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Contributions of tourism based small, medium and micro sized enterprises (smmes) in generating employment within the proposed Durban aerotropolis.
(2023) Adegunloye, Ife Omotaye.; Wissink, Henry Frank.
The concept of Aerotropolis, whereby, cities grow around airport operations infrastructure is becoming more popular globally. This has significant impact in improving employment generation within the environment that embraces the concept. Airports have become important employers and centers for urban growth. An indication of employment opportunities within the airport environment reflect that Heathrow airport employs 76,500 people while Dubai Airport employs 90,000. Small, Medium and Micro Enterprises (SMMEs) are generally seen to be the main driver of growth of any economy. This study therefore investigated how the TB-SMMEs can be enhanced for employment creation within the Durban Aerotropolis. The study also investigated the factors hampering the growth of TB-SMMEs. A mixed methods approach was employed for the research. Interviews were conducted with members of Dube Trade Port and some members of the Durban Tourism Unit. Quantitative data was collected through structured questionnaires conducted among some SMMEs within the tourism sector through respondents employing probability sampling and participants for non- probability sampling. The sample size was 243 respondents, and both descriptive and inferential statistics were employed.
The data were presented with the utilization of tables, pie charts, and percentages. The Statistical Package for the Social Science (SPSS) - version 26, was used to analyse the quantitative data. Content analysis with the aid of triangulation of data was utilised to analyse the qualitative data gathered from interviews. The results indicate the financial gap within the TB-SMMEs, poor infrastructural amenities, lack of innovation for creative ideas, poor knowledge sharing, deficient of necessary skills and increased crime rates that can pose an hinderance to the growth of TB-SMMEs within the Durban Aerotropolis. The study therefore recommends the upgrade of infrastructure that will enhance the operations of the TB-SMMEs within the Durban Aerotropolis, improvement of required skills among the TB-SMMEs, accessibility to funds and the mitigation of crime in order to enhance their productivity. This will hopefully result in growth that can further generate employment opportunities within the Durban Aerotropolis. The research adds to the body of knowledge on South African SMMEs and points to the need for continued research, particularly in developing other areas that can aid employment generation through the Durban Aerotropolis.
Tricarbonyl rhenium(I) complexes with Schiff base chelates : bioinorganic chemistry to 186Re radiolabelling studies.
(2024) Mapapiro, Tariro Talent.; Booysen, Irvin Noel.
In the first experimental chapter, the synthetic approach of a lead rhenium metalcomplex, fac-[Re(CO)3(urbzt)Br] (urbzt = amino-5-((benzothiazol-2-ylmethylene)amino)-1,3-dimethyluracil) is reported from metallic rhenium and theurbzt free Schiff base. In addition, the formation of this metal complex was confirmedby LC-MS. This optimized synthetic approach was successfully mimicked in the 186Reradiolabelling experiments of urbzt and again confirmed by LC-MS. The second experimental chapter describes the synthesis and characterization of thenovel 2-aminoguanidine-derived Schiff base rhenium(I) compounds: fac-[Re(CO)3(Hguabs)Br]Br (1) (Hguabs· Cl = 2-((benzothiazole)methyleneamino)guanidine chloride) and fac-[Re(CO)3(guaquin)Br](2) (guaquin = 2-((quinolin-2-yl)methyleneamino)guanidine). Time-dependent UV-Visspectrophotometry show that these metal compounds undergoes sequential chloroligand substitution in DMSO followed by hydrolysis. The affinities of these metalcomplexes towards Calf Thymus Deoxyribonucleic acid (CT-DNA) and Bovine SerumAlbumin (BSA) were investigated. In particular, these metal compounds afforded highintrinsic DNA binding constants (Kb > 107 M-1) suggesting they both occupy within themajor and minor DNA grooves. Density functional theory calculations were conductedto rationalize the electronic transitions of the metal compounds. Molecular dockingsimulations were performed to probe the nature of the interaction between CT-DNAand the individual optimized conformers of the metal complexes. The in vitrocytotoxicity of 1 and 2 were assessed in various cancerous cell lines and benign cellswhere they showed activities in the low micromolar range.
