ANCA: A Family of Fluorescent Probes that Bind and Stain Amyloid Plaques in Human Tissue

A new family of fluorescent markers containing an amino naphthalenyl-2-cyano-acrylate (ANCA) motif has been synthesized and evaluated for its capability to associate with aggregated beta-amyloid (A beta) peptides. These fluorescent probes contain a nitrogen donor group that is connected via a naphthalene unit to an electron acceptor motif containing water solubilizing groups (WSGs). Chemical modifications were introduced to explore their effect on the capability of the ANCA-based probes to fluorescently label aggregated A beta peptides. All synthesized probes bind to aggregated A beta fibrils with low micromolar affinity and fluorescently stain amyloid deposits in human brain tissue from patients with Alzheimer's disease. We found that structural modifications of the WSG site do not affect considerably the binding affinity. However, changes of the nitrogen donor group alter significantly the binding affinity of these probes. Also, increasing the hydrophilicity of the donor group leads to improved contrast between the A beta deposits and the surrounding tissue in histological staining experiments.