Rational Design of Sequentially Activated Dual-Locked Near-Infrared Fluorescent Probe for Simultaneous Imaging of Cerebral Amyloid-β Plaques and ClO- in Alzheimer's Disease.

Alzheimer's disease (AD) is a complex neurodegenerative disorder mediated by multiple pathological factors, including amyloid-β (Aβ) plaque deposition and oxidative stress. Herein, we report a new class of sequentially activated dual-lock-responsive fluorescent probes, D-BDY and T-BDY, which were designed by integrating pyrrole-based electron-donating units and molecular rotors into the BODIPY scaffold. This strategic design enabled photoinduced electron transfer (PET) and twisted intermolecular charge transfer (TICT) modulated fluorescence responses to both Aβ1-42 aggregates and hypochlorite (ClO-). The probes exhibited remarkable fluorescence enhancement (50-100-fold) when exposed to a mixed solution containing both ClO- and Aβ1-42 aggregates. Confocal imaging and staining of Aβ-containing brain slices revealed that the probes preferentially bind to the dense β-sheet-rich cores of plaques, and their colocalization with thioflavin-T (ThT) was further enhanced following ClO- activation. Furthermore, in vivo imaging in an APP/PS1 transgenic AD mouse model demonstrated that D-BDY successfully crossed the blood-brain barrier (BBB), enabling real-time monitoring of Aβ1-42 plaques and the oxidative microenvironment. The observed fluorescence intensity exhibited a strong correlation with pathological severity and was significantly attenuated upon antioxidant treatment. These results established D-BDY as a promising single-molecule dual-locked fluorescent probe capable of sensitively visualizing Aβ1-42 aggregation and ClO--related oxidative stress in vivo, offering a valuable tool for AD diagnosis and pathological progression monitoring.