Departamento de Física, ICEx, Universidade Federal de Minas Gerais, Belo Horizonte, MG 31270-901, Brazil.
Departamento de Saúde Mental, Faculdade de Medicina, Universidade Federal de Minas Gerais, Belo Horizonte, MG 31270-901, Brazil.
Analyst. 2021 May 4;146(9):2945-2954. doi: 10.1039/d1an00074h.
Given the long subclinical stage of Alzheimer's disease (AD), the study of biomarkers is relevant both for early diagnosis and the fundamental understanding of the pathophysiology of AD. Biomarkers provided by Amyloid-β (Aβ) plaques have led to an increasing interest in characterizing this hallmark of AD due to its promising potential. In this work, we characterize Aβ plaques by label-free multimodal imaging: we combine two-photon excitation autofluorescence (TPEA), second harmonic generation (SHG), spontaneous Raman scattering (SpRS), coherent anti-Stokes Raman scattering (CARS), and stimulated Raman scattering (SRS) to describe and compare high-resolution images of Aβ plaques in brain tissues of an AD mouse model. Comparing single-laser techniques images, we discuss the origin of the SHG, which can be used to locate the plaque core reliably. We study both the core and the halo with vibrational microscopy and compare SpRS and SRS microscopies for different frequencies. We also combine SpRS spectroscopy with SRS microscopy and present two core biomarkers unexplored with SRS microscopy: phenylalanine and amide B. We provide high-resolution SRS images with the spatial distribution of these biomarkers in the plaque and compared them with images of the amide I distribution. The obtained spatial correlation corroborates the feasibility of these biomarkers in the study of Aβ plaques. Furthermore, since amide B enables rapid imaging, we discuss its potential as a novel fingerprint for diagnostic applications.
鉴于阿尔茨海默病（AD）的漫长亚临床阶段，生物标志物的研究对于早期诊断和 AD 病理生理学的基本理解都很重要。由于其有很大的潜力，淀粉样蛋白-β（Aβ）斑块提供的生物标志物引起了人们对其特征描述的极大兴趣，该标志物是 AD 的一个显著特征。在这项工作中，我们通过无标记多模态成像来对 Aβ斑块进行特征描述：我们结合双光子激发自发荧光（TPEA）、二次谐波产生（SHG）、自发拉曼散射（SpRS）、相干反斯托克斯拉曼散射（CARS）和受激拉曼散射（SRS）来描述和比较 AD 小鼠模型脑组织中 Aβ斑块的高分辨率图像。通过比较单激光技术图像，我们讨论了 SHG 的起源，这可以可靠地用于定位斑块核心。我们用振动显微镜研究了核心和晕环，并比较了 SpRS 和 SRS 显微镜在不同频率下的表现。我们还将 SpRS 光谱学与 SRS 显微镜相结合，并提出了两个以前未用 SRS 显微镜探索过的核心生物标志物：苯丙氨酸和酰胺 B。我们提供了具有这些生物标志物在斑块中空间分布的高分辨率 SRS 图像，并将其与酰胺 I 分布图像进行了比较。获得的空间相关性证实了这些生物标志物在 Aβ斑块研究中的可行性。此外，由于酰胺 B 可以实现快速成像，我们讨论了它作为诊断应用的新型指纹的潜力。
