Nanoparticle transport and sequestration: Intracellular titanium dioxide nanoparticles in a neotropical fish

Intracellular titanium dioxide nanoparticles (TiO₂-NP) with rutile crystalline form and dimensions varying from 43 to 67 nm × 64 to 93 nm are reported for the first time as being sequestered from the environment. TiO₂-NP were identified inside all organs/tissues (muscle, kidney, gonad, hepatopancreas and gill) in both the cytoplasm and nucleus of the neotropical fish Centropomus parallelus, captured in an area affected by metallurgical activity. Atmospheric particulate matter (PM) sampled in the same area showed the presence of TiO₂-NP with the same rutile crystalline form and dimensions varying from 16 to 93 nm × 45 to 193 nm, thus indicating the smelting and iron processing industries as the most probable source of TiO₂-NP. In any sample, chemical analyses identify and quantify Ti concentration and nanocrystallography identified the structure of TiO₂-NP. The Ti concentration in the sediment and atmospheric PM varied between years and it was mirrored by the Ti concentration in the fish organs. The gill has a higher Ti concentration varying from 5.50 to 14.57 μg g^-1 dry weight and the gonad was the organ with lowest Ti level, 0.25 to 0.87 μg g^-1 dry weight. In the muscles, Ti concentration varied from 0.85 to 3.34 μg g^-1 dry weight. This contamination may be likely to affect the surrounding biota and food uptake, including the humans living in the city close to the metallurgical complex. These findings emphasised the needs to improve methods to reduce PM (including nanoparticles) arising from human activities and to evaluate the toxicokinetic and effects of TiO₂-NP in the biota and human health.