Surface-Specific Explorations at the Nano-Bio InterfacePublic Deposited
The increasing production and use of nanoscale transition metal oxide materials in the next generation of consumer electronics and electric vehicle batteries, specifically lithium intercalation compounds, may lead to environmental release and exposure, with poorly understood biological outcomes. As the toxicity mechanism of nanomaterials may vary fundamentally from their bulk material counterparts due to specific nanoparticle properties, the environmental consequences of these materials need to be kept in mind as new materials are developed. When nanomaterials encounter unicellular and multicellular organism in the environment, the surface of the nanoparticles and the surface of the cell membrane are the first points of contact. Therefore, understanding the molecular level interactions at the nano-bio interface can provide insight into the mechanisms of nanotoxicity. However, it is difficult to elucidate specific molecular level information regarding the interactions between nanomaterials and cell membranes, given the inherently complex nature of the surface chemistries. To identify the roles that (1) nanomaterial surface charge and chemical composition and (2) membrane charge and constituents play in these interactions, this thesis uses idealized model membranes and transition metal oxide nanomaterials that are well characterized and allow control of chemical composition. This thesis focuses on mitigating non-contact interactions between nanomaterials and model membranes and point towards a path for enabling the design of new energy storage materials with reduced environmental impacts. Using vibrational sum frequency generation (SFG) spectroscopy to probe idealized model membrane-nanomaterial interactions, this thesis investigates the structural alterations in model membranes at the nano-bio interface in situ, in real time, with surface-specificity, and under environmentally relevant aqueous conditions. Along with complementary surface-specific techniques, this thesis highlights how electrostatics and nanomaterial transformations impact the interactions between the nanoscale transition metal oxides and supported lipid bilayers, identifying environmental behaviors that may be used in the future to predict the impact of nanomaterials based on their physical and chemical properties. Finally, this thesis demonstrates an approach to probe the C–H stretches of lipid alkyl tails in supported lipid bilayers detected along with the O–H stretching continuum of the hydrogen bonding network system to capture changes in the interfacial water structure. The ability to probe hydrogen bond networks over supported lipid bilayers along with the C–H stretches of alkyl tails holds the promise of opening paths for understanding specific and non-specific interactions at the nano-bio interface.
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