Effective Theranostic Cyanine for Imaging of Amyloid Species in Vivo and Cognitive Improvements in Mouse Model

We report herein an investigation of carbazole-based cyanine, (E)-4-(2-(9-(2-(2-methoxyethoxy)ethyl)-9-Hcarbazol-3-yl)-vinyl)-1-methyl-quinolin-1-iumiodide (SLM), as an effective theranostic agent for Alzheimer's disease (AD). This cyanine exhibited desirable multifunctional and biological properties, including amyloid-beta (A beta)-oligomerization inhibition, blood-brain barrier permeability, low neurotoxicity, neuroprotective effect against A beta-induced toxicities, high selectivity and strong binding interactions with A beta peptide/species, good biostability, as well as strong fluorescence enhancement upon binding to A beta species for diagnosis and therapy of AD. This cyanine has been successfully applied to perform near-infrared in vivo imaging of A beta species in transgenic AD mouse model. The triple transgenic AD mice intraperitoneally treated with SLM showed significant recovery of cognitive deficits. Furthermore, those SLM-treated mice exhibited a substantial decrease in both of oligomeric A beta contents and tau proteins in their brain, which was attributed to the induction of autophagic flux. These findings demonstrated for the first time that SLM is an effective theranostic agent with in vivo efficacy for diagnosis and treatment of AD in mouse models.