Label-Free Fluorescence Spectroscopy Detecting Alzheimer's Disease in Mouse Brains

Harvey, Thomas

Alzheimer’s disease (AD) kills neurons and causes cognitive degeneration, and its effects disable and kill millions of people in America and around the world. Diagnosing Alzheimer’s disease in its early stages can allow patients to make plans for their future before they lose their cognitive functions, but it is often difficult to diagnose before its symptoms appear. In this study, the differences in the levels of the fluorophores tryptophan, collagen, reduced nicotinamide adenine dinucleotide (NADH), and flavins (FAD), which are all naturally found in the brain, were measured using label-free fluorescence spectroscopy of normal mouse brain samples (N), and mouse brain samples with Alzheimer’s (AD). After excitation from a Xenon lamp at wavelengths 266nm, 300nm, and 400nm, the emission intensities and wavelengths of the fluorophores in the two samples were detected with a Perkin Elmer LS-50 fluorescence spectrometer. Intensity peaks at 340nm, 380nm, 460nm, and 525nm revealed the presence of tryptophan, collagen, NADH, and FAD, respectively. The four fluorophores naturally fluoresce at these wavelengths, so no dyes or tracking molecules needed to be added to the samples. The emission spectral profile levels of tryptophan and FAD were much higher in AD brain samples. Collagen emission levels were slightly higher in the normal brain sample, and NADH levels were much higher in the normal sample. These results yield a new optical method for detection of biochemical differences in mouse brain samples with and without Alzheimer’s disease, which can lead to a facilitated diagnosis of Alzheimer’s.