A Selective Imidazoline-2-thione-Bearing Two-Photon Fluorescent Probe for Hypochlorous Acid in Mitochondria

Hypochlorite (OCl–) plays a key role in the immune system and is involved in various diseases. Accordingly, direct detection of endogenous OCl– at the subcellular level is important for understanding inflammation and cellular apoptosis. In the current study, a two-photon fluorescent off/on probe (PNIS) bearing imidazoline-2-thione as an OCl– recognition unit and triphenylphosphine (TPP) as a mitochondrial-targeting group was synthesized and examined for its ability to image mitochondrial OCl– in situ. This probe, based on the specific reaction between imidazoline-2-thione and OCl–, displayed a selective fluorescent off/on response to OCl– with the various reactive oxygen species in a physiological medium. PNIS was successfully applied to image of endogenously produced mitochondrial OCl– in live RAW 264.7 cells via two-photon microscopy.