2-(4'-Aminophenyl)benzothiazole Labeled with Tc-Cyclopentadienyl for Imaging β-Amyloid Plaques.

The development of a Tc-radiotracer for imaging of β-amyloid (Aβ) plaques with single photon emission computed tomography (SPECT) is strongly anticipated to provide a low cost and broadly accessible diagnostic tool for Alzheimer's disease (AD). Within this framework, 2-(4'-aminophenyl)benzothiazole, known to display affinity and specificity for Aβ plaques, has been joined to the tricarbonyl -[M(CO)] (M = Re(I), Tc(I)) core through the cyclopentadienyl moiety to yield stable, neutral, and lipophilic complexes ( and , respectively). The complex was completely characterized with spectroscopic methods and was shown to selectively stain Aβ plaques on sections of human AD brain tissue. The complex displayed satisfactory initial brain uptake (0.53% ID/g at 2 min) and stability in healthy mice, while in transgenic 5xFAD mice, models for AD, a notable retention in the brain was noted (1.94% ID/g at 90 min). The results are encouraging and contribute to the effort of developing a SPECT amyloid imaging agent.