Polymeric organoiron compounds with carcinostatic properties (branched hydrazone linkers)

The insufficient efficaciousness of most currently used anticancer drugs has prompted worldwide efforts to reduce toxic and resistance effects, improve overall bioavailability, and widen the therapeutic window. A particularly promising technology to this end rests on the concept of polymer-drug conjugation, in which the bioactive agent is bound to a meticulously designed macromolecular water-soluble carrier through a biofissionable link. Drug release in the cancerous cell, strongly pH dependant, proceeds hydrolytically in the acidic intracellular compartment, and this represents an advanced drug delivery method in cancer chemotherapy. The synthesis of water-soluble macromolecular anticancer drugs composed of a polymeric carrier to which the antineoplastic agents are tied via biodegradable hydrazone links were investigated in this project. Carriers were synthesized essentially by polyaddition and ring-opening methods, and polycondensation process was utilized, refined and routinely used. Polyaspartamides derived from polysuccinimide by aminolytic ring-opening was the parent carrier’s structure, allowing for: a) A non-immunogenic and non-toxic chain construction, which was amenable to biodegradation and ensured catabolic elimination of the duly fragment polymer upon drug release; b) A highly flexible backbone and the presence of intrachain-type or side group-attached solubilizing groups, which ensured conjugate solution in aqueous media required for rapid dissipation in the central circulation system, even if the conjugated drug itself does not possess water solubility; and; c) The presence of functional groups as binding sites, represented by the hydrazone entity, which ensured drug attachment and release, was introduced by treatment of polysuccinimide with hydrazine hydrate under specially developed experimental conditions, followed by treatment with selected, functionally active amines providing the aforementioned structural features. Drug systems were modified so as to contain carbonyl functionality, the crucial reaction site in this hydrazone linking process, and bioactive aldehydes, such as ferrocenylpropenal. A cinnamaldehyde was the primary drug model. In order to illustrate the multidrug-binding capacity of the polyaspartamide type carriers, and at the same time ensuring target-specific drug delivery, folic acid, a potential cell entry facilitator, was co-conjugated to selected polymeric conjugate containing ferrocenylpropenal. Cell carrier and conjugate polymers were purified, fractionated by aqueous phase dialysis in membrane tubing with 12 000 – 14 000 molecular – mass cut - off, and isolated by freeze-drying in ultimate yields of 45 – 80 % as water-soluble materials; and they were structurally characterized by spectroscopic techniques. Inherent viscosities were in the range of 8 – 36 mL g-1. The resulting cinnamaldehyde, curcumin and iron contents of the conjugates were in the range of 4 - 7 %, 10 – 14 % and 1.5 – 2.8 % respectively. In vitro experiments done under buffered solution (performed in polymer laboratory of school of chemistry of the university of the Witwatersrand) showed the released of drugs in cancer cell's pH (pH<7). The results of these tests suggest that in acidic environment PSI-hydrazine carriers drugs systems can release active drug such as ferrocenylpropenal, and on the other hand the polymers drugs systems showed higher stabilities under neutral conditions. Therefore drugs released under pH control can play an important role in future cancer therapy

Determination of optimum blend of bioethanol-petrol mixture using utrasonication for environmental friendly fuel

A thesis submitted to the Faculty of Engineering and the Built Environment, University of the Witwatersrand, Johannesburg, in fulfilment of the requirements for the degree of Doctor of Philosophy.Increasing global energy demand as well as air quality concerns have in recent years led to the search for alternative clean fuels to replace fossil fuels. One such alternative is the blending of petrol (gasoline) with ethanol, which has numerous advantages such as ethanol’s ability to act as oxygenate thus reducing the carbon monoxide emissions from the exhaust of internal combustion engines of vehicles. However, the hygroscopic nature of ethanol is a major concern in obtaining a perfectly homogenized petrol-ethanol fuel. This problem has led to the study of ways of homogenizing the petrol-ethanol mixtures. Therefore, this thesis aimed at enhancing the homogenization of petrol-ethanol mixture. Ethanol concentration in ethanol-water mixture plays a key role in enhancing the homogenization of the fuel, thus the bioethanol employed in this study was dehydrated with silica gel using ultrasonication-enhanced adsorption. Afterwards, the dehydrated ethanol was used in studying the homogenization of the fuel blend. Water removal from the bioethanol using ultrasonication-enhanced adsorption shows a 28% increase when compared to the water removal using magnetic-stirring-enhanced adsorption, During ultrasonication-enhanced adsorption, the estimated adsorption enthalpy was – 1 592.82 J/mol (exothermic) and the entropy was -5.44 J/ K mol, indicating a non-ordered loading of water molecules in the adsorption site. In addition, a modified pseudo second order kinetic model given by was proposed for the ultrasonication-enhanced adsorption process. Effect of temperature during ultrasonication-enhanced adsorption was found to be directly proportional to the amplitude and the pulse rate. However, increase in the amplitudes at lower pulse rates resulted in better cavitation, and hence better adsorption. Furthermore, during phase behavior of ethanol-petrol blend, volume fractions of ethanol and petrol were studied with respect to t the depth within the storage container to confirm homogenization of the blend and time of storage. The binodal curve of the ternary diagram shows an increase of homogeneous region indicating an improved interaction between water and petrol. Therefore, the interesting results regarding the homogenization of the fuel blends resulted from using ultrasonication-enhanced blending were very promising, and could be a platform upon which further research efforts could be built on. The concentration distribution in the reactor showed proof of cavitation formation since in both directions, the variation of concentration with both time and distance was found to be oscillatory. On comparing the profiles in both directions, the concentration gradient, diffusion flux, and energy and diffusion rates were found to be higher in the vertical direction compared to the horizontal direction. It was therefore concluded that ultrasonication creates cavitation in the mixture which enhances mass transfer and mixing of ethanol and petrol. The horizontal direction was found to be the diffusion rate limiting step which proposed that the blender should have a larger height to diameter ratio. It is however recommended that further studies be done on the rate-limiting step so as to have actual dimensions of the reactor. Testing of the blended fuel in internal combustion engine showed an optimal performance of this fuel at 60 % volume ethanol content with higher fuel power. The results of fuel consumption and emissions (such as CO2 and CO) trends confirm various reports in literature on the performance of ethanol/petrol blended fuel

