Genotoxicity of titanium dioxide (TiO 2 ) nanoparticles at two trophic levels: Plant and human lymphocytes Manosij Ghosh, Maumita Bandyopadhyay, Anita Mukherjee ⇑ Centre of Advanced Study in Cell and Chromosome Research, Department of Botany, University of Calcutta, Kolkata, India article info Article history: Received 28 May 2010 Received in revised form 23 August 2010 Accepted 8 September 2010 Available online 29 September 2010 Keywords: TiO 2 nanoparticles Comet assay Lipid peroxidation Genotoxicity Allium cepa Nicotiana tabacum abstract The environmental fate and behaviour of titanium dioxide (TiO 2 ) nanoparticles is a rapidly expanding area of research. There is a paucity of information regarding toxic effect of TiO 2 nanoparticles in plants and to certain extent in humans. The present study focuses on the effect of exposure of TiO 2 nanoparticles in two trophic levels, plant and human lymphocytes. The genotoxicity of TiO 2 nanoparticles was evalu- ated using classical genotoxic endpoints, comet assay and DNA laddering technique. DNA damaging potential of TiO 2 nanoparticles in Allium cepa and Nicotiana tabacum as representative of plant system could be confirmed in the comet assay and DNA laddering experiments. In Allium micronuclei and chro- mosomal aberrations correlated with the reduction in root growth. We detected increased level of mal- ondialdehyde (MDA) concentration at 4 mM (0.9 lM) treatment dose of TiO 2 nanoparticles in Allium cepa. This indicated that lipid peroxidation could be involved as one of the mechanism leading to DNA damage. A comparative study of the cytotoxic and genotoxic potential of TiO 2 nanoparticles and bulk TiO 2 parti- cles in human lymphocytes also reveal interesting results. While TiO 2 nanoparticles were found to be genotoxic at a low dose of 0.25 mM followed by a decrease in extent of DNA damage at higher concen- trations; bulk TiO 2 particles reveal a more or less dose dependent effect, genotoxic only at dose 1.25 mM and above. The study thus confirms the genotoxic potential of TiO 2 nanoparticles in both plant and human lymphocytes. Ó 2010 Elsevier Ltd. All rights reserved. 1. Introduction With the advent of newer nanomaterials and their use in the industry ranging from health care products, to cosmetics to dietary supplements human exposure to nanomaterials is a driving con- cern. The increasing concentrations of nanomaterials in groundwa- ter and soil may present the most significant exposure avenues for assessing environmental risk (Colvin, 2003). The novel properties such as smaller size, large surface area, higher reactivity that im- parts nanomaterials such interesting property are a major point of concern. Nanomaterials when released into the environment through industrial or domestic waste might tend to disrupt the microflora of soil and water. This in turn might lead to alteration of the food chain and disrupt plant productivity by disrupting nitrogen assimilation and metabolism and can damage aquatic organisms too (Oberdorster et al., 2007). Amongst the manufactured nanoparticles, TiO 2 nanoparticles are used in a broad range of products as food colorant, in sunscreen and in cosmetics. In the recent past, it has also been used in certain sectors of agriculture and is one of the most widely used nanoma- terials. Recent evidences have shown TiO 2 nanoparticles to induce inflammatory and genotoxic response in different animal and hu- man cell lines (Wang et al., 2006; Reeves et al., 2007; Xu et al., 2009). In the present study, the DNA damaging potential of TiO 2 nanoparticles in two different trophic levels, in plants (Allium cepa and Nicotiana tabacum) and in human lymphocytes was evaluated. The genotoxicity of TiO 2 nanoparticles was evaluated using classi- cal genotoxic endpoints like Allium test, comet assay and DNA lad- dering technique in A. cepa roots; and using comet assay and DNA laddering technique in N. tabacum. Amongst different test systems used for genotoxicity testing, A. cepa and N. tabacum were selected, as they are known to be efficient assays for chemical screening and in situ monitoring for genotoxicity of environmental contaminants. Apart from Allium test, A. cepa has been used successfully in our laboratory as a biomarker of genotoxicity using comet assay (Cha- kraborty et al., 2009). The DNA damaging potential of TiO 2 nano- particles was evaluated and compared to that of bulk TiO 2 particles in human lymphocytes as representative of human test system. Comet assay is a simple, sensitive and effective technique used to quantitatively express the extent of genotoxicity of many 0045-6535/$ - see front matter Ó 2010 Elsevier Ltd. All rights reserved. doi:10.1016/j.chemosphere.2010.09.022 Abbreviations: TiO 2 , titanium dioxide; MDA, malondialdehyde; TCA, trichloro- acetic acid; TBAR, thiobarbituric acid reaction; CA, chromosomal aberration; MI, mitotic index; MN, micronuclei; RPMI-1640, Roswell Park Memorial Institute. ⇑ Corresponding author. Address: 35 Ballygunge Circular Road, Centre of Advanced Study, Cell and Chromosome Research, Department of Botany, University of Calcutta, Kolkata, India. Tel.: +91 9831061998; fax: +91 033 24614849. E-mail address: anitamukherjee28@gmail.com (A. Mukherjee). Chemosphere 81 (2010) 1253–1262 Contents lists available at ScienceDirect Chemosphere journal homepage: www.elsevier.com/locate/chemosphere