The detection of β-amyloid plaques in an Alzheimer's disease rat model with DDNP-SPIO

Aim 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). Materials and 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