The effect of multiwalled carbon nanotube agglomeration on their accumulation in and damage to organs in mice

Purified carboxylated multiwalled carbon nanotubes (MWCNTs) with different agglomeration propensities were evaluated in mice following a single dose intravenous injection. Both agglomerated and the well suspended MWCNTs were taken up by mononuclear phagocyte system organs. MWCNTs with higher degree of agglomeration were retained in lungs and later in the liver and were not eliminated completely in 28 days, while the well-dispersed ones remained well dispersed and formed fewer aggregates in the lungs and liver, and seemed to be easily eliminated. Persistent accumulation of agglomerated MWCNTs in the lungs caused inflammatory responses while the well-suspended ones did not. Although the elimination of MWCNTs is still to be evaluated quantitatively, the formation of a stable suspension is one of the key requirements for safe applications in medicine.