Metallic nanoparticles (MetNPs) with unique nanoscale properties, including novel optical behavior and superparamagnetism, are continually being developed for biomedical and industrial applications. In certain biomedical applications where extended blood half-lives are required, MetNPs are surface-functionalized using polymers, proteins, and other stabilizing agents to facilitate their resistance to salt-induced aggregation. Given their colloidal stability in high ionic-strength matrices, functionalized MetNPs are anticipated to be persistent aquatic contaminants. Despite their potential environmental significance, the persistence of surface- functionalized MetNPs as individually-stabilized nanoparticles in aquatic environments is largely unknown. Further, few studies have investigated the fundamental factors that influence MetNP uptake and fate/transport processes in ecologically susceptible aquatic biota, such as filter- feeding bivalves, which ingest and accumulate a broad range of dissolved- and particulate-phase contaminants. The present study describes a comprehensive approach to prepare and rigorously characterize MetNP test suspensions to facilitate fundamental examinations of nanoparticle uptake and fate/transport processes in freshwater and marine bivalves. We demonstrate the importance of accurately characterizing test suspensions in order to better understand MetNP persistence as individually-stabilized nanoparticles within aquatic test media, and define an optical-activity metric suitable for quantifying and comparing the persistence of variable MetNP formulations as National Nanotechnology Initiative (NNI) definable nanoscale materials. We also show that individually-stabilized MetNPs of variable elemental composition, particle diameter, and surface coating are accessible to bivalves in both freshwater and marine environments. Clearance rates for MetNPs are positively related to the diameter and initial concentration of MetNP suspensions. The observed size-dependence of particle filtration rates facilitates ‘size-selective biopurification' of particle suspensions with nanoscale resolution, and may have applicability in future sustainable nanomanufacturing processes. Filtered MetNPs are retained for extended periods post-exposure primarily within the bivalve digestive tract and digestive gland, but migration to other organ systems was not observed. Clusters of MetNPs were recovered in concentrated form from excreted feces, suggesting that biotransformation and biodeposition processes will play an important role in transferring MetNPs from the water column to benthic environments. / Ph. D.

Noble metal nanoparticles such as gold and silver are of interest because of the unique electro-optical properties (e.g., localized surface plasmon resonance [LSPR]) that originate from the collective behavior of their surface electrons. These nanoparticles are commonly developed and used for biomedical and industrial application. A recent report has predicted that the global market for gold nanoparticles will be over 12.7 tons by year 2020. However, these surface-functionalized nanoparticles can be potential environmental persistent contaminants post-use due to their high colloidal stability in the aquatic systems. Despite, the environmental risks associated with these nanoparticles, just a few studies have investigated the effect of nanofeature factors such as size and shape on the overall fate/transport and organismal uptake of these nanomaterials in the aquatic matrices. This study presents a comprehensive approach to evaluate the colloidal stability, fate/transport, and organismal uptake of these nanoparticles while factoring in the size and shape related properties. We demonstrate the importance and effect of anisotropicity of a gold nanoparticle on the colloidal behavior and interaction with ecologically susceptible aquatic biota. We also show how readily available characterization techniques can be utilized to monitor and assess the fate/transport of this class of nanoparticles. We further describe and investigate the relationship between the aspect ratio (AR) of these elongated gold nanoparticles with clearance mechanisms and rates from the aquatic suspension columns including aggregation, deposition, and biopurification. We illustrate how a fresh water filter-feeder bivalve, Corbicula fluminea, can be used as a model organism to study the size and shape-selective biofiltration and nanotoxicity of elongated gold nanoparticles. The results suggest that biofiltration by C. fluminea increases with an increase in the size and AR of gold nanoparticle. We develop a simple nanotoxicity assay to investigate the short-term exposure nanotoxicity of gold nanoparticles to C. fluminea. The toxicity results indicate that for the tested concentration and exposure period that gold nanoparticles were not acutely toxic (i.e., not lethal). However, gold nanoparticles significantly inhibited the activities of some antioxidant enzymes in gill and digestive gland tissues. These inhibitions could directly affect the resistance of these organisms to a secondary stressor (temperature, pathogens, hypoxia etc.) and threaten organismal health. / Ph. D. / Nanoparticles are fine particles that cannot be seen with naked eye and possess unique chemical and physical properties. Gold and silver nanoparticles are specifically of interest due to tunable optical properties and are commonly developed and used for biomedical and industrial applications. Unfortunately, these metallic nanoparticles can be potential environmental persistent contaminants post-use in the soil and aquatic systems. Despite, the environmental risks associated with these metallic nanoparticles, just a few studies have investigated the effect of size and shape of these nanoparticles on their interaction and transportation in the surrounding environment and with existing organisms. This study presents a comprehensive approach to evaluate the stability, transportation, and organismal uptake of these nanoparticles while factoring in the size and shape related properties. We also show how readily available detection techniques can be utilized to monitor and assess the presence and transport of this class of nanoparticles. We illustrate how a fresh water bivalve, Corbicula fluminea, can be used as a model organism to study the size and shape-selective uptake and toxicity of gold nanoparticles. The results suggest that nanoparticles uptake by C. fluminea increases with an increase in the size of gold nanoparticle. We develop a simple toxicity assay to investigate the short-term exposure toxicity of gold nanoparticles to C. fluminea. The toxicity results suggest that for the tested concentration and exposure period that gold nanoparticles were not acutely toxic (i.e., not lethal) but affect the resistance of these organisms to an environmental change (temperature, pathogens, hypoxia etc.) and threaten organismal health.

Pour valider une suite de biomarqueurs cellulaires en milieu dulçaquicole, nous avons étudié la structure des systèmes lysosomal et peroxysomal et les variations de contenus en lipofuscines et lipides neutres insaturés dans les tissus digestifs de plusieurs invertébrés, à travers une approche couplant histochimie et analyse d'images. Les expérimentations in situ et bioessais à plus ou moins long terme ont montré la pertinence des réponses cellulaires étudiées pour la mise en évidence de gradients de contamination. Les profils de réponse les plus communs chez les mollusques incluent un gonflement lysosomal, des déplétions de lipides neutres insaturés, une accumulation de lipofuscines et/ou un système peroxysomal plus volumineux. Ces réponses cellulaires précoces peuvent être associées, au niveau individuel, à une désynchronisation de la reproduction entre individus ou à une diminution de l'indice de condition. L'étude mensuelle à long terme a souligné l'absence de niveaux de base saisonniers de ces biomarqueurs et l'influence importante de la disponibilité trophique sur les contenus tissulaires en lipides neutres. Une mise en dépuration de 15 jours du bivalve, Dreissena polymorpha, sur son site d'origine, n'a pas montré de réversibilité du profil des réponses cellulaires à un gradient de contamination in situ, mais elle a tout de même de limité la déplétion des lipides neutres. Les réponses cellulaires les plus précoces et discriminatives sont le gonflement lysosomal et la déplétion en lipides neutres. Une comparaison d'outils d'analyse intégrative a montré le pouvoir discriminatif accru de la suite de biomarqueur entière, par rapport aux réponses individuelles.

Wetland wastewater treatment offers low-cost, energy efficient alternatives to conventional wastewater technologies. In this study, an artificial wetland was constructed at the City of Denton, Texas Pecan Creek Water Reclamation Plant to facilitate diazinon removal from treated effluent.