Due to the increase in the average age of humans, Alzheimer's disease (AD) has become one of the disorders with the highest incidence worldwide. Abnormal amyloid β protein (Aβ) accumulation is believed to be the most common cause of AD. Therefore, distinguishing the lesion areas can provide clues for AD diagnosis. Here, we present an optical spectroscopy and imaging approach based on coherent anti-Stokes Raman scattering (CARS). Label-free vibrational imaging of Aβ in a mouse model of AD was performed to distinguish the lesion areas by studying the spectra of regions with and without Aβ plaques. Raman spectra in Aβ and non-Aβ regions exhibited a specific difference in the intensity ratio of the wave peaks detected at 2850 and 2930 cm-1. In the non-Aβ region, the ratio of the peak intensity at 2850 cm-1 to that at 2930 cm-1 was approximately 1, whereas that in the Aβ region was 0.8. This label-free vibrational imaging may provide a new method for the clinical diagnosis and basic research of AD.
Keywords: Alzheimer’s disease; Raman scattering; amyloid; nonlinear optical microscopy.