Smart D-π-A Type Near-Infrared Aβ Probes: Effects of a Marked π Bridge on Optical and Biological Properties

To expand the scope of D-π-A based near-infrared (NIR) probes for detecting β-amyloid (Aβ) plaques and to systematically explore the relationship among their structural characteristics, optical properties, and biological properties, three series of smart NIR probes with different aromatic rings and up to seven trans double bonds were synthesized and evaluated. Marked correlations between the conjugated π system and properties of these probes, such as optical data, binding ability, and brain uptake, were observed. One probe, PHC-4, displayed improved properties as a NIR probe for the in vivo detection of Aβ plaques.