title: Silver nanoparticles: correlating nanoparticle size and cellular uptake with genotoxicity.
abstract: The focus of this research was to develop a better understanding of the pertinent physico-chemical properties of silver nanoparticles (AgNPs) that affect genotoxicity, specifically how cellular uptake influences a genotoxic cell response. The genotoxicity of AgNPs was assessed for three potential mechanisms: mutagenicity, clastogenicity and DNA strand-break-based DNA damage. Mutagenicity (reverse mutation assay) was assessed in five bacterial strains of Salmonella typhimurium and Echerichia coli, including TA102 that is sensitive to oxidative DNA damage. AgNPs of all sizes tested (10, 20, 50 and 100nm), along with silver nitrate (AgNO3), were negative for mutagenicity in bacteria. No AgNPs could be identified within the bacteria cells using transmission electron microscopy (TEM), indicating these bacteria lack the ability to actively uptake AgNPs 10nm or larger. Clastogenicity (flow cytometry-based micronucleus assay) and intermediate DNA damage (DNA strand breaks as measured in the Comet assay) were assessed in two mammalian white blood cell lines: Jurkat Clone E6-1 and THP-1. It was observed that micronucleus and Comet assay end points were inversely correlated with AgNP size, with smaller NPs inducing a more genotoxic response. TEM results indicated that AgNPs were confined within intracellular vesicles of mammalian cells and did not penetrate the nucleus. The genotoxicity test results and the effect of AgNO3 controls suggest that silver ions may be the primary, and perhaps only, cause of genotoxicity. Furthermore, since AgNO3 was not mutagenic in the gram-negative bacterial Ames strains tested, the lack of bacterial uptake of the AgNPs may not be the major reason for the lack of genotoxicity observed.
authors.affiliation: U.S. Food and Drug Administration, Office of Medical Products and Tobacco, Center for Devices and Radiological Health, Office of Science and Engineering Laboratories, Division of Biology, Chemistry, and Materials Science, 10933 New Hampshire Avenue, Silver Spring, MD 20993, USA.
authors.forename: Kimberly S
authors.initials: KS
authors.lastname: Butler
authors.affiliation: U.S. Food and Drug Administration, Office of Medical Products and Tobacco, Center for Devices and Radiological Health, Office of Science and Engineering Laboratories, Division of Biology, Chemistry, and Materials Science, 10933 New Hampshire Avenue, Silver Spring, MD 20993, USA.
authors.forename: David J
authors.initials: DJ
authors.lastname: Peeler
authors.affiliation: U.S. Food and Drug Administration, Office of Medical Products and Tobacco, Center for Devices and Radiological Health, Office of Science and Engineering Laboratories, Division of Biology, Chemistry, and Materials Science, 10933 New Hampshire Avenue, Silver Spring, MD 20993, USA.
authors.forename: Brendan J
authors.initials: BJ
authors.lastname: Casey
authors.affiliation: U.S. Food and Drug Administration, Office of Medical Products and Tobacco, Center for Devices and Radiological Health, Office of Science and Engineering Laboratories, Division of Biology, Chemistry, and Materials Science, 10933 New Hampshire Avenue, Silver Spring, MD 20993, USA.
authors.forename: Benita J
authors.initials: BJ
authors.lastname: Dair
authors.affiliation: U.S. Food and Drug Administration, Office of Medical Products and Tobacco, Center for Devices and Radiological Health, Office of Science and Engineering Laboratories, Division of Biology, Chemistry, and Materials Science, 10933 New Hampshire Avenue, Silver Spring, MD 20993, USA Rosalie.Elespuru@fda.hhs.gov.
authors.forename: Rosalie K
authors.initials: RK
authors.lastname: Elespuru
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D002470:Cell Survival / Q000187:drug effects / Q000235:genetics; D002478:Cells, Cultured; D020552:Comet Assay; D004249:DNA Damage / Q000187:drug effects* / Q000235:genetics; D004260:DNA Repair / Q000187:drug effects; D004926:Escherichia coli / Q000187:drug effects / Q000235:genetics* / Q000378:metabolism; D004927:Escherichia coli Infections / Q000188:drug therapy / Q000235:genetics / Q000382:microbiology; D006801:Humans; D019169:Jurkat Cells; D053768:Metal Nanoparticles / Q000008:administration & dosage* / Q000737:chemistry; D015162:Micronucleus Tests / Q000379:methods; D046529:Microscopy, Electron, Transmission; D009000:Monocytes / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D009152:Mutagenicity Tests / Q000379:methods; D009153:Mutagens / Q000494:pharmacology*; D012486:Salmonella typhimurium / Q000187:drug effects / Q000235:genetics* / Q000378:metabolism; D012834:Silver / Q000737:chemistry*
chemical_list: D000900:Anti-Bacterial Agents; D009153:Mutagens; D012834:Silver