Zhenzhen Tian

Half-Sandwich Iridium(III) and Ruthenium(II) Complexes Containing P^P-Chelating Ligands: A New Class of Potent Anticancer Agents with Unusual Redox Features

A series of half-sandwich IrIII pentamethylcyclopentadienyl and RuII arene complexes containing P^P-chelating ligands of the type [(Cpx/arene)M(P^P)Cl]PF6, where M = Ir, Cpx is pentamethylcyclopentadienyl (Cp*), or 1-biphenyl-2,3,4,5-tetramethyl cyclopentadienyl (CpxbiPh); M = Ru, arene is 3-phenylpropan-1-ol (bz-PA), 4-phenylbutan-1-ol (bz-BA), or p-cymene (p-cym), and P^P is 2,20-bis(diphenylphosphino)-1,10-binaphthyl (BINAP), have been synthesized and fully characterized, three of them by X-ray crystallography, and their potential as anticancer agents explored. All five complexes showed potent anticancer activity toward HeLa and A549 cancer cells. The introduction of a biphenyl substituent on the Cp* ring for the iridium complexes has no effect on the antiproliferative potency. Ruthenium complex [(η6-p-cym)Ru(P^P)Cl]PF6 (5) displayed the highest potency, about 15 and 7.5 times more active than the clinically used cisplatin against A549 and HeLa cells, respectively. No binding to 9-MeA and 9-EtG nucleobases was observed. Although these types of complexes interact with ctDNA, DNA appears not to be the major target. Compared to iridium complex [(η5-Cp*)Ir(P^P)Cl]PF6 (1), ruthenium complex (5) showed stronger ability to interfere with coenzyme NAD+/NADH couple through transfer hydrogenation reactions and to induce ROS in cells, which is consistent with their anticancer activities. The redox properties of the complexes 1, 5, and ligand BINAP were evaluated by cyclic voltammetry. Complexes 1 and 5 arrest cell cycles at the S phase, Sub-G1 phase and G1 phase, respectively, and cause cell apoptosis toward A549 cells.

Functionalized Ultrasmall Fluorinated Graphene with High NIR Absorbance for Controlled Delivery of Mixed Anticancer Drugs

Fluorinated graphene (FG) possess distinctively novel properties different from graphene and is suitable for many biomedical applications. However, the hydrophobic nature and inert properties of FG limit its further application as a biological material. Here we show the preparation of nano-sized FG (ca. 60 nm) that exhibits high NIR absorbance for photothermal therapy. In order to make it stable in physiological solutions, the FG is enriched with oxygen and followed by covalent binding with chitosan as a novel pH-responsive nanocarrier. Furthermore, controlled loading of two anticancer drugs, doxorubicin (DOX) and camptothecin (CPT) has been realized and the functionalized ultrasmall FG shows remarkably high cytotoxicity toward Hela cancer cells compared to that loaded with either CPT or DOX only. This work established nano-sized FG as a novel photothermal agent due to its small size and can be used a stimulus-responsive nanocarrier for mixed drug delivery and combined therapy.

Imine-N-Heterocyclic Carbenes as Versatile Ligands in Ruthenium(II) p-Cymene Anticancer Complexes: A Structure-Activity Relationship Study

A family of novel imine-N-heterocyclic carbene ruthenium(II) complexes of the general formula [(η6 -p-cymene)Ru(C^N)Cl]PF6 - (where C^N is an imine-N-heterocyclic carbene chelating ligand with varying substituents) have been prepared and characterized. In this imine-N-heterocyclic carbene chelating ligand framework, there are three potential sites that can be modified, which distinguishes this class of ligand and provides a body of flexibilities and opportunities to tune the cytotoxicity of these ruthenium(II) complexes. The influence of substituent effects of three tunable domains on the anticancer activity and catalytic ability in converting coenzyme NADH to NAD+ is investigated. This family of complexes displays an exceedingly distinct anticancer activity against A549 cancer cells, despite their close structural similarity. Complex 9 shows the highest anticancer activity in this series against A549 cancer cells (IC50 =14.36 μm), with an approximately 1.5-fold better activity than the clinical platinum drug cisplatin (IC50 =21.30 μm) in A549 cancer cells. Mechanistic studies reveal that complex 9 mediates cell death mainly through cell stress, including cell cycle arrest, inducing apoptosis, increasing intracellular reactive oxygen species (ROS) levels, and depolarization of the mitochondrial membrane potential (MMP). Furthermore, lysosomal damage is also detected by confocal microscopy.

