title: CdSe/ZnS quantum dots trigger DNA repair and antioxidant enzyme systems in Medicago sativa cells in suspension culture.
abstract: BACKGROUND
  Nanoparticles appear to be promising devices for application in the agriculture and food industries, but information regarding the response of plants to contact with nano-devices is scarce. Toxic effects may be imposed depending on the type and concentration of nanoparticle as well as time of exposure. A number of mechanisms may underlie the ability of nanoparticles to cause genotoxicity, besides the activation of ROS scavenging mechanisms. In a previous study, we showed that plant cells accumulate 3-Mercaptopropanoic acid-CdSe/ZnS quantum dots (MPA-CdSe/ZnS QD) in their cytosol and nucleus and increased production of ROS in a dose dependent manner when exposed to QD and that a concentration of 10 nM should be cyto-compatible.
  
  
  RESULTS
  When Medicago sativa cells were exposed to 10, 50 and 100 nM MPA-CdSe/ZnS QD a correspondent increase in the activity of Superoxide dismutase, Catalase and Glutathione reductase was registered. Different versions of the COMET assay were used to assess the genotoxicity of MPA-CdSe/ZnS QD. The number of DNA single and double strand breaks increased with increasing concentrations of MPA-CdSe/ZnS QD. At the highest concentrations, tested purine bases were more oxidized than the pyrimidine ones. The transcription of the DNA repair enzymes Formamidopyrimidine DNA glycosylase, Tyrosyl-DNA phosphodiesterase I and DNA Topoisomerase I was up-regulated in the presence of increasing concentrations of MPA-CdSe/ZnS QD.
  
  
  CONCLUSIONS
  Concentrations as low as 10 nM MPA-CdSe/ZnS Quantum Dots are cytotoxic and genotoxic to plant cells, although not lethal. This sets a limit for the concentrations to be used when practical applications using nanodevices of this type on plants are being considered. This work describes for the first time the genotoxic effect of Quantum Dots in plant cells and demonstrates that both the DNA repair genes (Tdp1β, Top1β and Fpg) and the ROS scavenging mechanisms are activated when MPA-CdSe/ZnS QD contact M. sativa cells.
authors.forename: Ana R
authors.initials: AR
authors.lastname: Santos
authors.forename: Ana S
authors.initials: AS
authors.lastname: Miguel
authors.forename: Anca
authors.initials: A
authors.lastname: Macovei
authors.forename: Christopher
authors.initials: C
authors.lastname: Maycock
authors.forename: Alma
authors.initials: A
authors.lastname: Balestrazzi
authors.forename: Abel
authors.initials: A
authors.lastname: Oliva
authors.affiliation: Plant Cell Biotechnology Laboratory, Instituto de Tecnologia Química e Biológica, Universidade Nova de Lisboa, Apartado 127, 2781-901 Oeiras, Portugal. psalema@itqb.unl.pt.
authors.forename: Pedro
authors.initials: P
authors.lastname: Fevereiro
mesh_terms: D000975:Antioxidants / Q000378:metabolism*; D002374:Catalase / Q000378:metabolism; D002478:Cells, Cultured; D004260:DNA Repair; D004264:DNA Topoisomerases, Type I / Q000378:metabolism; D043382:DNA-Formamidopyrimidine Glycosylase / Q000378:metabolism; D016166:Free Radical Scavengers / Q000378:metabolism; D005980:Glutathione Reductase / Q000378:metabolism; D000455:Medicago sativa / Q000166:cytology*; D010727:Phosphoric Diester Hydrolases / Q000378:metabolism; D059828:Plant Cells / Q000187:drug effects* / Q000378:metabolism; D045663:Quantum Dots; D017382:Reactive Oxygen Species / Q000378:metabolism; D013482:Superoxide Dismutase / Q000378:metabolism
chemical_list: D000975:Antioxidants; D016166:Free Radical Scavengers; D017382:Reactive Oxygen Species; D002374:Catalase; D013482:Superoxide Dismutase; D005980:Glutathione Reductase; D010727:Phosphoric Diester Hydrolases; C122147:tyrosyl-DNA phosphodiesterase; D043382:DNA-Formamidopyrimidine Glycosylase; D004264:DNA Topoisomerases, Type I