Mountain Scholar :: Browsing by Author "Reynolds, Melissa, committee member"

Browsing by Author "Reynolds, Melissa, committee member"

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Open Access
A calcium aluminate electride hollow cathode
(Colorado State University. Libraries, 2014) Rand, Lauren Paula, author; Williams, John, advisor; Reynolds, Melissa, committee member; Sampath, Walajabad, committee member; Yalin, Azer, committee member
The development and testing of a hollow cathode utilizing C12A7 (12CaO.Al2O3) electride as an insert are presented. Hollow cathodes are an integral part of electric propulsion thrusters on satellites and ground-based plasma sources for materials engineering. The power efficiency and durability of these components are critical, especially when used in flight applications. A low work function material internal to the cathode supplies the electrons needed to create the cathode plasma. Current state-of-the- art insert materials are either susceptible to poisoning or need to be heated to temperatures that result in a shortened cathode lifetime. C12A7 electride is a ceramic in which electrons contained in sub-nanometer sized lattice cages act as a conductive medium. Due to its unique atomic structure and large size, C12A7 electride has a predicted work function much lower than traditional insert materials. A novel, one-step fabrication process was developed that produced an amorphous form of C12A7 electride that had a measured work function 0.76 eV. A single electride hollow cathode was operated on xenon for over 60 hours over a two-month period that included 20 restarts and 11 chamber vent pump-down sequences with no sign of degradation, and on iodine for over 20 hours with no apparent reactivity issues. The operations of cathodes with three different orifice sizes were compared, and their effects on the interior cathode plasma modeled in a zero- dimensional phenomenological model.
Open Access
Antibacterial effects of sputter deposited silver-doped hydroxyapatite thin films
(Colorado State University. Libraries, 2011) Trujillo, Nathan Anthony, author; Popat, Ketul, advisor; Williams, John, advisor; Reynolds, Melissa, committee member; Crans, Debbie, committee member
Over recent years, researchers have studied innovative ways to increase the lifespan of orthopedic implants in order to meet the soaring demand of hip and knee replacements. Since many of these implants fail as a result of loosening, wear, and inflammation caused by repeated loading on the joints, coatings such as hydroxyapatite (HAp) on titanium with a unique topography have been shown to improve the interface between the implant and the natural tissue. Other serious problems with long-term or ideally permanent implants are bacterial colonization. It is important to prevent initial bacterial colonization as existing colonies have potential to become encased in an extracellular matrix polymer (biofilm) which is resistant to antibacterial agents. The following work considers the potential of etching using plasma based ion implantation and ion beam sputter deposition to produce hydroxyapatite thin films on etched titanium doped with silver as an antibacterial component. Plasma-based ion implantation was used to examine the effects of pre-etching on plain titanium. Topographical changes to the titanium samples were examined and compared via scanning electron microscopy. It was determined that plasma-based ion implantation at -700eV could etch titanium to produce similar topography as ion beam etching in a shorter processing time. Hydroxyapatite and silver-doped hydroxyapatite thin films were then sputter deposited on titanium substrates etched at -700eV. For silver-doped films, two concentrations of silver (~0.5wt% and ~1.5wt%) were used. Silver concentrations in the film were determined using energy dispersive x-ray spectroscopy. Film thicknesses were determined by measuring the surface profile using contact profilometry. Staphylococcus epidermidis (SE) and Pseudomonas aeruginosa (PA) adhesion studies were performed on plain titanium, titanium coated with hydroxyapatite, titanium coated with ~0.5 wt% silver-doped hydroxyapatite, and titanium coated with ~1.5wt% silver-doped hydroxyapatite. It was discovered during the study that the films were delaminating from the samples thus killing bacteria in suspension. Release studies performed in addition to adhesion confirmed that the silver-doped films prevented SE and PA bacterial growth in suspension. To prevent delamination, the films were annealed by heat treatment in air at a temperature of 600°C. X-ray diffraction confirmed the presence of a crystalline hydroxyapatite phase on each sample type. Films were immersed in PBS at 37°C and remained in incubation for four weeks to determine there was no delamination or silver leaching.
Open Access
Brush-like surface using heparin/chitosan based nanoparticles for blood-contacting applications
(Colorado State University. Libraries, 2013) Nijjar, Rajvir Singh, author; Kipper, Matt, advisor; Bailey, Travis, committee member; Reynolds, Melissa, committee member
With increasing applications of biomedical implants, it is crucial to develop surfaces that are blood compatible, meaning they do not induce platelet or protein adhesion. Many implants that are currently used to treat a wide range of problems have one major drawback, they can induce thrombosis. The endothelial glycocalyx plays a crucial role in preventing thrombosis. Based on this idea, we set out to develop a surface that has a brush-like structure similar to that of the endothelial glycocalyx. We developed the surface by adsorbing negatively charged heparin/chitosan polyelectrolyte complex nanoparticles onto a heparin/tri-methylchitosan polyelectrolyte multilayer. The surface was then characterized using surface plasmon resonance (SPR), quartz crystal microbalance (QCM), atomic force microsocopy (AFM), scanning electron microscope (SEM), and polarization modulation-infrared reflection absorption spectroscopy (PM-IRRAS). Using these techniques we confirmed that we had created a surface with brush- like structure. Our hypothesis that the nanoparticles on the surface swell and form a brush-like structure when exposed to physiological conditions seems to be correct, as a result, we feel the surface we have developed could have a wide range of applications in the biomedical field.
