2016 UMKC Dissertations - Freely Available Online
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This community contains the collections of dissertations submitted electronically to the School of Graduate Studies by doctoral degree candidates at the University of Missouri-Kansas City in the spring, summer, and fall semesters of 2016. The items in this collection are dissertations that are available to the general public.
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Item The Ins and Outs and ABCs of Antifungal Drug Transport: Characterizing the Role of Membrane Transporters in Pathogenic Fungi(2016) Esquivel, Brooke D.; White, Theodore C.Pathogenic fungi cause serious disease and even death in humans, animals and plants. In medicine and agriculture alike, fungal infections are widespread and represent a significant threat to global public health. The number and array of fungal species, each exhibiting diverse mechanisms of pathogenesis, makes the challenge of fungal infection prevention and treatment formidable. The current repertoire of effective antifungal treatment strategies is very limited. As a result of increased use of antifungals to treat and prevent clinical fungal infections in humans, as well as widespread use of fungicides in agriculture, fungal strains that are resistant to each of the classes of antifungals have emerged. A significant rise in the number of fungal infections in recent years, combined with an increasing amount of drug resistant fungal strains is great cause for concern and places urgency on the development of new and more effective fungal infection treatment and prevention strategies. New fungal drug targets may be discovered with a better understanding of basic fungal biological processes. New or improved fungal infection treatment strategies may stem from a more complete knowledge of fungal response to drug treatment, worldwide trends of fungal pathogenesis and development of resistance, and even fungal evolutionary relationships. The goal of this research was to characterize the most basic fungal/drug interactions, which includes the balance of uptake, retention, and efflux of antifungal drugs in the fungal cell. We analyzed a variety of environmental and cellular factors that affect antifungal drug uptake and retention in two medically and agriculturally important pathogenic fungi, Aspergillus fumigatus and Magnaporthe oryzae. We then identified and characterized a number of A. fumigatus plasma membrane ABC transporters that may contribute to antifungal drug resistance due to their role in the efflux of antifungal drugs. To analyze antifungal drug uptake and retention, we developed an assay to directly measure accumulation of radioactively-labeled azoles in A. fumigatus and M. oryzae. Our analysis of drug uptake under a variety of cellular and environmental conditions demonstrated that these filamentous fungi import azoles by a facilitated diffusion mechanism. Contrasts between the M. oryzae and A. fumigatus data revealed interesting differences that suggest variations in expression, induction, or function of efflux transporters in the two organisms. To analyze antifungal efflux, we cloned and expressed a selection of putative ABC transporter genes from the A. fumigatus genome and heterologously expressed each gene in S. cerevisiae for direct characterization of drug efflux potential. Our efflux transporter analysis showed differences in substrate specificity, drug susceptibilities, energy-dependent efflux activity, and effect of efflux-inhibitor treatment between the different transporters. These data illustrate the complexity of predicting and counteracting fungal drug treatment response, but also highlight the possibilities for identifying new drug targets.Item The Molecular Mechanisms of Antifungal Drug Resistance In Pathogenic Fungi(2016) Bhattacharya, Somanon; White, Theodore C.Pathogenic fungi including Candida albicans, cause oral, systemic, and vaginal infections, mostly in immune-compromised individuals. Azoles are the most common antifungals used in treating these infections. The most significant mechanisms of azole resistance include alterations or overexpression of the target enzyme, and overexpression of at least three distinct efflux pumps. Recently, azole-resistant vaginal C. albicans isolates have been detected in patients with recurring and refractory vaginal infections. However, the mechanisms of resistance in vaginal C. albicans have not been studied in detail. In oral and systemic resistant isolates, over-expression of ABC transporters Cdr1p and Cdr2p and the major facilitator transporter Mdr1p is associated with resistance. This is consistent with the molecular mechanisms of drug resistance observed in this study for the vaginal C. albicans clinical isolates. Another important mechanism of azole resistance in C. albicans is overexpression and/or point mutation of ERG11, which is a rate-limiting enzyme in the ergosterol biosynthetic pathway. Other antifungals also target the ergosterol pathway, including fenpropimorph,(morpholine) which targets Erg24p, and terbinafine (allylamines), which targets Erg1p enzymes. Aberrant levels of ergosterol may affect many cellular processes. Recent studies have used deletion mutants of the ergosterol genes to analyze their cellular phenotypes. Some of these mutants showed severe growth defects, compromised respiration, weak cell wall, and lower tolerance to osmotic stress. However, only seven of total 25 ergosterol biosynthetic genes (ERG genes) can be deleted as they are non-essential. This thesis studies the ergosterol