New information about Alzheimer's disease

The findings could potentially be used to diagnose Alzheimer’s disease in living people instead of during an autopsy, says Amanda J. Haes, Ph.D., a co-author of the study. At present, Alzheimer’s can only be accurately diagnosed after death.

Haes, in cooperation with Van Duyne, Northwestern professor William Klein and research associate Lei Chang developed a method to detect small harmful proteins in cerebrospinal fluid using nanoscale optical biosensors. The proteins, known as ADDLs are so small that they can’t be detected by conventional diagnostic tests. They are usually less than 5 nanometers wide and are found in extremely low concentrations.

"It’s becoming more evident that the size of â-amyloid (ADDL) molecules matters — that only ADDLs of a certain size cause problems for neurons in the early stages of Alzheimer’s disease," Haes says. "These nanoscale biosensors may one day allow us to determine, based on size, if an individual has ADDLs that will affect his or her cognitive function. However, there are still many hurdles that must be overcome before we can use it as a diagnostic tool."

The biosensors developed by the Northwestern team are based on tiny, triangular silver particles that absorb and scatter light. On the outside surfaces of nanoparticles is a layer of ADDL-specific antibodies. These antibodies bind specifically to any ADDL molecules found in cerebrospinal fluid. When this happens, the colour of the silver nanoparticles shifts slightly. The researchers detected these colour shifts using a specialized light detector called ultraviolet-visible spectrometer.

In a small sample pool, comparing cerebrospinal fluid extracted from two people diagnosed with Alzheimer’s disease and two people who weren’t, Haes found that ADDL levels were elevated in the diseased patient samples in comparison to control patient samples.; Source: American Chemical Society