Microbial Interactions with Biodegradable Polymer Nanocomposites that Incorporate Carbon Nanotubes

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This NSF award by the Environmental Health and Safety of Nanotechnology program supports multidisciplinary work by Professors Howard Fairbrother, Ed Bouwer and Seth Guikema to characterize the effect of microbial interactions with biodegradable polymers that incorporate carbon nanotubes (CNTs). Polymer nanocomposites containing CNTs represent an example of a next generation type of nanomaterial because of the beneficial effects that CNTs have on many polymer properties. However, following consumer use polymer nanocomposites will enter the environment where their ultimate fate and impact will be intimately dependent upon their interactions with microorganisms present in environmental regimes such as landfills, soils or surface waters. To better understand the life cycle of this new class of nanomaterials we plan to develop a systematic understanding of the persistence and fate of biodegradable polymer nanocomposites exposed to different microbial populations, including potential pathways for CNT release. Findings from these experiments will also be used as the basis to develop a risk-based decision making framework that can determine the most appropriate means for disposing of polymer nanocomposites. Such a proactive approach for risk assessment and life cycle analysis is necessary for new types of nanomaterials in the developmental stage. Intellectual Merit: The experimental design is to establish relationships that link important parameters, such as CNT loading, type and surface chemistry with biodegradation and biofilm accumulation rates and biotransformation mechanisms. Through this approach environments will be identified where CNTs could be released as particles from the solid phase composite and where biodegradable polymer nanocomposites could resist biodegradation and persist, in stark contrast to the behavior of the native polymer. The PIs will initially focus on preparing a selected suite of well characterized CNTs and CNT-containing biodegradable polymer nanocomposites where CNT type, surface chemistry, loading and the biodegradable polymer matrix will be varied. Using selected single and mixed culture populations to mimic different environmental regimes, microbial interactions with polymer nanocomposites and CNT particles will be explored by conducting three types of complementary experiments: (1) flow cell studies to evaluate attachment and biofilm accumulation on the surface of the polymer nanocomposites, (2) batch studies to quantify biodegradation and CNT release, and (3) isotopically labeled CNTs to determine the fate of CNT-carbon and potential CNT degradation mechanisms. Broader Impacts - This research will develop a fundamental and holistic scientific understanding of microbial interactions with CNT-containing biodegradable polymer nanocomposites, an emerging class of nanomaterial with enormous commercial potential. This information will also provide a predictive framework for the development of nanocomposites with material properties that have been engineered for positive social and economic consequences without long term industrial liability. The PIs will also provide research opportunities, guidance, and mentoring to female high school juniors through the Women in Science and Engineering program and female undergraduate students from the Notre Dame of Maryland University (a local, primarily teaching, women?s college). Additionally, the PIs and graduate students will give presentations in a pilot program, the City Springs Science Outreach Program, which focuses on enhancing scientific literacy and awareness for minority and underprivileged grade school students (5th grade) through exposure to hands-on science and engineering projects and activities.