A rhodamine-based fast and selective fluorescent probe for monitoring exogenous and endogenous nitric oxide in live cells

Nitric oxide, an important cellular messenger molecule, plays a wide range of physiological roles in neurotransmission, vascular relaxation, platelet activation, and immune response. In this work, we synthesized a selective and sensitive cationic fluorescent probe (ROPD) for monitoring exogenous and endogenous nitric oxide in live cells by grafting a NO-trapper o-phenylenediamine (OPD), via one of the amino groups of OPD, onto a rhodamine fluorophore at the C-3 position. The probe exhibited high selectivity and sensitivity towards NO with fast response in the water phase over a wide pH range. At the same time, the probe ROPD is cell-membrane permeable and can be used for the real-time visualization of exogenous NO in both L929 and HeLa cells, and endogenous NO in stressed RAW 264.7 cells.