If proven successful in further clinical studies, the procedure could become the first tool for early diagnosis of Alzheimer's, and the first test to conclusively identify the disease in living patients.

Chad Mirkin and William Klein of the National Science Foundation (NSF) Nanoscale Science and Engineering Center (NSEC) for Nanopatterning and Detection Technologies at Northwestern University, and their colleagues, announce their findings the week of Jan. 31 in the online edition of the Proceedings of the National Academy of Sciences.

Because of the extreme sensitivity of the BCA process that Mirkin's team developed, the researchers were able to detect within each fluid sample a miniscule amount of proteins called amyloid -derived diffusible ligands (ADDLs). The goal is to detect and validate infinitesimal amounts of the biomarkers in blood.

Research by Klein and his colleagues suggests that ADDLs first appear in the earliest stages of Alzheimer's. If the BCA process can identify the markers before symptoms develop, doctors may be able to combat the illness in its nascent form when treatments may be most effective.

In the first steps of the BCA process, unique microparticles latch onto the biomarker targets in this study, the ADDLs. The particles are magnetic, a property that aids collection at the end of the procedure. Researchers then add a second ingredient that consists of a gold nanoparticle core surrounded by hundreds of identical DNA strands, which serve as hundreds of "bio-bar-codes" the researchers can detect at the end of the test. Ultimately, the gold-DNA particles and magnetic particles sandwich the biomarker targets.

A magnet separates the sandwich complexes from the rest of the sample. The
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Contact: Josh Chamot
jchamot@nsf.gov
703-292-7730
National Science Foundation
31-Jan-2005