A Water-Soluble Fluorogenic Probe to Quantify Azide Concentrations in Biologically Relevant Environments.

Fluorogenic probes are highly useful tools for the detection of target molecules in chemical biology and (bio)material science, as they can often be applied in situ and do not depend on purification. Over the past years, a variety of alkyne-based fluorogenic probes have been proposed to detect azides, paving the way for live cell imaging and biomaterial analysis. Unfortunately, undesirable photophysical properties and poor solubility in aqueous solutions hamper the widespread use of these fluorogenic compounds. This work describes a water-soluble azide probe with high fluorescence enhancement (130-fold increase in intensity) upon reaction. We find accurate determination of azide densities on a polymer scaffold at low micromolar concentrations in PBS buffer. Additionally, by functionalizing the probe with biomolecules, we built a single-step (bio)molecule labeling and analysis vehicle. As proof of principle, a peptide was conjugated to polymer scaffolds and conversions could be accurately followed in situ. Altogether, our probe is a promising new chemical biology tool for analysis in physiological conditions.