A Quinoline-Benzothiazole Hybrid As The First Near-Infrared Fluorescent Probe For Transthyretin

Transthyretin (TTR) amyloidosis is a disease caused by the misfolding and aggregation of TTR protein, including familial amyloidotic polyneuropathies (FAP), senile systemic amyloidosis (SSA), familial amyloidotic cardiomyopathies (FAC), Alzheimer's disease (AD), etc. Nowadays, the emission wavelength of reported probes for wild-type TTR is relatively short, which restricts their further application. In this study, a quinoline-benzothiazole conjugated scaffold (QCN-2) was rationally designed and synthesized as the first near-infrared fluorescent (NIRF) probe for the determination of TTR content. QCN-2 displayed remarkable turn-on fluorescence (25-fold) with high sensitivity when bound to wild-type TTR (detection limit, 204.4 nM). Moreover, the molecular docking study indicated that the benzothiazole moiety could enter the inner cavity binding site, and the cyano group could form a hydrogen bond with LYS15 residues, which might restrict the rotation of the vinyl bond, leading to increasing the ICT process and emission intensity. All these excellent properties of this probe make it a robust and promising tool for the diagnosis of diseases related to TTR amyloidosis.