Echogenic liposomes for ultrasound-triggered drug delivery
- Authors: Izuchukwu, Ezekiel Charles
- Date: 2021-10
- Subjects: Liposomes , Drug delivery systems , Colon (Anatomy) Cancer Treatment , Transmission electron microscopy , Fourier transform infrared spectroscopy , Liquid chromatography , Echogenic liposomes , Ultrasound-triggered drug delivery
- Language: English
- Type: Masters theses , text
- Identifier: http://hdl.handle.net/10962/188997 , vital:44805
- Description: Colorectal cancer is one of common cancers worldwide. It is the third most diagnosed cancer and the second leading cause of death. The use of 5-fluorouracil (5-FU) alone or in a chemotherapy regime has been the effective treatment of colorectal cancer patients. The efficacy of 5-FU in colorectal cancer treatment is significantly limited by drug resistance, gastrointestinal, and bone marrow toxicity through high-level expression of thymidylate synthase, justifying a need to improve its therapeutic index. Liposomes are colloidal membranes comprising of one or more lipid bilayers enclosing an aqueous core. They have been used to improve the therapeutic index of many anti-cancer drugs by changing drug absorption, elongating biological half-life, reducing metabolism, and reducing toxicity to healthy tissues. Echogenic liposomes are specifically designed to respond to external triggering like ultrasound stimulation by entrapping a gas or an emulsion that can vaporize. A liposome's unique property is that it can entrap both hydrophobic and hydrophilic substances simultaneously in the lipid bilayer and the aqueous core, respectively. These stimuli-responsive liposomes can be triggered externally with ultrasound, to release the chemotherapeutic cargo only at the required site. This research aims to formulate echogenic liposomes encapsulating 5-FU for potential ultrasound triggered release (echogenic). Liposome formulations wereprepared with lipid composition of crude soybean lecithin and cholesterol by thin-filmhydration method and the drug was passively loaded in the formulation. The 5-FU loadedliposomes were evaluated by dynamic light scattering (DLS) for particle size, polydispersityindex, and zeta potential and transmission electron microscopy (TEM) for morphology.Encapsulated liposomal formulations were also evaluated using physicochemical techniquesincluding thermogravimetric analysis (TGA), differential scanning calorimetry (DSC),Fourier-transform infrared spectroscopy (FTIR), and X-ray diffraction (XRD). Theencapsulation efficiency and release kinetics were studied using a validated high-performanceliquid chromatography (HPLC) method. Echogenic properties were explored by entrapping abiocompatible gas (argon) at the same time as the drug (5-FU) using a pressure/freezemethodology. The liposomal formulations were typically spherical with a size of about 150 nmand encapsulation efficiency of 62%. Low-frequency ultrasound (20 kHz) was used to triggerthe drug release from the complete formulation at 10%, 15%, and 20% amplitude and exposuretime of 5 min and 10 min. The rate of drug release from the nano-carrier was a function of theultrasound amplitude and exposure time and reached a maximum of 65% release under theconditions investigated. The cumulative release was investigated, with and without theapplication of ultrasound. It was demonstrated that the application of ultrasound resulted in complete release (99%) after 12 h while this dropped to 70% without ultrasound. These results are encouraging for optimizing ultrasound parameters for triggered and controlled release of the 5-FU, for conditions such as the management of cancer where low-power ultrasound can be applied. , Thesis (MSc) -- Faculty of Science, Chemistry, 2021
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Nurturing an identity of land custodianship of young people through a biodiversity learning programme: The Moletele Youth Learning Programme
- Authors: Mponwana, William Oupa
- Date: 2021-10
- Subjects: Sustainable biodiversity South Africa Mopani District Municipality , Association for Water and Rural Development (South Africa) , Land reform beneficiaries South Africa Mopani District Municipality , Agricultural development projects South Africa Mopani District Municipality , Land use Study and teaching South Africa Mopani District Municipality , Identity (Psychology) Social aspects South Africa Mopani District Municipality , Identity (Psychology) in youth South Africa Mopani District Municipality , Moletele Youth Learning Programme , Moletele Communal Property Association (CPA) , RESILIM-O
- Language: English
- Type: Masters theses , text
- Identifier: http://hdl.handle.net/10962/188820 , vital:44789
