title: In vitro toxicity of silver nanoparticles at noncytotoxic doses to HepG2 human hepatoma cells.
abstract: Although it has been reported that silver nanoparticles (Ag-NPs) have strong acute toxic effects to various cultured cells, the toxic effects at noncytotoxic doses are still unknown. We, therefore, evaluated in vitro toxicity of Ag-NPs at noncytotoxic doses in human hepatoma cell line, HepG2, based on cell viability assay, micronucleus test, and DNA microarray analysis. We also used polystyrene nanoparticles (PS-NPs) and silver carbonate (Ag2CO3) as test materials to compare the toxic effects with respect to different raw chemical composition and form of silver. The cell viability assay demonstrated that Ag-NPs accelerated cell proliferation at low doses (< 0.5 mg/L), which was supported by the DNA microarray analysis showing significant induction of genes associated with cell cycle progression. However, only Ag-NPs exposure exhibited a significant cytotoxicity at higher doses (> 1.0 mg/L) and induced abnormal cellular morphology, displaying cellular shrinkage and acquisition of an irregular shape. In addition, only Ag-NPs exposure increased the frequency of micronucleus formation up to 47.9 +/- 3.2% of binucleated cells, suggesting that Ag-NPs appear to cause much stronger damages to chromosome than PS-NPs and ionic Ag+. Cysteine, a strong ionic Ag+ ligand, only partially abolished the formation of micronuclei mediated by Ag-NPs and changed the gene expression, indicating that ionic Ag+ derived from Ag-NPs could not fully explain these biological actions. Based on these discussions, it is concluded that both "nanosized particle of Ag" as well as "ionic Ag+" contribute to the toxic effects of Ag-NPs.
authors.affiliation: Department of Urban and Environmental Engineering, Graduate School of Engineering, Hokkaido University, North-13, West-8, Kita-ku, Sapporo 060-8628, Japan.
authors.forename: Koji
authors.initials: K
authors.lastname: Kawata
authors.forename: Masato
authors.initials: M
authors.lastname: Osawa
authors.forename: Satoshi
authors.initials: S
authors.lastname: Okabe
mesh_terms: D045744:Cell Line, Tumor; D003545:Cysteine / Q000737:chemistry; D004249:DNA Damage; D004354:Drug Screening Assays, Antitumor / Q000379:methods*; D020869:Gene Expression Profiling; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects*; D006801:Humans; D007477:Ions; D053768:Metal Nanoparticles / Q000737:chemistry* / Q000633:toxicity*; D015162:Micronucleus Tests / Q000379:methods; D036103:Nanotechnology / Q000379:methods; D020411:Oligonucleotide Array Sequence Analysis; D018384:Oxidative Stress; D017382:Reactive Oxygen Species; D012834:Silver / Q000737:chemistry* / Q000633:toxicity*
chemical_list: D007477:Ions; D017382:Reactive Oxygen Species; D012834:Silver; D003545:Cysteine