Understanding the Biological and Environmental Implications of Nanomaterials

The last two decades have witnessed the discovery, development, and large-scale manufacturing of novel nanomaterials. While nanomaterials bring in exciting and extraordinary properties in all areas of materials, electronics, mechanics, and medicine, they also could generate potential adverse effects in biological systems and in the environment. The currently limited application of nanomaterials in biological and ecological systems results from the insufficient and often controversial data on describing the complex behaviors of nanomaterials in living systems. The purpose of this dissertation intends to fill such a knowledge void with methodologies from the disciplines of biophysics, biology, and materials science and engineering. Chapter 1 of this dissertation provides a comprehensive review on the structures and properties of carbon nanomaterials (CBNMs), metal oxides, and quantum dots (QDs). This chapter also details the state-of-the-art on the biological applications, ecological applications, and toxicity of nanomaterials. With Chapter 1 serving as a background, Chapters 2-5 present my Doctor of Philosophy (PhD) research, an inquiry on the fate of nanomaterials in biological and ecological systems, on the whole organism and cellular levels. Specifically, CBNMs are introduced to rice plant seedlings and the uptake, translocation and generational transfer of fullerene C70 in the plant compartments are imaged and characterized. The interactions between CBNMs and rice plants on the whole organism level are initiated by the binding between CBNMs and natural organic matter (NOM), driven by the transpiration of water from the roots to the leaves of the plants and mediated by both the physiochemical properties of the CBNMs and plant physiology. In Chapter 3, semiconducting nanocrystals quantum dots (QDs) are introduced to green algae Chlamydomonas to probe the interactions of nanomaterials with ecological systems on the cellular level. The adsorption of QDs onto the algal cell wall is quantified by UV-vis spectrophotometry and fitted with the Freundlich isothem. Effects of the adsorption of QDs on the photosynthetic activities of the algae are evaluated using O2 evolution and CO2 depletion assays, and the ecological impact of such adsorption is discussed. To understand the effects of nanomaterials on the cell membrane, nanoparticles (Au, TiO2, and QDs) of different surface charges and chemical compositions are introduced to HT-29 mammalian cells in Chapter 4. The polarization of the cell membrane is investigated using a FLIPR membrane potential kit. The phase of the cell membrane, in the presence of both positively and negatively charged nanoparticles, are examined using laurden, a lipophilic dye that serves as a molecular reporter on the fluidic or gel phase of the host membrane. To address the effects of nanomaterials on biological and ecological systems within the same context, Chapter 5 offers a first parallel comparison between mammalian and plant cell responses to nanomaterials. This study is conducted using a plant cell viability assay, complimented by bright field, fluorescence, and electron microscopy imaging. Discussions of this study are presented based on the hydrophobicity and solubility of C60(OH)20 and of supramolecular complex C70-NOM, hydrophobicity and porous structure of the plant Allium cepa cell wall, and the amphiphilic structure and endocytosis of the plasma cell membrane of both Allium cepa and HT-29 cells. Chapter 6 summarizes and rationalizes results obtained from the entire dissertation research. Future work inspired by this research is presented at the end of the chapter. Specifically, this dissertation is structured to embody the following essential and complementary chapters: * Chapter 1: Literature review * Chapter 2: Nano-Eco interactions at the whole organism level; * Chapter 3: Nano-Eco interactions at the cellular level; * Chapter 4: Nano-Bio interactions at the cellular level; * Chapter 5: Parallel comparison of Nano-Eco and Nano-Bio interactions at the cellular level. * Chapter 6: Conclusions and future work The overarching goal of this research is to advance our understanding on the fate of nanomaterials in biological and ecological systems. Knowledge obtained from this dissertation is expected to benefit future research on the implications and applications of engineered nanomaterials