title: Comparative in vitro genotoxicity study of ZnO nanoparticles, ZnO macroparticles and ZnCl2to MDCK kidney cells: Size matters.
abstract: In the present study, we evaluated the roles that ZnO particle size and Zn ion release have on cyto- and genotoxicity in vitro. The Madin-Darby canine kidney (MDCK) cells were treated with ZnO nanoparticles (NPs), ZnO macroparticles (MPs), and ZnCl2as a source of free Zn ions. We first tested cytotoxicity to define sub-cytotoxic exposure concentrations and afterwards we performed alkaline comet and cytokinesis-block micronucleus assays. Additionally, the activities of both catalase (CAT) and glutathione S-transferase (GST) were evaluated in order to examine the potential impairment of cellular stress-defence capacity. The amount of dissolved Zn ions from ZnO NPs in the cell culture medium was evaluated by an optimized voltammetric method. The results showed that all the tested zinc compounds induced similar concentration-dependent cytotoxicity, but only ZnO NPs significantly elevated DNA and chromosomal damage, which was accompanied by a reduction of GST and CAT activity. Although Zn ion release from ZnO NPs in cell culture medium was significant, our results show that this reason alone cannot explain the ZnO genotoxicity seen in this experiment. We discuss that genotoxicity of ZnO NPs depends on the particle size, which determines the physical principles of their dissolution and cellular internalisation.
authors.affiliation: Department of Biology, Biotechnical Faculty, University of Ljubljana, Večna pot 111, SI-1000 Ljubljana, Slovenia. Electronic address: veno.kononenko@bf.uni-lj.si.
authors.forename: Veno
authors.initials: V
authors.lastname: Kononenko
authors.affiliation: Department of Biology, Biotechnical Faculty, University of Ljubljana, Večna pot 111, SI-1000 Ljubljana, Slovenia. Electronic address: neza.rugelj@bf.uni-lj.si.
authors.forename: Neža
authors.initials: N
authors.lastname: Repar
authors.affiliation: Department of Biology, Biotechnical Faculty, University of Ljubljana, Večna pot 111, SI-1000 Ljubljana, Slovenia. Electronic address: marusic.nika@gmail.com.
authors.forename: Nika
authors.initials: N
authors.lastname: Marušič
authors.affiliation: Department of Biology, Biotechnical Faculty, University of Ljubljana, Večna pot 111, SI-1000 Ljubljana, Slovenia. Electronic address: barbara.drasler@unifr.ch.
authors.forename: Barbara
authors.initials: B
authors.lastname: Drašler
authors.affiliation: Department of Biology, Biotechnical Faculty, University of Ljubljana, Večna pot 111, SI-1000 Ljubljana, Slovenia. Electronic address: tea.romih@seyens.com.
authors.forename: Tea
authors.initials: T
authors.lastname: Romih
authors.affiliation: Department of Analytical Chemistry, National Institute of Chemistry, Hajdrihova 19, SI-1000 Ljubljana, Slovenia. Electronic address: samo.hocevar@ki.si.
authors.forename: Samo
authors.initials: S
authors.lastname: Hočevar
authors.affiliation: Department of Biology, Biotechnical Faculty, University of Ljubljana, Večna pot 111, SI-1000 Ljubljana, Slovenia. Electronic address: damjana.drobne@bf.uni-lj.si.
authors.forename: Damjana
authors.initials: D
authors.lastname: Drobne
mesh_terms: D000818:Animals; D002374:Catalase / Q000378:metabolism; D002470:Cell Survival / Q000187:drug effects; D002712:Chlorides / Q000737:chemistry / Q000633:toxicity*; D020552:Comet Assay; D004249:DNA Damage; D004285:Dogs; D005982:Glutathione Transferase / Q000378:metabolism; D061985:Madin Darby Canine Kidney Cells; D053768:Metal Nanoparticles / Q000737:chemistry / Q000633:toxicity*; D015162:Micronucleus Tests; D009153:Mutagens / Q000737:chemistry / Q000633:toxicity*; D010316:Particle Size; D017382:Reactive Oxygen Species / Q000378:metabolism; D017967:Zinc Compounds / Q000737:chemistry / Q000633:toxicity*; D015034:Zinc Oxide / Q000737:chemistry / Q000633:toxicity*
chemical_list: D002712:Chlorides; D009153:Mutagens; D017382:Reactive Oxygen Species; D017967:Zinc Compounds; C016837:zinc chloride; D002374:Catalase; D005982:Glutathione Transferase; D015034:Zinc Oxide
keywords: DNA damage; Ion release; Nanoparticle dissolution; Nanotoxicology; Oxidative stress; Particle size