Molecular imaging of β-amyloid plaques with near-infrared boron dipyrromethane (BODIPY)-based fluorescent probes

The formation of β-amyloid (Aβ) plaques is a critical neurodegenerative change in Alzheimer disease (AD). We designed and synthesized novel boron dipyrromethane (BODIPY)-based Aβ probes (BAPs) and evaluated their utility for near-infrared fluorescence imaging of Aβ plaques in the brain. In binding experiments in vitro, BAPs showed high affinity for synthetic Aβ aggregates (Kd  =  18-149 nM). Furthermore, BAPs clearly stained Aβ plaques in sections of Tg2576 mice. In mouse brain tissue, BAPs showed sufficient uptake for optical imaging. In addition, ex vivo fluorescent staining of brain sections from Tg2576 mice after the injection of BAP-2 showed selective binding of Aβ plaques with little nonspecific binding. BAPs may be useful as a near-infrared fluorescent probe for imaging Aβ plaques.