title: The detection of β-amyloid plaques in an Alzheimer's disease rat model with DDNP-SPIO.
abstract: OBJECTIVE
  To detect the β-amyloid plaques (Aβ) in a rat model of Alzheimer's disease (AD) using superparamagnetic iron oxide nanoparticles coated with 1,1-dicyano-2-[6-(dimethylamino)-naphthalene-2-yl] propene carboxyl derivative (DDNP-SPIO).
  
  
  METHODS
  DDNP-SPIO was prepared in a previous trial. The binding affinity of DDNP-SPIO to Aβ was tested using fluorescence spectrophotometry in vitro. In vivo, five AD rats and five non-AD rats were intravenously injected with DDNP-SPIO at a dose of 76 μmol Fe/kg. Coronal T2*-weighted images were collected at baseline and repeated at 10, 30, and 60 min post-injection. Enhancement features of the two groups were analysed. After imaging, brain specimens were resected for Congo red and Prussian blue staining to assess the binding of DDNP-SPIO to Aβ deposits.
  
  
  RESULTS
  In vitro experiments indicated that the DDNP-SPIO nanoparticles displayed high binding affinities towards Aβ with a Kd value of 29.4 nmol/l. A significant decrease in SI was detected in the hippocampal area of AD rats after intravenous injection of the nanoparticles, but not in non-AD rats. The measurement of the percentage signal loss decreased to 52% in AD rats. In non-AD rats, only 10% signal loss was observed. There was a significant difference between the two groups (t = 4.533, p < 0.05). The signal decrease resulted from the binding of the DDNP-SPIO nanoparticles to the Aβ plaques, which was identified with Congo red and Prussian blue staining.
  
  
  CONCLUSIONS
  The DDNP-SPIO nanoparticles could potentially be used for visualizing Aβ plaques, which may be helpful for diagnosing the early stages of AD and monitoring the effects of drug therapy.
authors.affiliation: Department of Radiology, XinQiao Hosptial, Third Military Medical University, ChongQing 400037, People's Republic of China. Electronic address: hszhangd@163.com.
authors.forename: D
authors.initials: D
authors.lastname: Zhang
authors.affiliation: College of Chemistry and Chemical Engineering, ChongQing University, Chongqing 400044, People's Republic of China.
authors.forename: H-B
authors.initials: HB
authors.lastname: Fa
authors.affiliation: College of Chemistry and Chemical Engineering, ChongQing University, Chongqing 400044, People's Republic of China.
authors.forename: J-T
authors.initials: JT
authors.lastname: Zhou
authors.affiliation: Department of Neurosurgery, XinQiao Hosptial, Third Military Medical University, ChongQing 400037, People's Republic of China.
authors.forename: S
authors.initials: S
authors.lastname: Li
authors.affiliation: Department of Pathology, XinQiao Hosptial, Third Military Medical University, ChongQing 400037, People's Republic of China.
authors.forename: X-W
authors.initials: XW
authors.lastname: Diao
authors.affiliation: College of Chemistry and Chemical Engineering, ChongQing University, Chongqing 400044, People's Republic of China.
authors.forename: W
authors.initials: W
authors.lastname: Yin
mesh_terms: D015081:2-Naphthylamine / Q000031:analogs & derivatives*; D000181:Acrylonitrile / Q000031:analogs & derivatives*; D000544:Alzheimer Disease / Q000378:metabolism*; D000818:Animals; D016022:Case-Control Studies; D004396:Coloring Agents; D003224:Congo Red; D003287:Contrast Media; D004195:Disease Models, Animal; D005295:Ferrocyanides; D006624:Hippocampus / Q000378:metabolism*; D008279:Magnetic Resonance Imaging / Q000379:methods; D058185:Magnetite Nanoparticles; D058225:Plaque, Amyloid / Q000378:metabolism*; D051381:Rats; D013050:Spectrometry, Fluorescence
chemical_list: C116723:2-(1,1-dicyanopropenyl-2-)-6-dimethylaminonaphthaleney; D004396:Coloring Agents; D003287:Contrast Media; D005295:Ferrocyanides; D058185:Magnetite Nanoparticles; D003224:Congo Red; D015081:2-Naphthylamine; D000181:Acrylonitrile; C000170:ferric ferrocyanide