Open Access
Dual nickel- and photoredox-catalyzed enantioselective desymmetrization of meso anhydrides and C-O bond activation via phosphines and photoredox catalysis
(Colorado State University. Libraries, 2018) Stache, Erin Elizabeth, author; Rovis, Tomislav, advisor; Doyle, Abigail G., advisor; Chen, Eugene, committee member; McNally, Andy, committee member; Reynolds, Melissa, committee member; Kipper, Matt, committee member
Described herein is the application of photoredox catalysis in the development of new synthetic methods. A dual nickel- and photoredox catalyzed desymmetrization of meso succinic anhydrides was developed to generate stereodefined cis keto-acids in high enantioselectivity and diastereoselectivity. The approach employed benzylic radicals as a coupling partner, generated from a photoredox catalyzed single-electron oxidation of benzylic trifluoroborates using an inexpensive organic dye. A unique epimerization event was discovered and the degree of epimerization was rendered tunable by changing catalyst loadings to ultimately form the trans diastereomer preferentially in high enantioeselectivity. A method for the C–O bond activation of aliphatic alcohols and carboxylic acids was developed using phosphines and photoredox catalysis. This novel reaction platform was used to generate aliphatic or acyl radicals directly from benzylic alcohols and aliphatic and aromatic acids, and with terminal hydrogen atom transfer, afforded the desired deoxygenated alkanes and aldehydes. Additionally, the intermediate acyl radicals could be intercepted in an intramolecular cyclization reaction to generate new lactones, amides and ketones.
Open Access
Dynamics of protein interactions with new biomimetic interfaces: toward blood-compatible biomaterials
(Colorado State University. Libraries, 2019) Hedayati, Mohammadhasan, author; Kipper, Matt J., advisor; Krapf, Diego, committee member; Reynolds, Melissa, committee member; Bailey, Travis, committee member
Nonspecific blood protein adsorption on the surfaces is the first event that occurs within seconds when a biomaterial comes into contact with blood. This phenomenon may ultimately lead to significant adverse biological responses. Therefore, preventing blood protein adsorption on biomaterial surfaces is a prerequisite towards designing blood-compatible artificial surfaces.
Open Access
Efficacy of locally delivered parathyroid hormone for treatment of critical size bone defects
(Colorado State University. Libraries, 2018) Wojda, Samantha J., author; Donahue, Seth, advisor; Yaszemski, Michael, committee member; Popat, Ketul, committee member; Reynolds, Melissa, committee member
Large segmental defects in bone (e.g., due to trauma or tumor resection) commonly have complications or fail to heal properly, resulting in delayed or non-union. Around 2.2 million orthopaedic procedures utilize autografts or allografts each year to repair large defects; however, neither is without disadvantages. Disability due to orthopaedic injury has a significant impact on both the patient and the healthcare system. Quality of life for these patients can be severely impacted as healing time may exceed 9 months and multiple treatment attempts may be required if the first is unsuccessful. Research into bone graft substitutes, like Infuse® and OP-1® (Bone Morphogenetic Protein and a collagen sponge), has become prominent. PTH is another bioactive molecule that may promote bone regeneration and provide an alternative to autograft and BMP use for treatment of large segmental defects and non-unions. Daily injections of PTH are well known to have an anabolic effect on bone and are presently FDA approved for use as an osteoporosis treatment that results in increases in both bone mineral density and bone volume. Off label PTH 1-84 treatment also resulted in the healing of a non-union fracture that was unresponsive to BMP. Current FDA approval is for daily injections of PTH (intermittent administration), as continuously elevated PTH often has a catabolic effect on bone. However, post-menopausal women with mild primary hyperparathyroidism (PTH levels are not as severely elevated) demonstrate trabecular bone preservation. Low levels of continuous PTH have also been shown to increase bone formation rate and marrow vascularity in mice. Thus, there is some evidence to suggest that low dose continuous PTH could be beneficial as an anabolic therapy in bone and may enhance bone regeneration. Continuously released, locally delivered PTH has been shown to improve healing/formation around dental implants in dogs and drill defects in sheep. However, dose response to local continuously delivered PTH is still unknown. Whether or not the benefits of PTH treatment observed in these models translate to critical size defect models is also unknown. The contribution of the research described in this dissertation increases understanding of the effects of locally delivered PTH on osteoblasts as well as its potential to enhance bone regeneration in a critical size long bone defect. This contribution is significant because presently the effects of low dose continuous PTH are not well understood. Continued development of the approaches described herein could lead to improved therapies for treatment of non-union and critical size defects in bone. Bone regeneration through locally delivered parathyroid hormone has the potential to improve functional restoration, even beyond that of allografts and without the drawbacks of current treatments, which would improve the quality of life for patients.
