The size- and dose-dependent cytogenetic effects of gold NPs were evaluated for the first time by a simple and cost-effective Allium cepa (A. cepa) bioassay.

Amitava Mukherjee

Centre for Nanobiotechnology

Vellore Campus

Chandra Sekaran N

Rajeshwari A

Suresh S

Vellore Institute of Technology (VIT) is a private university located in&nbsp;Tamil Nadu, India. Founded in 1984, as Vellore Engineering College, the institution offers 20 undergraduate, 34 postgraduate, four integrated and four research programs. It has campuses in Vellore, Amravati, Bhopal and Chennai.

VIT is one of the top ranked private universities in India according to NIRF, THE and QS Rankings.&nbsp;Govt. of India has recognized&nbsp;VIT, Vellore as an&nbsp;Institution of Eminence. This has allowed VIT to take independent quality initiatives and move up in world ranking.

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VIT University

RSC Advances

With the increase in the use of nanotechnology, the release of engineered nanoparticles (NPs) in the environment also increased significantly. Among all the types of NPs available, mainly metal and metal oxide NPs are used widely. They can be used in wide ranges of products like medicines, food additives, cosmetics, sensors, semiconductors. For these reasons, testing their toxicity towards the environment is essential. Because of the availability and easy maintenance in the laboratory, Allium cepa acts as an excellent model system and are used to detect different kinds of environmental pollutants. Cytotoxicity and genotoxicity of different types of metal and metal oxide NPs were tested using A. cepa. Cytotoxicity of NPs was determined by the decrease in percentage mitotic index, which can be further established by estimating the extracellular reactive oxygen species (ROS) production. Measurement of different types of antioxidant enzyme activities could also help us to understand the effects of oxidative stress caused by the ROS. The ROS produced thus can then cause membrane damage by inducing lipid peroxidation, and in turn can enter the cells and damage the genetic materials, i.e., chromosomes. The genotoxicity of NPs towards A. cepa was found out by calculating percentage chromosomal aberrations, which were viewed under optical microscopes as the chromosome size is more prominent in comparison with other plants. Comet assays also confirmed the genotoxicity of NPs in A. cepa root tips. Thus, A. cepa can act as a biomonitoring agent and helps us to analyse the toxic profiles of different NPs, so that proper biosafety measurement can be taken by limiting NPs release in the environment. © 2019 Elsevier B.V.

Comprehensive Analytical Chemistry Analysis, fate, and toxicity of engineered nanomaterials in plants

Toxic effects of engineered nanoparticles (metal/metal oxides) on plants using Allium cepa as a model system

Europium oxides (Eu2O3) nanoparticles are extensively employed in diverse areas ranging from bioimaging to chemical sensing. However, still there is significant lack of information regarding their toxic behaviour on humans and the environment. The endeavor of this work is to develop structural/toxicity correlations for bare and surface functionalized Eu2O3 nanoparticles synthesized by low-temperature colloidal route. The detailed investigations revealed that Eu2O3 nanoparticles concentration have significant effect on the in vitro toxicity. On the basis of antibacterial, antimicrobial assays and assessment of the genotoxicity using Allium cepa and molecular studies on human blood DNA, it was discovered that surface modification of nanoparticles is an important parameter for reducing the toxicity of Eu2O3 nanoparticles. The phytotoxicity of the prepared nanoparticles has also been compared by the seed germination assay with wheat, green grams, and black chickpeas. The detailed results revealed the mechanism of Eu2O3 nanoparticles in vitro toxicity. © 2018

Journal of Molecular Liquids

A comparative multi-assay approach to study the toxicity behaviour of Eu2O3 nanoparticles

