Volume 50 (2013) Issue 7 Pages 472-477
The toxicity and behavior (internalization, adhesion, dispersion) of manufactured polystyrene latex (PSL) nanoparticles (nominal diameter : 50 nm) with various functional groups toward the yeast Saccharomyces cerevisiae as a model eukaryote were examined using the colony count method and microscopic observation. The colony count tests suggested that the PSL nanoparticles with a negative surface charge had little or no toxicity toward the yeast. In contrast, PSL nanoparticles with an amine functional group and a positive surface charge (p-Amine) displayed a high toxicity in 5 mol/m3 NaCl, whereas the p-Amine were mostly unharmed in 154 mol/m3 NaCl, which was quite different with the toxicological effects of Escherichia coli as a model prokaryote. Confocal and atomic force microscopy indicated that in 5 mol/m3 NaCl the p-Amine nanoparticles entirely covered the surface of the yeast, and cell death occurred, whereas in 154 mol/m3 NaCl were internalized by endocytosis, and cell death did not occur.