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      In Vivo Genotoxicity Assessment of Titanium Dioxide Nanoparticles by Allium cepa Root Tip Assay at High Exposure Concentrations

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          Abstract

          The industrial production and commercial applications of titanium dioxide nanoparticles have increased considerably in recent times, which has increased the probability of environmental contamination with these agents and their adverse effects on living systems. This study was designed to assess the genotoxicity potential of TiO 2 NPs at high exposure concentrations, its bio-uptake, and the oxidative stress it generated, a recognised cause of genotoxicity. Allium cepa root tips were treated with TiO 2 NP dispersions at four different concentrations (12.5, 25, 50, 100 µg/mL). A dose dependant decrease in the mitotic index (69 to 21) and an increase in the number of distinctive chromosomal aberrations were observed. Optical, fluorescence and confocal laser scanning microscopy revealed chromosomal aberrations, including chromosomal breaks and sticky, multipolar, and laggard chromosomes, and micronucleus formation. The chromosomal aberrations and DNA damage were also validated by the comet assay. The bio-uptake of TiO 2 in particulate form was the key cause of reactive oxygen species generation, which in turn was probably the cause of the DNA aberrations and genotoxicity observed in this study.

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          Allium cepa test in environmental monitoring: a review on its application.

          Higher plants are recognized as excellent genetic models to detect environmental mutagens and are frequently used in monitoring studies. Among the plant species, Alium cepa has been used to evaluate DNA damages, such as chromosome aberrations and disturbances in the mitotic cycle. Employing the A. cepa as a test system to detect mutagens dates back to the 40s. It has been used to this day to assess a great number of chemical agents, which contributes to its increasing application in environmental monitoring. The A. cepa is characterized as a low cost test. It is easily handled and has advantages over other short-term tests that require previous preparations of tested samples, as well as the addition of exogenous metabolic system. Higher plants, even showing low concentrations of oxidase enzymes and a limitation in the substrate specification in relation to other organism groups, present consistent results that may serve as a warning to other biological systems, since the target is DNA, common to all organisms. The A. cepa test also enables the evaluation of different endpoints. Among the endpoints, chromosome aberrations have been the most used one to detect genotoxicity along the years. The mitotic index and some nuclear abnormalities are used to evaluate citotoxicity and analyze micronucleus to verify mutagenicity of different chemicals. Moreover, the A. cepa test system provides important information to evaluate action mechanisms of an agent about its effects on the genetic material (clastogenic and/or aneugenic effects). In the face of all the advantages that the A. cepa test system offers, it has been widely used to assess the impacts caused by xenobiotics, characterizing an important tool for environmental monitoring studies, where satisfactory results have been reported.
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            Cytogenetic and genotoxic effects of zinc oxide nanoparticles on root cells of Allium cepa.

            Increasing use of zinc oxide nanoparticles (ZnO NP) in consumer products may enhance its release into the environment. Phytotoxicity study is important to understand its possible environmental impact. Allium cepa (Onion bulb) is the best model organism to study genetic toxicology of nanoparticles. Here we have reported cytogenetic and genotoxic effects of ZnO NPs on the root cells of A. cepa. The effects of ZnO NPs on the mitotic index (MI), micronuclei index (MN index), chromosomal aberration index, and lipid peroxidation were determined through the hydroponic culturing of A. cepa. A. cepa roots were treated with the dispersions of ZnO NPs at four different concentrations (25, 50, 75, and 100 μg ml(-1)). With the increasing concentrations of ZnO NPs MI decreased with the increase of pycnotic cells, on the other hand MN and chromosomal aberration index increased. The frequency of micronucleated cells was higher in ZnO NPs treated cells as compared to control (deionized distilled water). The number of cells in each mitotic phase changed upon ZnO NPs treatment. The effect of ZnO NPs on lipid peroxidation as examined by measuring TBARS concentration was evident at all the concentrations compared to bulk ZnO. The TEM image showed internalization of ZnO NPs like particles. SEM image of treated A. cepa demonstrated that the internalized nanoparticles agglomerated depending on the physico-chemical environment inside the cell. Our results demonstrated that ZnO NPs can be a clastogenic/genotoxic and cytotoxic agent. In conclusion, the A. cepa cytogenetic test can be used for the genotoxicity monitoring of novel nanomaterials like ZnO NPs, which is used in many consumer products. Copyright © 2011 Elsevier B.V. All rights reserved.
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              Author and article information

              Contributors
              Role: Editor
              Journal
              PLoS One
              PLoS ONE
              plos
              plosone
              PLoS ONE
              Public Library of Science (San Francisco, USA )
              1932-6203
              2014
              4 February 2014
              : 9
              : 2
              : e87789
              Affiliations
              [1 ]Centre for Nanobiotechnology, VIT University, Vellore, Tamilnadu, India
              [2 ]Department of Materials Engineering, Indian Institute of Science, Bangalore, Karnataka, India
              [3 ]Department of Chemical Technology, University of Johannesburg, Johannesburg, Gauteng, South Africa
              RMIT University, Australia
              Author notes

              Competing Interests: The authors have declared that no competing interests exist

              Conceived and designed the experiments: SP NJ. Performed the experiments: SP NJ SD JJ PTC. Analyzed the data: SP NJ SD JJ PTC. Contributed reagents/materials/analysis tools: AM AMR NC. Wrote the paper: SP NJ SD.

              Article
              PONE-D-13-38834
              10.1371/journal.pone.0087789
              3913665
              6320447e-d908-4cd0-a29b-7528889d0552
              Copyright @ 2014

              This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

              History
              : 18 September 2013
              : 1 January 2014
              Page count
              Pages: 12
              Funding
              We profoundly thank VIT University management for funding the research. SP and SD acknowledge fellowship support from Council of Scientific & Industrial Research (CSIR), India. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.
              Categories
              Research Article
              Biology
              Biochemistry
              Nucleic Acids
              DNA
              Biotechnology
              Bionanotechnology
              Molecular Cell Biology
              Chromosome Biology
              Chromosome Structure and Function
              Nucleic Acids
              DNA
              Plant Science
              Plant Biotechnology
              Toxicology
              Genetic Toxicology
              Toxic Agents
              Materials Science
              Material by Attribute
              Nanomaterials
              Nanotechnology
              Nanomaterials
              Medicine
              Toxicology
              Genetic Toxicology

              Uncategorized
              Uncategorized

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