A Nuclear-Localized Naphthalimide-Based Fluorescent Light-Up Probe for Selective Detection of Carbon Monoxide in Living Cells

A nuclear-localized fluorescent light-up probe, NucFP-NO₂, was designed and synthesized that can detect CO selectively in an aqueous buffer (pH 7.4, 37 °C) through the CO-mediated transformation of the nitro group into an amino-functionalized moiety. This probe triggered a more than 55-fold “turn-on” fluorescence response to CO without using any metal ions, e.g., Pd, Rh, Fe, etc. The enhanced response is highly selective over a variety of relevant reactive oxygen, nitrogen, and sulfur species and also various biologically important cationic, anionic, and neutral species. The detection limit of this probe for CO is as low as 0.18 μM with a linear range of 0–70 μM. Also, this fluorogenic probe is an efficient candidate for monitoring intracellular CO in living cells (RAW 264.7, A549 cells), and the fluorescence signals predominantly localize in the nuclear region.