Genotoxicity of titanium dioxide nanoparticles and triggering of defense mechanisms in <i>Allium cepa</i>

Santos, Ronaldo dos; Vicari, Taynah; Santos, Samuel A.; Felisbino, Karoline; Mattoso, Ney; Sant’Anna-Santos, Bruno Francisco; Cestari, Marta Margarete; Leme, Daniela Morais

doi:10.1590/1678-4685-GMB-2018-0205

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Mutagenesis • Genet. Mol. Biol. 42 (2) • Apr-Jun 2019 • https://doi.org/10.1590/1678-4685-GMB-2018-0205 copy

Genotoxicity of titanium dioxide nanoparticles and triggering of defense mechanisms in Allium cepa

Authorship SCIMAGO INSTITUTIONS RANKINGS

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.

Keywords:
Chromosomal aberrations; micronuclei; nucleolar alterations; cellular alterations; nanoparticle phase-change

Treatment	Concentration	SG	RL
	(mg/L)	M ± SD	M ± SD
NC	-	60 ± 1	1.93 ± 0.66
	10	53.3 ± 1.15*	1.60 ± 0.70*
TiO₂NP	100	49.3 ± 0.57*	1.46 ± 0.77*
	1000	49 ± 0.57*	1.44 ± 0.64*
PC	6	7.66 ± 1*	0.580.17*

Treatment	Concentration	MI	CA	MN
MN	(mg/L)	M ± SD	M ± SD	M ± SD
NC	-	246.9 ±1.55	0.70 ±0.67	0.60 ±0.69
TiO₂NP	10	244.2 ±1.75	1.10 ±0.73	0.60 ±0.69
	100	240.7 ±1.15^*	2.19 ±0.63	2.39 ±0.70
	1000	236.5 ±2.43^*	5.28 ±1.06^*	4.88 ±0.88^*
PC	10	226.5 ± 1.90^*	8.05 ±1.44^*	33.3 ±2.42^*

CA	NC	TiO₂NP (mg/L)			PC
		10	100	1000
Clastogenic
Chromosomal bridge	0.1	0.06	0.22*	0.36*	0.66*
Chromosomal breaks	0.02	0.08*	0.1*	0.36*	0.48*
Total	0.12	0.14	0.32	0.72	1.14
Aneugenic
Chromosomal loss	0	0.02	0.02	0	0.02
Chromosomal delay	0	0	0.04	0.1*	0.04
Chromosomal adherence	0	0.02	0.06	0.16*	0.22*
Nuclear bud	0	0.04	0	0.08*	0.12*
Total	0	0.08	0.12	0.34	0.40

Material	Profile	D_measured (nm)	D_tabulated (nm)	Δ (%)
			Brookite phase
	1	0.268 ± 0.04	0.2728	- 1.75
In A. cepa roots cells	1	0.132 ± 0.01	0.1335	- 1.12
	2	0.268 ± 0.04	0.2669	+ 0.41
	2	0.133 ± 0.01	0.1335	- 0.37
	3	0.228 ± 0.03	0.2295	- 0.65
	3	0.154 ± 0.02	0.1530	+ 0.65
			Anatase phase
	1	0.344±0.004	0.352	-2.3
	2	0.237±0.002	0.2378	-0.3
Nanopowder	3	0.185±0.001	0.1892	-2.2
form	4	0.169±0.001	0.16999	-0.6
	5	0.0934± 0.0005	0.09464	-1.3
	6	0.0853± 0.0004	0.08464	+0.8

Sociedade Brasileira de Genética Rua Cap. Adelmio Norberto da Silva, 736, 14025-670 Ribeirão Preto SP Brazil, Tel.: (55 16) 3911-4130 / Fax.: (55 16) 3621-3552 - Ribeirão Preto - SP - Brazil
E-mail: editor@gmb.org.br

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[1] Send correspondence to Daniela Morais Leme. Department of Genetics, Universidade Federal do Paraná, Avenida Coronel Francisco H. dos Santos, s/n, Jardim das Américas, 81531-970, Curitiba, PR, Brazil, Phone: +55 41 3361-1727; Fax: +55 41 3361-1793. E-mail: daniela.leme@ufpr.br.