Open Access
Engineering bacteriophage nanocarriers for targeted delivery of protein reagents to prostate cancer cells
(Colorado State University. Libraries, 2014) DePorter, Sandra M., author; McNaughton, Brian, advisor; Kennan, Alan, committee member; Crans, Debbie, committee member; Reynolds, Melissa, committee member; Di Pietro, Santiago, committee member
Proteinaceous reagents, including antibodies and synthetic proteins, have become some of the most effective reagents for targeted treatment and diagnosis of disease. The unique catalytic activity of some proteins and ability to bind disease-relevant receptors that can evade small molecule discovery, make these reagents well suited for use as therapeutic and bioimaging reagents. However, the large size and charge distribution of most proteins greatly inhibits their intracellular delivery to diseased cells, limiting targets to those displayed on the cell surface. In response to this challenge, we have developed a bacteriophage nanocarrier to deliver large payloads of proteinaceous cargo to the interior of prostate cancer cells. This reagent employs two distinct components: a genetically defined prostate cancer cell-selective protein transduction domain, and a biotinylation site on an orthogonal coat protein, which allows for complexation with streptavidin fusion proteins. Collectively, this approach permits targeted intracellular delivery of ~20 exogenous proteins per phage to human prostate cancer cells. This multifunctional technology offers a cell-selective solution to the challenges associated with delivering protein cargo to the interior of diseased cells and may lead to an expansion in the use of protein reagents.
Open Access
Engineering phthalocyanines and carbon composites for use in sensing, microfluidics and dye sensitized solar cells
(Colorado State University. Libraries, 2018) Klunder, Kevin Jay, author; Henry, Charles, advisor; Prieto, Amy, committee member; Reynolds, Melissa, committee member; Barisas, George, committee member; Jathar, Shantanu, committee member
The focus of this thesis is on fundamental and applied electrochemistry in the areas of photovoltaics, sensors, and microfluidics. Photovoltaics are important as they are needed to reduce the amount of greenhouse gases, pollution, and reliance on finite energy sources that are currently associated with energy production. A thin film photovoltaic device known as a dye sensitized solar cell (DSSC) is studied in his work. Specifically the cathode of the DSSC is studied in detail. A new method to create a highly transparent and catalytic DSSC cathode coating is proposed. The phthalocyanine based coatings have ~97% transmittance at 550 nm and low charge transfer resistance of ~1.3 Ω cm2, representing one of the best cathode coatings in terms of transparency and charge transfer resistance to date. Electrochemical sensors and electrochemical microfluidics can be used to monitor air, water and soil pollution, both of which can occur from anthropogenic and/or natural sources. Quantifying this pollution is vital for human and animal safety. Electrochemical sensors are also used for health diagnostics and are commonly applied in blood glucose monitoring. It is projected that wearable forms of electrochemical sensors will emerge as a vital class of real-time point-of-care sensors to monitor health indicators in the near future. To advance the field of electrochemical sensors and electrochemical microfluidics low cost, easily miniaturized, patterned, and shaped electrodes are needed. The work here introduces a new fabrication method for carbon composites which enables electrodes to be patterned and made into micron features in a facile manor through solvent or melt processing. The composites are also shown to be easily integrated into microfluidic devices, demonstrated with the assembly of electrochemical droplet microfluidics. The ease of fabrication of the new composites represents a milestone for the widespread use of low cost carbon composites in complex electrochemical systems. Within this thesis, Raman, SEM, XRF, and a wide range of electrochemical redox species and techniques are used to determine what factors affect the electrochemical activity, capacitance, and conductivity of the carbon composites. Finally, phthalocyanines for uses in electrochemical catalysis are a recurring theme throughout the thesis. Chapter 4 is dedicated to creating new types of electropolymerizable phthalocyanines. Cobalt phthalocyanine is integrated into the carbon composites from Chapter 2 for uses in thiol oxidation and the sensing of thiols. The thiol of interest was dithiothreitol (DTT) which is used in the "DTT assay". The DTT assay is a chemical measure of oxidative potential of particulate matter, and is commonly used to try and understand health effects relating to air pollution. Here, low volume disposable cells, as well as flow based sensors are developed for the detection of DTT.
Open Access
Evaluating the effects of fire on carbon and nitrogen biogeochemistry in forested ecosystems
(Colorado State University. Libraries, 2023) Roth, Holly, author; Borch, Thomas, advisor; Henry, Chuck, committee member; Reynolds, Melissa, committee member; Prenni, Jessica, committee member; Wilkins, Mike, committee member
Forests provide ecosystem services (e.g., carbon storage, nutrient processing, and water filtration) valued at ~$5 trillion per year which are vulnerable to disturbances such as wildfire. Although fires are a natural component of healthy forests, climate change has begun to increase the size, frequency, and severity of wildfires outside of their historic range. Expected increases in burn severity have implications for carbon (C) and nitrogen (N) cycling, with the potential to shift forests from C sinks to C sources due to long delays in tree re-establishment. There is great interest in resolving changes to soil organic matter (SOM) composition, especially organic nitrogen, to predict how forests respond to wildfires. Therefore, the purpose of the work included in this dissertation was to improve nitrogen analysis in fire-impacted forest systems and apply these methods to soil and water samples. In the following work, a suite of advanced analytical approaches were used to determine the molecular composition of SOM, which was evaluated for the impacts of severe wildfires on microbially-mediated SOM processing and water quality in fire-impacted watersheds. Field-based soil and water samples were collected from subalpine forests in the Colorado Rocky Mountains and investigated for shifts in the water-soluble and solid fractions of SOM in lodgepole pine-dominated forests and their influence on microbial processing and water quality was determined. The objectives of this study were to leverage ultrahigh mass spectrometry to improve N analysis in fire-impacted systems (Objective 1), determine the post-fire changes to surface water C and N chemistry in reducing conditions (Objective 2) and to characterize how fire severity influences SOM composition along soil burn severity gradients (Objective 3). Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) currently achieves the highest mass resolving power in the world, which allows for the study of complex mixtures with tens of thousands of compounds that are separated by the mass of an electron across a wide molecular weight range. The most widely used FT-ICR MS analytical approach uses negative-ion mode electrospray ionization (-ESI) to selectively ionize highly abundant carboxylic acids in SOM. The application of this approach has allowed for rigorous analysis of C composition; however, -ESI FT-ICR MS vastly underestimates N-dense species which are formed during combustion. The biases associated with ionization are propagated in chemical property calculations that are determined by elemental compositions and which must be fully understood for proper use in C and N cycling models. We compared traditional -ESI with positive-ion mode electrospray ionization (+ESI) of burned soil extracts and found that +ESI increased compositional coverage by 87%, including nearly 10,000 additional N species (Objective 1). We applied our +ESI FT-ICR MS findings on a burn severity gradient (low, moderate, and high severity) to evaluate the compositional changes to SOM with increasing severity, with a specific focus on organic nitrogen. We collected soils from burned lodgepole pine forests along the Colorado-Wyoming border from two depths to characterize changes to organic N chemistry. Since organic N is the most abundant form of soil N in conifer forests, a better understanding of post-fire organic N will help address a critical gap in our understanding of fire severity-induced changes in the molecular composition of soil organic nitrogen. Nuclear magnetic resonance spectroscopy and FT-ICR MS analysis showed that N content and aromaticity of water-extractable SOM (0-5 cm depth) increased with burn severity, while minimal changes to the 5-10 cm depth were observed. Heterocyclic N species are generally higher in toxicity compared to their non-nitrogenated counterparts, which prompted soil toxicity measurements. We used Microtox ® to determine that soil toxicity increased with increasing burn severity, which may be partly attributed to newly formed N-species (Objective 2). In conjunction with increased fire activity, North American beaver (C. canadensis) populations have steadily increased since the early 1900s. The ponds that beavers create slow or impound hydrologic and elemental fluxes, increase soil saturation, and have a high potential to transform redox active elements (e.g., oxygen, nitrogen, sulfur, and metals). While surface water runoff composition has been studied in many environments, the effects of reducing conditions (i.e., beaver ponds) on these products are not well known. We collected surface water and sediment samples to investigate the impact of beaver ponds on the chemical properties and molecular composition of dissolved forms of C and N, and the microbial functional potential encoded within these environments from a combination of FT-ICR MS and metagenomics. We found that N-containing compounds and aromaticity increased in the surface water of burned beaver ponds, and that C/N and O/C ratios decreased. Microbial communities within the ponds did not have the capacity to process aromatic species, but they did have the potential for anaerobic metabolism and the potential to respire on microbial necromass (Objective 3). Fires burn heterogeneously across the landscape, and overstory vegetation likely plays a large role both in the way fires burn and how soils recover post-fire. Site factors such as soil type affect the interactions of SOM with abiotic soil components and can have cascading effects on soil C storage, including SOM partitioning between particulate organic matter (POM) and mineral associated organic matter (MAOM). POM is generally considered to have a faster turnover time than MAOM, which is physically protected from microbial degradation. Soil under two common trees in Colorado (lodgepole pine and aspen) are known to differ in SOM quantity and composition, including their relative proportions of POM and MAOM but post-fire products in these soils are relatively uncharacterized. To determine the differences in post-fire SOM between aspen and pine soils, we collected soils from under aspen and pine stands and burned them in open-air pyrocosms to minimize environmental variables which confound field-based studies. We concluded that fire influenced the dissolved fraction of the soils, with higher concentrations of dissolved organic carbon, dissolved total nitrogen, ammonium-N, and nitrate-N in burned aspen soil extracts. To determine the implications for less bioavailable carbon fractions, we will determine %C and %N in soils that have only been dried and sieved, as well as separated into POM and MAOM. We will also characterize the dissolved fractions using FT-ICR MS and NMR to evaluate differences in soil functional groups. Complementary microbiome analyses will be performed to determine the implications of shifts in soil functionality for microbial processing and C and N sequestration. The novel application of +ESI in this dissertation allowed for the identification of increasingly N-dense species at high burn severities which were not previously observed in field samples. N-dense species are enriched under reducing conditions as they are unable to be processed by local microbial communities. In total, these findings contribute to our understanding of newly formed organic C and N species in soils, with implications for microbial activity in fire-affected watersheds.
