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College of Sciences

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School of Biological Sciences

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School of Chemistry and Biochemistry

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School of Earth and Atmospheric Sciences

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School of Mathematics

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School of Physics

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Sub-Stoichiometric Titania as a Viable Support for Pt Electrodes

(Georgia Institute of Technology, 2021-05-18) Bell, Crystal Nacolle

The growing demand for fossil fuels has resulted in inevitable environmental consequences along with the gradual depletion of fuel sources. As a result, extensive efforts are focused on developing environmentally benign and sustainable alternatives such as fuel cells. While fuel cells alone would not rid greenhouse gas emissions, they can contribute to their reduction. Barriers hindering the commercialization of fuel cells include performance, durability, cost, and storage. A major contributor to the high cost of fuel cells is the use of Pt at the electrode. Therefore, research has been devoted to overcoming these issues by reducing the loading of Pt, alloying Pt with a less noble metal, implementing Pt free catalyst. Furthermore, carbon has been the most traditionally used catalyst support in fuel cell applications; however, carbon is susceptible to corrosion resulting in the loss of the support and Pt nanoparticle agglomeration/detachment. In this thesis, I showcase the synthesis, characterization, and use of Ti2O3 and Ti3O5 supports as a stable support for Pt-based electrocatalyst use in several prominent fuel cell reactions.
HETEROFUNCTIONAL PARTICLES AS SINGLE CELL SENSORS FOR THE LIVE-CELL ANALYSIS AND QUANTIFICATION OF SECRETED PROTEINS

(Georgia Institute of Technology, 2021-05-04) Ramirezmendez, Katily Angelica

Identification of individual cells that are actively secreting a specific protein is a challenging proposition due the difficulty to assign secreted cellular products to the specific cell. Two challenges to individual cell secretion analysis and separation include the rapid diffusion and mixing of secreted products and the inability to relate the low levels of protein secretion to individual cells at scale. This thesis focuses on the design and testing of heterofunctional particles to target specific cells and collect and detect secreted protein that overcomes these limitations to enable a quantitative single-cell secretion analysis platform. The particles offer a non-destructive, simple protocol to bind to specific targeted cells and detect targeted secreted products through fluorescent labeling compatible with fluorescent activated cell sorting (FACS). Two types of heterofunctional particles were tested: Janus particles, defined as a particle with two spatially segregated functional proteins responsible for both cell binding and secreted protein collection, and particles that display mixed functional proteins. This dissertation discovers: 1) an optimized protocol to collect low concentration of soluble antibodies onto particles of different sizes and materials; 2) the design of a fabrication process to create heterofunctional particles displaying both the targeting and collecting molecules, and a protocol to isolate specific protein secreting cells; and 3) the demonstration of the particle platform to not only target specific cells but also to simultaneously collect secreted proteins to identify and isolate both high and low protein producing cells. The innovations of this study include the ability to characterize millions of cells for cell surface markers, protein secretion, as well as the ability to multiplex detection of two types of secreted protein to be simultaneously assessed. This work demonstrates that H1 influenza virus (H1IV)-specific antibody secreting cells (ASCs) can be identified and collected from blood of infected and/or vaccinated patients by the particles using an antigen specific H1IV fluorescently labeled tetramer By changing the targeting and collector molecules on the beads, the workflow was easily adapted to isolate other high and low producing cells, including IgG-producing hybridoma and VEGF-secreting human mesenchymal stem cells (hMSCs)
Studies in using gold nanoparticles in treating cancer and inhibiting metastasis

