The effects of titanium dioxide nanoparticles on ultrastructure of zebrafish testis (Danio rerio)

Nanotechnology investigates materials at nanoscale level (0.1-100nm in diameter). There are many commercially nanoproducts such as silver, silicon, titanium, zinc, and gold. They are used in a variety of applications and released to the environment. Titanium dioxide (TiO₂) is one of the most commonly used nanoparticles (NP). In this study, the ultrastructural effects of TiO₂-NP on zebrafish testis tissue were evaluated.

Zebrafish were divided into four groups (N=60) as one control and 3 experimental groups (1mg/L, 2mg/L and 4mg/L TiO₂). Testis tissues were dissected after 5days of the exposure. Tissues were fixed with 2.5% glutaraldehyde at 4°C. After routine electron microscopy tissue processing, the testis were embedded in epon resin. Ultrathin sections were counterstained with 1% uranyl acetate and lead citrate and examined using a transmission electron microscope.

Mitochodrial degeneration with swelling and cristae loss were detected in Sertoli cells and spermatogonial cells of TiO2-NP treated groups in a dose-dependent manner. Moreover, autophagic vacuole accumulation were seen in Sertoli cell cytoplasms of the experimental groups. Necrosis was also detected in the 4mg TiO2-NP-treated group.

TiO2-NP has been used in crop production, food additives, medicine, toothpastes, sunscreens, cosmetics, and in waste water treatment, which contaminated the environment. Our findings showed TiO₂-NP-induced autophagy and necrosis at higher doses in Sertoli cells, which consequently negatively affected spermatogenic cells and testicular morphology of Zebrafish. It is important to give much more attention to the use of this NP to minimise the possible effects on nature and organisms.