Guanying Li

Synthesis, DNA-binding and topoisomerase inhibitory activity of ruthenium(II) polypyridyl complexes.

Two ruthenium(II) complexes [Ru(bpy)(2)(bfipH)](2+) (1) and [Ru(phen)(2)(bfipH)](2+) (2) have been synthesized and characterized. The DNA-binding behaviors of complexes were studied by using spectroscopic and viscosity measurements. Results suggested that the two complexes bind to DNA in an intercalative mode. Complexes 1 and 2 can efficiently photocleave pBR322 DNA in vitro under irradiation, singlet oxygen ((1)O(2)) was proved to contribute to the DNA photocleavage process. Topoisomerase inhibition and DNA strand passage assay confirmed that two Ru(II) complexes acted as efficient dual inhibitors of topoisomerases I and II. In MTT cytotoxicity studies, two Ru(II) complexes exhibited antitumor activity against BEL-7402, HeLa, MCF-7 tumor cells. The AO/EB staining assay indicated that Ru(II) complexes could induce the apoptosis of HeLa cells.

Synthesis, crystal structure, DNA interaction and anticancer activity of tridentate copper(II) complexes

Three new tridentate copper(II) complexes [Cu(dthp)Cl(2)] (1) (dthp=2,6-di(thiazol-2-yl)pyridine), [Cu(dmtp)Cl(2)] (2) (dmtp=2,6-di(5-methyl-4H-1,2,4-triazol-3-yl)pyridine) and [Cu(dtp)Cl(2)] (3) (dtp=2,6-di(4H-1,2,4-triazol-3-yl)pyridine) have been synthesized and characterized. Crystal structure of complex 1 shows that the complex existed as distorted square pyramid with five co-ordination sites occupied by the tridentate ligand and the two chlorine anions. Ethidium bromide displacement assay, viscosity measurements, circular dichroism studies and cyclic voltammetric experiments suggested that these complexes bound to DNA via an intercalative mode. Three Cu(II) complexes were found to efficiently cleave DNA in the presence of sodium ascorbate, and singlet oxygen ((1)O(2)) and hydrogen peroxide were proved to contribute to the DNA cleavage process. They exhibited anticancer activity against HeLa, Hep-G2 and BEL-7402 cell lines. Nuclear chromatin cleavage has also been observed with AO/EB staining assay and the alkaline single-cell gel electrophoresis (comet assay). The results demonstrated that three Cu(II) complexes cause DNA damage that can induce the apoptosis of BEL-7402 cells.

Phosphorescent iridium(III) complexes as multicolour probes for imaging of hypochlorite ions in mitochondria

Mitochondria are one of the major sources of cellular reactive oxygen species (ROS) and the hypochlorite ion (ClO-) is one kind of highly ROS involved in many important biological events. Herein, we present a novel class of mitochondrial ClO- probes. A series of iridium(iii) complexes, Ir1-Ir4, were synthesized which exhibited a highly specific response of their phosphorescence signal toward ClO- over other ROS. By changing the cyclometalated ligands, the turn-on phosphorescent emission colours can be tuned from green to red. ICP-MS results and Mito-tracker co-staining experiments revealed that Ir1-Ir4 localized specifically in mitochondria. Finally, complexes Ir1-Ir4 were successfully applied in subcellular imaging for detection of endogenous ClO- in mitochondria.

Azo-Based Iridium(III) Complexes as Multicolor Phosphorescent Probes to Detect Hypoxia in 3D Multicellular Tumor Spheroids.

Hypoxia is an important characteristic of malignant solid tumors and is considered as a possible causative factor for serious resistance to chemo- and radiotherapy. The exploration of novel fluorescent probes capable of detecting hypoxia in solid tumors will aid tumor diagnosis and treatment. In this study, we reported the design and synthesis of a series of “off-on” phosphorescence probes for hypoxia detection in adherent and three-dimensional multicellular spheroid models. All of the iridium(III) complexes incorporate an azo group as an azo-reductase reactive moiety to detect hypoxia. Reduction of non-phosphorescent probes Ir1-Ir8 by reductases under hypoxic conditions resulted in the generation of highly phosphorescent corresponding amines for detection of hypoxic regions. Moreover, these probes can penetrate into 3D multicellular spheroids over 100 μm and image the hypoxic regions. Most importantly, these probes display a high selectivity for the detection of hypoxia in 2D cells and 3D multicellular spheroids.

Iridium(III) Anthraquinone Complexes as Two-Photon Phosphorescence Probes for Mitochondria Imaging and Tracking under Hypoxia

In the present study, four mitochondria-specific and two-photon phosphorescence iridium(III) complexes, Ir1-Ir4, were developed for mitochondria imaging in hypoxic tumor cells. The iridium(III) complex has two anthraquinone groups that are hypoxia-sensitive moieties. The phosphorescence of the iridium(III) complex was quenched by the functions of the intramolecular quinone unit, and it was restored through two-electron bioreduction under hypoxia. When the probes were reduced by reductase to hydroquinone derivative products under hypoxia, a significant enhancement in phosphorescence intensity was observed under one- (λ=405 nm) and two-photon (λ=720 nm) excitation, with a two-photon absorption cross section of 76-153 GM at λ=720 nm. More importantly, these probes possessed excellent specificity for mitochondria, which allowed imaging and tracking of the mitochondrial morphological changes in a hypoxic environment over a long period of time. Moreover, the probes can visualize hypoxic mitochondria in 3D multicellular spheroids and living zebrafish through two-photon phosphorescence imaging.

Interfering with DNA High‐Order Structures using Chiral Ruthenium(II) Complexes

In this work, it was found that DNA can undergo B-Z transformational changes and compaction in the presence of DNA intercalators such as ruthenium(II) polypyridyl complexes. The link between B-Z transition and condensation is weak but can be strengthened under certain circumstances with slight alterations to the structures of the ruthenium(II) complexes. Here, following on from previous research, this work reports a series of ruthenium(II) complexes with imidazophenanthroline ligands, which vary in size and planarity. The complexes exhibit distinct effects on DNA structures, ranging from little impact to the transformation of DNA secondary structures to the formation of higher-order DNA structures. Further studies on DNA morphological changes induced by chiral ruthenium(II) complexes are observed by atomic force microscopy and transmission electron microscopy.