Exploration of cytotoxic and genotoxic endpoints following sub-chronic oral exposure to titanium dioxide nanoparticles

Abstract

Health hazards of titanium dioxide nanoparticles (TiO2-NPs) have raised severe concerns because of the paucity of information regarding the toxic effects among the population. In the present research, the in vitro and in vivo cytotoxic potential of TiO2-NPs were evaluated using flow cytometric techniques. Further, in vitro and in vivo genotoxic endpoints were estimated by means of comet, micronucleus (MN), and chromosomal aberration (CA) assays. In vitro analysis was performed at the concentration range of 10–100 µg/mL using murine RAW 264.7 cells. In vivo experiments were conducted on Albino mice (M/F) by exposing them to 200 and 500 mg/kg TiO2-NPs for 90 days. Decreased percentage of cell viability with higher doses of TiO2-NPs was evident in both in vitro and in vivo flow cytometric analysis. Further, an impaired cell cycle (G0/G1, S, and G2/M) was reflected in the present investigation following the exposure to TiO2-NPs. Increased comet scores such as tail length, % DNA in tail, tail moment, and olive moment were also observed with the higher doses of TiO2-NPs in vitro and in vivo comet assays. Finally, the in vivo MN and CA assays revealed the formation of MN and chromosomal breakage following the exposure to TiO2-NPs.

Possible Adverse Effects of Food Additive E171 (Titanium Dioxide) Related to Particle Specific Human Toxicity, Including the Immune System

“…Intestinal inflammation was often accompanied by alterations in gene expression and activity TNF-α, IFN-γ, IL-2, IL-8, IL-10, NF-kB, cytochrome p450 (CYP450), cyclooxygenase-2 (COX-2), Ki67, and T-helper cells 1 (Th-1) [15,86,88,90]. Some studies reported increased genotoxicity in the form of DNA damage, micronuclei, and dysplastic alterations of tissues including the distal colon and liver, while others did not [15,35,[90][91][92][93][94]. Markers indicating the progression of tumors (COX-2, Ki68, p65, TNF-α, α-catenin), alteration of tumor-related pathways mitogenactivated protein kinase (MAPK) and olfactory/G-protein-coupled receptor family (GPCR) have been measured [15,88,92,95].…”

Basal Ti level in the human placenta and meconium and evidence of a materno-foetal transfer of food-grade TiO2 nanoparticles in an ex vivo placental perfusion model

“…In vivo studies in rodents exposed to TiO 2 reported toxic effects such as inflammation, impairment of biological barrier functions (intestinal, placental, blood-testis), as well as the promotion of cancer development [ 7 , 10 , 11 ]. Overall, repeated exposure to these particles exhibiting cytotoxic, genotoxic and immunotoxic effects is considered to be an important health issue [ 12 – 14 ]. For the general population, there is accumulating evidence that the main uptake route is ingestion, since TiO 2 is produced at high volumes as a food grade pigment (E171 in EU) incorporated in many foodstuffs as well as in toothpaste, medicines and food supplements.…”

Comparative toxicity assessment of nano- and bulk-phase titanium dioxide particles on the human mammary gland in vitro

“…31 Our results extended knowledge of the previous in vitro genotoxicity studies with the comet assays in other human cells where the toxicity of nano-TiO 2 was shown. 5 Apoptosis is recognized as a distinct mode of programmed cell death for the elimination of cells with irreparable genetic damage. On the same line, our results of increased DNA damage through Comet assay ( Figure 7) were verified by getting increased apoptosis levels in nano-TiO 2 -treated cells (Figure 8).…”

“…6 Owing to their mega-production and wide use, the safety and toxicity concerns have equally become important for nano-TiO 2 . They behave differently, in comparison to bulk-TiO 2 , due to their small size and large surface area that increase their reactivity and penetration into human system 5 . It has been shown through various in vitro and in vivo studies that nano-TiO 2 entered the bloodstream after gastrointestinal absorption and damaged the liver, spleen, kidney, lungs, brain, and reproductive organs.…”

“…4 Interestingly, in vitro mechanistic studies (especially for adverse outcomes) have been suggested to be deemed imperative for generation of primary data, which would pave the way for future in vivo trials. 5,14 Considering the abovementioned facts and gaps in knowledge, the comparative preclinical data of TiO 2 (bulk and nano) toxicity was generated through experiments on morphology, cytotoxicity, genotoxicity, and apoptosis of human mammary epithelial cells (MCF-7 cells). Importantly, this study may be helpful in establishing an in vitro nanotoxicity model system for human mammary gland.…”