The onset of Alzheimer’s disease is preceded by years of slowly growing levels of amyloid-β aggregates in the brain. There is an equilibrium between amyloid-β in the brain and amyloid-β in the bloodstream, and so the research community has worked towards blood tests that can determine who is at risk of developing the condition. This goal is complicated by the sensitivity required, given the low levels of amyloid-β in blood samples, but the results here suggest that this problem may be sufficiently well solved to proceed towards an widely used assay. While the failure of clinical trials testing amyloid-clearing immunotherapies strongly suggests that amyloid-β is not the right target for the development of treatments for Alzheimer’s disease, it may still be helpful as a biomarker.
Scientists are in the initial stages of development of a method to detect the biomarkers for Alzheimer’s disease that is 10 times more sensitive than current blood testing technology. For Alzheimer’s disease, doctors most often diagnose patients based on their symptoms. By that time, the patients often already have severe brain damage. Imaging technology such as magnetic resonance imaging and CT scans can also be used to help confirm the disease, but they are not suitable for early stage diagnosis. Occasionally, doctors may test spinal fluid to look for beta-amyloid proteins, markers of the disease, but the process is more invasive than a simple blood test would be.
One common way of testing blood is the ELISA, or enzyme-linked immunosorbent assay, which is used to test for a variety of diseases. The ELISA uses a natural enzyme found in the roots of horseradish that can change color to indicate the presence of disease biomarkers. But, using the technique to detect the beta-amyloid proteins of Alzheimer’s is difficult because their levels in the blood are too small.
Last year, researchers created an artificial enzyme using a single-atom architecture that was able to work as efficiently as natural enzymes. Their artificial enzyme, called a nanozyme, is made of single iron atoms embedded in nitrogen-doped carbon nanotubes. For this work, the researchers were able to use their single-atom nanozyme to mimic the active site of a natural enzyme and to detect the Alzheimer’s disease proteins at levels 10 times lower than commercially available ELISA tests. The nanozyme was also more robust than natural enzymes, which can degrade in acidic environments or in high temperatures. It is also less expensive and could be stored for long periods of time.