Just published! A German study by Fraunhofer of toxicity of nanoparticles with the same core but different chemical surface modifications. Conclusions are:
"This study compared the toxic effects of a triple of TiO2
nanoparticles after a 28-day nose-only inhalation. Three TiO2 varieties
used for this study did not show pronounced differences in the exhibited
toxicity. Thus, the variation in properties regarding crystal structure
and surface modification did not alter considerably the interactions
with biological structures in the respiratory tract. This was not
expected as surface modifications sometimes are reported to trigger a
dramatically increased toxic potential as compared to uncoated core
particles. Translocation to remote organs was negligible and values
higher than the detection of limits observed in some few animals. This
confirms for the poorly soluble TiO2 particles no considerable
translocation to liver and no translocation at all to brain."
Full study report
Remarkeble! But how far can we extrapolate? Is the effect of the chemical surface limited?