A new Cu2+-selective fluorescent probe with six-membered spirocyclic hydrazide and its application in cell imaging.

A new N-heterocyclic fluoran based dye BiF is facilely prepared in high yield by reaction of 5-methoxybenzimidazole and 2-(4-diethylamino-2-hydroxy)benzoylbenzoic acid in concentrated H 2 SO 4 , which keeps stable optical signals in water at pH values ranging from 4 to 10 and exhibits good living cell membrane permeability. By modification of the spirolactone in molecule BiF , a fluorescent probe BiF–Cu with specific and sensitive response to Cu2+ has been further developed, which contains a six-membered spirolic hydroxyethylhydrazide moiety that can be selectively triggered by Cu2+ among various metal ions through a specific cascade reaction of Cu2+-promoted spirolactam ring-opening and hydrolysis. A limit of detection for Cu2+ is calculated as 7.12 × 10−8 mol/L. In addition, the utilization of BiF–Cu for bioimaging Cu2+ in L929 cells demonstrates its living cell membrane permeability and makes it promising candidate for monitoring Cu2+ by cell imaging technology. A new N-heterocyclic fluoran BiF has been efficiently prepared by hybridizing benzimidazole and fluoran moieties. Based on this dye, fluorescent probe BiF–Cu with unique six-membered spirocyclic hydrazide has been developed for selective and sensitive detection of Cu2+ and cell imaging. Image 1 • A new N -heterocyclic fluoran dye was prepared with stable optical signal over a wide pH range. • A fluorescent probe containing a novel six-membered spirocyclic hydrazide trigger has been developed. • The probe was empolyed for highly selective and sensitive detection of Cu2+ with a detection limit of 71.2 nM. • The probe can be utilized in tracing Cu2+ in living cell. [ABSTRACT FROM AUTHOR]