Browsing by Subject "biocompatibility"

Now showing 1 - 3 of 3
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    Development and Applications of Gold Nanoparticles and Elastomeric Polymers as Biomaterials
    (2021-07) Siehr, Allison
    This thesis is focused on the development and applications of two different types of biomaterials: nanoparticles and polymers. In chapter 1, I briefly review these biomaterials. In chapter 2, we develop gold nanoparticles (GNPs) that can be driven to either self-assemble or remain colloidally stable using coiled-coil protein interactions. Control over the GNP self-assembly or stability is critical for specific biomedical applications. In chapter 3, we use the self-assembling GNPs to inhibit human immunodeficiency virus type-1 (HIV-1) by adding a targeting ligand for HIV-1. However, we found our GNPs are weak inhibitors of HIV-1. Methods to improve the inhibitor design are then discussed. In chapter 4, a biomaterials-based approach is used to elucidate the structures of HIV-1 and human T-cell leukemia virus type-1 (HTLV-1). A GNP immunolabeling strategy is used to identify HIV-1 and HTLV-1 envelope proteins, critical for viral entry and targets for vaccine development. However, the immunolabelling strategy was not robust, and alternative methods to study envelope proteins are discussed. Lastly, in chapter 5, a novel elastomeric polymer is evaluated for biomedical applications. PLA-PβMδVL-PLA polymers were synthesized in this work and shown to exhibit elastomeric properties. Next, the polymers were found to be biocompatible and biodegradable both in vitro and in vivo. Overall, this thesis demonstrates the development and applications of both gold nanoparticles and elastomeric polymers as biomaterials.
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    Development of Electrochemical Sensors for Analytical and Biomedical Applications
    (2019-08) Chen, Xin
    The focus of this dissertation is on two main topics: the development of chemical sensors with reduced biofouling for applications in biological samples (Chapter I–II), and the development of chemical sensors with improved biocompatibility (Chapter III–V). Conventional polymeric membrane-based ion-selective electrodes (ISEs) rely on plasticized poly(vinyl chloride) (PVC) as sensor membranes. The plasticizers that solubilize PVC backbone—a prerequisite for PVC-phase ISEs—leach out gradually, resulting in a limited sensor lifetime. Polar groups in the plasticizer may also lower the sensor selectivity. To improve selectivity and expand working ranges, fluorous-phase ISEs relying on nonpolar perfluorinated compounds as sensing membrane were developed. A novel fluorophilic ionophore was synthesized and used to make ionophore-doped fluorous-phase ISEs with Nernstian responses and an optimal working range centered around neutral pH—suitable for most biological samples. The reproducibility of fluorous-phase ISEs was enhanced by a new electrode body design. Importantly, fluorous-phase ISEs maintained their excellent selectivity after prolonged exposure in serum whereas PVC-phase ISEs lost selectivity considerably. Insights were also obtained on the optimal ionophore-to-ionic site ratio. To improve biocompatibility, silicone-based reference and ion-selective electrodes were developed to eliminate plasticizers. Reference electrodes doped with several ionic liquids showed sample-independent and long-term stable potentials in artificial blood electrolytes and serum samples. Potassium-selective silicone-based ISEs developed with two ionophores and two silicones showed Nernstian responses and good selectivities. In an attempt to prevent leaching of ionophores from ISE membrane into samples, a well-known potassium ionophore was covalently attached to silicone membranes. Miniaturized microelectrodes suitable for implantable devices were also developed based on this platform. In a similar effort, plasticizer-free polymethacrylate-based ISEs exhibited Nernstian responses to pH and selectivities comparable to PVC-phase ISEs. To further improve biocompatibility for applications in the pharmaceutical and food industries, either an ionophore or ionic site or both were covalently attached to sensor membranes. Sensors with either ionophore or ionic site attached provided similar good characteristics whereas when both were attached, Nernstian responses were not found consistently. Furthermore, heating experiments showed that sensors exposed to 90 ˚C heating maintained good selectivity.