Toxicity assessment of silica nanoparticles on Allium cepa

Abstract

Nanotechnology is rapidly expanding, and several new nanoparticle products with improved performance have been developed. The environmental fate and toxicity of nanoparticles (NP) is poorly understood and should be studied to enable the safe use of this technology. This study aims to investigate genotoxic and phytotoxic impacts of silica nanoparticles (SiNP) using root tip cells of Allium cepa as an indicator system. A. cepa root tip cells were exposed to different concentrations (1.82 to 0.54 g L-1 ; dilution factor of 1.5x) of three engineered dispersions of SiNP (TM40-22 nm; HS30-12 nm; SM30-7 nm). The following endpoints were measured: mitotic index, different types of chromosomal aberrations, germination index and root length. A decrease in the mitotic index was observed with increasing NP concentration, and significant decreases in the MI for all tested NP were found. For all NP cytological effects including chromosomal aberrations were observed in treated cells. Phytotoxic effects were also observed as germination rate and root growth were significantly reduced (p<0.05). Plants are an essential component of ecosystems and these findings suggest that they should be included when evaluating the toxicological impact of NP on the environment.

Higher toxicity of nano-scale TiO2 and dose-dependent genotoxicity of nano-scale SiO2 on the cytology and seedling development of broad bean Vicia faba

“…However, the mitotic index at the highest n-TiO 2 concentration (75 mg/L) was significantly lower than that at the lowest n-SiO 2 concentration (25 mg/L) ( Table 1). The positive effect of n-SiO 2 at the low concentration is in contrast to the previous results on L. culinaris at the same concentrations [24] and A. cepa at concentrations of 540-1820 mg/L [51]. Although n-TiO 2 may [7,20,32].…”

“…For n-SiO 2 , similar results were obtained at the concentrations of 90 and 180 mg/L on V. faba [42] and at even higher concentrations (400-4000 mg/L) on Arabidopsis thaliana [31]. On the other hand, n-SiO 2 decreased the germination percentage of A. cepa at 540, 810 and 1820 mg/L [51] and L. culinaris by increasing the concentration up to 300 mg/L [24]. Similar to our result, n-TiO 2 treatments did not influence the seed germination of Triticum aestivum (wheat) [18], Hordeum vulgare (barley) [32] and various plant species even at high concentrations (Table S3).…”

“…This illustrates that n-SiO 2 had less toxic effect than n-TiO 2 on V. faba root-tip cells particularly at 25 mg/L. The dose-dependent induction of total chromosomal aberrations by n-SiO 2 in our study contrasts to the increased mitotic index on L. culinaris at 200 and 300 mg/L [24] and on A. cepa at the concentration of 810 mg/L [51]. On the other hand, application of n-TiO 2 increased aberration frequency in V. faba root-tip cells.…”

“…Also, these materials can exert genotoxicity by direct and indirect mechanisms [33]. They can penetrate plant cells [26] to interrupt cell division causing chromosomal abnormalities and cell degeneracy, for example in Lens culinaris (lentil) and Allium cepa (onion) [24,36,38,51], and can generate reactive oxygen species (ROS) which cause DNA damage and cell death [37]. Nano-scale materials show high toxicity and are believed to be more toxic than their bulk material [16].…”

Comparison of the Level and Mechanisms of Toxicity of Carbon Nanotubes, Carbon Nanofibers, and Silicon Nanotubes in Bioassay with Four Marine Microalgae

“…Previous works showed that the toxicity from the silica nanotubes increases with the increase of microalgae cell diameter [48]. The other research described an increase in the phytotoxic action for silica NPs with increase of particle size [49]. For C. muelleri and P. purpureum, which are the algae species having smaller cell sizes, both types of silica nanotubes demonstrated a comparable level of toxicity, though the minor predominance could be seen for the sample SNT-1 (Table 3, Figure 1) with smaller diameter of nanotubes but a more developed surface area.…”