Size- and coating-dependent cytotoxicity and genotoxicity of silver nanoparticles evaluated using in vitro standard assays

Abstract

The physicochemical characteristics of silver nanoparticles (AgNPs) may greatly alter their toxicological potential. To explore the effects of size and coating on the cytotoxicity and genotoxicity of AgNPs, six different types of AgNPs, having three different sizes and two different coatings, were investigated using the Ames test, mouse lymphoma assay (MLA) and in vitro micronucleus assay. The genotoxicities of silver acetate and silver nitrate were evaluated to compare the genotoxicity of nanosilver to that of ionic silver. The Ames test produced inconclusive results for all types of the silver materials due to the high toxicity of silver to the test bacteria and the lack of entry of the nanoparticles into the cells. Treatment of L5718Y cells with AgNPs and ionic silver resulted in concentration-dependent cytotoxicity, mutagenicity in the Tk gene and the induction of micronuclei from exposure to nearly every type of the silver materials. Treatment of TK6 cells with these silver materials also resulted in concentration-dependent cytotoxicity and significantly increased micronucleus frequency. With both the MLA and micronucleus assays, the smaller the AgNPs, the greater the cytotoxicity and genotoxicity. The coatings had less effect on the relative genotoxicity of AgNPs than the particle size. Loss of heterozygosity analysis of the induced Tk mutants indicated that the types of mutations induced by AgNPs were different from those of ionic silver. These results suggest that AgNPs induce cytotoxicity and genotoxicity in a size- and coating-dependent manner. Furthermore, while the MLA and in vitro micronucleus assay (in both types of cells) are useful to quantitatively measure the genotoxic potencies of AgNPs, the Ames test cannot.

Particle coatings but not silver ions mediate genotoxicity of ingested silver nanoparticles in a mouse model

“…Both coatings provide a negative surface charge to the nanoparticle. Studies that comparatively assessed citrate- and PVP-coated AgNPs found that coating, relative to size, has a small effect (Guo et al, 2016) or results were mixed (Prasad et al, 2013; Vecchio et al, 2014). Only a few studies examined the effect of coating in vivo in rodent animals.…”

“…long-term health effects, especially, cancer. Studies that utilized the Ames test measuring point mutations in bacterial stains of S. typhimurium and/or E. coli reported that AgNPs tested negative for mutagenicity in bacteria (Butler et al, 2015; Guo et al, 2016). The lack of mutagenicity was explained by the inability of bacteria to take up AgNPs (Butler et al, 2015; Guo et al, 2016).…”

“…Studies that utilized the Ames test measuring point mutations in bacterial stains of S. typhimurium and/or E. coli reported that AgNPs tested negative for mutagenicity in bacteria (Butler et al, 2015; Guo et al, 2016). The lack of mutagenicity was explained by the inability of bacteria to take up AgNPs (Butler et al, 2015; Guo et al, 2016). However, AgNPs induced mutagenic and clastogenic effects in mammalian cells as shown by mouse lymphoma and micronucleus assays, respectively (Butler et al, 2015; Guo et al, 2016; Vecchio et al, 2014).…”

Cytotoxic and Antiproliferative Effects of Nanomaterials on Cancer Cell Lines: A Review

“…Several works have confirmed this relationship and some authors have identified NP sizes that correlate well with the level of toxicity observed on in vitro tests [15]. A range of toxic mechanisms leading to apoptosis, necrosis and genotoxicity is triggered by NPs of different range of dimensions.…”

“…Toxicity concerns have, however, slowed their faster development and translation. Green chemistry or biologically mediated synthesis of coated metallic NPs is on the rise, and consequently their nanotoxicity evaluation on biological media has been pursued and published [15,16].…”