Chemically-modulated turn-on fluorescence for rapid and visual discrimination of norepinephrine and epinephrine and its application for dopamine-β-hydroxylase detection

Monitoring the concentration of norepinephrine (NE), epinephrine (Ep) and dopamine-beta-hydroxylase (D beta H) is of great importance in studying and diagnosing related diseases. In this study, a simple chemically-modulated turn-on fluorescence strategy is proposed for rapid, selective and visual discrimination of trace NE and Ep. Herein, Ep is differentiated from other catecholamines via its fast fluorescence response in 1.0M NaOH medium. Furthermore, NE is alkalized with 0.01M NaOH and is then immediately triggered by polyethyleneimine to emit bright cyan fluorescence, whereas Ep and DA show no any fluorescence response. The fluorescence intensity of resultant solution is linearly proportional to the concentration of Ep and NE in the range of 50.0-10000.0 nM and 10.0-10000.0 nM, respectively. Moreover, NE and Ep as low as 500.0 nM can be fluorescently identified with naked-eye, which is convenient for rapidly preliminary diagnosis and self-test of hypercatecholaminism. Inspired by the catalytic property of D beta H transforming DA into NE, the proposed strategy enables a simple and high-efficient fluorescence method to monitor D beta H by using trace DA as substrate and directly quantifying NE. The method is simple, smart, highly efficient and eco-friendly, and has been applied to the rapid assay of NE, Ep and D beta H in real samples.