Synthesis, Biomacromolecular Interactions, Photodynamic NO Releasing and Cellular Imaging of Two...

Two light-activated NO donors [RuCl(qn)(Lbpy)(NO)]X with 8-hydroxyquinoline (qn) and 2,2'-bipyridine derivatives (Lbpy) as co-ligands were synthesized (Lbpy₁ = 4,4'-dicarboxyl-2,2'-dipyridine, X = Cl^- and Lbpy₂ = 4,4'-dimethoxycarbonyl-2,2'-dipyridine, X = NO₃^-), and characterized using ultraviolet-visible (UV-vis) spectroscopy, Fourier transform infrared (FT-IR) spectroscopy, nuclear magnetic resonance (¹H NMR), elemental analysis and electrospray ionization mass spectrometry (ESI-MS) spectra. The [RuCl(qn)(Lbpy₂)(NO)]NO₃ complex was crystallized and exhibited distorted octahedral geometry, in which the Ru-N(O) bond length was 1.752(6) Å and the Ru-N-O angle was 177.6(6)°. Time-resolved FT-IR and electron paramagnetic resonance (EPR) spectra were used to confirm the photoactivated NO release of the complexes. The binding constant (K_b) of two complexes with human serum albumin (HSA) and DNA were quantitatively evaluated using fluorescence spectroscopy, Ru-Lbpy₁ (K_b~10⁶ with HSA and ~10⁴ with DNA) had higher affinity than Ru-Lbpy₂. The interactions between the complexes and HSA were investigated using matrix assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF-MS) and EPR spectra. HSA can be used as a carrier to facilitate the release of NO from the complexes upon photoirradiation. The confocal imaging of photo-induced NO release in living cells was successfully observed with a fluorescent NO probe. Moreover, the photocleavage of pBR322 DNA for the complexes and the effect of different Lbpy substituted groups in the complexes on their reactivity were analyzed.