>Magister Scientiae - MSc / Nanotechnology has emerged as a promising field in the quest to address health conditions. Green nanotechnology is a fairly new branch of nanotechnology, which aims to produce and utilize nanomaterials in a way that is safe for living organisms and their environment. Plant extracts are increasingly used in the green synthesis of gold nanoparticles (AuNPs), which involves the reduction of sodium tetrachloroaurate (III) dehydrate by phytochemicals present in the plant extract. It is probable that the green synthesised AuNPs are more biocompatible than chemically synthesised AuNPs as biomolecules of plant origin are involved in the synthesis process. Therefore, this study aimed to explore various water extracts from indigenous South African plants, which included Perlagonium capitatum, Otholobium bracteolatum, Gerbera linnae, Morrella quercifolia, Searsia lucida, Phylica bubescens, Euclea racemosa, Tetragonia fruticosa, and Searsia glauca for their potential to synthesize AuNPs and to investigate their toxicity towards several microorganisms known to cause skin infections. These organisms play a significant role in delaying the healing of wounds. The antimicrobial properties of nanoparticles are increasing exploited in the production of wound treatments.

Pulverizações foliares são amplamente utilizadas para evitar ou reverter sintomas de deficiência de manganês (Mn). A demanda por fertilizantes com maior eficiência de utilização dos nutrientes introduziu novas tecnologias às fontes utilizadas, com destaque para os nanomateriais. Fontes insolúveis em água (suspensão concentrada) são comercializadas sob o argumento de liberação gradual, com efeito prolongado de fornecimento do nutriente à planta. Contudo, o aproveitamento pelas plantas é em grande parte ainda desconhecido. Perante essa problemática, o objetivo dessa pesquisa foi comprovar a eficiência da aplicação foliar de fontes insolúveis para o fornecimento de Mn em plantas de soja; avaliando seu efeito na absorção, transporte e redistribuição do Mn, nos componentes de produção, produtividade e metabolismo da soja, comparado a uma fonte solúvel de Mn. Dois experimentos foram conduzidos em campo nas safras 2015/2016 e 2016/2017 e outros dois em casa de vegetação utilizando solos de diferentes texturas. Os tratamentos foram compostos pelas fontes de Mn (Carbonato e Sulfato); quatro doses (150, 250, 350 e 450 g ha-1) e um controle (sem Mn), aplicados via foliar no estádio V4. Outros dois experimentos foram desenvolvidos em câmara de crescimento sob condições controladas em solução nutritiva. Os tratamentos foram compostos por duas fontes insolúveis (MnCO3-nano, 80-100 nm e MnCO3-suspensão concentrada) e uma fonte solúvel (MnSO4), comparados a um controle positivo (Mn-Adequado) e a um controle negativo (Mn-Baixo). No primeiro experimento, o primeiro trifólio totalmente expandido foi imerso nos tratamentos por 10 segundos duas vezes por dia, durante 4 dias. No segundo experimento, as aplicações foliares foram realizadas no estádio V5 pulverizando os tratamentos em toda a parte aérea. Nos experimentos em campo as fontes de Mn e as doses não proporcionaram incrementos de produtividade, apesar do teor de Mn nos trifólios ser maior nas plantas que receberam aplicação de MnSO4 em comparação ao MnCO3. Em casa de vegetação a textura do solo não influenciou a resposta da soja à aplicação foliar de Mn. As plantas que receberam aplicação de MnSO4 apresentaram maiores teores nos trifólios. Em câmera de crescimento, as folhas de soja foram capazes de absorver e transportar o Mn proveniente das fontes MnSO4, MnCO3-nano e MnCO3-SC. O MnSO4 foi absorvido e transportado em maiores quantidades pelas plantas de soja, sua aplicação atenuou os sintomas visuais de deficiência de Mn, promoveu aumento na concentração de clorofila e carboidratos solúveis e reduziu a atividade da enzima guaiacol peroxidase, amenizando os efeitos do estresse oxidativo ocasionado pela deficiência de Mn nas plantas de soja. Os resultados indicam que fontes insolúveis de Mn tem baixa capacidade de absorção