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

Abstract

Abstract 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 H2SO4, 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\u202f×\u202f10−8\u202fmol/L. In addition, the utilization of BiF–Cu for bioimaging Cu2+ in L929\u202fcells demonstrates its living cell membrane permeability and makes it promising candidate for monitoring Cu2+ by cell imaging technology.