A near-infrared fluorescent probe based on a novel rectilinearly π-extended rhodamine derivative and its applications

Abstract

We designed and synthesized a novel near-infrared (NIR) mitochondria-targeted fluorescent probe RQNA for the specific detection of mitochondrial Cu²⁺ because mitochondria are important reservoirs of intracellular copper. For the preparation of this probe, a novel π-extended fluorescent xanthene dye RQN was firstly synthesized via an intramolecular nucleophilic substitution of aromatic hydrogen (S_NAr^H) strategy. Then, probe RQNA was prepared by the reaction of RQN and hydrazine hydrate, followed by treatment with acetone. RQNA exhibited selectivity, sensitivity (22 nM), and fast response time (20 s) for the detection of Cu²⁺via a specific Cu²⁺-triggered ring-opening and hydrolysis cascade reaction. RQNA is cell-membrane permeable and mitochondria-targetable, and can be used for monitoring mitochondrial Cu²⁺ in living cells.