- Description: This study was an exploration of value creation through scaffolding in a context specific learning programme with young people within the Moletele Communal Property Association (CPA) who own land through the land reform programme in South Africa. The study aimed to support the development the identity of land custodianship amongst young people by developing their skills and competencies in a situated learning context. The study also informed ongoing support work through the RESILIM-O resilience building project implemented by the Association for Water and Rural Development (AWARD) to help the Moletele Community Property Association to better understand the implications of biodiversity and land use for developing sustainable beneficiation projects and planning. A case study approach was adopted through a learning programme with young people as an in-depth exploration of the complexities of land and biodiversity. Data were collected during sessions in the learning programme where we used a spiral framework to facilitate learning focusing on four themes for primary data: knowledge competence, technical skills, self-organization and collective agency which are linked to building an identity of custodianship. Semi structured interviews were conducted at the end of the learning programme as a secondary data source. The study found that scaffolding remained an important process throughout the learning programme, and different types of scaffolding was needed to support the learning processes and themes. Furthermore, different types of value were created over time through the interactions and activities of the learning programme. The study also found that young people have a desire to participate in their communal property association. Lastly the study revealed that building custodianship as an identity is a continuous, long term process that needs commitment of time, resources and supportive learning processes, for an identity of custodianship to emerge. , Thesis (MEd) -- Faculty of Education, Education, 2021
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Physiological winners and losers in an ocean warming hotspot: a Case study on argyrosomus off the Namibian coast, with implications for their future management
- Authors: Pringle, Brett Andrew
- Date: 2021-10
- Subjects: Argyrosomus Benguela Current , Ocean temperature Benguela Current , Sciaenidae Benguela Current , Argyrosomus Physiology Benguela Current , Argyrosomus Geographical distribution Climatic factors Benguela Current , Argyrosomus Effect of temperature on Benguela Current , Sciaenidae fisheries Namibia , Fishery management Namibia , Sustainable fisheries Namibia
- Language: English
- Type: Masters theses , text
- Identifier: http://hdl.handle.net/10962/188987 , vital:44804
- Description: Anthropogenic-induced climate change is having a profound impact on aquatic ecosystems, and the resilience of fish populations will be determined by how they respond to these impacts. Changes in ocean water temperature is regarded as the most pervasive change, and affects the biological, physiological and distribution response of species, particularly ectotherms. The increasingly variable biological responses to a changing environment suggest that some species and populations will likely prove to be more tolerant than others. The northern Namibian coast is an ocean warming hotspot, with temperatures rising at approximately ten times the global average. These rapid changes are predicted to have a considerable impact on the marine fauna. One recently documented change in distribution is a southern extension of the sciaenid, Argyrosomus coronus, from southern Angola into northern Namibian waters, where it now overlaps with the closely related Namibian species, Argyrosomus inodorus. Understanding how these species perform at current and future temperatures and where they overlap is vital to optimise any adaptive management for the Argyrosomus species, which forms a large component of Namibia’s coastal commercial, recreational and subsistence fisheries. The aim of this study was to quantify the aerobic scope of both species (A. coronus and A. inodorus), to determine which Argyrosomus species will be a winner at the current and future climate predictions and to provide recommendations for the sustainable management of the Namibian Argyrosomus fishery. Intermittent flow-through respirometry was used to quantify standard and maximum metabolic rates for both species across a range of temperatures. Results showed that metabolic rates scaled positively with temperature. It appears that the aerobic scope of A. inodorus was notably higher at most temperatures (12, 15, 18 and 21˚C), while that of A. coronus was only higher at the warmest test temperature of 24˚C. This corresponded with the contemporary biogeographic patterns of each species. Based on these findings, it is likely that the warming ocean conditions in northern Namibia and the cold Lüdertiz upwelling cell south of Walvis Bay will constrain these fish to central Namibia. While both species demonstrated signs of resilience to high temperatures, it is likely that the warming conditions will increasingly favour A. coronus, and that the leading edge of their distribution will shift southward in Namibia. The distribution of A. inodorus is likely to contract, as the energy budget of those on the northern trailing edge will be compromised. To promote the sustainable utilisation of the complex Argyrosomus fishery, adaptive management strategies need to be implemented. This will only be possible with a comprehensive monitoring program, including the collection of genetic data to inform the changing proportions of the two species. To maintain the A. coronus population, the current regulations need to be re-assessed, and harvest slots should be introduced to protect juvenile A. coronus and the fecund large females of both species. , Thesis (MSc) -- Faculty of Science, Ichthyology and Fisheries, 2021
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Potential Synergism between Entomopathogenic Fungi and Entomopathogenic Nematodes for the control of false codling moth (Thaumatotibia leucotreta)
