Toxicological and morphological aspects of nano-TiO2 and nano-TiO2-Ag acute action on the liver of mice

Abstract

Aim. To study the toxic effect of TiO₂ and TiO₂-Ag nanopowders on the morphology and elemental composition of the laboratory mice liver.

Materials and methods. The study used a model of acute intoxication on laboratory animals. Mice were injected intraperitoneally with TiO₂ and TiO₂-Ag nanopowders at 4000 mg/kg, 7000 mg/kg, or 10000 mg/kg doses. During two weeks, the animals were observed, lethality was assessed, the accumulation of nanopowder in the organ and the morphology of liver tissues were investigated. The content of titanium and silver in liver samples was determined by optical emission spectroscopy with inductively coupled plasma. Liver tissue micropreparations were examined using an Olympus BX51 light microscope. Also, the micropreparations of the liver were examined by scanning electron microscopy (SEM) using the Tescan Mira 3 device, and the elemental composition was determined using an energy dispersive spectrometer Oxford instrument, X-max 80 mm².

Results. The dependence of the mice lethality on the nanopowders dose was revealed; mortality was higher when exposed to nano-TiO₂-Ag compared to nano-TiO₂. Average lethal doses were calculated using probit analysis. For nano-TiO₂, the LD₅₀ is 4783.30 mg/kg; for nano-TiO₂-Ag – 724.44 mg/kg. The accumulation of titanium, titanium, and silver in the liver after exposure to nano-TiO₂ and nano-TiO₂-Ag was established. In general, there was a tendency to increase the content of titanium in the skin tissue with an increase in the administered dose of nanopowders.

Morphological changes in the liver were studied by histological methods. The most characteristic morphological signs of the toxic effect of nano-TiO₂ on tissue were dystrophic changes at the level of 67.7 % (cytoplasmic vacuolization in hepatocytes), and when exposed to nano-TiO₂-Ag – initial necrotic changes at the level of 70 % (hepatocytes with nuclear pyknosis). It is worth noting that the toxic effect of nano-TiO₂ and nano-TiO₂-Ag is much less often manifested by focal necrosis and inflammatory reactions (focal infiltration), in some cases, there were adaptive changes that provoked an increase in the number of binuclear hepatocytes. In case of detection agglomerates of a foreign object (crystalline inclusions) were obtained, which were examined spectrally and showed a high content of titanium (Ti). SEM morphometry showed that the size of nanoparticles and their agglomerates ranged from 80 nm to 20 μm.

Conclusions. The lethality of mice was higher when the composition of nano-TiO₂-Ag was introduced compared to nano-TiO₂. Based on the calculated average lethal doses, both nanopowders were assigned to the 3^rd class (moderately dangerous) of the danger of chemical substances according to the classification of GOST 12.1.007-76. It was established that with an increase in the injected dose in the tissue of the products of laboratory mice, the accumulation of titanium (under the action of nano-TiO₂) and titanium and silver (under the action of nano-TiO₂-Ag) increases. Characteristic microscopic signs of the toxic effect of TiO₂ and TiO₂-Ag nanopowders after intraperitoneal injection in laboratory bags are dystrophic changes in hepatocytes, necrosis of parenchymal disease, while inflammatory reactions occur less often. SEM and the method of elemental mapping of titanium confirmed the presence of TiO₂ nanoparticles and their agglomerates in skin tissue when TiO₂ nanopowder was administered.