Synthesis And Applications Of Organelle-targeted Luminescent Probes Based On Ruthenium Complexes For Reactive Species

Compared to organic fluorescent probes,ruthenium（Ⅱ）polypyridyl complexes have prominent advantages which are widely applied to molecule biosensors due to their excellent photochemical properties and luminescence characters,good biocompatibility as well as low cell toxicity.In this paper,the polypyridyl ligands around the Ru（Ⅱ）metal centre were modified to obtain two luminescent probes with different properties to detect two reactive species and these probes were successfully applied for the imaging of reactive species in vivo.In the first work,a novel ruthenium（Ⅱ）complex-cyanine energy transfer scaffold has been established for the development of a ratiometric luminescence probe for ONOO^-detection.The ratiometric changes in luminescence intensities at two emission wavelengths mainly arise from the factor of F?rster resonance energy transfer（FRET）.Before addition of ONOO^-,the emission derives from acceptor Cy5.In the presence of ONOO^-,the ET from the Ru（Ⅱ）complex to Cy5 is significantly interrupted by oxidation of Cy5,leading to the decrease of Cy5 emission at 660 nm and the increase of Ru（Ⅱ）emission at 610 nm for ratiometric(I₆₁₀/I₆₆₀)detection of ONOO^-with a 46 fold enhancement of I₆₁₀/I₆₆₀.Furthermore,owing to the mitochondria targeting feature of Cy5 after cellular internalization,Ru-Cy5 is expected to be localized in mitochondria where ONOO^-generates,to enable ONOO^-in this organelle to be visualized under a ratiometric mode.With laser confocal microscope,Ru-Cy5for the visualization of exogenous ONOO^-in live cells under ratiometric mode was successfully carried out.In the following work,we investigated the biological application value of Ru-NA,a ruthenium complex for the detection of hypochlorous acid（HClO）in vivo.As HClO can oxidize the hydrazine linker to produce two emissive parts of ruthenium complex and8-amino-1-naphtholactam derivative,both of which showed strong fluorescence signals at620 nm and 538 nm,respectively.Hence,Ru-NA can be served as dual-emissive probe for the detection of HClO in vivo.According to laser confocal microscope,we visualized the dual-emissive fluorescence images of endogenous and exogenous HClO in Raw 264.7 cells and exogenous HClO in Daphnia magna and zebrafish.The distribution of Ru-NA in lysosome of live cells was confirmed by colocalization analysis with a commercially available lysosome labeling agent.The overlap result with the Pearson’s correlation coefficient（0.83）revealed the good lysosome-targeted function of Ru-NA.