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 TiO2NP in our lab for the use of inhalation studies. These NP
underwent a detailed physical and chemical characterization providing pure polycrystalline anatase TiO2NP 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 TiO2NP translocate across the airbloodbarrier and accumulate in secondary target organs, soft tissue
and skeleton. The amount of translocated TiO2NP is approximately 2% of TiO2NP deposited in the lungs. A prominent
fraction of these translocated TiO2NP was found in the remainder. Smaller amounts of TiO2NP accumulate in
secondary
organs following particular kinetics. TiO2NP translocation was grossly accomplished within the first 24 hours after
inhalation followed by retention in all organs and tissues studied without any detectable clearance of these biopersistent
TiO2NP within 28 days.

Therefore, the data suggest crossing of the airbloodbarrier of the lungs and subsequent accumulation in secondary
organs and tissues depends on the NP material and its physicochemical 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 twohours 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.
