A highly sensitive fluorescent HClO probe for discrimination between cancerous and normal cells/tissues

Elevated level of hypochlorous acid (HClO) is closely associated with cancer development. Identifying HClO level in cancer cells would provide important evidence in either early-stage cancer diagnostics or monitoring of its treatment efficiency. In this work, a new pyronine-based fluorescent probe for rapid and sensitive detection of HClO was developed by condensing meso-formyl pyronine (PyCHO) with 2-hydrazinopyridine to form meso-pyridylhydrazone-functionalized pyronine PyHP. PyHP is nonfluorescent due to the excited-state C=N isomerization nonradiative decay, whereas the HClO-triggered formation of meso-triazolopyridyl pyronine PyTP abolishes the C=N isomerization and thus greatly enhances the fluorescence. With the probe, the cancer cells/tumor were distinguished with high-contrast from normal ones by laser confocal fluorescence imaging, and the tumor-to-normal (T/N) ratios obtained exceed the clinically acceptable threshold of 2.0; moreover, its capability of in vivo imaging tumor was also demonstrated. These results indicate the potential of PyHP as an effective tool in the early clinical diagnosis of cancers.