DNA-binding and cytotoxicity studies of ruthenium(II) mixed-ligand complexes containing two intercalative ligands

RNA-binding of Ru(II) complexes [Ru(phen)2(7-OCH3-dppz)]2+ and [Ru(phen)2(7-NO2-dppz)]2+: The former serves as a molecular "light switch" for poly(A)•poly(U)

To further determine the factors that affect the binding properties of ruthenium(II) polypyridine complexes with RNA duplex and to find excellent RNA-binding agents, the binding properties of ruthenium(II) complexes [Ru(phen)₂(7-OCH₃-dppz)]²⁺ (Ru1, phen = 1,10-phenan- throline, 7-OCH₃-dppz = 7-methoxy-dipyrido-[3,2-a,2',3'-c]-phenazine) and [Ru(phen)₂(7-NO₂- dppz)]²⁺ (Ru2, 7-NO₂-dppz = 7-nitro-dipyrido-[3,2-a,2',3'-c]-phenazine) with RNA poly(A)•poly(U) duplex have been investigated by spectroscopic methods and viscosity measurements in this work. The results show that complexes Ru1 and Ru2 bind to poly(A)•poly(U) through intercalation and the binding affinity between Ru2 and poly(A)•poly(U) is greater than that of Ru1. Thermal denaturation experiments suggest that both ruthenium(II) complexes exhibit a significant stabilizing effect on poly(A)•poly(U) duplex. Moreover, fluorescence emission spectra exhibit that, deviating from Ru2, Ru1 exhibits a "light switch" effect for poly(A)•poly(U). This effect can be observed by the naked eye under UV light and adjusted by pH, meaning that Ru1 may act as a reversible pH controlled molecular "light switch". The results obtained in this work will contribute to our understanding of the significant influence of the intercalative ligand substituent effect in the binding process of ruthenium(II) complexes with RNA duplex.

The development of ruthenium(ii) polypyridyl complexes and conjugates for in vitro cellular and in vivo applications

Ruthenium(ii) [Ru(ii)] polypyridyl complexes have been the focus of intense investigations since work began exploring their supramolecular interactions with DNA. In recent years, there have been considerable efforts to translate this solution-based research into a biological environment with the intention of developing new classes of probes, luminescent imaging agents, therapeutics and theranostics. In only 10 years the field has expanded with diverse applications for these complexes as imaging agents and promising candidates for therapeutics. In light of these efforts this review exclusively focuses on the developments of these complexes in biological systems, both in cells and in vivo, and hopes to communicate to readers the diversity of applications within which these complexes have found use, as well as new insights gained along the way and challenges that researchers in this field still face.

DNA-binding, topoisomerases I and II inhibition and in vitro cytotoxicity of ruthenium(II) polypyridyl complexes: [Ru(dppz)2L](2+) (L=dppz-11-CO2Me and dppz)

Two ruthenium(II) polypyridyl complexes, [Ru(dppz)2dppz-11-CO2Me](ClO4)2 (Ru1) and [Ru(dppz)3](ClO4)2 (Ru2), have been synthesized and characterized. The spectral characteristics of Ru1 and Ru2 were investigated by fluorescence spectroscopy and revealed that both complexes were sensitive to solvent polarity. The binding properties of the two complexes towards calf-thymus DNA (CT-DNA) have been investigated by different spectrophotometric methods and viscosity measurements, indicating that both complexes bind to CT-DNA by means of intercalation, but with different binding affinities. Topoisomerase inhibition and DNA strand passage assay demonstrates that the two complexes are dual inhibitors of topoisomerases I and IIa. On the other hand, the cytotoxicity of both complexes has been evaluated by MTT assays and Giemsa staining experiments. The main results reveal that the ester functional group has a significant effect on the DNA-binding affinities and topoisomerases inhibition effects of Ru1 and Ru2, and further advance our knowledge on the DNA-binding and topoisomerase inhibition by Ru(II) complexes.

Spectroscopic and Modelling Analysis on the Interaction of 3'-Azidodaunorubicin Semicarbazone with ctDNA

The synthesis and characterisation of a new anthracycline, 3′-azidodaunorubicin semicarbazone (ADNRS) is reported. The interaction between ADNRS and calf thymus DNA (ctDNA) was investigated by absorption and fluorescence spectroscopy in combination with melting temperature (Tm) curves and molecular modelling in physiological buffer (pH 7.4). Evidence indicates that ADNRS binds in the groove of ctDNA and the fluorescence quenching mechanism is a static quenching type. Calculated thermodynamic parameters show that hydrophobic interactions may play a predominant role in the binding. Furthermore, molecular modelling results corroborate the spectroscopic investigations.

Spectroscopic, viscositic and molecular modeling studies on the interaction of 3'-azido-daunorubicin thiosemicarbazone with DNA

A new daunorubicin has been synthesized and structurally characterized. The interaction of native calf thymus DNA (ctDNA) with 3′-azido-daunorubicin thiosemicarbazone (ADNRT) was investigated under simulated physiological conditions by multi-spectroscopic techniques, viscometric measurements and molecular modeling study. It concluded that ADNRT could intercalate into the base pairs of ctDNA, and the fluorescence quenching by ctDNA was static quenching type. Thermodynamic parameters calculated suggested that the binding of ADNRT to ctDNA was mainly driven by hydrophobic interactions. The relative viscosity of ctDNA increased with the addition of ADNRT, which confirmed the intercalation mode. Furthermore, molecular modeling studies corroborate the above experimental results.