Abstract
Titanium dioxide nanoparticles (TiO2NPs) are widely used and may impact the environment. Thus, this study used a high concentration of TiO2NP (1000 mg/L) to verify the defense mechanisms triggered by a plant system – an indicator of toxicity. Furthermore, this study aimed at completely characterizing TiO2NP suspensions to elucidate their toxic behavior. TiO2NPs were taken up by meristematic cells of Allium cepa, leading to slight inhibition of seed germination and root growth. However, severe cellular and DNA damages were observed in a concentration-dependent manner (10, 100, and 1000 mg/L). For this reason, we used the highest tested concentration (1000 mg/L) to verify if the plant cells developed defense mechanisms against the TiO2NPs and evaluated other evidences of TiO2NP genotoxicity. Nucleolar alterations and plant defense responses (i.e., increased lytic vacuoles, oil bodies and NP phase change) were observed in meristematic cells exposed to TiO2NP at 1000 mg/L. In summary, TiO2NPs can damage the genetic material of plants; however, plants displayed defense mechanisms against the deleterious effects of these NPs. In addition, A. cepa was found to be a suitable test system to evaluate the cyto- and genotoxicity of NPs.
Highlights
Titanium dioxide nanoparticles (TiO2NPs) are among the most used manufactured nanomaterials, being produced in thousands of tons per year around the world (Robichaud et al, 2009)
The nanopowder form was analyzed by transmission electron microscopy, as well as by X-ray diffraction
The analysis showed that the crystal structures of TiO2NPs comprise 100% anatase phase, consisting of 28.42% titanium and 71.58% oxygen
Summary
Titanium dioxide nanoparticles (TiO2NPs) are among the most used manufactured nanomaterials, being produced in thousands of tons per year around the world (Robichaud et al, 2009). This NP occurs in three forms in nature: anatase, brookite, and rutile (Clement et al, 2013). Damages to plants can generate an imbalance in the ecosystems, emphasizing the importance of phytotoxicity studies (Ma et al, 2010) Within this context, there is a concern about the toxicological impacts of NPs on living organisms, such as plants – target organisms of NPs through different environment compartments (air, water, and soil)
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