Smart Chemiluminescence Probes and Dual-Amplification of Signal for Detection of Amyloid Beta Species in Alzheimer’s Disease Model

Fluorescence and chemiluminescence imaging are the most widely applied optical emissive imaging methods in biomedical research. “Smart” (turn-on) fluorescence imaging has been routinely used for in vitro, cellular, and in vivo imaging; however, smart chemiluminescence imaging has been rarely explored. In this report, we designed chemiluminescence probe ADLumin-1 and validated that ADLumin-1 was a smart chemiluminescence probe for amyloid beta (Ab) species, evidenced by a 216-fold amplification of chemiluminescence intensity upon mixing with Abs in vitro. In vivo two photon imaging indicated that ADLumin-1 could efficiently cross blood-brain- barrier (BBB) and provided excellent contrast both for Ab plaques and cerebral amyloid angiopathy (CAA). In vivo whole brain imaging showed that the chemiluminescence signal of ADLumin-1 from 5-month-old transgenic AD (5xFAD) mice was 1.80-fold higher than that from the age-matched wild-type mice. Moreover, we demonstrated that it was feasible to further dually-amplify signal via chemiluminescence resonance energy transfer (DAS-CRET) using two non-conjugated smart probes (ADLumin-1 and CRANAD-3) in solutions, brain homogenates, and in vivo whole brain imaging. Our results showed that DAS-CRET could provide a 2.25-fold margin between 5- month-old 5xFAD mice and wild type mice. To our knowledge, this is the first report that a chemiluminescence probe could be used for detecting Ab species both in vitro and in vivo. Although ADLumin-1 was designed for Abs, we believe that our strategy could be potentially extended to a wide range of targets, including other aggregating-prone proteins. Notably, our results suggested that the strategies for turning-on fluorescence could be used for amplifying chemiluminescence, and we believe that our studies could inspire considerably more research on chemiluminescence imaging