Charge-Based Discrimination of Amyloids Using an Amyloid-Targeting Chemiluminescent Probe

Fluorescent probes have been widely developed for detecting amyloid biomarkers associated with neurodegenerative diseases (NDs). The requirement for external light for excitation, however, limits their utility for research and in vivo applications. Chemiluminescent probes, which use chemical reactions to generate emissive excited states rather than externally applied light, may offer a promising alternative to overcome some limitations for optical imaging of amyloid biomarkers. Here, we designed and synthesized a chemiluminescent amyloid-binding probe (CLIP-1) and evaluated its capability to label three amyloid biomarkers for NDs-amyloid β (Aβ), α-synuclein (α-syn), and tau protein aggregates. We found that CLIP-1 exhibits markedly enhanced chemiluminescence (CL) in aqueous solution when activated by ambient oxygen in the presence of aggregated Aβ, whereas little to no emission is observed in the absence of aggregates or in the presence of monomeric Aβ. Additionally, CLIP-1 displayed a different wavelength of emission when bound to tau aggregates compared to Aβ or α-syn aggregates, which we attribute to differences in the relative overall charge of the amyloids at neutral pH. Imaging of brain slices confirmed enhanced CL of CLIP-1 in an Alzheimer's disease mouse model, highlighting the potential for amyloid-targeting chemiluminescent probes as new tools for aiding in diagnosis of amyloid-associated neurodegenerative diseases.