A water-soluble BODIPY derivative as a highly selective “Turn-On” fluorescent sensor for H2O2 sensing in vivo

• Several new water-soluble BODIPY derivatives synthesized.
• A water-soluble BODIPY-based “Turn-On” fluorescent sensor.
• Highly selective fluorescent response to H2O2 under physiological conditions.
• Application of monitoring and imaging of H2O2 both in vitro and in vivo.

A type of BODIPY derivatives was designed and synthesized by the N-alkylation reaction of meso-(4-pyridinyl)-substituted BODIPY. The water-solubility of entire molecule was improved to a large extent as a result of the formation of cationic quaternary ammonium salt, while the strong fluorescence inherent to the BODIPY dye fragment is extinguished on alkylation of the pyridine N atom due to the photo-induced electron transfer (PET) process. The N-alkylated BODIPY derivative 4, as a novel water-soluble “Turn-On” fluorescent probe for the discrimination of H2O2, was constructed by incorporating 4-(Bromomethyl)benzeneboronic acid pinacol ester moiety, which showed highly selective fluorescent response to H2O2 against other interferences of ROS and RNS species under physiological conditions, and the reaction mechanism of boronate oxidation was confirmed by 1H NMR, mass spectrum and optical spectroscopy analysis. As a biocompatible probe in biological systems, probe 4 was successfully applied for monitoring and imaging of H2O2 both in vitro and in vivo using HepG2/LO2 cells and angelfish.