Structure-activity relationships of novel anti-diabetic ruthenium compounds : synthesis, characterization, mechanistic and in vitro studies.
(2024) Makanyane, Madikoloha Daniel.; Booysen, Irvin Noel.; Mambanda, Allen.
Type 2 Diabetes Mellitus (T2DM) is a chronic metabolic disorder which is globally responsible for millions of fatalities per year. Management of T2DM typically involves orally administered anti-hyperglycaemic drugs in conjunction with dietary interventions. However, the current conventional therapy seems to be largely ineffective as patients continue to develop complications such as cardiovascular diseases, blindness and kidney failure. Existing alternative treatment entails the administration of organic therapeutic pharmaceuticals, but these drugs have various side effects such as nausea, headaches, weight gain, and respiratory and liver damage. Transition metal complexes have shown promise as anti-diabetic agents owing to their diverse mechanisms of activity. In particular, selected ruthenium compounds have exhibited intriguing biological behaviours as Protein Tyrosine Phosphatase (PTP) 1B and Glycogen Synthase Kinase 3 (GSK-3) inhibitors, as well as aggregation suppressants for the human islet amyloid polypeptide (hIAPP). The introduction chapter served as a survey on studies pertaining to ruthenium compounds as metallo-drugs for T2DM. Herein, we also provide perspectives on directions to fully elucidate in vivo functions of this class of potential metallopharmaceuticals. More specifically, there is still a need to investigate the pharmacokinetics of ruthenium drugs in order to establish their biodistribution patterns which will affirm whether these metal complexes are substitutionally inert or serve as pro-drugs. In addition, embedding oral-administered ruthenium complexes into bio-compatible polymers can be a prospective means of enhancing stability during drug delivery. This chapter was concluded with a descriptive rationale of the research study as well as specifying the specific research aims and objectives. Our prior studies have illustrated that the uracil ruthenium(II) diimino complex, [Ru(H3ucp)Cl(PPh3)] (1) (H4ucp = 2,6-bis-((6-amino-1,3-dimethyluracilimino)methylene)pyridine) displayed high hypoglycaemic effects in diet-induced diabetic rats. To rationalize the anti-diabetic effects of 1 in the first experimental chapter, three new derivatives have been prepared, cis-[Ru(bpy)2(urdp)]Cl2 (2) (urdp = 2,6-bis-((uracilimino)methylene)pyridine), trans-[RuCl2(PPh3)(urdp)] (3), and cis-[Ru(bpy)2(H4ucp)](PF6)2 (4). Various physicochemical techniques were utilized to characterize the structures of the novel ruthenium compounds. Prior to biomolecular interactions or in vitro studies, the stabilities of 1 – 4 were monitored in anhydrous DMSO, aqueous phosphate buffer containing 2% DMSO, and dichloromethane (DCM) via UV-Vis spectrophotometry. Time-dependent stability studies showed ligand exchange between DMSO nucleophiles and chloride co-ligands of 1 and 3, which was suppressed in the presence of an excess amount of chloride ions. In addition, the metal complexes 1 and 3 are stable in both DCM and an aqueous phosphate buffer containing 2% DMSO. In the case of compounds 2 and 4 with no chloride co-ligands within their coordination spheres, high stability in aqueous phosphate buffer containing 2% DMSO was observed. Fluorescence emission titrations of the individual ruthenium compounds with bovine serum albumin (BSA) showed that the metal compounds interact non-discriminately within the protein's hydrophobic cavities as moderate to strong binders. The metal complexes were capable of disintegrating mature amylin amyloid fibrils. In vivo, glucose metabolism studies in the liver (Chang) cell lines confirmed enhanced glucose metabolism as evidenced by the increased glucose utilization and glycogen synthesis in liver cell lines in the presence of complexes 2 – 4.
