A novel approach to the identification and quantitative elemental analysis of amyloid deposits--insights into the pathology of Alzheimer's disease.

There is considerable interest in the role of metals such as iron, copper, and zinc in amyloid plaque formation in Alzheimer's disease. However to convincingly establish their presence in plaques in vivo, a sensitive technique is required that is both quantitatively accurate and avoids isolation of plaques or staining/fixing brain tissue, since these processes introduce contaminants and redistribute elements within the tissue. Combining the three ion beam techniques of scanning transmission ion microscopy, Rutherford back scattering spectrometry and particle induced X-ray emission in conjunction with a high energy (MeV) proton microprobe we have imaged plaques in freeze-dried unstained brain sections from CRND-8 mice, and simultaneously quantified iron, copper, and zinc. Our results show increased metal concentrations within the amyloid plaques compared with the surrounding tissue: iron (85 ppm compared with 42 ppm), copper (16 ppm compared to 6 ppm), and zinc (87 ppm compared to 34 ppm).