Discovery of a novel fluorescent probe for the sensitive detection of β-amyloid deposits

Here we reported the development of the first photoinduced electron transfer (PeT) probe (1) to directly locate β-amyloid aggregates (Aβ plaques) in the brain without the need of post-washing procedures. The probe showed a high affinity for Aβ aggregates with a K_d value of 3.5 nM. It is weakly emissive by itself with its fluorescence quenched by electron transfer from PeT donor to the excited fluorophore. But selective binding to Aβ plaques would attenuate the PeT process and restore the fluorescence, therefore facilitating the tracking of Aβ plaques. The probe is advantageous in that its fluorescence is environment-less-sensitive and no washing procedure is required to provide high contrast fluorescent signal when applied to stain brain tissues. As a proof of concept, its application has been exemplified by staining Aβ plaques in slices of brain tissue from double transgenic (APP/PS1) mice of Alzheimer's disease.