(Georgia Institute of Technology, 2019-04-01) Wu, Yue

Based on statistics from the World Health Organization, cancer is among the top killers in the world. Metastasis, which is the process of cancer cells leaving their primary location and forming secondary tumor(s) in remote places in the body, is responsible for the majority of cancer-related deaths. The current anti-metastasis treatments are rarely effective therefore, this dissertation aims at developing new techniques of using gold nanoparticles (AuNPs) for cancer treatments and inhibiting metastasis. Chapter 1 introduces the general background of gold nanoparticles including their synthesis, physical and optical properties, their usage in cancer treatment and their biocompatibility. In Chapter 2, we introduce the AuNPs to cancer cells, and use their optical properties as sensing and imaging probes in order to study their impact on cancer cells for diagnosis and treatment. Chapter 3 focuses on the impact of AuNPs on the mechanical properties of cancer cells for inhibiting cancer cell migration and invasion. Chapter 4 studies the molecular mechanism in inhibiting cancer cell migration and invasion. After studying the AuNPs impact on cells, the purpose of Chapter 5 is to check the feasibility of utilizing AuNPs treatments for the inhibition of cancer metastasis in animals. This work differs from the previous studies in two major aspects: 1) Rational designs of AuNPs to achieve high specificity for inhibiting cancer cell migration and invasion, with a greatly reduced effective AuNP concentration to enhance biocompatibility. 2) Use of state-to-the-art high resolution microscopy imaging techniques and systematic mass spectrometry-based proteomics to gain deep understanding of the underlying principles involved. Biomechanical properties (such as nuclear stiffness) were also studied for revealing the mechanisms.
The effects of nanoparticle properties on biological imaging and photothermal cancer treatment

(Georgia Institute of Technology, 2017-06-22) Aioub, Mena

Over the past two decades, gold nanoparticles (AuNPs) have emerged as promising tools for biomedical applications. Their unique optical properties enable sensitive detection and effective treatment strategies. Additionally, the expanding toolkit of AuNP colloidal synthesis, combined with their straightforward surface functionalization, allowing for their conjugation with a variety of targeting and / or therapeutic ligands, contribute to their increasing use. This thesis explores the effects of nanoparticle size, shape, composition, and surface chemistry in the design and application of AuNPs for biological imaging and cancer treatment applications. The 1st chapter introduces various AuNP synthesis, characterization, and conjugation strategies, and presents an overview of their tunable optical properties. Recent AuNP applications such as biological imaging, diagnostics, and cancer treatments (Chapter 1) are reviewed to prepare the reader for the remaining chapters. Then, Chapter 2 discusses the effect of varying surface chemistries on nanoparticle localization within living cells. Using different targeting ligands, a dynamic profile of AuNP localization was obtained. Cellular localization was found to critically affect AuNP scattering properties, a crucial component of biological imaging. Increased subcellular targeting was found to result in greater and more rapid localization, resulting in increased light scattering and enhanced imaging (Chapter 2). Subsequently, the nuclear-targeted AuNPs (NT-AuNPs) previously found to give the greatest imaging enhancement were employed as probes to increase the inherent light scattering from cells. Chapter 3 describes a technique to use these NT-AuNPs to compare the relative efficacies of three clinically relevant chemotherapeutic drugs. This allows the use of a single sample of cells in real-time using inexpensive lab equipment, saving time and material costs while imparting the potential to rapidly screen drugs or analogs to determine the most effective option. The remainder of this thesis focuses on plasmonic photothermal therapy (PPT), an emerging treatment where AuNPs convert light into heat, causing cell death specifically in the vicinity of the targeted AuNPs. Chapter 4 discusses the use of NT-AuNPs to induce PPT cell death while simultaneously serving as scattering probes to monitor the associated molecular changes through time-dependent surface-enhanced Raman spectroscopy of single cells. The same molecular changes were observed using different AuNP sizes, concentrations, and laser intensities, indicating the consistency mechanism of action of PPT. Finally, the use of platinum-coated gold nanorods (PtAuNRs) is introduced in Chapter 5 to mitigate the side effects of PPT. Platinum, commonly used for oxygen reduction in catalysis, is incorporated to scavenge reactive oxygen species (ROS), allowing the decoupling of thermal and chemical effects during PPT. The PtAuNRs protected untreated cells from the ROS byproducts of PPT, making them ideal candidates to advance the treatment while reducing deleterious side effects. This thesis presents a fundamental investigation of the influence of AuNP properties on imaging and cancer treatment, which can be used to continue advancing their utility and applications.
Energy transfer in nanostructured systems