Open Access
Functional nanostructured ionic liquid-based block copolymer systems for energy applications
(Colorado State University. Libraries, 2021) May, Alyssa Winter, author; Bailey, Travis S., advisor; Reynolds, Melissa, committee member; Sambur, Justin, committee member; Lear, Kevin, committee member
Room-temperature ionic liquids (RTILs) are pure molten salts that have zero vapor pressure, a wide range of thermal stability, negligible flammability, and high ionic conductivity. These qualities make them desirable as electrolyte replacements for the more common lithium salt-doped carbonate solvents which are ubiquitous in current battery technology despite being exceptionally flammable. Use of liquid electrolytes, even non-flammable ones, has its drawbacks and challenges, like preventing leakage of the electrolyte and maintaining good contact with electrode surfaces, particularly when the battery electrodes or container become physically warped. With the emergence of flexible electronics technologies like foldable phones, bendable displays, and "wearables," interest has grown in developing solid electrolytes that are mechanically robust and sufficiently good ionic conductors, as they greatly expand the design possibilities for batteries. Block copolymers (BCPs) are an ideal platform from which to develop solid electrolyte materials as the variety of polymerizable blocks and physical properties that can be derived from them are nearly limitless. In this dissertation, we explore two methods for incorporating ionic liquid components into solid BCP materials, and thoroughly delve into their interesting chemical, physical, and mechanical properties to demonstrate their potential as functional materials. The first method is the direct, sequential polymerization of both ionic liquid-based and traditional monomers to create poly(ionic liquid) (PIL) BCPs that can microphase separate to form ordered nanostructures. We report on the synthesis of both cobalt-containing and imidazolium-based PIL BCPs and provide a comprehensive examination of their melt-state phase behavior, including the observation of all four equilibrium morphologies available to diblock copolymers: lamellae (Lam), bicontinuous gyroid (Gyr), hexagonally packed cylinders (Hex), and spheres (S). From the morphological phase behavior, we were able to build two phase diagrams and extract critical information about the materials, such as block density of the methyl-imidazolium PIL block. This is an essential parameter for BCP design that enables researchers to target specific morphologies when creating similar materials in the future. The morphology of solid-state conductive materials like PIL BCPs has direct implications on their transport properties, as only certain morphologies (Gyr, S) can have fully continuous domains in which ions can flow, so fully understanding the spectrum of phase behavior in a BCP material is incredibly important for creating truly functional materials from them. The second method is the integration of RTIL into amphiphilic, non-ionic BCPs as a selective swelling solvent to create ion gels, or gel polymer electrolytes (GPEs). We have designed these BCPs, based on melt-state phase separating blends of polystyrene-b-poly(ethylene oxide) (SO) and polystyrene-b-poly(ethylene oxide)-polystyrene (SOS) in which the hydrophilic O block is the majority component, to form hydrophobic spherical domains of S that form a tethered, physically crosslinked networked that acts like an elastic solid when swollen. We demonstrate that SOS BCPs swollen in the RTIL 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, or [EMIM][TFSI], have exceptional ionic conductivity, elasticity, distensibility, recovery rates, bulk toughness, and fracture toughness. This rare combination of multiple excellent mechanical properties and high ionic conductivity makes SOS GPEs auspicious candidates as solid electrolytes in energy transport and storage applications.
Open Access
Functionalization of pyridines and other azines via phosphorus ligand-coupling reactions
(Colorado State University. Libraries, 2019) Hilton, Michael C., author; McNally, Andrew, advisor; Reynolds, Melissa, committee member; Crans, Debbie, committee member; Montgomery, Tai, committee member
Nitrogen heterocycles are ubiquitous in pharmaceutical compounds with pyridine being one of the most frequently occurring examples. The discovery and development of new drugs rely heavily on our ability to modify these commonly occurring structures. The functionalization of pyridine has a long history but despite this, there remain some deficiencies in this area of synthesis. Reactions which expand upon the known methodologies are of tremendous value to medicinal chemists who frequently work with pyridines and similar azines. Chapter one will cover the relevance of pyridines in pharmaceuticals and will explain how structural features contribute to their presence in drugs. Conventional and newer methods to functionalize pyridine are also addressed. Chapter two will describe the work of the McNally lab in the development of heterocyclic phosphonium salts as reagents to selectively functionalize pyridines. An application of these salts is as precursors to form C−O bonds from alkoxide nucleophiles. Chapter three presents the development of a strategy to construct bis-heterobiaryls using phosphorus ligand-coupling. This method offers an alternative to the widely used metal-catalyzed approaches which often struggle in the synthesis of bis-heterobiaryls. Lastly, chapter four will expand upon this work showing a new approach to prepare bis-heterobiaryls using heteroaryl halides. This route enables easy access to 2,2'-bipyridines which are difficult to synthesize using conventional methods.
Open Access
Hemocompatibility of hyaluronan enhanced linear low-density polyethylene for heart valve leaflet applications
(Colorado State University. Libraries, 2018) Simon-Walker, Rachael, author; Popat, Ketul C., advisor; Reynolds, Melissa, committee member; Orton, Christopher, committee member; Chicco, Adam, committee member
Heart valve disease is a major concern in both developed countries with advanced ageing populations and undeveloped countries which experience a high incidence of rheumatism leading to valvular disease. To reduce mortality and improve quality of life, heart valve implantations have been widely used to assist in improving function of the native cardiovascular system. While mechanical heart valves and tissue-based heart valves have been successfully used to improve quality of life compared to untreated valvular disease, draw-backs are inherent. Mechanical heart valves are prone to thrombosis and require life-long supplemental anti-coagulation therapy. Tissue-based valves are more hemocompatible, but lack the durability required for long-term implantation. To address these issues, polymeric heart valves have been highly sought after due to polymers' abilities to enhance durability and be manufactured to be similar to the native heart valve leaflet. In addition, their surfaces can be modified to increase hemocompatibility. In this work we explore the hemocompatibility and immune response to a novel polymer for use in heart valve leaflet applications; hyaluronan enhanced linear low-density polyethylene. It is proposed that the combination of linear low-density polyethylene with hyaluronan will create a highly durable material that will reduce thrombosis and inflammation due to the anionic and hydrophilic nature of the glycosaminoglycan.