- Authors: Prinsloo, Samantha Lee
- Date: 2021-10
- Subjects: Cryptophlebia leucotreta , Entomopathogenic fungi , Insect nematodes , Citrus Diseases and pests , Cryptophlebia leucotreta Biological control , Pests Integrated control , Biological pest control agents
- Language: English
- Type: Masters theses , text
- Identifier: http://hdl.handle.net/10962/188832 , vital:44790
- Description: False codling moth, Thaumatotibia leucotreta (Meyrick) (Lepidoptera: Tortricidae) (FCM), is a major phytosanitary pest of citrus in South Africa. Sufficient control measures for the soil-dwelling life stages of FCM have yet to be identified and owing to restrictions on the use of insecticides, non-chemical control options have been investigated including the use of entomopathogenic fungi (EPF) and entomopathogenic nematodes (EPN). Laboratory and field trials on an indigenous EPF, Metarhizium anisopliae FCM Ar 23 B3, have shown that this isolate is capable of inducing mortality in FCM soil-dwelling life stages. Other agents that have been highlighted as potential controls for soil-dwelling FCM life stages are the EPN species Steinernema yirgalemense 157-C, S. jeffreyense J194 and H. noenieputensis 158-C. This study conducted laboratory bioassays to assess the virulence of these four control agents on fifth instar FCM, in 24-well plates. These results reaffirmed the virulence of the four microbial control agents at their recommended doses of 50 IJs (EPN) and 1×107 conidia/ml (EPF) against fifth instar FCM with 80 to 96% larval mortality recorded. The EPF isolate exhibited the lowest mortality whilst S. yirgalemense induced the greatest mortality. In addition, the lethal concentration (LC) values for each isolate were determined using dose response bioassays. These values were previously unknown for all EPN species and for the EPF isolate based on the methodology used in this study. The LC50 results in order from lowest to highest EPN IJ concentration requirements were 4.38 IJs (S. yirgalemense), 4.47 IJs (S. jeffreyense) and 7.11 IJs (H. noenieputensis). The EPF isolate exhibited an LC50 of 3.42×105 conidia/ml. Lastly, research has shown that the combination of two control agents may increase control of late instar lepidopteran and coleopteran larvae, through synergistic interactions. Thus, the interactions that occurred between the combination of these EPN species with the EPF isolate were determined. This study found that when all three EPN species were combined simultaneously and sequentially with the EPF isolate M. anisopliae FCM AR 23 B3, additive interactions took place with exception of the simultaneous application of S. yirgalemense and H. noenieputensis, with the EPF and S. jeffreyense applied 24 h post EPF application. For the former, a synergistic interaction was found, whilst for the latter two, an antagonistic interaction. Although no strongly synergistic interactions were observed, additive interactions have been shown to reach a synergistic level when certain parameters are changed. Moving forward, a uniform methodology for conducting EPF/EPN interaction experiments has been suggested. It has also been recommended that due to the additive interactions observed in this study, laboratory soil-bioassays and field trials should be carried out for all three EPN species in combination with the EPF isolate. This research will inevitably facilitate the constant knowledge into management strategies for the phytosanitary pest, FCM in South African citrus. , Thesis (MSc) -- Science, Zoology and Entomology, 2021
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Quantifying the ecological and socioeconomic implications of a recovery/collapse of South Africa’s West Coast rock lobster fishery
- Authors: Eggers, Jessica Marguerite
- Date: 2021-10
- Subjects: Jasus lalandii South Africa , Lobster fisheries South Africa , Lobster fisheries Catch effort South Africa , Fishery management South Africa , Small-scale fisheries South Africa , Economics Sociological aspects , Value chain analysis
- Language: English
- Type: Masters theses , text
- Identifier: http://hdl.handle.net/10962/188854 , vital:44792
- Description: The West Coast rock lobster (WCRL) Jasus lalandii fishery is South Africa’s third most valuable fishery, but the stock is currently at less than 2% of its pristine biomass. Scientists are warning that if no measures are taken, the WCRL could face commercial extinction. The necessary reductions in the global Total allowable Catch (TAC) seen in past years have had large economic implications for the WCRL value chain, but research into the socio-economic aspects of this fishery is limited. This study, therefore, aims to establish an overview of the economic revenue over the seasons 2016/17 – 2018/19 by exploring changes and trends in the net seasonal income (NSI) for the fishery, sectors within the fishery and different stakeholders. It also investigates the prospects for the sectors and different actors in this fishery over the seasons 2019/2020 - 2030/31 through analysis of the net present value (NPV) under three proposed global TAC management scenarios (global TAC of 640 tonnes, 1084 tonnes and 1280 tonnes). Data concerning costs and incomes as well as dynamics, mechanisms and concerns surrounding the fishery were collected from stakeholders