Dual-functional red-emitting fluorescent probes for imaging beta-amyloid plaques and viscosity

A series of dual-functional red-emitting fluorescent probes were rationally designed, synthesized and evaluated through the introduction of amine chains based on a neutral merocyanine dye (MC-1) for in vivo imaging of beta-amyloid plaques as well as viscosity at cellular level. After optimization, the MC-N derivatives with higher fluorescence quantum yield and rational Log P showed high sensitivity to the surrounding environment and A beta aggregates. Besides, the MC-N derivatives can distinguish A beta plaques and viscosity changes through differences in the emission wavelengths in different environments. In vivo NIRF imaging demonstrated that the probe MC-N-2 was capable of readily penetrating the blood-brain barrier and efficiently made a distinction between transgenic and wild type mice at a low injection dosage (0.1 mg/kg).