The second experimental chapter, reports on the formation and characterization of new diamagnetic ruthenium uracil mono-imine compounds: [(η6-p-cymene)RuII(L)Cl] (L = urpda = 5-((pyridin-2-yl)methyleneamino)-6-aminouracil) for 1, urdpy = 6-amino-1,3-dimethyl-5-((pyridin-2-ylmethylene)amino)uracil) for 2 or urqd = 5-((quinolin-2-yl)methyleneamino)-6-aminouracil) for 3); cis-[RuII(L)(bipy)2] (L = urpy = 5-((pyridin-2-yl)methyleneamino)uracil) for 4 and H2dadp = 5,6-diaminouracil for 5); trans-[RuII(L)(PPh3)Cl2] (L = urpda for 6) are described. Various physicochemical techniques were utilized to characterize the structures of the novel ruthenium compounds. Furthermore, the DPPH and NO radical scavenging capabilities of metal complexes (2 – 10) were investigated. UV-Vis spectrophotometry data of the time-dependent (for 24 h) studies show that 4 and 5 are stable in aqueous phosphate buffer containing 2% DMSO. Similarly, the stabilities of 1 - 3 and 6 monitored in chloro-containing and non-coordinating solvent dichloromethane show that they are kinetically inert, whereas, in a high nucleophilic environment, the chloride co-ligands of 1 - 3 and 6 were rapidly substituted by DMSO. In contrast, the substitution of the labile ligand of the complexes by DMSO molecules from its solution with a high chloride content was suppressed. Solution chemical reactivities of the different metal complexes were rationalized by density functional theory computations. Furthermore, the binding affinities and strengths between BSA and the respective metal complexes were monitored using fluorescence spectroscopy. Mutually, these metal complexes showed comparable capabilities of denaturing mature BSA aggregates which was established by fluorescence spectroscopy and Transmission Electron Microscopy (TEM). The final experimental chapter entails the encapsulation of the ruthenium complexes 1 - 10 into separate organic chitosan (CS)-polyvinyl alcohol (PVA) blends and the subsequent nanofabrication of their electrospun nanofiber (ENF) conjugates, Ru-CS-PVA ENFs. Intravenous injections of insulin can be regarded as a primitive method for Diabetes Mellitus management which characteristically leads to patients developing insulin resistance while oral-administered anti-diabetic organodrugs such as Metformin have exhibited low bio-availability and typically induce gastrointestinal (GI) side-effects. Although the intravenous injections of selected metal compounds in Streptozocin (STZ)-diabetic results have delivered promising results, limited work has been done to evaluate their efficiencies during oral administration. Herein, the fabricated chitosan (CS)-polyvinyl alcohol (PVA) electrospun nanofibers (CS-PVA ENFs) of the leading insulin-enhancing ruthenium complex 1, cis-[Ru(bipy)2(H4ucp)](PF6)2 and its analogs: 2 – 10. The Ru-CS-PVA ENFs nanocomposites were characterized by using (SEM-EDX), powder X-ray diffraction, and FTIR spectroscopy. The Ru-CS-PVA ENF nanohybrids exhibited randomly oriented fiber mat morphology with mean diameters in the range of 118 - 280 nm. Metal-based drug release kinetics of 1 - 10 from the ENF polymer matrix were measured spectrophotometrically at pH 1.5 and 7.4, respectively. Electronic spectral trends and data analysis over a 24-hour data collection period reveals variable dissolution rates with first-order rate (kobs) constants ranging from 0.0146 to 2.74 μM h-1 with accompanying hyperchromism effects between 5.69 to 37.6% at a pH of 1.5 while at a pH of 7.4, kobs value limits were 0.0104 and 3.89 μM h-1 rendering corresponding 19.14 and 87.32% hypochromic shifts. The release kinetics data of 1 - 10 were spontaneously released into the aqueous media from the Ru-CS-PVA ENFs, with the highest and releasing rates recorded for complexes 8 and 4, respectively.
Construction of functional and robust cobalt phthalocyanines modified electrodes for the electrocatalytic detection of metal-based and pharmaceutically derived pollutants.
(2024) Moodley, Danica.; Booysen, Irvin Noel.; Mambanda, Allen.
