the LDH. This is supported by the different growth habits and sizes of platelets observed through scanning electron microscopy (SEM). Moreover, the organo-LDH platelets were found to have varying MII/MIII compositions, ranging from 1.65 to 6, indicating that the one-pot synthesis yields an array of mixed metal hydroxides. Polymer composites, containing 5% and 10 wt.% of stearate intercalated layered double hydroxides (LDH-stearate) and neat layered double hydroxides (LDH-CO3), were prepared via melt-compounding to explore the use of LDHs as an additive. The stearate modified starting material was bilayer-intercalated clay. During melt compounding, excess stearates were released and the clay reverted to a monolayer-intercalated form. Comprehensive characterisation and study of the fatty acid-intercalated LDH showed that these organoclay hybrids exhibit thermotropic behaviour. This behaviour ultimately leads to the exudation of excess fatty acid. The exuded stearates were found to have lubricating and plasticising effects on the poly(ethylene-co-vinyl acetate) (EVA) and linear low density polyethylene (LLDPE) matrices. Strong hydrogen bond interactions between the chains of poly(ethyleneco- vinyl alcohol) (EVAL) and the clay platelet surfaces overwhelmed the lubrication effect and caused an increase in the melt viscosity of this matrix. The notched Charpy impact strength of this composite was almost double that of the neat polymer. It appears that this can be attributed to the ability of the highly dispersed and randomly oriented nanosized clay platelets to promote extensive internal microcavitation during impact loading. The creation of a large internal surface area provided the requisite energy dissipation mechanism. The study also considered fatty acid-intercalated LDH as an argillaceous mineral for potential use as a rheological additive in Jojoba oil. A minimum of 20 wt.% LDH in Jojoba oil formulation was found to be stable, i.e. it did not form separate layers on standing. The viscosity of the neat Jojoba oil demonstrated Newtonian behaviour, whereas the modified LDH/Jojoba oil formulation shear thinned, which is a typical non-Newtonian behaviour. Viscosity as a function of temperature showed complex rheological behaviour for the long chain fatty acids C16 to C22. The viscosity increase is assumed to be due to a combination of three events, which include the formation and changes of LDH microstructures within the oil, the loss of excess fatty acids into the oil matrix, and the formation of fatty acid crystal networks. Shear action also induced some delamination of the clay platelets. / Thesis (PhD(Eng))--University of Pretoria, 2012. / Chemical Engineering / unrestricted

Surfactant-mediated intercalation of aliphatic fatty acids into a commercial,layered double hydroxide (LDH) with the approximate composition of [Mg0.689Al0.311(OH2)] (CO3)0.1569nH2O was explored. The reactions were conducted at elevated temperatures with the LDH powder suspended in a fatty acid oil-water emulsion. The acidic fatty acid, e.g. stearic acid, reacts with the basic carbonate anions from LDH-CO3. In the process, CO2 is released as a gas and the fatty acids are intercalated as a bilayer. A high concentration of anionic or non-ionic surfactants, i.e. sodium dodecylsulphate or Tween 60, facilitates the intercalation process by emulsifying the molten fatty acids and dispersing the LDH particles. The presence of carboxylate anions in the interlayer region was confirmed by the carboxylate absorption peaks observed in the region 1700–1000 cm-1 on Fouriertransform infrared spectroscopy (FT-IR). Several bands were observed, i.e. ionised and non-ionised. An increase in the d-spacing of the d003 plane of the brucite-like LDH layers was observed on X-ray diffraction (XRD) analysis of all the LDH intercalates. The d-spacing increased linearly with the length of the carboxylic acid chain. Sharp reflection peaks were obtained on XRD, showing the high crystallinity of the LDH intercalates. The thermal decomposition of these materials was explored on thermogravimetric or differential thermogravimetric analysis (TGA/DTA) and temperature-scanned XRD. The mole ratio of Mg to Al was obtained by XRF and the morphology by scanning electron microscopy (SEM). The present method works well with long-chain aliphatic fatty acids at temperatures above or at the melting point of the desired acid. Temperature proved to be the most important parameter to control during the preparation process, i.e. at low temperatures incomplete reactions were obtained. The method is convenient, economical and environmentally friendly. It employs the readily available carbonate form of LDH as a starting reagent, water is used as medium rather than organic solvents, there are no high-temperature calcinations, and an inert atmosphere is not required. Copyright / Dissertation (MSc)--University of Pretoria, 2008. / Chemistry / unrestricted

No / Most cancer cells use aerobic glycolysis to fuel their growth. The enzyme lactate dehydrogenase-A (LDH-A) is key to cancer’s glycolytic phenotype, catalysing the regeneration of nicotinamide adenine dinucleotide (NAD+) from reduced nicotinamide adenine dinucleotide (NADH) necessary to sustain glycolysis. As such, LDH-A is a promising target for anticancer therapy. Here we ask if the tumour suppressor p53, a major regulator of cellular metabolism, influences the response of cancer cells to LDH-A suppression. LDH-A knockdown by RNA interference (RNAi) induced cancer cell death in p53 wild-type, mutant and p53-null human cancer cell lines, indicating that endogenous LDH-A promotes cancer cell survival irrespective of cancer cell p53 status. Unexpectedly, however, we uncovered a novel role for p53 in the regulation of cancer cell NAD+ and its reduced form NADH. Thus, LDH-A silencing by RNAi, or its inhibition using a small-molecule inhibitor, resulted in a p53-dependent increase in the cancer cell ratio of NADH:NAD+. This effect was specific for p53+/+ cancer cells and correlated with (i) reduced activity of NAD+-dependent deacetylase sirtuin 1 (SIRT1) and (ii) an increase in acetylated p53, a known target of SIRT1 deacetylation activity. In addition, activation of the redox-sensitive anticancer drug EO9 was enhanced selectively in p53+/+ cancer cells, attributable to increased activity of NAD(P)H-dependent oxidoreductase NQO1 (NAD(P)H quinone oxidoreductase 1). Suppressing LDH-A increased EO9-induced DNA damage in p53+/+ cancer cells, but importantly had no additive effect in non-cancer cells. Our results identify a unique strategy by which the NADH/NAD+ cellular redox status can be modulated in a cancer-specific, p53-dependent manner and we show that this can impact upon the activity of important NAD(H)-dependent enzymes. To summarise, this work indicates two distinct mechanisms by which suppressing LDH-A could potentially be used to kill cancer cells selectively, (i) through induction of apoptosis, irrespective of cancer cell p53 status and (ii) as a part of a combinatorial approach with redox-sensitive anticancer drugs via a novel p53/NAD(H)-dependent mechanism.

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