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Investigating the impact of nanoparticles on the environment

On Tuesday 4 September, Martina Vijver delivered the scientific lecture during the academic opening of the Faculty of Science. Martina is professor in Ecotoxicology at CML and would like to have collaborations with colleagues from the Leiden Centre of Data Science. We had a brief interview with her.

Can you tell us about your background and scientific work?

Martina Vijver

I am an ecotoxicologist, which means that I am studying the impact of chemicals to biodiversity. In recent years I became interested in nanomaterials. From 2000 onwards, nanoparticles (NPs) are rapidly finding their way into ever more products. Currently virtually every material can be synthesized at the nanoscale.

Can you provide some examples?

Nanoparticles (NPs) can be found in cosmetics. For instance, sun block contains combinations of ZnO-NP and TiO2-NP because these materials absorb UV-light very strongly, preventing your skin from feeling the unwanted effects of ultra-violet exposure. GaAs-NP and Pb-based NPs can be found in solar panels to enhance the sun light to be captured, in electronic devices, and in many products because of the unique properties of NPs making surfaces more smooth, scratch resistant, stronger and lighter. Because they are in so many products, also emissions appear and the NPs are likely to end up in the environment. With the enhanced exposure of the NPs, the potential of adverse effects is increasing and the need for proper risk assessment is therefore prominent.

What is the relation to micron particles and to molecules?

At the nanosize range, properties differ substantially from larger sized (e.g., micron) particles of the same composition, because NPs have a high proportion of surface atoms, high surface energy, spatial confinement, and reduced imperfections. NPs behave differently from molecules. NPs form a suspension in watery environmentals and molecules will form a solution. Their specific behavior makes that current environmental risk assessment cannot be used for NPs.Therefore, my overall research question is: what is the added risk of size (and shape features) on fate, uptake and effects?

How do you address this question?

Currently, in my group 8 PhD-students work on nanomaterials, and many results are gathered. We use an experimental approach in the laboratory as well as perform modelling. We focus on unravelling the mechanistic knowledge at environmental relevant exposure conditions and long term exposure of organisms.

What is the progress of your research?

We have learned that there is (1) time-dependent size distribution of dispersed and internalized nanoparticles (NPs),(2) how metal-based NPs can penetrate cell membranes, and (3) why do particles < 50 nm show adsorption followed by absorption, whereas particles with a size larger than 50 nm showed only adsorption.

How can we collaborate?

NPs behave different from molecules, that makes why expressing a dosage on a concentration or on a mass basis is not fully justifying the underlying processes. Total number of particles, surface area or volume have been suggested as potential simplified dose metrics, but are also as a sole descriptor not enough. The identification of an appropriate dose metric for NPs is of utmost importance for the interpretation of results from toxicity experiments and for risk assessment purposes, but so far a systematic evaluation is lacking of what such a dose metric may be. As a consequence, conclusions cannot easily be compared or generalized to other materials and experimental systems.
My question is: what would be the accurate dosimetry to describe the toxicity? We have many experimental data now collected under different conditions. Here to tackle this question, we would like to have help from mathematics and from data scientists.

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