A Copper Complex of a Thiosemicarbazone-Pyridylhydrazone Ligand Containing a Vinylpyridine Functional Group as a Potential Imaging Agent for Amyloid-beta Plaques

Complexes containing positron-emitting radionuclides of copper have the potential to be of use for diagnostic imaging with positron emission tomography. Alzheimer's disease is characterised by the presence of amyloid-beta plaques in the brain. A new thiosemicarbazone-pyridyl hydrazone tetradentate ligand with a pyridyl-4-vinylpyridine functional group was prepared with the aim of making a copper complex that binds to amyloid-beta plaques to assist in the diagnosis of Alzheimer's disease. The ligand forms a charge neutral complex with copper(II) that was characterised by X-ray crystallography and the electrochemical behaviour of the complex was investigated by cyclic voltammetry. The new ligand can be radiolabelled with positron-emitting copper-64 at room temperature in excellent radiochemical yields. The new complex interacts with synthetic amyloid-beta fibrils and binds amyloid-beta plaques present in post-mortem Alzheimer's disease brain tissue.