Imaging of peroxynitrite in mitochondria by a near-infrared fluorescent probe with a large Stokes shift

Abstract

As a result of large imaging depth, low background biofluorescence, facile operation, and high tempo-spatial resolution, the small-molecule near-infrared (NIR) fluorescence imaging technique has been one of the most popular tools for in situ monitoring of cellular oxidative stress (OS) processes. Nevertheless, the recent near infrared probes have low signal-to-noise ratio due to the small stokes shift. To this end, this work quinone-cyanine-7 (QCy7, λmaxabs = 582 nm, ε = 9329 M−1 cm−1 and λmaxem = 719 nm, Ф = 0.12) with large Stokes shift (137 nm) was used as a fluorophore, and 1-methylindoline-2,3-dione was used as the “Turn-ON” cyanine NIR Peroxynitrite (ONOO−) fluorescent probe HJ-ONOO-P3 (with 41-fold fluorescence enhancement with ONOO− concentration in the range of 0–35 μM). The indole quaternary ammonium heterocycle with a positive charge itself could be used as the targeted group for mitochondria. This probe exhibited a rapid response (5 min complete response) and high selectivity and sensitivity to ONOO− (detection limit as low as 25.4 nM). Meanwhile, this probe could achieve the task of in-situ imaging of OS during cellular oxygen-glucose deprivation/reperfusion (OGD/R) and middle cerebral artery occlusion (MCAO) in mice. The results demonstrated that the mitochondria-targeted NIR probe with a large Stokes shift possess great potential in studies of stroke and the induced cellular OS.