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Posted: Dec 23, 2010

New study determines the biokinetics of titanium dioxide nanoparticles

(Nanowerk News) A new study just published by the Umweltbundesamt (Federal Environment Agency) in Germany has looked at the quantitative biokinetic analysis of radioactively labelled, inhaled titanium dioxide nanoparticles in a rat model.
The aim of this project was the determination of the biokinetics of TiO2 nanoparticles (NP) in the whole body of healthy adult rats after NP administration to the respiratory tract – either via inhalation or instillation. We developed an own methodology to freshly synthesize and aerosolize TiO2-NP in our lab for the use of inhalation studies. These NP underwent a detailed physical and chemical characterization providing pure polycrystalline anatase TiO2-NP of about 20 nm (geometric standard deviation 1.6) and a specific surface area of 270 m²/g. In addition, we developed techniques for sufficiently stable radioactive 48V labelling of the TiO2 NP. The kinetics of solubility of 48V was thoroughly determined. The methodology of quantitative biokinetics allows for a quantitative balance of the retained and excreted NP in control of the administered NP dose and provides a much more precise determination of NP fractions and concentrations of NP in organs and tissues of interest as compared to spotting biokinetics studies.
Small fractions of TiO2-NP translocate across the air-blood-barrier and accumulate in secondary target organs, soft tissue and skeleton. The amount of translocated TiO2-NP is approximately 2% of TiO2-NP deposited in the lungs. A prominent fraction of these translocated TiO2-NP was found in the remainder. Smaller amounts of TiO2-NP accumulate in secondary organs following particular kinetics. TiO2-NP translocation was grossly accomplished within the first 2-4 hours after inhalation followed by retention in all organs and tissues studied without any detectable clearance of these biopersistent TiO2-NP within 28 days.
Therefore, the data suggest crossing of the air-blood-barrier of the lungs and subsequent accumulation in secondary organs and tissues depends on the NP material and its physico-chemical properties. Furthermore, we extrapolate that during repeated or chronic exposure to insoluble NP the translocated fraction of NP will accumulate in secondary target organs. When these NP are biopersistent as the materials we have studied, much higher NP doses are expected to accumulate in secondary target organs than after our two-hours inhalation studies. In this case accumulated NP doses may well reach levels of the initiation or the modulation of adverse health effects. Hence, further studies are neces investigating the biokinetics and toxicologically re sary levant responses and the underlying mechanisms of TiO2 NP in secondary target organs after chronic exposure.
Source: Umweltbundesamt
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