A Radical-Generating Probe to Release Free Fluorophores and Identify Artemisinin-Sensitive Cancer Cells.

The smart light-up probes have been extensively developed to image various enzymes and other bioactive molecules. Upon activation, these probes result in light-up fluorophores that exist in a protein-bound or a free form. The difference between these two forms has not yet been reported. Here, we present a pair of smart light-up probes that generate a protein-bound fluorophore and a free fluorophore upon activation by heme. Probe generated a radical-attached fluorophore that predominantly existed in the free form, while probe generated an α,β-unsaturated ketone-attached fluorophore that showed extensive labeling of proteins. In live-cell imaging, probe showed greater fluorescence intensity than probe when low concentrations (0.1-5 μM) of the probes were used, but probe was less fluorescent than probe when the concentrations of the probes were high (10 μM). Finally, probe was used to reflect the activation level of the endoperoxide bond in cancer cells and to effectively distinguish ART-sensitive cancer cells from ART-insensitive ones.