Tissue distribution and excretion of intravenously administered titanium dioxide nanoparticles

As the biosafety of nanotechnology becomes a growing concern, the in vivo nanotoxicity of nanoparticles (NPs) has been drawn an increasing attention. Titanium dioxide nanoparticles (TiO₂-NPs) have been developed for versatile use, but the pharmacokinetics of intravenously administered TiO₂-NPs have not been investigated extensively. In the present study, the rutile-type TiO₂-NPs with a size about 20 nm were labeled with CF680 and ¹²⁵I. The labeled TiO₂-NPs were injected in mice or rats with the concentration of 1 mg/ml and the dose of 10 mg/kg body weight and their tissue distribution and excretion were investigated by using ex vivo fluorescent imaging, γ-counter and TEM. The results indicated that the TiO₂-NPs mainly accumulated in liver and spleen and could be retained for over 30 days in these tissues due to the phagocytosis by macrophages. The excretion assay found that the excretory rate of TiO₂-NPs through urine was higher than that of feces, indicating that renal excretion was the main excretion pathway of TiO₂-NPs. Overall results of the present study provided important information on distribution and excretion of TiO₂-NPs in vivo, which would greatly promote the pharmacokinetics and in vivo nanotoxicity research of TiO₂-NPs.