Mosquito-borne diseases are of major concern as they cause devastating health effects, morbidity, and mortality in the human population. Conventional pesticides have failed to curb the mosquito population due to the development of insensitivity in mosquitoes. Hence, higher dosages of pesticides along with their toxic solubilizers have been employed, which have led to raise in pesticide pollution load, environmental toxicity, and human health concerns. As a realisation for the requirement of alternative pesticides, the present study has involved in the formulation of a hydrodispersive nanometric colloidal form of deltamethrin (NDM), a type-II pyrethroid pesticide, from its hydroimmisicible parental form (PDM). The mean hydrodynamic diameter of the droplets was found to be 30.6 ± 4.6 nm by dynamic light scattering study (DLS). High-resolution transmission electron micrographs have revealed the spherical structure of the droplets with a size range of 35–40 nm. The NDM was found to possess sedimentation resistance, intrinsic and hydrodispersive stability. The toxicity of NDM and PDM was comparatively investigated on target organisms (Culex tritaeniorhynchus and Culex quinquefasciatus mosquitoes) and non-target organisms (Allium cepa – Bioindicator of toxicants and Rhizobium sp. – Soil bacteria). As comparative to PDM, NDM has exerted higher efficacy on adult mosquito and larval population, even at low-level concentrations. However, in the case of non-target organisms, the NDM toxicity was lower than PDM. Comprehensively, the study has concluded the potential advantage of formulating conventional pesticides into nanometric soft colloidal form for the improved toxic precision on target organisms (mosquitoes). This ensures the ability of NDM to combat against the mosquito population even at lower concentrations, thereby reducing the pesticide exposure load towards the environment and human population. © 2016 Elsevier B.V.

Science of The Total Environment

Environmental benignity of a pesticide in soft colloidal hydrodispersive nanometric form with improved toxic precision towards the target organisms than non-target organisms

The current study reveals the impact of gold nanorods (NRs) capped with CTAB (cetyltrimethylammonium bromide) or PEG (polyethylene glycol) on Allium cepa. The morphology and surface charge of CTAB- and PEG-capped gold NRs were characterized by electron microscopic and zeta potential analyses. The chromosomal aberrations like clumped chromosome, chromosomal break, chromosomal bridge, diagonal anaphase, disturbed metaphase, laggard chromosome, and sticky chromosome were observed in the root tip cells exposed to different concentrations (0.1, 1, and 10 μg/mL) of CTAB- and PEG-capped gold NRs. We found that both CTAB- and PEG-capped gold NRs were able to induce toxicity in the plant system after 4-h interaction. At a maximum concentration of 10 μg/mL, the mitotic index reduction induced by CTAB-capped gold NRs was 40-fold higher than that induced by PEG-capped gold NRs. The toxicity of gold NRs was further confirmed by lipid peroxidation and oxidative stress analyses. The unbound CTAB also contributed to the toxicity in root tip cells, while PEG alone shows less toxicity to the cells. The vehicle control CTAB contributed to the toxic effects in root tip cells, while PEG alone did not show any toxicity to the cells. The results revealed that even though both the particles have adverse effects on A. cepa, there was a significant difference in the mitotic index and oxidative stress generation in root cells exposed to CTAB-capped gold NRs. Thus, this study concludes that the surface polymerization of gold NRs by PEG can reduce the toxicity of CTAB-capped gold NRs. © 2016 Elsevier Masson SAS

Plant Physiology and Biochemistry

Cytogenetic evaluation of gold nanorods using Allium cepa test

Nanoparticles (NPs) are an emerging environmental threat. However, studies of NPs in different environmental components are limited. In this review, we discuss studies that have evaluated the genotoxicity of NPs in higher plants. Among the 29 studies reviewed, silver NPs were most studied (n = 7 articles), with fewer studies reporting the genotoxicity of carbon nanotubes (n = 3), titanium dioxide NPs (n = 4), and zinc oxide NPs (n = 3). Most of the genotoxicity studies were performed in the model plant systems Allium sp (n = 22), Nicotiana sp (n = 4) and Vicia sp (n = 4) using chromosome aberration (n = 22), micronucleus (n = 15) and comet assays (n = 14). Genotoxicity was observed in most of the studies; however, many studies did consider key determinants of NP toxicity such as particle characterization, dissolution, and uptake. From this review, we propose a set of guidelines that should be considered when reporting results of NP toxicity in plants. © 2019 Elsevier B.V.