Water pollution has become a detrimental global concern in a world that continues to grow through industrialisation, population, and demand in sales from agricultural and pharmaceutical industries. It is therefore imperative for innovative methods of continuous water monitoring to be implemented to avoid the harsh effects that pollution poses to human, animal and environmental preservation. Advances from traditional analytical methods have been made to combat associated drawbacks such as tedious sample preparation, high maintenance costs, and lack of mobility. Electrochemical sensors can be used for the analysis of a vast range of water pollutants while offering on-site, simple analysis and inexpensive fabrication. Metallophthalocyanines have been utilised extensively as electrode modifiers due to their excellent redox properties and stability which can be fine-tuned by alteration of the metal centre and substituents. In addition, thes3e alterations improve selectivity, solubility and immobilisation onto electrode substrates. This research is aimed at the application of gold electrodes modified with CoPc-cou nanoconjugates and CoPc-cou electrospun nanofibers (ENFs) for the electrocatalytic detection of pollutants, paraquat and mercury, in real water samples. Experimental chapter one explores the optimization and application of a gold-modified electrode, CoPc-cou-f-MWCNTs/3-HT|Au, for the electrocatalytic detection of a water pollutant, paraquat (PQ). It was fabricated via a sequential modification procedure entailing the formation of self-assembled monolayers (SAMs) of a nanocomposite comprising of a coumarin tetra-substituted cobalt phthalocyanine (CoPc-cou) and carboxylic acid functionalized multiwalled carbon nanotubes (f-MWCNTs). This was followed by the in-situ immobilization of poly(3-hexylthiophene) ([3-HT]n) through electropolymerisation to render the chemically modified electrode (CME). Subsequently, the CME illustrated enhanced sensitivity towards PQ compared to the bare or CoPc-cou-f-MWCNTs modified electrodes. The CoPc-cou-f-MWCNTs/3-HT|Au electrode displayed a linear PQ detection range of 0.193 – 1000 μM with a limit of detection (LOD) and limit of quantification (LOQ) of 0.193 μM and 0.584 μM, respectively. Comparison between calibration curves for the modified electrode and HPLC-MS illustrates that the former method has a lower but comparable calibration sensitivity for PQ. In addition, this CME could electrocatalytically distinguish PQ within a real water sample collected from the Durban lagoon. Furthermore, the direct recovery of PQ in the lagoon water by the modified Au electrode was found to be 86%, which is lower than the calculated value of 97% obtained by HPLC-MS after rigorous solid-phase microextraction of the analyte. However, the lower percentage recovery could be rationalized by the interference studies. In experimental chapter two fabricated electrospun nanofibers containing CoPc-cou, polyaniline (PANI) and poly-vinyl alcohol (PVA) were used to modify a gold substrate which was subsequently immobilised using a 5% Nafion solution affording the CoPc-cou-ENFs-Nf|Au modified electrode. Comparison of the chemically modified electrode with the bare and other modified electrodes under optimised conditions displayed superior detection of mercury (Hg(II)) attaining a linear range of 10 – 3000 μM and an LOD and LOQ of 0.14 μM and 0.46 μM, respectively. This can be attributed to the affinity between Hg(II) and the mercaptocoumarin substituent (Hg-S) as well as the higher surface area occupied by the ENFs resulting in an increased number of active sites. Furthermore, the chemically modified electrode exhibit selectivity and sensitivity in an interference sample containing multiple heavy metals (Pb2+, Cd2+ and Hg2+). A good percentage recovery of 96% was attained when the CoPc-cou-ENFs-Nf|Au electrode was applied to a real water sample which was comparable to a percentage recovery of 98% which was attained using the ICP-OES to analyse the same water samples.
Removal of antiretrovirals using low-cost adsorbents: adsorption kinetics, adsorption isotherms and thermodynamics studies.
(2023) Simelane, Lindokuhle Anele.; Mahlambi, Precious Nokwethemba.; Rochat, Sebastien.; Baker, Ben.
