Microbial Interactions with Biodegradable Polymer Nanocomposites that Incorporate Carbon Nanotubes

这项由纳米技术环境健康与安全计划颁发的NSF奖支持Howard Fairbrother、Ed Bouyer和Seth Guikema教授的多学科工作，以表征微生物与包含碳纳米管(CNT)的可生物降解聚合物相互作用的影响。含有碳纳米管的聚合物纳米复合材料是下一代纳米材料的一个例子，因为碳纳米管对许多聚合物性能具有有益的影响。然而，随着消费者的使用，聚合物纳米复合材料将进入环境，在那里，它们的最终命运和影响将密切依赖于它们与存在于垃圾填埋场、土壤或地表水等环境体系中的微生物的相互作用。为了更好地了解这类新的纳米材料的生命周期，我们计划系统地了解可生物降解的聚合物纳米复合材料在不同微生物种群中的持久性和命运，包括碳纳米管释放的潜在途径。这些实验的结果也将被用作开发基于风险的决策框架的基础，该框架可以确定处理聚合物纳米复合材料的最合适的方法。对于处于开发阶段的新型纳米材料来说，这种积极主动的风险评估和生命周期分析方法是必要的。智力优势：实验设计是建立重要参数，如碳纳米管载量、类型和表面化学与生物降解、生物膜积累速率和生物转化机制之间的联系。通过这种方法，将确定碳纳米管可以作为颗粒从固相复合材料中释放出来的环境，以及生物可降解聚合物纳米复合材料可以抵抗生物降解并持续存在的环境，这与天然聚合物的行为形成了鲜明的对比。PI最初将专注于制备一套表征良好的碳纳米管和含碳纳米管的可生物降解聚合物纳米复合材料，其中碳纳米管的类型、表面化学、负载和可生物降解聚合物基质将有所不同。利用选定的单一和混合培养群体来模拟不同的环境条件，微生物与聚合物纳米复合材料和碳纳米管颗粒的相互作用将通过三种类型的补充实验来探索：(1)流动细胞研究，以评估聚合物纳米复合材料表面的附着和生物膜积累，(2)批量研究，以量化生物降解和碳纳米管的释放，以及(3)同位素标记的碳纳米管，以确定碳纳米管-碳的命运和潜在的碳纳米管降解机制。更广泛的影响--这项研究将对微生物与含碳纳米管的可生物降解聚合物纳米复合材料之间的相互作用产生基础性和整体性的科学理解，这是一种具有巨大商业潜力的新兴纳米材料类别。这些信息还将为开发具有材料特性的纳米复合材料提供一个预测框架，这些材料的性能已被设计为在没有长期工业责任的情况下产生积极的社会和经济后果。PIs还将通过女性科学与工程项目为女性高三学生和马里兰大学圣母大学(当地一所主要教学的S女子学院)的女性本科生提供研究机会、指导和指导。此外，PIs和研究生将在一个名为城市泉水科学外展计划的试点计划中发表演讲，该计划的重点是通过接触实际操作的科学和工程项目和活动来提高少数民族和贫困小学生(5年级)的科学素养和意识。

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.