Dual-Mode Chalcone-Based Fluorescent Probe for Distinguishing Amyloid-β Oligomers and Fibrils via Microenvironment Sensitivity

Alzheimer's disease (AD) is characterized by amyloid-β (Aβ) aggregates, including oligomers and fibrils, which exert distinct neurotoxic effects. Existing diagnostic probes face limitations in selectively differentiating these species, likely due to insufficient sensitivity to conformational transitions and microenvironmental variations. Here, we report a rationally engineered chalcone-based fluorescent probe, leveraging signal difference amplification and precise microenvironment matching through dual-microenvironment-responsive mechanisms via precise energy barrier modulation. By incorporating ortho-hydroxyl and para-dimethylamino groups into the chalcone scaffold, we synergistically regulated the energy barriers of twisted intramolecular charge transfer (TICT) and excited-state intramolecular proton transfer (ESIPT). This design not only enables sensitive detection of viscosity-polarity changes during Aβ aggregation but also achieves signal difference amplification to generate distinct ratiometric fluorescence signals for oligomers and fibrils, while the precise microenvironment matching of probe-group interactions ensures accurate response to Aβ species' microenvironmental traits, surpassing conventional single-response probes. Our study underscores the critical need to differentiate Aβ species and provides an advanced tool for AD pathology research.