foliar e transporte, não alterando o metabolismo da soja quando comparado a fonte solúvel. / Foliar application is widely used to prevent or reverse symptoms of manganese (Mn) deficiency. Demand for fertilizers with greater use efficiency of nutrients introduced new technologies to used sources, with emphasis on nanomaterials. Water-insoluble sources (concentrated suspension) are marketed under the argument of gradual release, with prolonged effect of supplying the nutrient to the plant. However, the use by plants is largely remains unknown. Faced with this problem, the objective was to prove the efficiency of foliar application of insoluble sources for Mn supply in soybean plants; evaluating the effect on the absorption, transport and redistribution of Mn on soybean production components, yield and metabolism, compared to a soluble source of Mn. Two field experiments were conducted during 2015/2016 and 2016/2017 crop seasons and others two experiments in greenhouse using soils of different textures. The treatments were composed of the sources of Mn (Carbonate and Sulfate); four rates (150, 250, 350 and 450 g ha-1) and one control (without Mn), applied in the V4 stage. Two other experiments were carried out in a growth chamber under controlled conditions in nutrient solution. The treatments were composed for two insoluble sources (MnCO3-nano, 80-100 nm and MnCO3-concentrated suspension) and a soluble source (MnSO4), compared to a positive control (Mn-Adequate) and a negative control. In the first experiment, the first fully expanded trifoliate leaflet was immersed in the treatments for 10 seconds twice a day for 4 days. In the second experiment, the foliar applications were carried out in the V5 stage, spraying the treatments in all shoot part. In the field experiments the Mn sources and the rates did not provide yield increases, although Mn content in trifoliate leaflets was higher in the plants that received MnSO4 application comparing to MnCO3. In greenhouse the soil texture did influence the soybean response to Mn foliar application. Plants that received MnSO4 application had higher trifoliate leaflets levels of Mn. In a growth chamber, soybean leaves were able to absorb and transport Mn present in MnSO4, MnCO3-nano and MnCO3-SC. MnSO4 was better absorbed and transported by soybean plants, its application attenuated the visual symptoms of Mn deficiency, increased chlorophyll concentration, soluble carbohydrates and reduced the guaiacol peroxidase activity, dropping the effects of oxidative stress caused by Mn deficiency in soybean plants. The results indicate that insoluble sources of Mn have low foliar absorption and transport capacity, not altering the soybean metabolism when compared to soluble source.

Magister Scientiae (Medical Bioscience) - MSc(MBS) / Graphene oxide (GO) is a single carbon layer, oxygen bearing graphene derivative, containing hydroxyl and carboxyl groups. Graphene oxide nanoparticles (GONPs) are promising nanomaterials for a variety of applications such as electrochemical analysis, adsorption of biomolecules, biosensors and drug and vaccine delivery systems. While these newly engineered nanoparticles hold great potential for developments in industry and medicine, the widespread use of these material will inevitably result in GO residues in the environment where they could possibly pose a risk to human and wildlife health. Interaction of the nanoparticles and biota can affect numerous biological processes. In humans they can affect any of the physiological systems such as the immune, endocrine, reproductive and cardiovascular systems. Although studies have indicated that GO exposure cause increased reactive oxygen species in cells, they mechanisms whereby GO act on the cell are still poorly understood. A few studies have investigated the effects of GONP and other graphene nanoparticle derivatives on the immune system. The aim of this study was to investigate the in vitro effects of GONPs on the immune system by the exposure of the murine macrophage cell line, RAW 264.7, to different concentrations of GONPs.

