Non-invasive continuous monitoring of the interaction between nanoparticles and aquatic microorganisms

The present PhD topic is a 3-year research project in the environmental research module of the National Research Program 64 (www.nfp64.ch) on the “Opportunities and Risks of Nanomaterials” funded by the Swiss National Science Foundation. The main focus of this module lies on the interactions between engineered nanoparticles (ENPs) and the environment.

Nanomaterials are anthropogenically produced materials with at least one dimension between 1 and 100 nm such as nanofilms (one dimension), nanowires and nanotubes (two dimensions), or nanoparticles (three dimensions), which have unique properties that bulk materials of the same chemical composition do not possess. In the past few years the broad field of nanotechnology has developed rapidly and with it the commercial applications of nanomaterials, ranging from daily consumer goods to highly sophisticated industrial uses. The potential societal benefits of nanomaterials are still being explored and are expected to be great.

One nanometer (nm) is one billionth, or 10-9 of a meter. To put that scale into context the comparative size of a nanometer to a meter is the same as that of a marble to the size of the earth. A DNA double-helix has a diameter of about 2 nm.(http://www.greenearthnanoscience.com/nanotechnology.php, 08/02/2011)

However, with the rising use of nanomaterials, increasing amounts are directly or indirectly being released into the environment. The ecological impacts of engineered nanoparticles (ENPs) in the environment are not yet well understood and their effects are difficult to assess due to their complex life cycles, interactions and transformations they undergo in environmental systems.

The release of ENPs into the environment has become an issue of major concern in ecotoxicology. According to current consensus, oxidative stress is one of the major toxicity mechanisms of ENPs at the cellular level among the many potential adverse effects they may cause in the environment. Toxicants such as ENPs can trigger the cellular defense mechanisms of aquatic organisms and thus activate the production of scavenging enzymes, reducing agents and other reactive oxygen species which diffuse into the extracellular matrix and can then be detected with biomarkers for oxidative stress. Still, little is known about the underlying toxicity mechanisms, especially at the cellular level and in aquatic microorganisms which, as primary producers at the base of the food chain, are vital to a healthy ecosystem. Therefore, the aim of the present multidisciplinary study is to develop and optimize a non-invasive, continuous real-time sensing tool to monitor oxidative stress on the basis of the extracellular trace levels of stress agents of aquatic phytoplanktonic cells exposed to ENPs, in cooperation with the Swiss Federal Institute of Technology in Lausanne. The biosensor is based on the different absorption peaks of the redox states of cytochrome c, which is oxidized in the presence of reactive oxygen species and can spectroscopically be detected with dark field microscopy. Our goal is to systematically investigate the effects of different metal-containing ENPs on freshwater algae.

Our research contributes to the advancement of the general understanding of the interactions between ENPs and the biota and thereby reinforces the knowledge foundation upon which well-informed risk assessments and environmental management plans can be developed and established for a responsible exploitation of nanomaterials.

Contact: Nadia von Moos, Prof. Vera Slaveykova

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