Profiling of the toxicity mechanisms of coated and uncoated silver nanoparticles to yeast Saccharomyces cerevisiae BY4741 using a set of its 9 single-gene deletion mutants defective in oxidative stress response, cell wall or membrane integrity and endocytosis

摘要

The widespread use of nanosilver in various antibacterial, antifungal, and antiviral products warrants the studies of the toxicity pathways of nanosilver-enabled materials toward microbes and viruses. We profiled the toxicity mechanisms of uncoated, casein-coated, and polyvinylpyrrolidone-coated silver nanoparticles (AgNPs) using Saccharomyces cerevisiae wild-type (wt) and its 9 single-gene deletion mutants defective in oxidative stress (OS) defense, cell wall/membrane integrity, and endocytosis. The 48-h growth inhibition assay in organic-rich growth medium and 24-h cell viability assay in. deionized (DI) water were applied whereas AgNO3, H2O2, and SDS served as positive controls. Both coated AgNPs (primary size 8-12 nm) were significantly more toxic than the uncoated (similar to 85 nm) AgNPs. All studied AgNPs were similar to 30 times more toxic if exposed to yeast cells in DI water than in the rich growth medium: the IC50 based on nominal concentration of AgNPs in the growth inhibition test ranged from 77 to 576 mg Ag/L and in the cell viability test from 2.7 to 18.7 mg Ag/L, respectively. Con focal microscopy showed that wt but not endocytosis mutant (endael) internalized AgNPs. Comparison of toxicity patterns of wt and mutant strains defective in OS defense and membrane integrity revealed that the toxicity of the studied AgNPs to S. cerevisiae was not caused by the OS or cell wall/membrane permeabilization. (C) 2016 Elsevier Ltd. All rights reserved.