Hydrogen Storage: Materials, Kinetics and Thermodynamics

The need for cleaner sources of energy has become a serious need now more than ever due to the rising effects of fossil fuels on the environment. Technological advancement in society today has necessitated the need for fast and robust materials that will match the speed at which society is moving forward. Hydrogen as an alternative source, has garnered a lot of attention due to its zero emission characteristic. In this chapter, a background on hydrogen storage and its impact on the ‘envisaged green environment’ is discussed. Graphene and borohydrides hydrogen storage materials are reviewed extensively and the kinetic models thereof. Furthermore, the reaction mechanism of graphene nanocomposites is also discussed

Experimental Kinetic Evaluation of Carbon Dioxide Hydrate-Based Concentration for Grape, Pineapple, and Bitter Melon Juices

Hydrate-based technology has emerged as a promising approach to address the industry’s energy demands and product quality challenges in the food industry. Despite reported successes in the literature where higher dehydration ratios were achieved, technological problems like slow formation rates and poor process scale-up economics need to be addressed. Moreover, with little hydrate formation data available, the major focus is on the technology’s ability to remove water content, but studies on the kinetics of hydrate formation are scarce. In the present work, the effects of varying grape/pineapple/bitter melon juice water cuts (88.5 to 97.4 ± 2.53 wt %) on the formation kinetics of carbon dioxide (CO2) hydrates were investigated. Such information can provide insight into the possibile commercialization of the hydrate-based technology. The reported experimental data were determined using the isochoric pressure-search method in a high-pressure reactor at a target initial temperature from 274.15 to 276.15 K and varying initial pressures. Kinetic parameters were calculated using the relative kinetic models proposed in the literature. Lower relative values of investigated kinetic parameters and longer induction times were obtained at lower juice water cuts and lower degrees of subcooling. Despite observed inhibition effects, the study provides useful experimental and modeled kinetic data for filling the knowledge gap in understanding the controlling mechanism of CO2 hydrate formation. Therefore, it is believed that the reported findings may highlight some important practical aspects related to CO2 hydrate technology as an alternative juice concentration process

Effect of Support Particle Size in Fischer–Tropsch Synthesis: the Use of Natural Clinoptilolite as Support

In the past, Fischer–Tropsch (FT) coal/biomass-to-liquids projects have required a significant initial investment. The high price of the catalysts used is one area where costs could be reduced. This research explored the possibility of using clinoptilolite as a catalyst to reduce costs without sacrificing performance. The as-received clinoptilolite was ground and sieved to yield different size classes. For this study, three size classes were investigated as the support for an FT catalyst: −75 to +53 μm; −53 to +38 μm; less than 25 μm. Using a fixed bed reactor, 10% cobalt supported on these various supports was synthesized and evaluated. The maximum CO conversion obtained was 44.97% when using the −53 to +38 μm size class with the experiments carried out at 220 °C, 2 L(NTP)/(gcat h) and 10.85 bar(abs). A one-way analysis of variance was performed. Then a posthoc Bonferroni adjustment test was carried out to determine whether or not the utilization of different support size classes affected CO conversion. The results indicated a significant difference in CO conversion, with P(T ≤ t) two-tail values ranging from 6.08 × 10–5 to 2.37 × 1027. At 220 °C and 10.85 bar(abs), methane selectivity ranged between 14.95 and 16.97% for the support class sizes studied, while C2–C4 selectivity ranged between 14.55 and 19.01%, and C5+ selectivity ranged between 66.04 and 70.29%. The acquired product selectivity results using this cheaper support are comparable to those reported in the literature. These discoveries might have valuable implications for the design of a catalyst that can be used in the coal/biomass to liquid process