A novel enzyme-activated tandem fluorescent probe for dual detection of BChE and A β plaques in Alzheimer's disease.

Alzheimer's disease (AD) has early symptoms that are subtle and easily confused with other brain disorders, necessitating the development of precise diagnostic technologies for AD. This study reported novel tandem detection molecular probes (HCys) for two key pathological markers in the AD process, namely butyrylcholinesterase (BChE) and β-amyloid (A β). The probe undergoes BChE-specific esterase hydrolysis, resulting in a 48-fold enhancement of fluorescence. After hydrolysis, the probe formed could further bind to A β aggregates and triggered a 6-7-fold fluorescence enhancement, establishing an "enzyme-activated" cascade detection mechanism. In ex vivo brain tissue experiments, the probe successfully visualized the spatial distribution of BChE in the brains of AD mice, and the hydrolyzed probe specifically labeled A β plaques in the brains of AD mice. The low molecular weight of the probes HCys enable it to rapidly cross the blood-brain barrier (BBB) and identify both early and late-stage AD models. This study is the first time to report near-infrared fluorescent probes targeting BChE and A β aggregates, providing a new tool for the early diagnosis of AD.