Bithiophene Scaffold for PET Imaging and Photosensitization as a Novel Theranostic Platform Targeting Amyloid-β Aggregates

Amyloid β (Aβ) aggregates are primary targets for the diagnosis and curative treatment of Alzheimer’s disease (AD). While various theranostic agents targeting Aβ aggregates have been developed, most rely on fluorescent imaging, which has limited clinical translation. In contrast, nuclear medicine imaging, particularly positron emission tomography (PET), offers high sensitivity and deep tissue permeability suitable for clinical settings. Moreover, photosensitization has emerged as a promising strategy to attenuate Aβ toxicity. In this study, we designed and synthesized novel bithiophene derivatives as PET/photosensitization theranostic agents. Western blotting analysis and MALDI-TOF MS spectrometry demonstrated that FABT-2 selectively oxidized Aβ aggregates under light irradiation, leading to a significant reduction in Aβ-induced cytotoxicity, as demonstrated by CCK8 and LDH assays. Furthermore, 18 F-labeled FABT-2 showed blood–brain barrier permeability in normal mice. These results suggest that FABT-2 may be a promising lead compound for the development of theranostic agents targeting Aβ aggregates.