The current study was directed to the synthesis and application of low-cost adsorbent for the removal of antiretroviral drugs (ARVDs) such as nevirapine, abacavir and efavirenz in wastewater samples. The study involved the modification and application of liquid chromatography photo diode array (LC-PDA) for the detection of the ARVDs of interest. The good separation of ARVDs was achieved using a gradient elution 50 % ACN: 50 % H2O (0-2 minutes), 70 %ACN: 30 % H2O (3-20 minutes).The macadamia nutshells, Platanus acerifolia leaves (London plane) were explored as easily accessible and eco-friendly adsorbents. The single synthetic route and high surface area of the polymer of intrinsic microporosity number-1(PIM-1) were the distinct properties that were ideal for exploring this adsorbent for removal of ARVDs in wastewater samples. The adsorbents were synthesized and characterized using Fourier transform infrared spectroscopy (FTIR),Scanning electron microscopy (SEM), Brunauer Emmett Teller (BET), Powder X-ray diffraction (PXRD). The results obtained from macadamia nutshell and Platanus acerifolia adsorbent for FTIR characterization were functional groups such O-H, C=O and C=C and many others whereas Platanus acerifolia adsorbent had additional N-H from in addition to one obtained in macadamia adsorbent. The PIM-1 showed CN, C=O and C-H functional groups. SEM showed rod-folded structure and flaky-folded structure for macadamia nutshell adsorbent and Platanus acerifolia leaves adsorbent respectively, whereas PIM-1 exhibited microporous to mesoporous pore on adsorbent surface. The BET showed a surface area, pore diameter and pore volume of 0.1180 m2/g, 27.98 nm, and 8.3×10-5 cm3/g for macadamia nutshells adsorbent and 1.14 m2/g, 0.0024 cm3/g and 4.09 nm for Platanus acerifolia leaves adsorbent. The PIM-1 had a surface of 557.39 cm2/g, pore volume 0.4123 cm3/g and pore diameter 2.96 nm. The PXRD of macadamia and Platanus acerifolia adsorbents had native crystalline cellulose structure whereas PIM-1 had an amorphous material. These characterization results indicated that the adsorbents have the potential to efficiently remove the ARVDs from in contaminated wastewater. Prior to the application of adsorbents, parameters such as adsorption time (5-240 minutes), solution pH (2-10), initial concentration (0.2-2 mg/L), adsorbent mass dosage (0.2-10 mg) and adsorption temperature (15-40°C) were investigated to access the removal efficiency of all the synthesized adsorbents on their ability to remove ARVDs in wastewater samples. Under optimum conditions the adsorption was conducted using 10 mg of the adsorbent in 10 mL wastewater sample spiked at a concentration 1.0 mg/L, at a pH of 7 and stirred at 150 rpm at 30°C. These conditions yielded a removal efficiency greater than 80 %, 90 % and 86 % using macadamia nutshells, Platanus acerifolia leaves and PIM-1 adsorbent, respectively in all ARVDs of interest. The study of adsorption kinetics, adsorption isotherms and thermodynamic model was essential for designing an efficient adsorption process to remove ARVDs which are pollutants of emerging concern. The results obtained showed that pseudo-second-order model well defined the kinetic data, and the adsorption isotherms was well fitted in Langmuir isotherm and adsorption process was exothermic in nature for macadamia nutshells and Platanus acerifolia leaves adsorbent. For PIM-1 adsorbent, the pseudo-second-order was dominant, and the adsorption isotherm was well defined by Freundlich model. Thermodynamic parameters showed that the adsorption was thermodynamically favored, spontaneous, and exothermic in nature. The adsorbents were then applied under optimum conditions and the amount adsorbed of ARVDs from wastewater samples were 94.41, 88.84 and 83.06 mg/g for nevirapine, abacavir and efavirenz respectively for macadamia nutshell adsorbent. For Platanus acerifolia leaves adsorbent, 97.56, 84.75 and 81.56 mg/g amount adsorbed of nevirapine, abacavir and efavirenz. On the other hand, PIM-1 adsorbent had an adsorption capacity of 83.65, 93.83 and 94.56 mg/g amount for nevirapine, abacavir and efavirenz, respectively. Overall, the macadamia nustshells, Platanus acerifolia leaves and PIM-1 adsorbents have illustrated to be efficient and cost-effective adsorbents for removal ARVDs in wastewater samples. However, the two agricultural adsorbents, macadamia nutshell and Platanus acerifolia leaves adsorbents could be highly recommended since their usage is able to reduce land and water pollution which is compromises water quantity which is already at stake across the globe.