Colloidal gold nanoparticles (10nm) were used to label single walled carbon nanotubes (SWCNT) in studies aimed at determining how SWCNT clear from the lungs. Gold labeled SWCNT were delivered to the lungs by pharyngeal aspiration to C57BL/6 mice. Neutron activation analysis (NAA) of lung, blood and other organs was carried out at various time points after aspiration to determine if the gold labeled SWCNT translocated out of the lungs. Five mice per group were studied at 1 hour, 1 day, 3, 7 and 28 days after exposure to a single dose (40ug) of gold labeled SWCNT. A phosphate buffered saline (PBS) aspiration group served as the negative control. At sacrifice, the lungs, GI tract, heart, brain, liver, kidneys, right cranial mediastinal lymph node and a blood sample were taken for analysis of gold content by NAA. Lungs from additional mice were fixed and sectioned for study of the gross distribution of gold labeled SWCNT in the lungs. Gold content of the PBS aspiration group was negligible. For labeled SWCNT, blood gold content was below detectable levels for all time points. Lymph node gold content was not significantly different from the PBS group at any time point. Only lung and GI tract had significant labeled SWCNT at any time point. Lung gold content was 0.181+/-.008, 0.13+/-0.006, 0.089+/-.014, 0.096+/-.006 and 0.049+/-.007 ug (mean+/-SE) at 1 hr, 1 day, 3, 7 and 28 days, respectively. Initially there was a rapid decline of burden from the lungs due to mucociliary clearance which was correlated with GI tract content. Lung burden decreased by 49% between 7 and 28 days. Histological examination demonstrated significant gold labeled SWCNT still present in the airways at 7 and 28 days. While it is uncertain as to the mechanism of the slower phase clearance of lung burden between 7 and 28 days it does not appear to be due to transport to major organs.
Airborne-particles; Biological-effects; Biological-factors; Cell-morphology; Cellular-reactions; Cell-biology; Cytology; Exposure-assessment; Exposure-levels; Exposure-methods; Inhalation-studies; Laboratory-animals; Lung-cells; Lung-disorders; Lung-irritants; Microscopic-analysis; Microscopy; Particle-aerodynamics; Particulates; Pulmonary-disorders; Pulmonary-function; Respiratory-irritants; Respiratory-hypersensitivity; Risk-factors; Statistical-analysis; Tissue-culture; Nanotechnology
The Toxicologist. Society of Toxicology 48th Annual Meeting and ToxExpo, March 15-19, 2009, Baltimore, Maryland