Fulltext

Mutation Research - Genetic Toxicology and Environmental Mutagenesis

Genotoxicity of engineered nanoparticles in higher plants

The current study evaluates the cytogenetic effects of chromium (III) oxide nanoparticles on the root cells of Allium cepa. The root tip cells of A. cepa were treated with the aqueous dispersions of Cr2O3 nanoparticles (NPs) at five different concentrations (0.01, 0.1, 1, 10, and 100μg/mL) for 4hr. The colloidal stability of the nanoparticle suspensions during the exposure period were ascertained by particle size analyses. After 4hr exposure to Cr2O3 NPs, a significant decrease in mitotic index (MI) from 35.56% (Control) to 35.26% (0.01μg/mL), 34.64% (0.1μg/mL), 32.73% (1μg/mL), 29.6% (10μg/mL) and 20.92% (100μg/mL) was noted. The optical, fluorescence and confocal laser scanning microscopic analyses demonstrated specific chromosomal aberrations such as-chromosome stickiness, chromosome breaks, laggard chromosome, clumped chromosome, multipolar phases, nuclear notch, and nuclear bud at different exposure concentrations. The concentration-dependent internalization/bio-uptake of Cr2O3 NPs may have contributed to the enhanced production of anti oxidant enzyme, superoxide dismutase to counteract the oxidative stress, which in turn resulted in observed chromosomal aberrations and cytogenetic effects. These results suggest that A. cepa root tip assay can be successfully applied for evaluating environmental risk of Cr2O3 NPs over a wide range of concentrations.

Journal of Environmental Sciences (China)

Cytogenetic studies of chromium (III) oxide nanoparticles on Allium cepa root tip cells

The commercial usage of Al2O3 nanoparticles (Al2O3 NPs) has gone up significantly in the recent times, enhancing the risk of environmental contamination with these agents and their consequent adverse effects on living systems. The current study has been designed to evaluate the cytogenetic potential of Al2O3 NPs in Allium cepa (root tip cells) at a range of exposure concentrations (0.01, 0.1, 1, 10, and 100 μg/mL), their uptake/internalization profile, and the oxidative stress generated. We noted a dose-dependent decrease in themitotic index (42 to 28 %) and an increase in the number of chromosomal aberrations. Various chromosomal aberrations, e.g. sticky, multipolar and laggard chromosomes, chromosomal breaks, and the formation of binucleate cells, were observed by optical, fluorescence, and confocal laser scanning microscopy. FT-IR analysis demonstrated the surface chemical interaction between the nanoparticles and root tip cells. The biouptake of Al2O3 in particulate form led to reactive oxygen species generation, which in turn probably contributed to the induction of chromosomal aberrations. © Springer-Verlag Berlin Heidelberg 2015.

Environmental Science and Pollution Research

Cytotoxicity of aluminum oxide nanoparticles on Allium cepa root tipâ€”effects of oxidative stress generation and biouptake

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 TiO2 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 TiO2 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 TiO2 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. © 2014 Pakrashi et al.

PLoS ONE

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

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 100μgml-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. © 2011 Elsevier B.V.

Journal of Hazardous Materials

Cytogenetic and genotoxic effects of zinc oxide nanoparticles on root cells of Allium cepa

Potential health and environmental effects of nanoparticles need to be thoroughly assessed before their widespread commercialization. Though there are few studies on cytotoxicity of nanoparticles on mammalian and human cell lines, there are hardly any reports on genotoxic and cytotoxic behavior of nanoparticles in plant cells. This study aims to investigate cytotoxic and genotoxic impacts of silver nanoparticles using root tip cells of Allium cepa as an indicator organism. A. cepa root tip cells were treated with four different concentrations (25, 20, 75, and 100 ppm) of engineered silver nanoparticles (below 100 nm size) dispersion, to study endpoints like mitotic index, distribution of cells in mitotic phases, different types of chromosomal aberrations, disturbed metaphase, sticky chromosome, cell wall disintegration, and breaks. For each concentration five sets of microscopic observations were carried out. No chromosomal aberration was observed in the control (untreated onion root tips) and the mitotic index (MI) value was 60.3%. With increasing concentration of the nanoparticles decrease in the mitotic index was noticed (60.30% to 27.62%). The different cytological effects including the chromosomal aberrations were studied in detail for the treated cells as well as control. We infer from this study that silver nanoparticles could penetrate plant system and may impair stages of cell division causing chromatin bridge, stickiness, disturbed metaphase, multiple chromosomal breaks and cell disintegration. The findings also suggest that plants as an important component of the ecosystems need to be included when evaluating the overall toxicological impact of the nanoparticles in the environment. © 2009 Elsevier B.V. All rights reserved.

Journal	Data powered by TypesetRSC Advances
Publisher	Data powered by TypesetRoyal Society of Chemistry (RSC)
ISSN	20462069
Open Access	0