biosynthetic pathway in detail. All 25 S. cerevisiae ERG genes were overexpressed under a galactose inducible promoter. Nine of the 25 strains overexpressing the ERG genes showed severe growth defects. Furthermore, phenotypic changes in these strains were compared to wild-type under various stress agents. These agents affect several cellular processes that include cell wall biosynthesis, respiration, protein synthesis, osmotic stress, iron and calcium metabolism. A majority of the overexpressed strains were affected by high salt or by a calcium chelator. Two of the nine slow growing strains were affected by all the stress agents used. This project increases our understanding of the ergosterol pathway, and may identify potential targets for future drug design.Item Silicon on Ferroelectric Insulator Field Effect Transistor (SOFFET): A Radical Alternative to Overcome the Thermionic Limit(University of Missouri--Kansas City, 2016) Es-Sakhi, Azzedin D.; Chowdhury, Masud H.The path of down-scaling traditional MOSFET is reaching its technological, economic and, most importantly, fundamental physical limits. Before the dead-end of the roadmap, it is imperative to conduct a broad research to find alternative materials and new architectures to the current technology for the MOSFET devices. Beyond silicon electronic materials like group III-V heterostructure, ferroelectric material, carbon nanotubes (CNTs), and other nanowire-based designs are in development to become the core technology for non-classical CMOS structures. Field effect transistors (FETs) in general have made unprecedented progress in the last few decades by down-scaling device dimensions and power supply level leading to extremely high numbers of devices in a single chip. High density integrated circuits are now facing major challenges related to power management and heat dissipation due to excessive leakage, mainly due to subthreshold conduction. Over the years, planar MOSFET dimensional reduction was the only process followed by the semiconductor industry to improve device performance and to reduce the power supply. Further scaling increases short-channel-effect (SCE), and off-state current makes it difficult for the industry to follow the well-known Mooreβs Law with bulk devices. Therefore, scaling planar MOSFET is no longer considered as a feasible solution to extend this law. The down-scaling of metal-oxide-semiconductor field effect transistors (MOSFETs) leads to severe short-channel-effects and power leakage at large-scale integrated circuits (LSIs). The device, which is governed by the thermionic emission of the carriers injected from the source to the channel region, has set a limitation of the subthreshold swing (S) of 60 ππ/ππππππ at room temperature. Devices with βSβ below this limit is highly desirable to reduce the power consumption and maintaining a high πΌππ/πΌπππ current ratio. Therefore, the future of semiconductor industry hangs on new architectures, new materials or even new physics to govern the flow of carriers in new switches. As the subthreshold swing is increasing at every technology node, new structures using SOI, multi-gate, nanowire approach, and new channel materials such as IIIβV semiconductor have not satisfied the targeted values of subthreshold swing. Moreover, the ultra-low-power (ULP) design required a subthreshold slope lower than the thermionic emission limit of 60 ππ/ππππππ. This value was unbreakable by the new structure (SOI FinFET). On the other hand, most of the preview proposals show the ability to go beyond this limit. However, those pre-mentioned schemes have publicized very complicated physics, design difficulties, and process non-compatibility. The objective of this research is to discuss various emerging nano-devices proposed for sub-60 mV/decade designs and their possibilities to replace the silicon devices as the core technology in the future integrated circuit. This dissertation also proposes a novel design that exploits the concept of negative capacitance. The new field-effect-transistor (FET) based on ferroelectric insulator named Silicon-On-Ferroelectric Insulator Field effect-transistor (SOFFET). This proposal is a promising methodology for future ultra low-power applications because it demonstrates the ability to replace the silicon-bulk based MOSFET, and offers a subthreshold swing significantly lower than 60 ππ/ππππππ and reduced threshold voltage to form a conducting channel. The proposed SOFFET design, which utilizes the negative capacitance of a ferroelectric insulator in the body-stack, is completely different from the FeFET and NCFET designs. In addition to having the NC effect, the proposed device will have all the advantages of an SOI device. Body-stack that we are intending in this research has many advantages over the gate-stack. First, it is more compatible with the existing processes. Second, the gate and the working area of the proposed SOFFET is like the planar MOSFET. Third, the complexity and ferroelectric material interferences are shifted to the body of the device from the gate and the working area. The proposed structure offers better scalability and superior constructability because of the high-dielectric buried insulator. Here we are providing a very simplified model for the structure. Silicon-on-ferroelectric leads to several advantages including low off-state current and shift in the threshold voltage with the decrease of the ferroelectric material thickness. Moreover, having an insulator in the body of the device increases the controllability over the channel, which leads to the reduction in