Nano-sized paramagnetic and fluorescent fluorinated carbon fiber with high NIR absorbance for cancer chemo-photothermal therapy

Nano-sized fluorinated carbon fiber possesses unique charge distribution and special chemical bonds and holds great promise in biomedicine. However, its synthesis remains a big challenge on account of the chemical inertness and strong hydrophobicity of C-F bonds. Herein, an up-bottom method to prepare nano-sized and water-soluble fluorinated carbon fiber oxide (FCO) with tunable lengths and adjustable fluorine levels was first developed. It was found that the effective control over structure and composition endowed the FCO with high photoluminescence (PL) and near-infrared (NIR) light absorbance, which was further employed to monitor the drug loading by turn-off PL and treat cancer by photothermal therapy (PTT). We also reported the first experimental example of paramagnetic FCO, whose novel paramagnetism was generated by point defects from fluorine invasion. Moreover, the FCO was noncovalently functionalized with polyvinylpyrrolidone, loaded with doxorubicin of high capacity (1.15 mg mg-1) and exhibited acid-triggered and photothermally enhanced drug release behavior. The application of FCO in cancer treatment achieved much better therapeutic effects than single chemotherapy or PTT. This work established FCO as a novel nano-carrier with high PL, NIR absorbance, paramagnetism, and drug loading capacity, and demonstrated its first application in cancer chemo-photothermal therapy.

Electronic effects on reactivity and anticancer activity by half-sandwich N,N-chelated iridium(III) complexes

The synthesis and characterization of a series of organometallic half-sandwich N,N-chelated iridium(III) complexes bearing a range of electron-donating and withdrawing substituents were described. The X-ray crystal structures of complexes 1, 3 and 5 have been determined. This work demonstrated how the aqueous chemistry, catalytic activity in converting coenzyme NADH to NAD+ and anticancer activity can be controlled and fine-tuned by the modification of the ligand electronic perturbations. In general, the introduction of an electron-withdrawing group (–Cl and –NO2) on the bipyridine ring resulted in increased anticancer activity, whereas an electron-donating group (–NH2, –OH and –OCH3) decreased the anticancer activity. Complex 6 bearing a strongly electron-withdrawing NO2 group displayed the highest anticancer activity (7.3 ± 1.2 μM), ca. three times as active as cisplatin in the A549 cell line. Notably, selective cytotoxicity for cancer cells over normal cells was observed for complexes 1 and 6. DNA binding does not seem to be the primary mechanism for cancer fighting. However, the aqueous chemistry, cell apoptosis and cell cycle, which show similar dependence on the ligand electronic perturbations as the anticancer activity, appear to together contribute to the anticancer potency of theses complexes. This work may provide an alternative strategy to enhance anticancer activity for these N,N-chelated organometallic half-sandwich iridium(III) complexes.

Half-sandwich IridiumIII N-heterocyclic carbene antitumor complexes and biological applications

Series of half-sandwich IrIIIN-heterocyclic carbene (NHC) antitumor complexes [(η5-Cp*)Ir(C^C)Cl] have been synthesized and characterized (Cp* is pentamethyl cyclopentadienyl, and C^C are four NHC chelating ligands containing phenyl rings at different positions). IrIII complexes showed potent antitumor activity with IC50 values ranged from 3.9 to 11.8 μM against A549 cells by the MTT assay. Complexes can catalyze the conversion of the coenzyme NADH to NAD+ and induce the production of reactive oxygen species (ROS), and bonding to BSA by static quenching mode. Complexes can arrest the cell cycle in G1 or S phase and reduce the mitochondrial membrane potential. Confocal microscopy test show complexes could target the lysosome and mitochondria in cells with the Pearsons colocalization coefficient of 0.82 and 0.21 after 12 h, respectively, and followed by an energy-dependent cellular uptake mechanism.

