Rhodamine-based ‘turn-on’ fluorescent probe for Cu(II) and its fluorescence imaging in living cells

Abstract

A novel rhodamine spirolactam derivative 3′,6′-Bis(diethylamino)-2-(2-hydroxyethylamino) spiro[isoindoline-1,9′-xanthen]-3-one (RO1) was synthesized, and characterized by high-resolution mass spectrometry (HRMS), X-ray crystallography, Infrared spectroscopy (IR), and 1H NMR and 13C NMR spectroscopy. RO1 exhibited highly sensitive and exclusively selective fluorescence response toward Cu2+ over other metal ions with a detection limit of 0.56ppb in mixed aqueous solution. The fluorescence was pH-independent in the wide range pH 3.1–11.6. The turn-on fluorescence enhancement of the probe is based on Cu2+ induced ring-opening mechanism of the rhodamine spirolactam. Moreover, by means of fluorescence microscopy experiments, it was demonstrated that RO1 could monitor trace Cu2+ changes by live cell imaging.