Open Access
Hemocompatibility of polymeric materials for blood-contacting applications
(Colorado State University. Libraries, 2015) Woodbury, Jodi Marie, author; Popat, Ketul, advisor; Dasi, Prasad, committee member; Reynolds, Melissa, committee member
Hemocompatibility of a biomaterial plays a vital role in the overall success of the biomaterial in the body. Every implanted biomaterial tends to cause an immune response by the host tissue. The intensity of said response depends on many factors, including the properties of the material itself. In this study, we have assessed the hemocompatibility of expanded polytetrafluoroethylene (ePTFE), linear low-density polyethylene (LLDPE) and polyethylene terephthalate (PET); 3 potential materials for blood-contacting applications. The surface morphology was characterized using scanning electron microscopy (SEM), and surface wettability was characterized using contact angle goniometry. The cytotoxicity was investigated using lactate dehydrogenase (LDH) assay. The adsorption of key blood serum proteins was evaluated using micro-bicinchoninic acid (micro-BCA) assay. The results were visualized using SEM. Platelet adhesion and activation was investigated using live cell staining and SEM. Whole blood clotting kinetics were evaluated using a hemolysis assay and the results visualized using SEM. The results indicate that none of these materials are cytotoxic. Protein adsorption was highest on PET, and platelet adhesion was significantly higher on PET. However, the percentage of activated platelets and whole blood clotting kinetics was comparable on all materials. This work successfully creates a baseline against which the hemocompatibility of modified ePTFE, LLDPE and PET can be measured.
Embargo
Leveraging bio-based monomers, chemical recyclability, and sustainable polymerization techniques for sustainable polymer synthesis
(Colorado State University. Libraries, 2024) Bernsten, Simone Noelle, author; Miyake, Garret, advisor; McNally, Andy, committee member; Reynolds, Melissa, committee member; Reisfeld, Brad, committee member
Polymeric materials have become vital to everyday life since their commercialization. Although polymers are integral to many industries and consumers, their synthesis and use brings with them a myriad of environmental concerns. Unsustainability can arise even before polymer synthesis in that many synthetic polymers are made from petroleum-derived monomers which are inherently nonrenewable. Next, many polymers are synthesized using one or more unsustainable components such as precious metals including iridium and ruthenium. Finally, at the end of a polymer's useful life, options for recycling are limited by the inability to make virgin-quality materials that can be used for the same application as the original polymer. The work described in this thesis aims to address each of these issues. The polymerizations of several bio-based monomers are described. The use of organic photoredox catalysis to enable polymerization represents sustainable synthesis of polymers. Polymers exhibiting chemical recyclability are also investigated, wherein end-of-life materials can be depolymerized and used to produce virgin- quality materials. Ultimately, this work represents a diverse array of methodologies for increasing the overall sustainability of polymeric materials.
Open Access
Methods for detecting and developing protein-protein or protein-RNA interactions
(Colorado State University. Libraries, 2014) Blakeley, Brett D., author; McNaughton, Brian, advisor; Kennan, Alan, committee member; Fisk, Nick, committee member; Reynolds, Melissa, committee member; Peersen, Olve, committee member
Potent and selective recognition of disease-relevant macromolecules - such as proteins and RNA - is the molecular basis of most pharmaceuticals . Historically, small (< 500 Da) molecules have filled this role. However, the overwhelming majority (~85%) of the proteome - and emerging therapeutic targets such as RNA - present a serious challenge to small molecule-dependent recognition. An alternative approach to potent and selective recognition and regulation of disease-relevant proteins and RNA is to use synthetic proteins. In contrast to small molecules, the size, relatively high folding energies (>10 kcal/mol) and functional group diversity (by virtue of proteinaceous amino acids) allow proteins to recognize - and potentially control - macromolecular receptors that evade small molecules. Presented here are two approaches to advancing the discovery of new proteins that recognize either disease-relevant protein or RNA targets. The first part of this thesis describes split superpositive GFP reassembly as a method to identify novel protein-protein interacting pairs in living cells (E. coli). The second part of this thesis describes basic studies to evaluate the suitability of a naturally occurring RNA Recognition Motif (RRM) as a scaffold for targeting disease-relevant RNA hairpins, and the development of new RRMs that target TAR RNA, a hairpin critical to HIV proliferation.
Open Access
Molecular design of a fatigue-resistant and energy-dissipative hydrogel
(Colorado State University. Libraries, 2022) Klug, Allee Shiryce, author; Bailey, Travis, advisor; Reynolds, Melissa, committee member; Chen, Eugene, committee member; Weinberger, Chris, committee member
Hydrogels at the most basic iteration are cross-linked polymer networks swollen in water. They show promise in biomedical applications due to their high water content and flexibility. However, intentional design of new hydrogel networks by modification of the choice of polymer, the fabrication of the polymer network, and the choice of cross-link have resulted in hydrogels which have useful properties ranging from fatigue resistance to elasticity to bulk toughness. Of particular interest is a hydrogel which can dissipate energy as a way to resist failure of the polymer network. Unfortunately, many of the design strategies previously used to insert an mechanism for energy dissipation into the hydrogel result in hydrogels which are not elastic or their mechanical properties fatigue throughout multiple cycles of use. Therefore, our goal was to design a hydrogel network that is able to both dissipate energy and be resistant to fatigue of mechanical properties. This design strategy is based on the self-assembly of blends of ABC and ABCBA block polymers, specifically polystyrene-b-polyisoprene-b-poly(ethylene oxide) (PS-PI-PEO, SIO) and polystyrene-b-polyisoprene-b-poly(ethylene oxide)-b-polyisoprene-b-polystyrene (PS-PI-PEO-PI-PS, SIOIS) into a sphere morphology where the A block is spheres of glassy, hydrophobic polystyrene surrounded by the B block of rubbery, hydrophobic polyisoprene as the surface of the sphere. These AB spherical domains sit in a matrix of the C block, poly(ethylene oxide). The spherical domains are tethered together by the SIOIS polymer so that the glassy spheres are evenly-spaced physical crosslinks in the polymer network. The tethered spheres provide the network with elasticity and fatigue resistance while the hydrophobic PI block is accessible to forcibly mix with water as a way to dissipate energy when the hydrogel is strained. This dissertation describes the design, testing, and optimization of a hydrogel where an energy dissipation mechanism was placed directly onto every crosslink of a known elastic and fatigue-resistant network. The possibility of even designing such a network was tested by studying the self-assembly of the SIO polymers into the ABC block polymer sphere morphology. Once, the formation of the sphere morphology in the tethered micelle network was confirmed, the effectiveness of the design strategy of a fatigue-resistant network with an intrinsic energy dissipation mechanism was studied by comparison of the mechanical properties of the SIOIS hydrogel to a similar hydrogel that is fatigue-resistant but does not contain an energy dissipation mechanism. Finally, the design of the SIOIS hydrogel is optimized by studying the effect of changes to the hydrogel processing method and changes to the PS molecular weight on the self-assembly of the energy dissipation PI block and the formation of the tethered micelle network.
