Syntheses, Spectra, Photoinduced Nitric Oxide Release and Interactions with Biomacromolecules of Three Nitrosylruthenium Complexes

Three nitrosylruthenium complexes, [RuCl(qn)L(NO)] (qn = 8-hydroxyquinoline; L = L-Asp, L-Lys and picp), have been synthesized. The photodynamic reactions of the three complexes were analyzed with time resolved FTIR spectroscopy and the photoinduced release of NO was confirmed by EPR via spin trapping of the NO free radical. The binding constants of the complexes with calf thymus DNA and human serum albumin were quantitatively determined by fluorescence spectroscopy, with a stronger binding being found for the [RuCl(qn)(picp)(NO)] (picp = 2-(4-carboxylphenyl)-imidazolium[4,5-f][1,10] phenanthroline) complex compared to the other two complexes. Photoirradiation of the complexes mixed with HSA solution resulted in a blue-shift of the vibrational frequency of NO and an increased amount of released NO. The cell toxicity of the complexes was screened to understand the effects of the different ligands on the biological activity of the Ru complexes. The [RuCl(qn)(picp)(NO)] complex showed better activity against the HepG-2 cell, with an IC50 value of 24.9 mu M without light and 13.8 mu M upon photoirradiation. Moreover, a comparison of photoinduced DNA cleavage and photodynamic cellular toxicity suggests the important role of the NO free radical. This study provides a strategy for the design of NO-donors and the potential application of Ru-NO complexes in photodynamic therapy. (C) 2020 Elsevier Ltd. All rights reserved.