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.