The present projects aim at gathering scientific information on the environmental fate and effects of silver- and cerium oxide nanoparticles. AgNP belong to the most important materials incorporated in consumer products and used because of their toxicity to microorganisms. Cerium oxide is industrially exploited because of its catalytic properties also as diesel fuel additive.
In the MeNanoqa project (SNSF, NRP 64) we are examining interactions between the algae Euglena gracilis and citrate coated AgNP. Toxicity experiments with AgNP show a concentration dependent inhibition of algal photosynthesis and effects on cell morphology. However, AgNP toxicity is not detectable in presence of the strong silver ligand cysteine, indicating Ag+ ions as major contributors to AgNP toxicity. Uptake experiments with AgNP indicated silver being associated with E. gracilis cells. Analysis of cells by TOF SIMS showed AgNP to be adsorbed onto the algal surface, suggesting that particles are not internalized in algae cells (PhD thesis X. Li; Li et al. 2015).
In case of CeO2NP, long-term exposures of C. reinhardtii did not evidence any toxicity to photosynthesis, growth or cellular ATP content. Slight toxicity of these particles was detected when phosphate was omitted from exposure media which was shown to be caused by Ce3+ ions present in particles suspensions. There was no evidence that the CeO2NP are internalized in algae cells (PhD thesis L. Röhder).
The NanoMILE project (Engineered nanomaterials mechanisms of interaction with living systems and the environment: a universal framework for safe nanotechnology, http://www.nanomile.eu-vri.eu) aims to investigate the mechanism of interaction and the effects of the same nanoparticles on a selected range of target organisms, which represent a variety of wildlife taxa. The nanoparticles used in the NanoMILE project are selected according to their industrial relevance and include zinc oxide, silver, cerium oxide, iron oxides, titanium oxide, gold, graphene and carbon based nanoparticles. As a partner in NanoMILE project, Dr. Smitha Pillai at Utox intend to obtain a mechanistic and systematic understanding of the toxicity of manufactured nanomaterials in the alga Chlamydomonas reinhardtii at the molecular and physiological level. The toxic effects observed, at several physiological endpoints, in C. reinhardtii on exposure to metal nanoparticles are due the dissolved metals. Moreover, the effects co-relate to the bioaccumulated metal in C. reinhardtii. A systems biology approach which elucidates the response at the transcriptome, proteome and metabolite levels will provide a mechanistic insight into the toxicity in and response of C. reinhardtii (Dr. S. Pillai, A. Tierbach).