A red-emitting luminescent probe for sequentially detecting Cu2+ and cysteine/histidine in aqueous solution and its imaging application in living zebrafish

Abstract

A unique red-emissive luminescent probe based on dipicolyl amine (DPA) tethered ruthenium(II) tris(bipyridine) derivative (Ru-DPA) has been developed for the sequential and specific detection of Cu2+ and cysteine (Cys)/histidine (His) in pure aqueous medium. The probe Ru-DPA displayed an ‘on–off’ luminescence response at 610 nm specifically toward Cu2+, accompanied by a distinct naked-eye luminescence color change from orange-red to colorless. Also, Ru-DPA enabled analysis of Cu2+ with a detection of limit as low as 0.04 μM. Additionally, the in situ generated Ru-DPA-Cu ensemble detected specifically Cys/His based on the strong affinity for Cu2+ to Cys and His, giving rise to a significant increase in the MLCT-based luminescence of Ru(II) complex and a relevant chromogenic change from colorless to orange-red. This copper (II) ion competitive-displacement detection strategy offered a good linearity with a low detection limit for Cys at 0.24 μM and His at 1.4 μM under pure aqueous medium. Moreover, Ru-DPA exhibited extremely low cytotoxicity (>90% viability at a concentration range from 20 to 100 μM), excellent membrane permeability and was successfully applied to the luminescence imaging of Cu2+ and Cys/His both in living bone mesenchymal stem cells (BMSCs) and zebrafish. The results demonstrated the great potential of Ru-DPA for monitoring Cu2+ and Cys/His in environmental and biological systems.