CAREER: Nanoparticle-Bacterial Membrane Interactions and their Role in Nanotoxicology

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Cellular responses ultimately determine the toxicological impacts of nanoparticles released intentionally or unintentionally into the environment. Physical nanoparticle-cell membrane interactions are emerging as an important factor in determining cell uptake and cytotoxicity as membranes are the point-of-contact for nanoparticle-cell interactions and membranes integrity is vital to cell function. However, these interactions are poorly understood and have not been examined in or connected to biomimetic membranes that exhibit heterogeneity or asymmetry. The research objective of this CAREER proposal is to elucidate nanoparticle-membrane interactions in model bacterial membranes as a function of nanoparticle size and surface chemistry, and salt concentration. AIM 1 will employ cryogenic microscopy and microcalorimetry examine how local nanoparticle-membrane interactions can yield global changes in membrane structure and function. AIM 2 will employ microscopy and spectroscopy techniques to specifically examine the role of nanoparticle aggregation at membrane/water interfaces and its effects on inducing membrane invagination (i.e. engulfing nanoparticles) and poration. Finally, AIM 3 will employ the aforementioned experimental techniques to examine polysaccharide (dextran)-coated vesicles as model cell wall/membrane barriers to link underlying nanoparticle-membrane interactions with a realistic composite membrane. The CAREER plan of the PI integrates research with the educational and outreach objective of engaging underrepresented students and local communities, enhancing career preparedness in emerging technologies, specifically at the nanotechnology/environmental/biological interface, and advancing curriculum. Building on the PI?s previous experiences, a new high school program Think Small/Dream Big! will be developed for science classes in urban schools in the greater Providence, RI area. This program will leverage the remote operating capabilities of the recently awarded NSF MRI-funded transmission electron microscope and provide students ?virtual? exposure to analyzing nanomaterials using state-of-the-art instrumentation. This proposal will also enhance a new freshman general education course at URI aimed at educating students about the social, economic, and environmental impacts of nanotechnology, as well as the need to effectively communicate emerging technologies to broad audiences. Professional development activities, including research and specialized workshops, will supplement curriculum development and provide enhanced ?soft? and technical skills needed for research careers and graduate studies. Taken together, the research and education plans will support the independent career path of the PI as a successful scholar and educator. Intellectual Merit. Research is driven by the hypotheses that (1) an ?optimal? combination of size and surface chemistry exists to facilitate nanoparticle-membrane binding and membrane restructuring, which is balanced by the net adhesive strength and energetic penalty for distorting a membrane; (2) nanoparticle aggregation at membrane/water interfaces leads to size-dependent membrane pore formation and nanoparticle invagination; and that (3) polysaccharide-coatings mimicking cell walls will reduce, but not eliminate nanoparticle-induced membrane restructuring. Quantitative information, which is currently lacking, relating to the degree of nanoparticle binding, how this affects membrane structure, phase behavior, and permeability will be gained for environmentally-relevant bacterial membranes. This work is transformative because nanoparticle-membrane interactions and the role of the cell wall have not been examined for bacterial membrane. Broader Impacts. A quantitative understanding of nanoparticle-membrane interactions will provide new insight into cytotoxicity mechanisms, and could help develop general guidelines for predicting nanoparticle-cell association and designing biocompatible nanomaterials. Beyond cytotoxicity, this understanding could be used to create or modify nanoparticle-based therapeutics, design hybrid organicinorganic colloids, and identify new biosensing or drug delivery strategies. Dissemination will be achieved through publications, presentations, and integration into courses and outreach activities. The crux of this proposal is that the research concepts can be used as educational and outreach material to inspire underrepresented students to achieve STEM careers, engage and inform community organizations