The β-amyloid (Aβ) plaques presented within the brain parenchyma have been
widely proved to be one of the hallmarks of Alzheimer’s disease (AD). According to the amyloid
cascade hypothesis, the accumulation of Aβ plaques in the brain is intrinsic and fundamental
for disease onset, and much research about the early diagnosis of AD is based on this.
A recent development in Aβ detection has focused on the mapping of the molecule events in
the brain using an exquisite, noninvasive, and inexpensive optical imaging technique, which
has stimulated the rapid development of Aβ-specific fluorescent probes. Among them, nearinfrared
(NIR) fluorophores have gained adequate attention due to the weak light attenuation
in tissues and avoidance from auto-fluorescence of biological matter. In this review, we
showcase the current developments of fluorescent probes that are subject to in vitro or in vivo
detection of Aβ plaques in the brain, and give an emphasis on the probes used for in vivo twophoton
microscopy and NIR imaging by highlighting their biological and photochemical
Keywords: Alzheimer’s disease, β-amyloid plaque, optical imaging, fluorescent probes, small molecular, nearinfrared.
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