Synthesis of fluorescein derivatives containing metal-coordinating heterocycles

Rhodols - synthesis, photophysical properties and applications as fluorescent probes

The formal replacement of one dialkylamino group in rhodamines with a hydroxyl group transforms them into rhodols. This apparently minor difference is not as small as one may think; rhodamines belong to the cyanine family whereas rhodols belong to merocyanines. Discovered in the late 19th century, rhodols have only very recently begun to gain momentum in the field of advanced fluorescence imaging. This is in part due to the increased understanding of their photophysical properties, and new methods of synthesis. Rationalization of how the nature and arrangement of polar substituents around the core affect the photophysical properties of rhodols is now possible. The emergence of so-called π-expanded and heteroatom-modified rhodols has also allowed their fluorescence to be bathochromically shifted into regions applicable for biological imaging. This review serves to outline applicable synthetic strategies for the synthesis of rhodols, and to highlight important structure-property relationships. In the first part of this Review, various synthetic methods leading to rhodols are presented, followed by structural considerations and an overview of photophysical properties. The second part of this review is entirely devoted to the applications of rhodols as fluorescent reporters in biological imaging.

Synthesis of new hydrophilic rhodamine based enzymatic substrates compatible with droplet-based microfluidic assays

Here we report the conception, synthesis and evaluation of new hydrophilic rhodamine-based enzymatic substrates for detection of peptidase activity compatible with high-throughput screening using droplet-based microfluidics.

A red-emitting naphthofluorescein-based fluorescent probe for selective detection of hydrogen peroxide in living cells

We report the synthesis, properties, and cellular application of Naphtho-Peroxyfluor-1 (NPF1), a new fluorescent indicator for hydrogen peroxide based on a red-emitting naphthofluorescein platform. Owing to its boronate cages, NPF1 features high selectivity for hydrogen peroxide over a panel of biologically relevant reactive oxygen species (ROS), including superoxide and nitric oxide, as well as excitation and emission profiles in the far-red region of the visible spectrum (>600nm). Flow cytometry experiments in RAW264.7 macrophages establish that NPF1 can report changes in peroxide levels in living cells.