Cette thèse visait à développer des techniques d'ablation au laser et de fragmentation dans des liquides pour la synthèse de nouveaux NPs ayant des fonctionnalités utiles. L’approche de la thèse est axée sur l’élaboration de la technique ablative au laser pour la synthèse de matériaux conventionnels avec des paramètres pour des applications biomédicales sélectionnées, ainsi que sur le développement de cette technique pour la synthèse de nouveaux nanomatériaux destinés à des applications biomédicales. En particulier, il comprend:1. Nous avons élaboré un régime de fragmentation laser fs à partir de colloïdes de Si pour la synthèse de NPs de Si ayant une taille, une cristallinité et un état d'oxydation contrôlables.Nous avons testé un certain nombre d’applications biomédiales particulières de Si Si préparés de cette manière.2. Nous avons développé une technique d'ablation et de fragmentation au laser fs pour fabriquer des noyaux Au NPs et des carottes en Au-Si nus pour SERSapplications. Une approche est basée sur l'ablation au laser de la cible Au dans une solution colloïdale de NP Si.3. Pour la première fois, nous avons synthétisé de nouveaux NP plasmoniques à base de nitrure de titane. Nous avons également montré qu’une étape supplémentaire de fragmentation du laser fs entraînait une diminution de la taille des NP à 5 nm. En outre, nous avons constaté que ces NP ont un très large pic d'extinction dans le proche IR.4. Pour la première fois, nous avons démontré la synthèse de NPs organiques fluorescentes d'un luminophore à émission induite par agrégation spécialement conçu (AIE LP). La luminosité de ces NP a été jugée comparable à celle des points quantiques. / This thesis as aimed at the development of techniques of fs laser ablation and fragmentation in liquids for the synthesis of novel NPs having useful functionalities. The approach of the thesis is focused on the elaboration of the laser ablative technique for the synthesis of conventional materials with parameters for selected biomedical applications, as well as the development of this technique for the synthesis of novel nanomaterials for biomedical applications. In particular it includes:1. We elaborated a regime of fs laser fragmentation from Si colloids for the synthesis of Si NPs having controllable size, crystallinity and oxidation state. We tested so-prepared Si NPs a number of particular biomedial applications.2. We elaborated a technique of fs laser ablation and fragmentation to fabricate bare Au NPs and Au-Si core-shells for SERSapplications. One approache is based on laser ablation of Au target in colloidal solution of Si NPs. 3. For the first time we synthesized novel plasmonic NPs based on titanium nitride. We also showed that an additional fs laser fragmentation step leads to the decrease of NPs size to 5 nm. Besides, we found that such NPs have a very broad extinction peak in the near IR.4. For the first time we demonstrated the synthesis of fluorescent organic NPs of specially designed aggregation-induced emission luminophore (AIE LP). The brightness of such NPs was determined to be comparable to that of quantum dots.

>Magister Scientiae - MSc / Microfluidic paper based electrochemical sensing devices (μPEDs) provides a new way for point of care testing (POCT). μPEDs offer an inexpensive, portable, easy to use technology too monitor the environment and diagnose diseases, especially in developing countries in cases where there is not enough infrastructure and a limited trained medical and health professionals. The aim of this work is to develop a paper based electrode which can be further integrated into a microfluidic paper device to develop miniature point of care devices. Paper was used as a substrate for printing of the electrode because it is found everywhere, inexpensive and it is compatible with a number of chemical, biochemical and medical applications. Polyamic acid (PAA) was incorporated into commercial carbon ink and was used to print the working electrode. The first part of the study was conducted using the commercial screen printed carbon electrodes (SPCE) to study and understand the electrochemical behaviour of PAA. Cobalt nanoparticles and cobalt nanoparticles‐polyamic acid composites were electrochemically deposited onto SPCE. The modified electrodes were characterised using cyclic voltammetry. As synthesised polyamic acid were characterised using Scanning Electron Microscopy (SEM) to evaluate the morphology and chemical composition of polyamic acid. Transmission Electron Microscopy (TEM) was used to study the particle size and chemical composition of cobalt nanoparticles. Fourier Transform Infrared Spectroscopy (FTIR) was used to study the chemical nature of polyamic acid and cyclic voltammetry (CV) was used to study the electrochemical behaviour of polyamic acid and cobalt nanoparticle electrodes. The diffusion coefficients and formal potential of the electrodes were calculated. The modified and bare electrodes were also used to electrochemically detect Norfloxacin in an aqueous solution by CV and square wave voltammetry (SWV) and the analytical performance of the electrochemical systems are reported here. The obtained limit of detection for the bare SPCE was 3.7 x 10‐3 M and 14.7 x 10‐3 M for the PAA‐SPCE.

