Initial Study on the Toxicity of Silver Nanoparticles (NPs) against Paramecium caudatum

In this initial study, the toxicity effect of silver NPs against a model unicellular eukaryotic organism of Paramecium caudatum was studied. For the purpose of this study, a dialysis-based method was adapted, which allowed the preparation of stable aqueous dispersions of silver NPs in various silver concentrations that were necessary for the evaluation of toxicity limits of these particles. The obtained results demonstrate that the silver NPs do not exhibit any toxicity action against the tested unicellular eukaryotic organism below the concentration of 25 mg·L−1 whereas ionic silver retains its toxicity even at a concentration of 0.4 mg·L−1. Such a considerable difference in the toxicity effect of these two forms of silver has not been observed in the previously published study concerning bacteria (Panáček, A.; Kvítek, L.; Prucek, R.; Kolář, M.; Večeřová, R.; Pizúrová, N.; Sharma, V. K.; Nevěčná, T.; Zbořil, R. J. Phys. Chem. B 2006, 110, 16248−16253). Additionally, it was proven that the surfactant/polymer modification can increase the toxicity of the silver NPs against the tested organism.