in the different sectors through interviews and surveys. Further, official records from DEFF (catches, actors, vessels and quotas) and projections made by the Marine Resource Assessment (MARAM) team at the University of Cape Town (rates of recovery of the resource and future catches under the different TAC scenarios) were obtained and analysed. Cost and income data were summarised and models characterising the economic flows within the fishery were created. Calculations regarding the NSI and NPV were made using Monte Carlo simulations to account for the uncertainty surrounding many of the input variables. Results show that while the fishery as a whole made economic profits for the three seasons, the decreasing quotas in 2018/19 had a disproportionately negative impact on some of the representative individuals examined within the different sectors. The projections indicate that while each of the sectors as a whole would continue to make profits largely proportional to their allocation under the different TAC scenarios, many vessel owners in the fishery are likely to face economic losses or very marginal gains under the lower quota options, while the NPV for quota holders who outsource the catching of their quota are likely to be proportionally less affected by the changes in global TAC. This dynamic is important to consider for the future of this fishery. If the resource is to recover, and fishing activity is to continue equitably under the decreased quotas that the recovery of the biomass necessitates, the socio-economic context and the dynamics within which the fishers operate must be considered and studied more extensively and socio-economic consequences of a lower global TAC mitigated while improving the ecological status of the resource. , Thesis (MSc) -- Faculty of Science, Ichthyology and Fisheries Science, 2021
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The factors to be considered by the competition authorities when a fine may cause the firm to exit
- Authors: Quilliam, Layne Edwin
- Date: 2021-10
- Subjects: South Africa. Competition Act, 1998 , Competition Tribunal (South Africa) , Business enterprises Law and legislation South Africa , Debt-to-equity ratio South Africa , Bankruptcy Prevention , Causation , Competition
- Language: English
- Type: Masters theses , text
- Identifier: http://hdl.handle.net/10962/188408 , vital:44751
- Description: The Competition Act empowers the Competition Tribunal to levy fines against a firm for certain contraventions of the Act. Such fines are statutorily capped to prevent the fine from causing the firm’s exit. This maximum is based on the overarching principle of fairness which precludes a fine, on its own, from destroying a firm’s business. However, the Competition Appeal Court acknowledged in 2013 that fines below this cap may still cause a firm to exit. The purpose of this paper is to propose the factors that should be considered when determining a firm’s ability to pay such a below-cap fine. These factors are the calculation of the fine, probable exit, causation of exit and the competitive effect of the firm’s exit. The fining provisions of the Act are initially explored to provide context for the discussion and are then compared to equivalent provisions in Europe. Liquidation and business rescue proceedings are then described as the most common forms of a firm’s exit from the market. Methods for determining the causal relationship between the fine and the firm’s exit are explored through delictual law’s factual and legal causation. The competitive effects of the firm’s exit are premised on the purpose of the Competition Act and are evaluated through the Competition Act’s merger provisions, specifically, the failing firm factor. These proposed factors are then tested through hypothetical facts to analyse their possible interactions and efficacy. , Thesis (LLM) -- Faculty of Law, Law, 2021
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The synthesis and characterisation of Sn(IV) porphyrin derivatives and their potential application in anti-cancer and antimicrobial photodynamic therapy
- Authors: Dingiswayo, Somila
- Date: 2021-10
- Subjects: Porphyrins , Photochemotherapy , Cancer Photochemotherapy , Active oxygen Physiological effect , Aromaticity (Chemistry) , Tetrapyrroles , Magnetic circular dichroism , Corroles , Chlorins , Photodynamic antimicrobial chemotherapy (PACT)
- Language: English
- Type: Masters theses , text
- Identifier: http://hdl.handle.net/10962/188843 , vital:44791
- Description: In photodynamic therapy (PDT), the activation of light-sensitive drugs in tumour cells produces reactive singlet oxygen species, which cause tumour destruction through a cascade of biochemical reactions. Over the years, the wavelength of activation has been shown to be a critical factor in the penetration of light. Hence the properties of photosensitiser dyes in this context shape their ability to treat deep-seated tumours. In this study, the synthesis, structural characterisation and photophysicochemical properties of a series of Sn(IV) porphyrins with meso-methylthiophenyl rings that have been prepared to study their PDT and photodynamic antimicrobial chemotherapy (PACT) activity properties are reported. The series of Sn(IV) complexes is comprised of a porphyrin (1-Sn), a corrole (2-Sn), a chlorin (3-Sn) and an N-confused porphyrin (4-Sn). Herein, the low symmetry