Date of Award
Doctor of Philosophy in Civil and Environmental Engineering
Civil and Environmental Engineering
As the field of nanotechnology advances, it is becoming more important to understand nanomaterial interactions with microorganisms. New methods for examining bacterial response to and interaction with nanomaterials are presented in the studies included here. First, bacterial response to two-dimensional nanomaterials is evaluated using a high throughput approach. Next, a calibrated water jet is used to demonstrate the effect of ship speed on biofouling release. Finally, methods of purifying biogenic nanoparticles were reviewed and evaluated for potential application at large scale. Each of these studies utilizes novel techniques for examining bacterial responses or interactions with nanomaterials or nano-enabled surfaces.
The goal of the first study was to explore the role of the metabolic stage of Escherichia coli (E. coli) in its response to graphene oxide (GO), MoS2, and MoSe2 colloidal nanosheets at different growth stages. Bacterial responses were quantified in terms of respiration and growth rate and membrane permeability using a novel high throughput approach. E. coli response to nanosheet exposure was dependent on the concentration and type of nanomaterial, and the bacterial growth stage. Growth rate increased for bacteria that were actively growing (exponential phase) and growth rate and respiration rate decreased for slow growing bacteria (transitional, stationary, and respiration) post-GO exposure. MoS2 and MoSe2 have little impact on metabolic activity of E. coli regardless of the growth stage. This study demonstrates that the physiological condition of the bacteria and the nanosheet type play important roles in their response.
The negative impacts of biofouling on marine shipping can be mitigated by biofouling release surfaces. The calibrated water jet (CWJ) was developed to study the effectiveness of fouling release coatings as a function of ship speed. We examine the theory and application of the CWJ for simulating the effect of ship speed on biofilm release for surfaces fouled under (1) laboratory conditions and (2) natural seawater. A commercial antifouling coating (HullKote) was fouled by Ulva cf. linza under controlled laboratory conditions and fouling release was examined at several simulated ship speeds. Greater fouling release corresponded with an increase in simulated ship speed for the surface coated with HullKote. The effectiveness of the CWJ was further confirmed for biofilm release from naturally fouled surfaces. This study is the first to utilize the pressure of a CWJ to simulate biofouling release as a function of ship speed.
Biosynthesis is regarded as an environmentally friendly method of nanoparticle production. The methods of purifying nanoparticles synthesized by bacteria utilize arduous cleaning procedures and toxic solvents, limiting the benefits of a biosynthesis technique. The goal of this paper is to examine the currently available methods for purifying nanoparticles synthesized by bacteria. A laboratory examination of the purification techniques used for manganese oxide nanoparticles (MnONPs) was undertaken to support a literature review. Most studies using chemical separations require hazardous reagents to dissolve or oxidize the biomass. Three procedures (Mandernack, oxidation, and sonication) were examined for application in purifying MnONPs based on their yield of Mn particles. Overall, this study summarizes potential environmental issues with nanoparticle biosynthesis and demonstrates a path forward through an experimental study focusing on the purification of MnONPs using multiple cycles of oxidation to break down biomass.
Shepard, Zachary, "NANO/BIO INTERACTIONS FOR SYNTHETIC AND NATURAL NANOMATERIALS" (2023). Open Access Dissertations. Paper 1536.
Available for download on Thursday, May 08, 2025