Highly dispersed gold nanoparticles on metal oxide surfaces have recently been reported to exhibit high catalytic activity for low-temperature carbon monoxide oxidation. Amongst the metal oxides, titanium dioxide, more often the commercial form Degussa P25, has been the most studied support for gold as a catalyst for CO oxidation because it yields some of the most active and stable catalysts. Physical and chemical modification of catalysts supports has been shown to affect their catalytic properties. In this research, modified gold supported catalysts have been prepared, characterized and tested for CO oxidation. Their properties have been compared with those of the unmodified catalysts. Catalysts containing1wt% Au supported on MxOy and TiO2/MxOy mixed oxide (M = Zn, Mg, Ni, Fe, Cr, Cu, Mn and Co; TiO2:MxOy mole ratio of 5:1; TiO2 = Degussa P25) were prepared by the single step borohydride reduction method and it was found that TiO2 gave the most superior activity as support for gold for CO oxidation, followed by TiO2/MxOy and the corresponding MxOy. The specific activities for CO oxidation of Au/TiO2 catalysts per unit of prepared in the range 0.05 to 1 wt% of Au indicates that for catalysts prepared by deposition precipitation, there is a significant decrease in specific activities with an increase with gold loading. For the single step borohydride reduction procedure, specific activities decrease less significantly with increasing gold content, implying that for economic and practical reasons, it would be advantageous to prepare gold catalysts with low gold loadings. Cyanide leaching of 1 wt% Au/TiO2 catalysts at different Au:CN- ratios, to selectively remove some of the gold in the catalysts, shows the activity per unit mass of gold to increases as more gold is removed from the catalyst. This is consistent with the idea that gold exists in more than one oxidation state in the systems and a significant fraction of the gold present in the catalysts do not contribute to catalytic activity. A number of anions and cations have been incorporated into TiO2 as support for gold catalysts and also into as-prepared Au/TiO2 catalysts at levels ranging from 0.05 mol% to 2.5 mol% with respect to the support. The activities of the catalysts for CO oxidation reveal that at the highest concentration levels of the ions, in all cases, a decrease in activity compared with unmodified Au/TiO2 is observed. However, addition of 0.05 to 0.4 mol% of the ions with respect to the support, prior to gold addition, in most cases, resulted in activity enhancement which increased with a decrease in the ion content. Similar addition of 0.05 to 0.4 mol% of the ions with respect to TiO2 to Au/TiO2 resulted in a decrease in activity. Attempts to understand the origins of these effects show that there is a degree of chemical interaction between the added ions and gold.