Open Access
New methods to access functionalized N-heterocycles
(Colorado State University. Libraries, 2021) Patel, Chirag, author; McNally, Andrew, advisor; Bandar, Jeffrey, committee member; Reynolds, Melissa, committee member; Kipper, Matthew, committee member
N-heterocycles are ubiquitous in pharmaceuticals and agrochemicals. Their prevalence is due to the unique properties they can impart to a molecule. Due to their ubiquity, it is vital that synthetic chemists be able to modify the structure of these valuable scaffolds. Despite a great deal of literature on the functionalization of these important motifs, challenges toward the functionalization of N-heterocycles remain. Chapter 1 will highlight the importance of azaarenes in pharmaceuticals and explain the properties that make these structures so prevalent in drugs. Classical and modern methods to functionalize pyridines and diazines will also be discussed. Chapter 2 will describe the development of the phosphonium salt chemistry in the McNally lab and the use of these reactive intermediates to aminate pyridines and diazines via the Staudinger reaction. Chapter 3 will introduce the concept of phosphorus ligand-coupling and briefly describe its previous application toward the synthesis of bis-heterobiaryls. This chapter will also cover the importance of fluoroalkyl groups in both the pharmaceutical and agrochemical industries. Current methods to fluoroalkylate azaarenes will be discussed, and the development of a novel fluoroalkylation strategy via a phosphorus ligand-coupling reaction will be explained. Finally, chapter 4 covers ongoing research into the synthesis of N-alkyl/aryl pyridiniums and their hydrogenation to N-substituted piperidines. The importance of N-substituted piperidines and the limitations to their synthesis are described.
Open Access
Novel approaches to characterizing feline-associated dermatophytic fungi
(Colorado State University. Libraries, 2022) Moskaluk, Alexandra Elizabeth, author; VandeWoude, Sue, advisor; Daniels, Josh, committee member; Schissler, Jennifer, committee member; Reynolds, Melissa, committee member
Dermatophytes are highly infectious fungi that cause superficial infections in keratinized tissues in humans and animals. This group of fungi is defined by their ability to digest keratin and encompasses a wide range of species. Classification of many of these species has recently changed due to genetic analysis, potentially affecting clinical diagnosis and disease management. In Chapter One, we review dermatophyte classification including name changes for medically important species, current and potential diagnostic techniques for detecting dermatophytes, and an in-depth review of Microsporum canis, a prevalent zoonotic dermatophyte. M. canis commonly causes dermatophytosis in humans and cats, and is adapting to its primary host (domestic cats) as one of its mating types (MAT1-2) appears to be going extinct. Assessment of genetic variation among M. canis isolates in the United States has not been conducted. Further, M. canis mating type and assessment of disease severity associated with genotypic characteristics have not been rigorously evaluated. In Chapter Two, M. canis was isolated from 191 domestic cats across the US and characterized genotypes by evaluation of ITS sequence, MAT locus, and microsatellite loci analysis. The genes SSU1 and SUB3, which are associated with keratin adhesion and digestion, were sequenced from a subset of isolates to evaluate potential genetic associations with virulence. Analysis of microsatellite makers revealed three M. canis genetic clusters. Both clinic location and disease severity were significant predictors of microsatellite variants. 100% of the M. canis isolates were MAT1-1 mating gene type, indicating that MAT1-2 is very rare or extinct in the US and that asexual reproduction is the dominant form of replication. No genetic variation at SSU1 and SUB3 was observed. These findings pave the way for novel testing modalities for M. canis and provide insights about transmission and ecology of this ubiquitous and relatively uncharacterized agent. Chapter Three evaluated four dermatophytosis cases occurring in kittens collected from the study in Chapter Two that yielded fungi with colony morphology more similar to Arthroderma species than Microsporum. Morphologic and microscopic examinations were conducted, and gene segments for the ITS, β-tubulin, and translation elongation factor 1-alpha (TEF1) regions were sequenced from DNA extracted from these cultures. Sequences were aligned to other dermatophytes using maximum likelihood and neighbor-joining trees and were compared to previously described fungal species to assess nucleotide homology. We identified two previously undescribed fungal species, herein as Arthroderma lilyanum sp. nov. and Arthroderma mcgillisianum sp. nov. M. canis co-cultured in two of the four cases. Other physiologic tests supported this diagnosis. These species have significance as potential pathogens and should be considered as rule-outs for dermatophytosis in cats. The potential for infection of other species, including humans, should be considered. In Chapter Four, we investigated a critical adhesion protein (Sub3) utilized by M. canis during initial stages of infection, analyzing its production and expression under varying growth conditions. Additionally, as this protein must be expressed and produced for dermatophyte infections to occur, we developed and optimized a diagnostic antibody assay targeting this protein. While clinical samples of M. canis were found to have low Sub3 production, Sub3 levels were increased in culture when grown in baffled