Specific chemical determinants are central for achieving ligands for selective detection of amyloid-β deposits in Alzheimer’s disease

Protein deposits are common hallmarks of several neurodegenerative diseases, including Alzheimer’s disease (AD), and ligands that selectively detect specific protein aggregates are crucial. Herein, we investigated the molecular requirements of a thiophene-based ligand, denoted HS-276, for selective detection of Aβ deposits in human brain tissue sections with AD pathology. The staining of Aβ deposits was altered when replacing the terminal thiophene moiety with other heterocyclic moieties. In addition, when changing the central thiophene moiety of the ligand to a phenylene, a quinoxaline, or a benzothiadiazole moiety, the staining of Aβ aggregates was completely abolished, verifying that specific molecular interactions between these ligands and the aggregates were required. The experimental observations were also verified by theoretical calculations of the ligands’ binding mode towards Aβ filaments. Our findings provide chemical insights for developing ligands that selectively target Aβ deposits and highlight the importance of certain chemical requirements for achieving a selective ligand, such as HS-276, for detecting Aβ deposits in sporadic AD. We foresee that these findings might aid in creating novel agents for clinical imaging of Aβ aggregates in AD.