Respiratory tract toxicity of Titanium dioxide nanoparticles and multi-walled carbon nanotubes on mice after intranasal exposure

Titanium dioxide nanoparticles (TiO₂-NPs) and multi-walled carbon nanotubes (MWCNTs) have been used in various industrial and household products. Due to their small size they may be able to penetrate into the body and interfere with cell function and biological structure, which raises serious concerns regarding the possible adverse health effects on human beings from inhalation exposure to TiO₂-NPs and MWCNTs. To evaluate the toxicological effects of TiO₂-NPs and MWCNTs on the respiratory system, intranasal exposure of TiO₂-NPs and MWCNTs in mice was performed. The release of lactate dehydrogenase (LDH), total protein content, and pro-inflammatory cytokines (tumour necrosis factor-alpha and interleukin-6) into the bronchoalveolar lavage fluid of mice was measured at 24 h postintranasal instillation. The ICR (Institute for Cancer Research) mouse strain was used as a model. A significant induction of LDH was found in ICR mice treated with TiO₂-NPs and MWCNTs at a concentration of 500 μg (kg bw)^-1. However, a higher degree of induction was detected in mice treated with TiO₂-NPs than the ones that were treated with MWCNTs. In contrast, MWCNTs at the same concentration had more effect on the release of protein content and pro-inflammatory cytokines. The results in this work also suggest that the toxic effects of both TiO₂-NPs and MWCNTs on the respiratory tract depend on their concentration. A higher concentration of both particles mostly induced the production of inflammatory signals.