the short-channel-effect (SCE). The proposed SOFFET offers low value of subthreshold swing (S) leading to better performance in the on-state. The off-state current is directly related to S. So, the off-state current is also minimum in the proposed structure.Item Discovery of Peptide and Aptamer Ligands for Targeted Drug Delivery to Hepatic Stellate Cells(University of Missouri--Kansas City, 2016) Chen, Zhijin; Cheng, Kun (Professor)The objective of this dissertation is to present two approaches to identify Hepatic Stellate Cells (HSCs) targeting ligands using phage-display library biopanning and systematic evolution of ligands by exponential enrichment (SELEX). These HSC-specific ligands can be used for diagnosis and therapy of liver fibrosis. The mechanism of fibrogenesis and potential treatments of liver fibrosis are summarized in Chapters 1 and 2. In Chapter 3, we identified HSC-specific peptides using a peptide phage display for diagnosis and treatment of liver fibrosis. Caused by chronic injuries, such as hepatitis, alcohol abuse, and nonalcoholic steatohepatitis, liver fibrosis is characterized by the excessive accumulation of extracellular matrix (ECM) in the liver. Activation of HSCs is the most critical step during liver fibrogenesis due to the production of excessive ECM and profibrogenic cytokines. Therefore, development of HSC-specific delivery systems is essential for the success of antifibrotic agents. The objective of this Chapter is to identify peptide ligands targeting the insulin like growth factor II receptor (IGFIIR), which is overexpressed in HSCs during liver fibrogenesis. A combinatorial phage display biopanning against IGFIIE protein- and HSC-T6 rat hepatic stellate cells was conducted to identify phage/peptide candidates. Phage ELISA, cellular uptake and cell viability assay were employed to evaluate the binding affinity and specificity of these peptide ligands to recombinant human IGFIIR and HSCs. IGFIIR siRNA was used to silence the IGFIIR expression in human HSCs (LX-2) to confirm the specificity of the identified peptide ligands. Among the identified peptide candidates, the peptide-431 shows the highest binding affinity and specificity to recombinant human IGFIIR protein and HSCs. The apparent equilibrium dissociation constant (Kd) of the peptide-431 is 6.19 Β΅M for LX-2 cells and 12.35 ΞΌM for rat hepatic stellate cells HSC-T6. Cellular uptake of the peptide-431 in LX-2 cells is significantly reduced after silencing IGFIIR with siRNA. The peptide-431 also enhances the uptake of a proapoptotic peptide (KLA peptide) in LX-2 and HSC-T6 cells, indicating that the peptide-431 can be used as a targeting ligand to deliver antifibrotic agents into not only rat but also human HSCs. In order to improve the potential of the application of peptide-431 in liver fibrosis targeted delivery, we developed a dimerized peptide-431 which is also descripted in Chapter 3. The binding affinity of peptide-431 has improved 9 fold by forming dimer comparing with monomer peptide-431. We also screened aptamer ligands using SELEX for targeted delivery to HSCs. In Chapter 4, IGFIIR-specific aptamers were identified using SELEX. The binding affinity and specificity of the aptamers were studied by flow cytometry and Surface Plasma Resonance (SPR). The identified aptamer was annealed with the PCBP2 siRNA and delivered it into HSCs. The recovered aptamers result shows that the aptamers were enriched after seven rounds of SELEX. The binding affinity (Kd) of the aptamer-20 on IGFIIR protein is approximately 35.5 nM. Knocking down the expression of IGFIIR with siRNA decreased the binding affinity of aptamer-20, indicating the specificity of the aptamer to IGFIIR in HSCs. Cellular uptake of the aptamer-siRNA chimera is much higher than the siRNA. PCBP2 expression in HSCs is significantly downregulated after incubation with the aptamer-siRNA chimera in LX-2 cells. After systemic administration, the aptamer-siRNA chimera is primarily located in the liver of rats with CClβ-induced liver fibrosis. Therefore, aptamer-20 is a very promising IGFIIR-specific ligand for drug delivery to HSCs.Item Internet of Things (IoT) Applications With Diverse Direct Communication Methods(University of Missouri--Kansas City, 2016) Dhondge, Kaustubh; Choi, Baek-YoungInternet of Things (IoT) is a network of physical objects or things that are embedded with electronics, software, sensors, and network connectivity - which enable the object to collect and exchange data. Rapid proliferation of IoT is driving the intelligence in things used daily in homes, workplaces and industry. The IoT devices typically communicate via radio frequency (RF), such as WiFi and Bluetooth. In this dissertation we deeply analyze the various characteristics of different wireless communication methods in terms of range, energy-efficiency, and radiation pattern. We find that a well-established communication method might not be the most efficient, and other alternate communication methods with the desired properties for a particular application could exist. We exploit radically alternative, innovative, and complimentary wireless communication methods, including radio frequency, infrared (IR), and visible lights, through the IoT applications we have designed and built with those. We have developed various IoT applications which provide security and authentication, enable vehicular communications with smartphones or other smart devices, provide energy-efficient and accurate positioning to smart devices, and enable energy-efficient communications in Industrial Internet of Things (IIoT).