Sn(IV) porphyrin derivatives are shown to have excellent singlet oxygen generation capabilities, and lifetimes of the triplet excited states were in the microsecond range. For example, 4-Sn had a singlet oxygen quantum yield (ФΔ) and an excited triplet state lifetime (τT) of 0.88 and 27 μs, respectively. The complexes were studied using UV-visible and magnetic circular dichroism (MCD) spectroscopies. Interestingly, the positive-to-negative sign sequences of the Faraday B0 terms of 2-Sn and 3-Sn reveal that the structural modifications involved break the degeneracy of the MOs derived from the 1eg* LUMO of the porphyrin 1-Sn. In contrast, a conventional negative-to-positive sign sequence is observed for 4-Sn, since the confusion of a pyrrole moiety also results in a large separation of the 1a1u and 1a2u MOs of the porphyrin 1-Sn that are derived from the HOMO of a C16H162−parent hydrocarbon perimeter. The trends in the electronic structures of the Sn(IV) complexes were further investigated through a series of time-dependent density functional theory calculations, so that the suitability of the different types of complex for use in singlet oxygen applications could be further explored. During in vitro photodynamic antimicrobial chemotherapy (PACT) studies, chlorin derivative 3-Sn had the highest activity towards S. aureus and E. coli with log10 reductions of 10.5 and 8.74, respectively. The unusually high activity of 3-Sn against E.coli suggests that the interaction of neutral photosensitisers with gram-negativebacteria is more complex than previously understood. Anti-cancer PDT studies demonstrated that the photosensitisers had negligible dark cytotoxicity. Upon photoirradiation, the Sn(IV) complexes consistently exhibited IC50 values lower than 15 μM against MCF-7 adenocarcinoma cells. An IC50 value of 1.4 μM for 4-Sn after activation at the deep-red region of the spectrum demonstrates that complexes of this type merit further in-depth investigation. The results provide evidence that the low-symmetry Sn(IV) chlorins and N-confused porphyrins merit further in-depth study for use in singlet oxygen applications. , Thesis (MSc) -- Faculty of Science, Chemistry, 2021
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Towards Reconfiguring the Agricultural Expert System (AES) for Black Small to Medium Farmer Development for Commercialization: A progressively focused policy literature review and social learning dialogue in the Eastern Cape Raymond Mhlaba Local Municipality
- Authors: Maqwelane, Lwanda
- Date: 2021-10
- Subjects: Farms, Small South Africa Amathole District Municipality , Minority farmers , Public-private sector cooperation South Africa Amathole District Municipality , Social learning South Africa Amathole District Municipality , Agricultural expert system (AES) , Black small to medium farmers (BSMF)
- Language: English
- Type: Masters theses , text
- Identifier: http://hdl.handle.net/10962/188876 , vital:44794
- Description: This study focuses on the agricultural expert system (AES), its inherited and potential reframing capabilities for the development, growth and transition of black small to medium farmers (BSMF) into the commercial sector. The study was conducted as a critical analytical policy review of implemented policies pre-and post 1994 that subsequently highlighted the thematic continuities and discontinuities of policy reform and the subsequent impact on BSMFs using the AES as a conceptual lens. The study aimed working with stakeholders in the AES in the Raymond Mhlaba Local Municipality as a case study to critically engage and question the AES and its contemporary framing and potential reframing and continued impact on the BSMFs development. This was conducted through a dialogical social learning process in partnership with diverse voices that cut across the contemporary agrarian landscape that included “universities, think tanks, vocational training providers, standards-setting agencies, trade associations that provide specialized training, education, information, research and technical support” (Porter, 2000, p.17). The data for the social learning dialogue process was generated through an iterative analysis of dialogical social learning workshops, focus groups and semi-structured interviews. The analysis focused on the framing (Chapters 2, 3, and 5) and reframing of the AES (Chapter 6). Through dynamic engagement within the knowledge hub (contextual social learning and literature), the study surfaces a potential alternative discourse that actively includes the BSMFs as a crucial component of the commercial sector AES as the analysis shows these are largely excluded. This alternative discourse occurred through dialogical interactions with all participants via a pro-actively constituted social learning process, enriched and deepened by literature as indicated above. Main recommendations of the study are: 1. The AES must be framed to address the holistic value chain of BSMFs to help address underlying policy dualism, 2. Public Private Partnerships are needed to support BSMFs development and these should adopt a social learning approach that is reflective of complex realities 3. There is need for better understanding of roles and contributions of stakeholders in the AES to avoid duplications. , Thesis (MEd) -- Faculty of Education, Education, 2021
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