Biological and Environmental Implications and Applications of Two-Dimensional Layered NanomaterialsPublic Deposited
To accelerate the implementation of technologies enabled by two-dimensional (2D) nanomaterials, the human health and environmental implications of these materials need to be addressed. Fundamental studies which elucidate the mechanisms of toxicity and environmental fate will allow for the safer design of these materials and promote their widespread use. This thesis presents a multidisciplinary approach to assess the potential hazards of 2D nanomaterials by establishing structure-activity relationships between the properties of the 2D nanomaterials to biological outcomes. In particular, interactions with the cell or bacterial membrane, cellular uptake, and intracellular localization and processing are investigated using a library of graphene oxide (GO) nanomaterials. By systematically varying GO surface oxidation and lateral size, we successfully deduce the toxicological mechanisms in mammalian and bacterial systems. Next, the environmental fate of GO nanomaterials is studied by measuring the influence of pH, ionic strength, ion valence, and presence of natural organic matter (NOM) on the aggregation and stability of GO nanomaterials in aquatic environments. A similar library of GO nanomaterials is used to determine the influence of surface oxidation on both the aggregation as well as the chemical degradation under direct sunlight. Based on the observed interactions of GO with NOM, the antifouling properties of GO are investigated by observing the deposition kinetics of bacteria and NOM. Based on our findings with GO, we further expand our studies to other 2D materials, such as molybdenum disulfide (MoS2). The attachment efficiency of foulants on both 2D-nanomaterial functionalized surfaces is significantly lower than that of a control polymer surface, encouraging the potential use of GO and MoS2 for antifouling water filtration membrane technologies. The environmental instability of black phosphorus (BP), a 2D layered nanomaterial which decomposes in the presence of oxygen and water, is studied in detail to encourage the development biodegradable constructs for a wide range of biomedical applications. Aqueous dispersions of few-layer BP nanosheets are prepared and the chemical and dispersion stability are studied by controlling the type of surfactants and overall flake size and thickness. Furthermore, the stability of the BP dispersions is investigated in biologically relevant media; environmental factors such as dissolved oxygen, temperature, and ionic strength are considered for their role in the stability of the BP nanosheets. These results will enable improved efficacy and lifetime of potential BP constructs for biomedical applications, as well as provide a foundation for investigating the biological impact of these nanomaterials. Finally, we demonstrate the incorporation of a 2D layered material into a biocompatible polymer composite for potential applications in bioelectronics. Hexagonal boron nitride (hBN)â€”a thermally conductive yet electrically insulting two-dimensional layered materialâ€”is dispersed at high concentrations in the presence of a biocompatible polymer, which can be 3D printed at room temperature through an extrusion process to form complex architectures with features as small as 100 Î¼m. These robust, free-standing constructs can have high solids content while maintaining their mechanical intergrity when flexed and stretched. Furthermore, the presence of hBN within the matrix results in enhanced thermal conductivity. The high cytocompatibility of these constructs makes them potentially suitable for use in the field of printed bioelectronics. Overall this work contibutes to a better understanding of the behavior and interactions of 2D nanomaterials at the nano-bio interface, allowing for the safe design and implementation of these materials into a wide range of biomedical applications.