flasks and supplemented with either L-cysteine or cat hair. As Sub3 was also produced in cultures not supplemented with keratin or cysteine, this study demonstrated that Sub3 expression is not reliant on the present of keratin or its derivatives. These findings could help direct future metabolic studies of dermatophytes, particularly during the adherence phase of infections. Chapter Five explored two molecular approaches for developing diagnostic assays for dermatophytosis based on keratin metabolites: sulfite and S-sulfocysteine (SSC). Currently, fungal culture is still considered the "gold standard" for diagnosing dermatophytosis, however, modern molecular assays have overcome the main disadvantages of culture, allowing for tandem use with cultures. The first approach involved a starch and iodine indicator that reacts with sulfite and SSC, resulting in a visual color change. While this method had a low limit of detection, the indicator had many off-target reactions, leading to low specificity for dermatophyte metabolites. The second approach utilized tandem liquid chromatography with mass spectrometry, targeting SSC. Using the same cultures performed in Chapter Four, we were able to detect and quantify SSC from M. canis cultures grown with hair at days 15 and 18 post inoculation. These findings demonstrated that SSC is consumed/degraded by the fungi, particularly during early growth stages. Collectively, this work provides future directions for genetic and metabolic studies of dermatophytes and how to leverage unique characteristics of dermatophytes for developing novel diagnostic assays. We conclude that M. canis genetics influence clinical disease presentation and further whole genome studies could help elucidate key genetic regions involved in dermatophyte pathogenesis. Furthermore, as M. canis continues to adapt to its primary host of cats, having a rapid, accurate diagnostic assay will become even more critical, particularly in high-density populations.
Open Access
Novel in silico-designed SMYD3 inhibitors eliminate unrestrained proliferation of breast carcinoma cells
(Colorado State University. Libraries, 2021) Alshiraihi, Ilham Mohammed, author; Brown, Mark, advisor; Kato, Takamitsu, advisor; Reynolds, Melissa, committee member; Snow, Christopher, committee member
SMYD3 is a lysine methyltransferase that regulates the expression of over 80 genes and is required for the uncontrolled proliferation of most breast, colorectal, and hepatocellular carcinomas. Elimination of SMYD3 restores normal expression patterns of these genes and halts aberrant cell proliferation. In this study, we used in silico screening to identify potential small molecule inhibitors of SMYD3 and tested the ability of these inhibitors to reduce its methyltransferase activity in vitro. Using breast cancer cell lines that overexpress SMYD3 and normal breast epithelial cell lines, we have confirmed the ability of one of these inhibitors, Inhibitor-4, to reduce cell proliferation, arrest the cell cycle, and induce apoptosis in breast cancer cells without affecting normal cell behavior. Our results provide a proof of concept for the in silico design of small molecule enzyme inhibitors and for the use of such an inhibitor to target SMYD3 for the treatment of cancer.
Open Access
Novel microfluidic devices for aerosol analysis
(Colorado State University. Libraries, 2012) Mentele, Mallory M., author; Henry, Charles, advisor; Barisas, George, committee member; Reynolds, Melissa, committee member; Ladanyi, Branka, committee member; Kreidenweis, Sonia, committee member
Widespread interest in microfluidic technology over the past 20 years has led to the development of microfluidic devices that are as varied in their complexity and capabilities as they are in the applications they are used for. This dissertation describes the development of two microfluidic devices, each designed for measurement of specific aerosol components. A microchip incorporating an interface between a continuous hydrodynamic sample flow and capillary electrophoresis separation was developed for analysis of atmospheric aerosols. The ability to separate and detect analytes from a continuous sample flow allows the microchip to be coupled to a particle-into-liquid aerosol sampler, providing a method for near real-time analysis of ionic aerosol components. Theoretical modeling of hydrodynamic and electroosmotic flows was used to predict flow behavior in the microchip and to optimize geometry. Separation and conductivity detection of common ionic aerosol components were carried out to observe device performance, and detection of nitrate and sulfate in Fort Collins air was accomplished with the coupled system. The simple design introduced here is the first example of a continuous flow microfluidic capillary electrophoresis device that incorporates conductivity detection, and is the first microfluidic device to be coupled to a continuous flow aerosol collector. A paper-based microfluidic device was also designed for the purpose of assessing occupational exposure to particulate metals. Assays were developed for colorimetric detection of metals on paper and these were employed in detection reservoirs of the device. A novel method was also developed for rapid digestion of particulate metals directly on a filter. Metal concentrations were quantified from color intensity images using a scanner in conjunction with image processing software. Finally, a standard incineration ash sample was aerosolized, collected on filters, and analyzed for the three metals of interest. This is the first paper-based device capable of multiplexed metal detection from a real, aerosolized sample.