Lysosome targeted drugs: rhodamine B modified N^N-chelating ligands for half-sandwich iridium(III) anticancer complexes

We designed and synthesized four rhodamine-modified half-sandwich iridium complexes ([(η5-Cpx)Ir(N^N)Cl]PF6). The fluorescence properties of the complexes were studied. Excitingly, the cytotoxicity of the complexes was superior to that of cisplatin for both A549 cells and HeLa cells. In particular, for A549 cells, the cytotoxicity of complexes 2 and 3 was 5 or 6-fold higher than that of cisplatin. Interactions with ctDNA and BSA have been investigated. The results show that the interaction with DNA does not seem to be the main anticancer mechanism. A binding experiment between BSA and complexes was carried out using a UV spectrophotometer and a fluorescence spectrophotometer. The catalytic conversion of the coenzyme NADH to NAD+ has also been investigated for hydrogen transfer of the complexes. In addition, complex 3 was studied in cell experiments because of its good antiproliferative activity. In addition, the cell distribution and targeting mechanisms of these complexes were studied using confocal microscopy. Complex 3 can induce cell death by blocking the G0/G1 phase of the cell cycle, affecting the mitochondrial membrane potential, then entering the cells and specifically targeting lysosomes. These seem to contribute to the anticancer activity of the complexes.

Lysosome-Targeted Chemotherapeutics: Half-Sandwich Ruthenium(II) Complexes That Are Selectively Toxic to Cancer Cells

Poor selectivity between cancer cells and normal cells is one of the major limitations of cancer chemotherapy. Lysosome-targeted ruthenium-based complexes target tumor cells selectively, only displaying rather weak cytotoxicity or inactivity toward normal cells. Confocal microscopy was employed for the first time to determine the cellular localization of the half-sandwich Ru complex.

Half-Sandwich Iridium and Ruthenium Complexes: Effective Tracking in Cells and Anticancer Studies

Half-sandwich metal-based anticancer complexes suffer from uncertain targets and mechanisms of action. Herein we report the observation of the images of half-sandwich iridium and ruthenium complexes in cells detected by confocal microscopy. The confocal microscopy images showed that the cyclopentadienyl iridium complex 1 mainly accumulated in nuclei in A549 lung cancer cells, whereas the arene ruthenium complex 3 is located in mitochondria and lysosomes, mostly in mitochondria, although both complexes entered A549 cells mainly through energy-dependent active transport. The nuclear morphological changes caused by Ir complex 1 were also detected by confocal microscopy. Ir complex 1 is more potent than cisplatin toward A549 and HeLa cells. DNA binding studies involved interaction with the nucleobases 9-ethylguanine, 9-methyladenine, ctDNA, and plasmid DNA. The determination of bovine serum albumin binding was also performed. Hydrolysis, stability, nucleobase binding, and catalytic NAD+/NADH hydride transfer tests for complexes 1 and 3 were also carried out. Both complexes activated depolarization of mitochondrial membrane potential and intracellular ROS overproduction and induced cell apoptosis. Complex 3 arrested the cell cycle at the G0/G1 phase by inactivation of CDK 4/cyclin D1. This work paves the way to track and monitor half-sandwich metal complexes in cells, shines a light on understanding their mechanism of action, and indicates their potential application as theranostic agents.

Highly potent half-sandwich iridium and ruthenium complexes as lysosome-targeted imaging and anticancer agents

In this study, six half-sandwich luminescent iridium (Ir) and ruthenium (Ru) anticancer complexes bearing P^P-chelating ligands 1,2-bis(diphenylphosphino)benzene (dppbz) and 1,8-bis(diphenylphosphino)naphthalene (dppn) were synthesized and characterized via1H-NMR spectroscopy, 31P-NMR spectroscopy, mass spectrometry, elemental analysis and X-ray crystallography. All the complexes displayed more potent anticancer activity than cisplatin towards A549 lung cancer cells and HeLa cervical cancer cells, especially the most potent iridium complex Ir3, which was 73 times more potent than cisplatin against A549 cells. Different from cisplatin, no nucleobase adducts of Ir3 were detected. With the help of the self-luminescence of complex Ir3 and confocal microscopy, it was observed that Ir3 efficiently penetrated into the A549 cells via energy-dependent active transport, and specifically accumulated in lysosomes, affected the permeabilization of the lysosomal membranes and induced caspase-dependent cell death through lysosomal damage. Both apoptosis and autophagy of the A549 cells were observed. The reactive oxygen species (ROS) elevation, reduction of the mitochondrial membrane potential and cell cycle arrest at the G0/G1 phase also contributed to the observed cytotoxicity of Ir3. We demonstrate that these half-sandwich Ir and Ru anticancer complexes have different anticancer mechanism of action from that of cisplatin, which can be developed as potential multifunctional theranostic platforms that combine bioimaging and anticancer capabilities.