Matching Items (4)
Description
Nanotechnology is becoming increasingly present in our environment. Engineered nanoparticles (ENPs), defined as objects that measure less than 100 nanometers in at least one dimension, are being integrated into commercial products because of their small size, increased surface area, and quantum effects. These special properties have made ENPs antimicrobial agents in clothing and plastics, among other applications in industries such as pharmaceuticals, renewable energy, and prosthetics. This thesis incorporates investigations into both application of nanoparticles into polymers as well as implications of nanoparticle release into the environment. First, the integration of ENPs into polymer fibers via electrospinning was explored. Electrospinning uses an external electric field applied to a polymer solution to produce continuous fibers with large surface area and small volume, a quality which makes the fibers ideal for water and air purification purposes. Indium oxide and titanium dioxide nanoparticles were embedded in polyvinylpyrrolidone and polystyrene. Viscosity, critical voltage, and diameter of electrospun fibers were analyzed in order to determine the effects of nanoparticle integration into the polymers. Critical voltage and viscosity of solution increased at 5 wt% ENP concentration. Fiber morphology was not found to change significantly as a direct effect of ENP addition, but as an effect of increased viscosity and surface tension. These results indicate the possibility for seamless integration of ENPs into electrospun polymers. Implications of ENP release were investigated using phase distribution functional assays of nanoscale silver and silver sulfide, as well as photolysis experiments of nanoscale titanium dioxide to quantify hydroxyl radical production. Functional assays are a means of screening the relevant importance of multiple processes in the environmental fate and transport of ENPs. Four functional assays – water-soil, water-octanol, water-wastewater sludge and water-surfactant – were used to compare concentrations of silver sulfide ENPs (Ag2S-NP) and silver ENPs (AgNP) capped by four different coatings. The functional assays resulted in reproducible experiments which clearly showed variations between nanoparticle phase distributions; the findings may be a product of the effects of the different coatings of the ENPs used. In addition to phase distribution experiments, the production of hydroxyl radical (HO•) by nanoscale titanium dioxide (TiO2) under simulated solar irradiation was investigated. Hydroxyl radical are a short-lived, highly reactive species produced by solar radiation in aquatic environments that affect ecosystem function and degrades pollutants. HO• is produced by photolysis of TiO2 and nitrate (NO3-); these two species were used in photolysis experiments to compare the relative loads of hydroxyl radical which nanoscale TiO2 may add upon release to natural waters. Para-chlorobenzoic acid (pCBA) was used as a probe. Measured rates of pCBA oxidation in the presence of various concentrations of TiO2 nanoparticles and NO3- were utilized to calculate pseudo first order rate constants. Results indicate that, on a mass concentration basis in water, TiO2 produces hydroxyl radical steady state concentrations at 1.3 times more than the equivalent amount of NO3-; however, TiO2 concentrations are generally less than one order of magnitude lower than concentrations of NO3-. This has implications for natural waterways as the amount of nanoscale TiO2 released from consumer products into natural waterways increases in proportion to its use.
ContributorsHoogesteijn von Reitzenstein, Natalia (Author) / Westerhoff, Paul (Thesis advisor) / Herckes, Pierre (Committee member) / Hristovski, Kiril (Committee member) / Arizona State University (Publisher)
Created2015
Description
The discovery and development of novel antibacterial agents is essential to address the rising health concern over antibiotic resistant bacteria. This research investigated the antibacterial activity of a natural clay deposit near Crater Lake, Oregon, that is effective at killing antibiotic resistant human pathogens. The primary rock types in the deposit are andesitic pyroclastic materials, which have been hydrothermally altered into argillic clay zones. High-sulfidation (acidic) alteration produced clay zones with elevated pyrite (18%), illite-smectite (I-S) (70% illite), elemental sulfur, kaolinite and carbonates. Low-sulfidation alteration at neutral pH generated clay zones with lower pyrite concentrations pyrite (4-6%), the mixed-layered I-S clay rectorite (R1, I-S) and quartz.
Antibacterial susceptibility testing reveals that hydrated clays containing pyrite and I-S are effective at killing (100%) of the model pathogens tested (E. coli and S. epidermidis) when pH (< 4.2) and Eh (> 450 mV) promote pyrite oxidation and mineral dissolution, releasing > 1 mM concentrations of Fe2+, Fe3+ and Al3+. However, certain oxidized clay zones containing no pyrite still inhibited bacterial growth. These clays buffered solutions to low pH (< 4.7) and oxidizing Eh (> 400 mV) conditions, releasing lower amounts (< 1 mM) of Fe and Al. The presence of carbonate in the clays eliminated antibacterial activity due to increases in pH, which lower pyrite oxidation and mineral dissolution rates.
The antibacterial mechanism of these natural clays was explored using metal toxicity and genetic assays, along with advanced bioimaging techniques. Antibacterial clays provide a continuous reservoir of Fe2+, Fe3+ and Al3+ that synergistically attack pathogens while generating hydrogen peroxide (H2O¬2). Results show that dissolved Fe2+ and Al3+ are adsorbed to bacterial envelopes, causing protein misfolding and oxidation in the outer membrane. Only Fe2+ is taken up by the cells, generating oxidative stress that damages DNA and proteins. Excess Fe2+ oxidizes inside the cell and precipitates Fe3+-oxides, marking the sites of hydroxyl radical (•OH) generation. Recognition of this novel geochemical antibacterial process should inform designs of new mineral based antibacterial agents and could provide a new economic industry for such clays.
