Dye May Diagnose Early Alzheimer's

"Before you can cure Alzheimer's, you have to be able to diagnose it and monitor its progress very precisely,” commented Dr. Timothy Swager, lead investigator of the study and a professor in the department of chemistry of the Massachusetts Institute of Technology (MIT, Cambridge, MA, USA).

To accomplish this task, Dr. Swager and worked with researchers at Massachusetts General Hospital (Boston, MA, USA) and the University of Pittsburgh (PA, USA) to develop a contrast agent that would first bind to the protein deposits, or plaques, in the brain that cause AD, and then fluoresce when exposed to radiation in the near-infrared range. The new dye could provide direct imaging of Alzheimer's plaques through a patient's skull.

Some of the first noninvasive methods for detecting AD involved agents labeled with radioactive elements that could enter the brain and target disease plaque for imaging with positron emission tomography (PET) imaging. However, these techniques were costly and limited by the short working lifetime of the labeled agents.

Dr. Swager and coworkers developed the new dye, called NIAD-4, through a targeted design process based on a set of certain requirements, including the ability to enter the brain rapidly upon injection, attach to amyloid plaques, absorb and fluoresce radiation in the right spectral range, and provide a clear contrast between the plaques and the surrounding tissue. The dye provided sharp visual images of amyloid brain plaques in living mice with specially prepared cranial windows.

To make the technique truly noninvasive, researchers must additionally refine the dye so it fluoresces at a slightly longer wavelength, closer to the infrared (IR) region. Light in the near-IR range can penetrate living tissue well enough to make brain structures visible.

The new dye was developed as part of a wider effort in sensing technology at MIT's Institute for Soldier Nanotechnologies. The study was published in the Aug. 26, 2005, issue of the journal Angewandte Chemie.