A thesis submitted to the Faculty of Science, University of the Witwatersrand, Johannesburg, in fulfilment of the requirements for the degree of Masters of Science. Johannesburg, 2016 / Gold nanoparticles are ideally suited as catalysts for selected low temperature reactions such as CO oxidation for catalytic convertors in the motor industry due to their high activity. But they are prone to sintering at high temperatures. Platinum-group-metal based catalysts are efficient at elevated temperatures and generally inactive at lower temperatures. This study explored the CO oxidation efficiency of gold nanoparticles and of a combination of gold and rhodium nanoparticles. Variables such as pH, loading concentration and type of support were varied to control the final properties of the Au based catalysts. Possible bimetallic systems of gold and rhodium were explored for wider temperature range activity than gold alone. All catalysts were characterised using Transmission Electron Microscopy (TEM), Energy Dispersive X-ray Spectroscopy (EDS) and X-Ray Diffraction (XRD). Activity was measured using a temperature controlled, custom-built reactor linked to a gas chromatograph. The conditions yielding the smallest gold nanoparticles were established by adding 5, 8 or 10 wt.% loadings of chloroauric acid to aqueous suspensions of either TiO2 or SiO2 at pH 5, 7 or 9 and at 70-75 °C over 60 minutes. Each preparation was sealed in parafilm, aged in the dark at room temperature for 3 days, vacuum-filtered and subsequently calcined at 300 °C. Gold nanoparticles were smallest when deposited onto TiO2 instead of SiO2, at pH 7 and at a loading of 5 wt. %. A combination of gold and rhodium catalysts were subsequently prepared using these conditions, with the simultaneous addition of rhodium at 1, 3, 5 or 10 wt. % loading. Hydrolysis of gold is highly dependent upon pH, resulting in the synthesis of smaller particles under alkaline conditions. Catalytic activity of samples analysed at 70 and 150 °C was highest for gold nanoparticles below 5 nm, in agreement with previous studies. In the proposed bimetallic catalysts, it was difficult to distinguish gold and rhodium nanoparticles in TEM images, although EDS confirmed their combined presence on the TiO2 support. Particle sizes remained below 5 nm, appearing monodispersed on the TiO2 support except at 10 % rhodium loading where some nanoparticle aggregation was observed. CO oxidation activity showed an apparent temperaturedependent shift in the optimal rhodium loading. Au-TiO2 catalysts with a 5% loading showed the highest activity up to 350 °C for a period of 10 hours and the catalyst deactivated due to sintering. At 150 and 200 °C the Au/Rh-TiO2 catalyst remained active for more than 12 hours. It was concluded that the inclusion of rhodium is a potentially-favourable method for stabilising the activity of gold catalysts.

<p>Many anti-cancer drugs are poorly water-soluble and show undesirable pharmacokinetics and low bioavailability. Nanoparticles (NP) are used as delivery vehicles to improve bioavailability and biodistribution of such drugs. For clinical translation of an NP product, it is critical that the NP carry a large amount of drug and maintain good stability during circulation. A typical drug loading capacity of current NP formulations is less than 20% of the total mass, which is concerning from the standpoint of safety and administration convenience. Current NP formulations are also limited in retaining a drug during circulation and release the drug prematurely before they reach target tissues. These challenges are responsible at least partly for recent failure of leading NP products in clinical trials. </p> Given these challenges, I have focused on developing a stable NP formulation with high drug loading capacity, drug-rich nanocores stabilized by interfacial assemblies of iron-tannic acid (pTA) and albumin. Tannic acid is a polyphenol of natural origin and can form coordination complexes with Fe³⁺ ions that stabilize the interface between drug rich core droplets and aqueous solution. The underlying hypotheses are that (i) NP core formed solely of drug will offer a high drug loading capacity and (ii) the strong interaction of TA with drug molecules will maintain the nanocore stability and avoid premature drug release. Carfilzomib (CFZ), an epoxyketone peptide and a second-generation proteasome inhibitor, the use of which is limited to multiple myeloma due to the low stability, was chosen as a model drug to encapsulate in the new NP formulation. The NP surface was further functionalized with albumin, quinic acid derivative and plasmid DNA based on their affinity for TA complex. With an additional albumin coating, CFZ nanocore (CFZ-pTA-alb) showed sustained drug release and metabolic stability. In murine syngeneic model of B16F10 melanoma, systemically administered CFZ-pTA-alb showed enhanced biodistribution and anti-tumor effect than commercial cyclodextrin-based CFZ (CFZ-CD). With localized intratumoral administration, CFZ-pTA-alb also outperformed CFZ-CD in antitumor efficacy, potentially by prolonged drug retention, reduced damage to tumor-infiltrating lymphocytes, and enhanced delivery of tumor antigens to DCs.