(Georgia Institute of Technology, 2017-05-23) O'Neil, Daniel Saldinger

This dissertation contains a number of projects involving the experimental and theoretical investigation of energy transfer within nanostructured systems. Chapter 1 begins with an overview of pump-probe spectroscopy - the primary tool used for these investigations. We then look at the two classes of materials considered in the later chapters: dye sensitized solar cells and plasmonic nanoparticles. This covers the motivation for examining these systems and their photophysics. Chapters 2 and 3 focus on exploring squaraine-based dye sensitized solar cells. The former deals with how the anchor and bridge groups within these molecules affect the energy loss and transfer processes which determine cell efficiency. We see how dye structure relates to aggregation and how this hinders effective charge transfer. The latter considers sensitizers which include an additional porphyrin chromophore. Although this improves the amount of light absorbed, it also changes the charge transfer kinetics. Chapters 4 and 5 explore plasmonic nanoparticle systems which could be used as optical sensors. Chapter 4 looks at the mechanical properties of gold and silver nanorods and how it relates to the crystalline structure and temperature. Chapter 5 is a theoretical investigation of how gold and silver nanocubes couple to each other – a pump-probe experiment is proposed to further study the interaction. Chapter 6 looks at hybrid metal oxide-gold nanoparticles for use in catalysis. The chapter focuses on the synthetic control of nanoparticle shape. It describes the future work of how pump-probe spectroscopy could be used to investigate catalytic enhancement mechanisms.
Synthesis and catalytic study of shell-shell, core-shell hollow gold nanocatalysts

(Georgia Institute of Technology, 2016-04-04) Garlyyev, Batyr

Metal nanoparticles have a large surface area to volume ratio compared to their bulk counterparts, which makes them attractive to use as catalysts. Atoms on the surface of metal nanoparticles are very active due to their high surface energy resulting from their unsatisfied valency. First synthesis of gold nanoparticles with different shapes and bimetallic structure are explored in detail. Then an experimental method which could distinguish between the two mechanisms (homogeneous or heterogeneous) by using hollow plasmonic gold nanocatalyst is developed. Furthermore the catalytic activity of gold nanocages was changed by adding an inner platinum or palladium nanoshell. Results suggested that adding palladium inner shell increased the activity of gold nanocages towards the reduction nitro groups to amino groups. Controlling the selectivity of the catalyst is an important goal of catalysis research. Lastly selectivity of the plasmonic nanocatalyst (Gold sphere-Gold shell Nanorattles) with multiple plasmon modes was studied for photo-dimerization of nitro groups into azo dimers were studied on gold nanocatalyst surface. Results showed that selectivity can be controlled by changing the wavelength of the light exciting surface plasmon.
Exploring some aspects of cancer cell biology with plasmonic nanoparticles

(Georgia Institute of Technology, 2014-07-29) Austin, Lauren Anne

Plasmonic nanoparticles, specifically gold and silver nanoparticles, exhibit unique optical, physical, and chemical properties that are exploited in many biomedical applications. Due to their nanometer size, facile surface functionalization and enhanced optical performance, gold and silver nanoparticles can be used to investigate cellular biology. The work herein highlights a new methodology that has exploited these remarkable properties in order to probe various aspect of cancer cell biology, such as cell cycle progression, drug delivery, and cell death. Cell death mechanisms due to localized gold and silver nanoparticle exposure were also elucidated in this work. Chapter 1 introduces the reader to the synthesis and functionalization of gold and silver nanoparticles as well as reviews their implementation in biodiagnostic and therapeutic applications to provide a foundation for Chapters 3 and 4, where their use in spectroscopic and cytotoxic studies are presented. Chapter 2 provides the reader with detailed explanations of experimental protocols for nanoparticle synthesis and functionalization, in vitro cellular biology experiments, and live-cell Raman spectroscopy experiments that were utilized throughout Chapters 3 and 4. Chapter 3 presents the use of nuclear-targeted gold nanoparticles in conjunction with a Raman microscope modified to contain a live-cell imaging chamber to probe cancer cell cycle progression (Chapter 3.1), examine drug efficacy (Chapter 3.2), monitor drug delivery (Chapter 3.3), and detect apoptotic molecular events in real-time (Chapter 3.4). In Chapter 4, the intracellular effects of gold and silver nanoparticles are explored through live-cell Rayleigh imaging, cell cycle analysis and DNA damage (Chapter 4.1), as well as through the elucidation of cytotoxic cell death mechanisms after nanoparticle exposure (Chapter 4.2) and live cell imaging of silver nanoparticle treated cancer cell communities (Chapter 4.3).
Gold nanoparticles in some chemical and photothermal applications of cancer therapy

(Georgia Institute of Technology, 2013-08-23) Mackey, Megan A.

