title: Effect of silver nanoparticles on the standard soil arthropodFolsomia candida(Collembola) and the eukaryote model organismSaccharomyces cerevisiae.
abstract: BACKGROUND
  Because of their antimicrobial properties, silver nanoparticles (AgNPs) have been widely used and have come into contact with the environment. In the present work, an effect of AgNPs on a standard soil organism,Folsomia candida,was studied (in comparison to silver nitrate) focusing on molecular and cellular alterations as ecotoxicological endpoints.
  
  
  RESULTS
  At the molecular level, an up-regulation of metallothionein-containing protein (MTC) mRNA in AgNP-treated groups indicated toxic heavy metal stress effects caused by the release of silver ions from AgNPs, which is similar to animal groups treated with silver nitrate. Alteration of the steady-state level of glutathione S-transferase (GST) mRNA was detected in animal treated with AgNPs and AgNO3. At the cellular level, the relation between GST activity and the size of the glutathione (GSH) was examined. Change of GST activity from different animal groups was not significant, whereas the GSH pool (reduced and oxidized forms) decreased with increasing concentration of AgNPs. In order to obtain direct evidence whether AgNPs cause oxidative stress, treated animals were incubated with the non-fluorescent probe, 2',7'-dichlorodihydrofluorescein diacetate (DCFH-DA). A fluorescence signal was observed in both AgNPs- and AgNO3-treated groups pointing to the production of reactive species (RS). Since RS formation inF.candidais difficult to quantify, yeast strain BY4742 (wild-type) and mutants lacking of oxidative stress-related protective enzymes were exploited as a further eukaryote model organism. AgNPs and AgNO3were found to also affect growth of yeast and induced oxidative stress.
  
  
  CONCLUSIONS
  An effect of AgNPs onCollembolaand yeast strains is similar to the one from AgNO3. However, AgNPs is less toxic due to the slow release of silver ions. In summary, the toxic effect of AgNPs onF. candidais caused by the combination of the release of silver ions from AgNPs and the formation of reactive species.
authors.affiliation: Institute for Environmental Research (Biology V), RWTH Aachen University, Worringerweg 1, D-52074 Aachen, Germany.
authors.forename: Panwad
authors.initials: P
authors.lastname: Sillapawattana
authors.affiliation: Institute for Plant Physiology (Biology III), RWTH Aachen University, Worringerweg 1, D-52074 Aachen, Germany.
authors.forename: Martin C H
authors.initials: MC
authors.lastname: Gruhlke
authors.affiliation: Institute for Environmental Research (Biology V), RWTH Aachen University, Worringerweg 1, D-52074 Aachen, Germany.
authors.forename: Andreas
authors.initials: A
authors.lastname: Schäffer
keywords: Ecotoxicological endpoint; Glutathione; Glutathione S-transferase; Metallothionein; Oxidative stress