La squalénisation est une méthode de vectorisation sous forme nanoparticulaire qui consiste àcoupler de manière covalente un dérivé du squalène à des principes actifs hydrophiles tels que lesanalogues nucléosidiques. Les conjugués amphiphiles obtenus sont capables de s’auto-organiserspontanément dans l’eau en nanoparticules d’une centaine de nanomètres de diamètre etpossèdent des activités anticancéreuses ou antivirales remarquables. Notre objectif était d’étendrecette stratégie à différentes classes d’antitumoraux, comme les antimétabolites, les antimitotiqueset les agents alkylants. Différents dérivés du squalène ont ainsi été synthétisés puis couplés à cesprincipes actifs pour former les bioconjugués squalénisés correspondants. Il a été montré que cesprodrogues étaient capables de s’auto-assembler en nanoparticules spontanément en milieuaqueux, que le principe actif soit hydrophile ou hydrophobe. Les suspensions nanoparticulaires deces prodrogues se sont montrées actives in vitro sur différentes lignées cellulaires cancéreuseshumaines et murines et in vivo chez la Souris sur des modèles de cancer. La squalénisation a donc étéétendue à diverses familles de composés anticancéreux confirmant qu’il s’agit d’une méthodegénérale de vectorisation pourvue d’un fort potentiel thérapeutique. / Squalenoylation is a strategy of vectorization consisting in coupling squalene derivatives tohydrophylic drugs as nucleoside analogues. The amphiphilic conjugates obtained are able to selfassembleinto nanoparticles with a diameter of 100 nm in water. In addition those nanoparticleshave shown impressive anticancer and antiviral activities. Our objective was to extend this strategyto different anticancer drugs as antimetabolites, antimitotics and alkylating agents. Differentsqualenoyl derivatives have been synthesised and then coupled to drugs to furnish thecorresponding squalenoylated biconjugates. It has been shown that those prodrugs were able toself-assemble into nanoparticles in water. Nanoparticles of the bioconjugates are active in vitro ondifferent human cancer cell lines and in vivo in Mice on different cancer models. Squalenoylation hasfinally been extended to numerous anticancer drugs, proving that this strategy is a general methodof vectorization with a high therapeutic potential.

DNA-functionalized gold nanoparticles (DNA-NPs) have enormous potential as building blocks for materials due to their ability to specifically recognize and respond to target molecules and surfaces. The ability of DNA aptamers to adopt different conformations and bind either complementary DNA sequences or analyte molecules allows them to mediate nanoparticle assembly or disassembly, generating selective colorimetric responses. Aptamer-mediated nanoparticle assembly and disassembly is sensitive to the nanoparticle ligand shell composition and structure, yet these topics have not been extensively explored. In this dissertation, a method for determining the ligand shell composition of DNA-NPs is described and a framework for understanding the impact of the DNA assembly arrangement and recognition strand density upon aptamer-mediated nanoparticle assembly and disassembly is developed. Design rules for creating sensors with desired properties are elucidated, leading to creation of sensors with improved detection limits and quantification ranges. A technique was needed to determine the number of DNA strands of any base composition attached to gold nanoparticles (AuNPs) of any core size. A rapid, convenient and inexpensive method to quantify the number of label-free DNA strands attached to AuNPs was therefore developed. This technique was extended to determine two different DNA sequences bound to AuNPs using UV-visible and fluorescence spectroscopy. Based on the results of quantifying the ligand shells of DNA-NPs functionalized with two sequences, disulfide-terminated DNA non-specifically adsorbs and then rearranges to specifically bind the gold surface. The position of the AuNPs and DNA strands within DNA-NP assemblies had a profound influence on their ability to assemble and sense adenosine. Assemblies designed for large inter-AuNP spacing were stable but unable to sense adenosine. Assemblies designed for short inter-AuNP spacing were unstable until the DNA ligand shell was diluted. AuNPs functionalized with the fewest number of aptamers produced assemblies with the lowest detection limit and apparent disassociation constant and the largest analyte quantification range. Increasing the number of aptamer strands per AuNP increased the cooperativity of the AuNP disassembly response to adenosine. This dissertation includes previously unpublished co-authored material.