In Situ Synthesis of Phenoxazine Dyes in Water: Application for “Turn‐On” Fluorogenic and Chromogenic Detection of Nitric Oxide**

Abstract

The synthesis of phenoxazine dyes was revisited in order to access these fluorescent N,O-heterocycles under mild conditions. The combined sequential use of nitrosonium tetrafluoroborate (NOBF 4 ) and triphenylphosphine enables the facile conversion of bis(3-dimethylaminophenyl) ether into the methyl analogue of popular laser dye oxazine 1. The ability of nitrosonium cation (NO + ) to initiate the domino reaction resulting in π-conjugated phenoxazine molecules under neutral conditions, then led us to explore the feasibility of expanding it in aqueous media. Thus, we explored the use of reactive signaling molecule nitric oxide (NO) as a biological trigger of phenoxazine synthesis in water. The implementation of a robust analytical methodology based on fluorescence assays and HPLC-fluorescence/-MS analyses, have enabled us to demonstrate the viability of this novel fluorogenic reaction-based process to selectively yield an intense "OFF-ON" response in the near-infrared (NIR-I) spectral region. This study is an important step towards the popularization of the concept of "covalent assembly" in the fields of optical sensing, bioimaging and molecular theranostics.

A benzophenoxazine-based NIR fluorescent probe for the detection of hydrogen sulfide and imaging in living cells

“…[20][21][22][23][24] Reaction-based methods have good specificity and biocompatibility since reactive groups react with sulfur to generate signals which avoid pollution or damage caused by direct catalysis and other methods to biological samples. 25,26 Benzophenoxazine-based dyes are wellknown fluorescent dyes with red emission, [27][28][29][30] which can provide favorable imaging with low background, high sensitivity and deep penetration. [31][32][33] Herein, we designed and synthesized an easily obtained NIR fluorophore probe NRDNP for the detection of H 2 S. The NRDNP contains a dinitrophenyl ether moiety as the recognition site and a benzophenoxazinebased dye as the fluorescent group and can highly selectively and sensitively detect H 2 S with low toxicity and excellent fluorescence properties (Scheme 1).…”