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New Dye Could Offer Early Test For Alzheimer's; MIT Technique Is Noninvasive

Date:
August 26, 2005
Source:
Massachusetts Institute of Technology
Summary:
MIT scientists have developed a new dye that could offer noninvasive early diagnosis of Alzheimer's disease, a discovery that could aid in monitoring the progression of the disease and in studying the efficacy of new treatments to stop it. The new dye, called NIAD-4, was developed through a targeted design process based on a set of specific requirements, including the ability to enter the brain rapidly upon injection, bind to amyloid plaques, absorb and fluoresce radiation in the right spectral range, and provide sharp contrast between the plaques and the surrounding tissue.

MIT scientists have found a new way to monitor Alzheimer's disease using a fluorescent marker (“bubbles” in the background). The dye enters the brain after an intravenous injection and selectively binds to the plaques associated with the disease. Subsequent scanning with a near-infrared laser beam (hv) makes it possible to monitor the plaques through the characteristic fluorescence of the dye (black circle).
Credit: Image courtesy of Evgueni Nesterov

CAMBRIDGE, Mass.--MIT scientists have developed a new dye that couldoffer noninvasive early diagnosis of Alzheimer's disease, a discoverythat could aid in monitoring the progression of the disease and instudying the efficacy of new treatments to stop it.

The work will be published in the Aug. 26 issue of Angewandte Chemie.

Today, doctors can only make a definitive diagnosis ofAlzheimer's-currently the fourth-leading cause of death in the UnitedStates-through a postmortem autopsy of the brain. "Before you can cureAlzheimer's, you have to be able to diagnose it and monitor itsprogress very precisely," said Timothy Swager, leader of the work and aprofessor in MIT's Department of Chemistry. "Otherwise it's hard toknow whether a new treatment is working or not."

To that end, Swager and postdoctoral associate EvgueniNesterov, also from the MIT Department of Chemistry, worked withresearchers at Massachusetts General Hospital and the University ofPittsburgh to develop a contrast agent that would first bind to theprotein deposits, or plaques, in the brain that cause Alzheimer's, andthen fluoresce when exposed to radiation in the near-infrared range.The new dye could allow direct imaging of Alzheimer's plaques through apatient's skull.

Some of the first noninvasive techniques for diagnosingAlzheimer's involved agents labeled with radioactive elements thatcould enter the brain and target disease plaque for imaging withpositron emission tomography (PET). However, these methods wereexpensive and limited by the short working lifetime of the labeledagents.

Swager and colleagues developed the new dye, called NIAD-4,through a targeted design process based on a set of specificrequirements, including the ability to enter the brain rapidly uponinjection, bind to amyloid plaques, absorb and fluoresce radiation inthe right spectral range, and provide sharp contrast between theplaques and the surrounding tissue. The compound provided clear visualimages of amyloid brain plaques in living mice with specially preparedcranial windows.

To make the technique truly noninvasive, scientists mustfurther refine the dye so it fluoresces at a slightly longerwavelength, closer to the infrared region. Light in the near-IR rangecan penetrate living tissue well enough to make brain structuresvisible. Swager likens the effect to the translucence produced when oneholds a red laser pointer against the side of a finger.

"This procedure could be done in a chamber with a photodetectorand a bunch of lasers, and it would be painless," he said, adding thatinfrared fluorescence and other optical techniques will lead to a wholenew class of noninvasive medical diagnostics. Swager says fluorescingdyes like NIAD-4 could be ready for clinical trials in the near future.

"What we have is a dye that lights up when it binds to amyloidsthat form in the brains of people with Alzheimer's. It's a completelynew transduction scheme-a way of translating a physical or chemicalevent that's invisible to the naked eye, into a recognizable signal.Further wavelength adjustments in these dyes will allow us to performin vivo analysis through human tissue."

The new dye was developed as part of a broader effort insensing technology at MIT's Institute for Soldier Nanotechnologies. Inaddition to its applications as a medical diagnostic, Swager saysfluorescing dyes like NIAD-4 could work as signals in a wide variety ofsensing schemes.


Story Source:

The above story is based on materials provided by Massachusetts Institute of Technology. Note: Materials may be edited for content and length.


Cite This Page:

Massachusetts Institute of Technology. "New Dye Could Offer Early Test For Alzheimer's; MIT Technique Is Noninvasive." ScienceDaily. ScienceDaily, 26 August 2005. <www.sciencedaily.com/releases/2005/08/050826075318.htm>.
Massachusetts Institute of Technology. (2005, August 26). New Dye Could Offer Early Test For Alzheimer's; MIT Technique Is Noninvasive. ScienceDaily. Retrieved October 21, 2014 from www.sciencedaily.com/releases/2005/08/050826075318.htm
Massachusetts Institute of Technology. "New Dye Could Offer Early Test For Alzheimer's; MIT Technique Is Noninvasive." ScienceDaily. www.sciencedaily.com/releases/2005/08/050826075318.htm (accessed October 21, 2014).

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