Abstract
BackgroundWe used fullerenes, whose dispersion at the nano-level was stabilized by grinding in nitrogen gas in an agitation mill, to conduct an intratracheal instillation study and an inhalation exposure study. Fullerenes were individually dispersed in distilled water including 0.1% Tween 80, and the diameter of the fullerenes was 33 nm. These suspensions were directly injected as a solution in the intratracheal instillation study. The reference material was nickel oxide in distilled water. Wistar male rats intratracheally received a dose of 0.1 mg, 0.2 mg, or 1 mg of fullerenes and were sacrificed after 3 days, 1 week, 1 month, 3 months, and 6 months. In the inhalation study, Wistar rats were exposed to fullerene agglomerates (diameter: 96 ± 5 nm; 0.12 ± 0.03 mg/m3; 6 hours/days for 5 days/week) for 4 weeks and were sacrificed at 3 days, 1 month, and 3 months after the end of exposure. The inflammatory responses and gene expression of cytokine-induced neutrophil chemoattractants (CINCs) were examined in rat lungs in both studies.ResultsIn the intratracheal instillation study, both the 0.1 mg and 0.2 mg fullerene groups did not show a significant increase of the total cell and neutrophil count in BALF or in the expression of CINC-1,-2αβ and-3 in the lung, while the high-dose, 1 mg group only showed a transient significant increase of neutrophils and expression of CINC-1,-2αβ and -3. In the inhalation study, there were no increases of total cell and neutrophil count in BALF, CINC-1,-2αβ and-3 in the fullerene group.ConclusionThese data in intratracheal instillation and inhalation studies suggested that well-dispersed fullerenes do not have strong potential of neutrophil inflammation.
Highlights
We used fullerenes, whose dispersion at the nano-level was stabilized by grinding in nitrogen gas in an agitation mill, to conduct an intratracheal instillation study and an inhalation exposure study
The diameter of fullerene nanoparticles by transmission electron microscope (TEM) was almost same level. These suspensions were directly injected as a solution in the intratracheal instillation study, and were used for generation of fullerene nanoparticles in the inhalation study
cytokine-induced neutrophil chemoattractants (CINCs) concentration in the lung (Figure 3) A transient and significant, though mild, increase in CINC-1 concentration was found after 1 month in the 0.1 mg and 0.2 mg fullerene groups
Summary
We used fullerenes, whose dispersion at the nano-level was stabilized by grinding in nitrogen gas in an agitation mill, to conduct an intratracheal instillation study and an inhalation exposure study. Fullerenes were individually dispersed in distilled water including 0.1% Tween 80, and the diameter of the fullerenes was 33 nm These suspensions were directly injected as a solution in the intratracheal instillation study. Unless an experiment examines the dispersed nanoparticles, any experiment in which animals are exposed to undispersed nanoparticles cannot eliminate the possibility that the result is caused by the influence of agglomerates, even if dispersed particles are observed in vivo For this reason, the characterization of nanoparticles is needed; in particular, it is necessary to confirm that the agglomerates are at the nano-size level under the exposure conditions of animal experiments, i.e. inside the inhalation chamber for inhalation studies and in the instillation liquid for intratracheal instillation studies. We controlled the size of fullerene particles at the nano-level by grinding them in nitrogen gas in an agitation mill to obtain a stable dispersion and realize the animal fullerene exposure study at the nano-size level [5]
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