Highly promising discrimination of various catecholamines using ratiometric fluorescence probes with intermolecular self-association of two sensing elements

Abstract

Two sensing elements based on fluorescence probes have been employed as the promising discriminating sensors of two catecholamines, dopamine (DA) and norepinephrine (NE), acting as a proper guest linker between two self-recognition sensing components. Surprisingly, in the presence of epinephrine (EPI), sensor NB containing boronic acid connected to a napthalimide unit demonstrated a very strong fluorescence enhancement while a large fluorescence quenching was observed in the case of DA and NE. To differentiate the structural similarity of DA and NE, an appropriately designed small fluorescence sensor CC containing a crown-ether attached to coumarin showed complementary recognition to an ammonium ion based catecholamine. The combination of NB and CC is capable of the differentiation of DA and NE with dual emission bands under a PET mechanism. The dual emission ratio (I₄₇₅/I₃₈₄) of the NB–DA–CC complex showed different values from those of the NB–NE–CC complex. Additionally, the PCA analysis using mixed sensors of NB and CC obviously separated DA and NE better than a single sensing element. This systematic approach is the first report showing a high potential for the identification of DA and NE using ratiometric fluorescence sensors with dual emission by two sensing elements.