Gold nanoparticles exhibit an array of properties, both intrinsic (chemical) and extrinsic (photothermal), that can be exploited for their use in cancer therapeutics. Owing to their size and ease with which they can be functionalized with various ligands, gold nanoparticles represent a class of highly functional biomedically relevant nanostructures. Here, we explore the use of gold nanoparticles as intrinsic (chemical) antineoplastic agents, with their ability to cause DNA damage and cytokinesis arrest, to induce apoptosis in a metallic composition-dependent manner, as well as their ability to enhance sensitivity to chemotherapy by regulation of the cell cycle. The extrinsic (photothermal) properties of gold nanoparticles are also examined, in detail, through both theoretical and experimental assessment, for their use as photothermal contrast agents in vitro. Based on this assessment, the gold nanoparticles are tested in the plasmonic photothermal therapy of head and neck cancer in a mouse model.
Theoretical and experimental investigation of the plasmonic properties of noble metal nanoparticles

(Georgia Institute of Technology, 2013-06-28) Near, Rachel Deanne

Noble metal nanoparticles are of great interest due to their tunable optical and radiative properties. The specific wavelength of light at which the localized surface plasmon resonance occurs is dependent upon the shape, size and composition of the particle as well as the dielectric constant of the host medium. Thus, the optical properties of noble metal nanoparticles can be systematically tuned by altering these specific parameters. The purpose of this thesis is to investigate some of these properties related to metallic nanoparticles. The first several chapters focus on theoretical modeling to predict and explain various plasmonic properties of gold and silver nanoparticles while the later chapters focus on more accurately combining experimental and theoretical methods to explain the plasmonic properties of hollow gold nanoparticles of various shapes. The appendix contains a detailed description of the theoretical methods used throughout the thesis. It is intended to serve as a guide such that a user could carry out the various types of calculations discussed in this thesis simply by reading this appendix.
An investigation into bimetallic hollow nanoparticles in catalysis

(Georgia Institute of Technology, 2013-04-03) Snyder, Brian

Nanocatalysis, catalysis using particles on the nanoscale, is an emerging field that has tremendous potential. Nanoparticles have different properties than bulk material and can be used in different roles. Macro sized precious metals, for example, are inert, but nanoparticles of them are becoming more widely used as catalysts. Understanding the manner in which these particles work is vital to improving their efficacy. This thesis focuses on two aspects of nanocatalysis. Chapter 1 begins with a brief introduction into nanotechnology and some of the areas in which nanoparticles are different than bulk particles. It then proceeds into an overview of catalysis and nanocatalysis more specifically. Focus is brought to the definitions of the different types of catalysis and how those definitions differ when applied to nanoparticles. Chapter 2 is in finding an inert support structure to more easily assist in recycling the nanoparticles. Polystyrene microspheres were studied and found to prevent platinum nanoparticles from aggregating in solution and possibly aid in recycling of the nanoparticles. These nanoparticles were used in catalysis, aiding in the reduction of 4-nitrophenol in the presence of sodium borohydride. While the rate decreased by a factor of ~ 7 when using the polystyrene, the activation energy of the reaction was unaltered, thus confirming the inactivity of the polystyrene in the reaction. In Chapter 3, nanocatalysis was studied by examining bimetallic hollow nanoparticles with specific attention to the effect of altering the ratios of the two metals. Ten different bimetallic nanocages were tested in an electron transfer reaction between hexacyanoferrate and thiosulfate. Five PtAg nanocages and five PdAg with varying metal ratios were prepared and studied. It was found that while silver cubes immediately precipitate out of solution when combined with thiosulfate, a small amount of either platinum or palladium allows the particles to remain in solution and function as a substantially more effective catalyst. However, as additional Pt was added the activation energy increased. To obtain a better understanding of the catalysis using bimetallic cages, the evolution of these cages was studied as the 2nd metal was added. Initially the particle edge length increased and then slowly decreased back to the size of the template cubes. The increase in edge length suggests of addition of material to the nanoparticles. This indicated the 2nd metal is on the outside of the cage, which was confirmed using UV-Vis spectroscopy and EDS mapping. By understanding how these bimetallic particles evolve, we may be able to manipulate these synthetic methods to more precisely design nanoparticles for catalysis.