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ABSTRACT Titanium dioxide (TiO2) is widely used nanoparticle all over the world. In this study, we have investigated the histopathological effect on zebrafish ovaries after exposure to TiO2 nanoparticles. Adult zebrafish individuals were exposed to 1, 2 and 4 mg/L TiO2 for 5 days, and then their ovaries were evaluated using light and transmission electron microscopy. Numerous degenerated follicles with cytoplasmic vacuolization, mitotic catastrophe in mitochondria , chromatin condensation, mitochondrial vesiculation and dispersion at ooplasm were observed. In mitochondria, mitotic catastrophe , vesiculation, swelling and loss of organization of cristae were detected. Here we showed that TiO2 exposure trigger paraptotic type cell death in zebrafish ovary.
Key words Nanoparticle, Cell death, Titanium dioxide, Danio rerio, Ovarian follicle paraptosis.
INTRODUCTION Titanium dioxide (TiO2) is one of the most commonly used nanoparticles. They are used in a range of products including sun screen, cosmetics, coatings, paint, plastics, papers, inks, medicine, medicines, pharmaceuticals, food products, toothpaste and building materials (Wolf et al., 2003; Kaida et al., 2004; Aitken et al., 2006; Wang et al., 2007). United States Environmental Protection Agency (USEPA) estimated the annual production of TiO2 nanoparticles (nano-TiO2) to be 2000 metric tons in around 2005, with 65% of this production used in products such as cosmetics and sunscreen lotions (USEPA, 2009). TiO2 is generally not considered to be obvious toxic (Park et al., 2006). It is photocatalytic and has the potential to produce cumulative cellular damage (Bar-Ilan et al., 2013).
It has been explored for use in water treatment to destroy chemicals such as polychlorinated biphenyls (PCBs), pesticides, and other complex organic contaminants. The conventional sized TiO2 is considered to be physiologically inert and poses little risk to humans, and can be used as food additives (colorants). However, when TiO2 is made at the nanoscale (particle size [LESS-THAN]100 nm), its biological and environmental effects deserve our emerging attention (Chen et al., 2011). It is inevitable for TiO2 NPs to aggregate in water due to its strong interparticle self absorption properties. Dispersed NPs which resulted in toxic effects on the growth of zebrafish (Ispas et al., 2009). Aquatic organisms can also exposed nanoparticles via food chain. Zhu et al. (2010) provide that nanoscale TiO2 particles (nTiO2) can transfer from Daphnia magna to Danio rerio by dietary exposure.