Antibacterial susceptibility testing reveals that hydrated clays containing pyrite and I-S are effective at killing (100%) of the model pathogens tested (E. coli and S. epidermidis) when pH (< 4.2) and Eh (> 450 mV) promote pyrite oxidation and mineral dissolution, releasing > 1 mM concentrations of Fe2+, Fe3+ and Al3+. However, certain oxidized clay zones containing no pyrite still inhibited bacterial growth. These clays buffered solutions to low pH (< 4.7) and oxidizing Eh (> 400 mV) conditions, releasing lower amounts (< 1 mM) of Fe and Al. The presence of carbonate in the clays eliminated antibacterial activity due to increases in pH, which lower pyrite oxidation and mineral dissolution rates.
The antibacterial mechanism of these natural clays was explored using metal toxicity and genetic assays, along with advanced bioimaging techniques. Antibacterial clays provide a continuous reservoir of Fe2+, Fe3+ and Al3+ that synergistically attack pathogens while generating hydrogen peroxide (H2O¬2). Results show that dissolved Fe2+ and Al3+ are adsorbed to bacterial envelopes, causing protein misfolding and oxidation in the outer membrane. Only Fe2+ is taken up by the cells, generating oxidative stress that damages DNA and proteins. Excess Fe2+ oxidizes inside the cell and precipitates Fe3+-oxides, marking the sites of hydroxyl radical (•OH) generation. Recognition of this novel geochemical antibacterial process should inform designs of new mineral based antibacterial agents and could provide a new economic industry for such clays.
ContributorsMorrison, Keith D (Author) / Williams, Lynda B (Thesis advisor) / Williams, Stanley N (Thesis advisor) / Misra, Rajeev (Committee member) / Shock, Everett (Committee member) / Anbar, Ariel (Committee member) / Arizona State University (Publisher)
Created2015
Description
Damage to the Central Nervous System (CNS), such as traumatic brain injury (TBI) can often lead to a systemic inflammatory response since inflammatory mediators can be carried through the cardiovascular system. Past studies indicate that this inflammatory response that started at the CNS can increase the risk of heart disease. This growing interest in the heart-brain axis led our lab to explore if there is any impact of TBI on cardiac function and remodeling. TBI has been shown to have short-term effects on the heart, but few studies evaluate the long-term impact of TBI on the heart. To analyze any long-term impacts, we extracted hearts from rats 6 months post TBI, or sham that had been treated with vehicle or lipopolysaccharide (LPS) injections. LPS was administered to assess how inflammation could impact protein expression in the heart. Reactive oxygen species (ROS) targets such as NOX2, NOX4, SOD1, SOD2, catalase, and osteopontin were measured as potential indicators of cardiac remodeling. Rats that received vehicle TBI and LPS TBI resulted in no statistically significant differences (p>0.05) when evaluated as fold-change over the vehicle. This trend was consistent when normalizing to LPS sham. Since there were no changes in ROS targets, the hypothesis that there is long-term cardiac remodeling in the heart post-TBI was rejected. Further investigation is warranted since the present design of this study may not be ideal for evaluating long-term impact as histology samples were not obtained nor cardiac function assessments.
ContributorsRubinov, Abraham (Author) / Hackney-Price, Jennifer (Thesis director) / Hale, Taben (Committee member) / Barrett, The Honors College (Contributor) / School of Life Sciences (Contributor)
Created2023-05
Description
Asphalt is a widely used mixture in the paving and roofing industries and its sales are expected to increase by 57% in the next eight years alone (Mandaokar, 2024). However, it is known to have highly toxic constituents such as benzo[a]pyrene (BaP) and catechol, (National Institute, 1977, Hazard Review, 2000, Neghab et al., 2015, and Rozewski et al., 2023). Lemon juice, which is an inexpensive and easily accessible natural substance that is shown to have health benefits such as increasing insulin sensitivity, aiding with weight loss, and preventing heart disease (Tejpal et al., 2020), may counteract the effects of asphalt. The question of what the biological effects of asphalt, lemon juice, and the combination of the two on adipocytes was tested via computational analysis and experiments. It was predicted that catechol and lemon juice components will show biological effects in adipocytes that could be opposing, additive, or synergistic. A computational analysis involving the docking of fourteen components of asphalt and thirty-five components of lemon juice constituents to a targetome of 7,529 proteins (Ovanessians et al., 2024) suggests that asphalt and lemon juice components have many possible protein targets. Experiments were carried out with 3T3L1 mouse adipocytes to study five different lemon extracts (crude, hexane organic and aqueous, and ether organic and aqueous), and two components of asphalt (catechol and BaP): 1) Thiazolyl Blue Tetrazolium Bromide (MTT) cell viability and toxicity assay, 2) reactive oxygen species fluorescence assay, 3) Nile red staining assay, 4) red oil o staining assay, and a 5) lipidomics analysis on the hexane and ether organic extracts of lemon juice. This study has shown that asphalt components BaP and catechol and lemon juice components combined have the following biological effects on adipocytes: 1) Of the 5 lemon extracts tested, the organic layer of the hexane extract solubilized in DMSO (LE4) decreases differentiation the most. 2) Nile red staining is inhibited by 0.1 mg/mL of LE4, 1 µM BaP, and 20 µM catechol at a similar level. 3) Cell morphology differs between LE4, BaP, and catechol. Future work will include an insulin sensitivity assay to confirm the indicative inhibitory relationship found between lemon juice and asphalt. Expanding upon the lipidomic results of the lemon juices, as well as maximizing the potential of dockings by connecting results with the experiments, may also prove to be useful in future studies.
ContributorsImtiaz, Shazeen (Author) / Klein-Seetharaman, Judith (Thesis director) / Wang, Shu (Committee member) / Singharoy, Abhishek (Committee member) / Barrett, The Honors College (Contributor) / School of Molecular Sciences (Contributor)
Created2024-05