Novel (E)-5-styryl-2,2'-bithiophene derivatives as ligands for β-amyloid plaques.

In continuation of our investigation on the bithiophene structure as potential β-amyloid probes, a series of (E)-5-styryl-2,2'-bithiophene (SBTP) derivatives was designed and synthesized. In vitro binding showed that all of them displayed high binding affinities to Aβ(1-42) aggregates (K(i)=0.10-41.05nM). Moreover, two radio-iodinated probes, [(125)I]-(E)-5-(4-iodostyryl)-2,2'-bithiophene ([(125)I]8) and [(125)I]-(E)-5-iodo-5'-(4-methoxystyryl)-2,2'-bithiophene ([(125)I]31) were prepared. Both of them displayed specific labeling of Aβ plaques in the brain sections of AD model mice with low background. In vivo biodistribution in normal mice indicated that [(125)I]8 exhibited high initial brain uptake (2.11% ID/g at 2 min) and rapid clearance (0.41% ID/g at 30 min). These preliminary results suggest that SBTP derivatives may be served as novel β-amyloid imaging probes.