title: Do inhaled carbon nanoparticles translocate directly into the circulation in humans?
abstract: BACKGROUND
  Increased exposure to particulate air pollution (PM(10)) is a risk factor for death and hospitalization with cardiovascular disease. It has been suggested that the nanoparticulate component of PM(10) is capable of translocating into the circulation with the potential for direct effects on the vasculature.
  
  
  OBJECTIVE
  The study's aim was to determine the extent to which inhaled technetium-99m ((99m)Tc)-labeled carbon nanoparticles (Technegas) were able to access the systemic circulation.
  
  
  RESULTS
  Ten healthy volunteers inhaled Technegas and blood samples were taken sequentially over the following 6 h. Technegas particles were 4-20 nm in diameter and aggregated to a median particle diameter of approximately 100 nm. Radioactivity was immediately detected in blood, with levels increasing over 60 min. Thin-layer chromatography of whole blood identified a species that moved with the solvent front, corresponding to unbound (99m)Tc-pertechnetate, which was excreted in urine. There was no evidence of particle-bound (99m)Tc at the origin. gamma Camera images demonstrated high levels of Technegas retention (95.6 +/- 1.7% at 6 h) in the lungs, with no accumulation of radioactivity detected over the liver or spleen.
  
  
  CONCLUSIONS
  The majority of (99m)Tc-labeled carbon nanoparticles remain within the lung up to 6 h after inhalation. In contrast to previous published studies, thin-layer chromatography did not support the hypothesis that inhaled Technegas carbon nanoparticles pass directly from the lungs into the systemic circulation.
authors.affiliation: Centre for Cardiovascular Science, The University of Edinburgh, Chancellor's Building, Edinburgh EH16 4SB, UK. nick.mills@ed.ac.uk
authors.forename: Nicholas L
authors.initials: NL
authors.lastname: Mills
authors.forename: Nadia
authors.initials: N
authors.lastname: Amin
authors.forename: Simon D
authors.initials: SD
authors.lastname: Robinson
authors.forename: Atul
authors.initials: A
authors.lastname: Anand
authors.forename: John
authors.initials: J
authors.lastname: Davies
authors.forename: Dilip
authors.initials: D
authors.lastname: Patel
authors.forename: Jesus M
authors.initials: JM
authors.lastname: de la Fuente
authors.forename: Flemming R
authors.initials: FR
authors.lastname: Cassee
authors.forename: Nicholas A
authors.initials: NA
authors.lastname: Boon
authors.forename: William
authors.initials: W
authors.lastname: Macnee
authors.forename: Alistair M
authors.initials: AM
authors.lastname: Millar
authors.forename: Ken
authors.initials: K
authors.lastname: Donaldson
authors.forename: David E
authors.initials: DE
authors.lastname: Newby
mesh_terms: D000328:Adult; D000397:Air Pollution / Q000009:adverse effects*; D005260:Female; D006108:Graphite; D006801:Humans; D001239:Inhalation; D008297:Male; D049329:Nanostructures / Q000032:analysis*; D013670:Sodium Pertechnetate Tc 99m / Q000097:blood*
chemical_list: C056708:Technegas; D006108:Graphite; D013670:Sodium Pertechnetate Tc 99m