Using ciliates to understand the environmental fate and impact of carbon nanotubes

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Carbon nanotubes (CNT) are nanoparticles that promise to revolutionize many industries. They are composed entirely of carbon, like diamond, but they are manufactured to be tiny tubes with diameters of 1 to 25 nm and with variable lengths. CNT have several exceptional properties, such as mechanical strength, that suggest applications in diverse fields. Whether CNT will be an environmental hazard is unknown but is of concern because no cell or organism evolved with these structures. Methods of evaluating the impact of CNT and their waste on the health of humans and ecosystems need to be developed and is the focus of this proposal. We are proposing to study the interactions between CNT and a group of single cell organisms, the ciliates. Ciliates are classified as protozoa or protista and are found in the waters and soils of the world. They are an important link between bacteria and multicellular organisms in food webs. Ciliates are also of economic importance: they are found in sewage treatment plants, where they function to produce good quality sewage effluent. Ciliates can be considered specialists at dealing with particles because they are constantly engulfing water and bacteria into food vacuoles. CNT can exist as individual nanotubes and as aggregates. From a toxicological point of view, the single nanotubes are likely much more toxic than aggregates. CNT aggregation can be viewed as a detoxifying mechanism, but also as a route for them to move through food chains and into humans. Therefore, we will investigate the aggregation of CNT in soil and water and the role of ciliates in this and whether the incorporation of CNT by ciliates modulates CNT transfer up food webs. Understanding these processes can lead to ways of minimizing the release and environmental impact of CNT, of monitoring CNT in the environment, and of undertaking remediation. A particularly exciting and beneficial spin off of this research could be the development of methods that use ciliates and CNT to monitor chemical contaminants in the environment.