That means what researchers are calling a breakthrough in nanotechnology and medicine could enable doctors to detect these illnesses at much earlier stages, when they are more treatable.

"This advance opens many new and exciting opportunities ... in disease early detection and treatment," said , a Princeton engineering professor, who led the research team. "You can have very early detection with our approach."

Princeton researchers used to improve a biological test called an immunoassay, which measures the concentration of a substance in a body fluid sample, and is used to find markers for cancers and Alzheimer's, in patients. The test produces a fluorescent glow when the disease is detected. The stronger the presence of the disease, the brighter the test glows.

However, if only faint, early-stage, traces of the disease are present, the glow can't be detected and the disease could be missed.

The Princeton researchers used nanotechnology to amplify the fluorescence, which gave them a 3-million-fold improvement in detection. It means the test now can detect disease with 3 million times fewer disease biomarkers present.