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 imagingmethods in biomedical research. “Smart” (turn-on) fluorescence imaging has been routinely used for invitro, 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 asmart chemiluminescence probe for amyloid beta (Ab) species, evidenced by a 216-fold amplification ofchemiluminescence intensity upon mixing with Abs in vitro. In vivo two photon imaging indicated thatADLumin-1 could efficiently cross blood-brain- barrier (BBB) and provided excellent contrast both for Abplaques and cerebral amyloid angiopathy (CAA). In vivo whole brain imaging showed that thechemiluminescence signal of ADLumin-1 from 5-month-old transgenic AD (5xFAD) mice was 1.80-foldhigher than that from the age-matched wild-type mice. Moreover, we demonstrated that it was feasible tofurther dually-amplify signal via chemiluminescence resonance energy transfer (DAS-CRET) using twonon-conjugated smart probes (ADLumin-1 and CRANAD-3) in solutions, brain homogenates, and in vivowhole 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 achemiluminescence probe could be used for detecting Ab species both in vitro and in vivo. AlthoughADLumin-1 was designed for Abs, we believe that our strategy could be potentially extended to a widerange of targets, including other aggregating-prone proteins. Notably, our results suggested that thestrategies for turning-on fluorescence could be used for amplifying chemiluminescence, and we believe thatour studies could inspire considerably more research on chemiluminescence imaging