Genotoxicity Studies of Titanium Dioxide Nanoparticles (TiO2NPs) in the Brain of Mice

Abstract

Titanium dioxide nanoparticles (TiO2NPs) are excessively used and represent one of the top five most commonly used nanoparticles worldwide. Recently, various studies referred to their toxic potential on various organs using different treatment route. Male Swiss Webster mice were orally administrated TiO2NPs (500 mg/kg b.w.) daily for five consecutive days and then animals were sacrificed at 24 h, 7 days, or 14 days after the last treatment. The present results report that exposure to TiO2NPs produces mild to moderate changes in the cytoarchitecture of brain tissue in a time dependent manner. Moreover, Comet assay revealed the apoptotic DNA fragmentation, while PCR-SSCP pattern and direct sequencing showed point mutation of Presenilin 1 gene at exon 5, gene linked to inherited forms of the Alzheimer's disease. Therefore, from these findings, the present study concluded that TiO2NPs is genotoxic and mutagenic to brain tissue which in turn might lead to Alzheimer's disease incidence.

Figure 1

Photomicrograph of brain sections of different groups, in which (a) represents negative control; (b) 24 h group showing extracellular brain edema (blue arrows) and intracellular brain edema (black arrow); (c) 7-day group showing an extracellular edema (arrows); (d), 14-day group showing vacuolation (arrows), respectively. Hematoxylin and eosin staining at 400x.

Figure 2

A 1.5% agarose gel separating PCR product for PSEN1 exon 5 (231 bp). Each lane represents an individual animal, in which lane M is low molecular weight DNA marker (100–1500 bp); lanes 1–3, PCR product for negative control group; lanes 4–6; lanes 7–9 and lanes 10–12, PCR products for 24 h; 7-day and 14-day groups, respectively.

Figure 3

A 9% polyacrylamide gel showing PCR-SSCP for PSEN1 exon 5. Each lane represents an individual animal, in which lane C represents negative control group; lanes 1–3; lanes 4–6 and lanes 7–9 represent PCR-SSCP pattern for 24 h; 7-day and 14-day groups, respectively. (∗) symbol referred to mutated samples that are found at lanes 6 and 7 in comparison with the negative control group.

Figure 4

DNA sequence chromatogram of (a) negative control, (b) representative TiO₂NPs 7-day and 14-day mutated groups, using PSEN1 exon 5 reverse primer, in which point of mutation is circled and indicated by arrow.

Figure 5

Representative photomicrograph showing (a) typical nuclei of undamaged cells of negative control group and (b) various degrees of DNA damage observed as comets that were seen in all different treated groups.

Figure 6

Effect of TiO₂NPs on the DNA (DNA damage was represented by Comet assay) in mice brain cells. Significant difference (p < 0.05) using Student's t-test, in which ^∗Statistically compared with negative control group; ^#Statistically compared with 24 h group; ^$Statistically compared with 7-day group.