title: Flow cytometric evaluation of the contribution of ionic silver to genotoxic potential of nanosilver in human liver HepG2 and colon Caco2 cells.
abstract: Exposure to nanosilver found in food- and cosmetics-related consumer products is of public concern because of the lack of information about its safety. In this study, two widely used in vitro cell culture models, human liver HepG2 and colon Caco2 cells, and the flow cytometric micronucleus (FCMN) assay were evaluated as tools for rapid predictive screening of the potential genotoxicity of nanosilver. Recently, we reported the genotoxicity of 20 nm nanosilver using these systems. In the current study presented here, we tested the hypothesis that the nanoparticle size and cell types were critical determinants of its genotoxicity. To test this hypothesis, we used the FCMN assay to evaluate the genotoxic potential of 50 nm nanosilver of the same shape, composition, surface charge and obtained from the same commercial source using the same experimental conditions and in vitro models (HepG2 and Caco2) as previously tested for the 20 nm silver. Results of our study show that up to the concentrations tested in these cultured cell test systems, the smaller (20 nm) nanoparticle is genotoxic to both the cell types by inducing micronucleus (MN). However, the larger (50 nm) nanosilver induces MN only in HepG2 cells, but not in Caco2 cells. Also in this study, we evaluated the contribution of ionic silver to the genotoxic potential of nanosilver using silver acetate as the representative ionic silver. The MN frequencies in HepG2 and Caco2 cells exposed to the ionic silver in the concentration range tested are not statistically significant from the control values except at the top concentrations for both the cell types. Therefore, our results indicate that the ionic silver may not contribute to the MN-forming ability of nanosilver in HepG2 and Caco2 cells. Also our results suggest that the HepG2 and Caco2 cell cultures and the FCMN assay are useful tools for rapid predictive screening of a genotoxic potential of food- and cosmetics-related chemicals including nanosilver.
authors.affiliation: Division of Toxicology, Office of Applied Research and Safety Assessment, Center for Food Safety and Applied Nutrition, U. S. Food and Drug Administration, Laurel, MD, 20708, USA.
authors.forename: Saura C
authors.initials: SC
authors.lastname: Sahu
authors.affiliation: Division of Toxicology, Office of Applied Research and Safety Assessment, Center for Food Safety and Applied Nutrition, U. S. Food and Drug Administration, Laurel, MD, 20708, USA.
authors.forename: Joyce
authors.initials: J
authors.lastname: Njoroge
authors.affiliation: Litron Laboratories, Rochester, NY, 14623, USA.
authors.forename: Steven M
authors.initials: SM
authors.lastname: Bryce
authors.affiliation: Division of Chemistry and Material Sciences, Office of Science and Engineering Laboratories, Center for Devices and Radiological Health, U.S.Food and Drug Administration, Silver Spring, MD, 20993, USA.
authors.forename: Jiwen
authors.initials: J
authors.lastname: Zheng
authors.affiliation: Division of Public Health Information and Analytics, Office of Analytics and Outreach, Center for Food Safety and Applied Nutrition, U.S. Food and Drug Administration, College Park, MD, 20740, USA.
authors.forename: John
authors.initials: J
authors.lastname: Ihrie
mesh_terms: D017209:Apoptosis / Q000187:drug effects; D018938:Caco-2 Cells; D003106:Colon / Q000166:cytology / Q000187:drug effects; D004249:DNA Damage / Q000187:drug effects*; D005434:Flow Cytometry; D056945:Hep G2 Cells; D006801:Humans; D008099:Liver / Q000166:cytology / Q000187:drug effects; D053768:Metal Nanoparticles / Q000737:chemistry / Q000633:toxicity*; D015162:Micronucleus Tests; D012834:Silver / Q000737:chemistry / Q000633:toxicity*; D018675:Toxicity Tests
chemical_list: D012834:Silver
keywords: Caco2 cells; HepG2 cells; flow cytometry; genotoxicity; ionic silver; micronucleus; nanoparticles; nanosilver; silver acetate