title: Long-term imaging effects in rat liver after a single injection of an iron oxide nanoparticle based MR contrast agent.
abstract: OBJECTIVE
  To investigate the duration of liver R2* enhancement and pharmacokinetics following administration of an iron oxide nanoparticle in a rat model.
  
  
  METHODS
  Rats were injected with 0, 1, 2, or 5 mg Fe/kg of NC100150 Injection, and quantitative in vivo 1/T2* liver measurements were obtained between 1 and 133 days after injection. The concentration of NC100150 Injection was determined by relaxometry methods in ex vivo rat liver homogenate.
  
  
  RESULTS
  At all dose levels, 1/T2* remained greater than control values up to 63 days after injection. In the highest dose group, 1/T2* was above control levels during the entire 133 day time-course investigated. There were no quantifiable amounts of NC100150 Injection present 63 days after injection in any of the dose groups. The half-life of NC100150 Injection in rat liver was dose dependent. For the lowest dose group, the degradation of the particles could be defined by a mono-exponential function with a half-life of eight days. For the 2 and 5 mg Fe/kg dose groups, the degradation was bi-exponential with a fast initial decay of seven to eight days followed by a slow terminal decay of 43-46 days.
  
  
  CONCLUSIONS
  NC100150 Injection exhibits prolonged 1/T2* enhancement in rat liver. The liver enhancement persisted at time points when the concentration of iron oxide particles present in the liver was below method detection limits. The prolonged 1/T2* enhancement is likely a result of the particle breakdown products and the induction of ferritin and hemosiderin with increasing iron cores/loading factors.
authors.affiliation: Amersham Health, Oslo, Norway. karen.briley.sabo@amersham.com
authors.forename: Karen
authors.initials: K
authors.lastname: Briley-Saebø
authors.forename: Svein-Olaf
authors.initials: SO
authors.lastname: Hustvedt
authors.forename: Anita
authors.initials: A
authors.lastname: Haldorsen
authors.forename: Atle
authors.initials: A
authors.lastname: Bjørnerud
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D003287:Contrast Media / Q000008:administration & dosage / Q000493:pharmacokinetics*; D003911:Dextrans; D052203:Ferrosoferric Oxide; D007501:Iron / Q000008:administration & dosage / Q000493:pharmacokinetics*; D008099:Liver / Q000378:metabolism*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D058185:Magnetite Nanoparticles; D008297:Male; D010087:Oxides / Q000008:administration & dosage / Q000493:pharmacokinetics*; D051381:Rats
chemical_list: D003287:Contrast Media; D003911:Dextrans; D058185:Magnetite Nanoparticles; D010087:Oxides; C097921:ferumoxtran-10; D007501:Iron; D052203:Ferrosoferric Oxide