1, 4-Dioxane biodegradation at low temperatures in Arctic groundwater samples

1,4-Dioxane is an emerging groundwater contaminant and a probable human carcinogen. Its biodegradation was investigated in microcosms prepared with groundwater and soil from an impacted site in Alaska. In addition to natural attenuation conditions (i.e., no amendments), the following treatments were tested: (a) biostimulation by addition of 1-butanol (a readily available auxiliary substrate) and inorganic nutrients; and (b) bioaugmentation with Pseudonocardia dioxanivorans CB1190, a well-characterized dioxane degrading bacterium, or with Pseudonocardia antarctica DVS 5a1, a bacterium isolated from Antarctica. Biostimulation enhanced the degradation of 50 mg L-1 dioxane by indigenous microorganisms (about 0.01 mg dioxane d-1 mg protein-1) at both 4 and 14°C, with a simultaneous increase in biomass. A more pronounced enhancement was observed through bioaugmentation. Microcosms with 50 mg L -1 initial dioxane (representing source zone contamination) and augmented with CB1190 degraded dioxane fastest (0.155 +/- 0.038 mg dioxane d-1 mg protein-1) at 14°C, and the degradation rate decreased dramatically at 4°C (0.021 +/- 0.007 mg dioxane d-1 mg protein-1). In contrast, microcosms with DVS 5a1 degraded dioxane at similar rates at 4 and 14°C (0.018 +/- 0.004 and 0.015 +/- 0.006 mg dioxane d-1 mg protein-1, respectively). DVS 5a1 outperformed CB1190 when the initial dioxane concentration was low (500 microg L-1). This indicates differences in competitive advantages of these two strains. Natural attenuation microcosms also showed significant degradation over 6 months when the initial dioxane concentration was 500 microg L-1. This is the first study to report the potential for dioxane bioremediation and natural attenuation of contaminated groundwater in sensitive cold-weather ecosystems such as the Arctic

Fabrication of cell culture scaffolds using micro/nanotechnologies to study the attachment and alignment of smooth muscle cells

This dissertation elaborates the design and fabrication of in vitro cell culture scaffolds using microfabrication and electrostatic layer-by-layer self-assembly (LbL) technologies, and develops the so-called layer-by-layer lift-off (LbL-LO) technique to control surface topography, surface properties, and underlying architectures of the scaffolds. Smooth muscle cells were cultured on the fabricated scaffolds with gelatin, fibronectin, and polyelectrolytes (PSS, PDDA, PAH, and PEI) as surface materials, multilayer polyelectrolytes as architectures, deposited in strip- and square-patterns. It was found that the exposed surface materials, which have different charge, hydrophobicity, and chemical structure (e.g., amino acid sequence), affect the adhesion of smooth muscle cells. Cells attached and grew on negatively-charged gelatin, PSS, and acid-treated glass surfaces rather than on positively-charged PDDA and PAH surfaces. The cell-adhesive proteins gelatin and fibronectin improve the attachment and further growth of smooth muscle cells, and cells attached to these surfaces showed more natural morphology than on PSS-coated surfaces. In addition, the underlying architectures of the polyelectrolyte thin films also significantly influence the cell morphologies and attachment. Cells on thicker nanofilms (20-bilayer) showed more elongated and spread-out morphology than on the thinner ones (e.g., 2-bilayer). Cells cultured on the gelatin- and fibronectin-coated strip patterns showed aligned patterns along the main axis of the strips. It was observed cells on 60μm wide strips had better alignment than on the 120μm strips. The experimental results indicate that the LbL-LO technique is an efficient method to fabricate in vitro cell culture scaffolds with precise control of the surface properties and topography in three dimensions, and therefore, to study the cell behavior. The results of study suggest that a combination of micro/nanotechnologies for biosurface engineering has great potential in the application of tissue engineering and other related areas