👤 Zhu H

A new ligand MHPIP (MHPIP = 2-(1-methyl-1H-pyrazol-4-yl)-1H-imidazo[4,5-f][1,10]phenanthroline) and its three ruthenium (II) complexes [Ru(N-N)₂(MHPIP)](ClO₄)₂ (N-N = phen: 1,10-phenanthroline 1; dmp = 2,9-dimethyl-1,10-phenanthroline 2; ttbpy = 4,4'-ditertiarybutyl-2,2'-bipyridine 3) were synthesized and characterized. The cytotoxic activity in vitro was studied by MTT method. The complexes 1-3 show moderate cytotoxic effects on the cell growth in HepG2 cells with an IC₅₀ value of 25.5 ± 3.5, 35.6 ± 1.9 and 27.4 ± 2.3 μM, respectively. The apoptosis was investigated with AO/EB and Annex V/PI staining methods and comet assay. The reactive oxygen species, mitochondrial membrane potential were investigated under a fluorescent microscope. Autophagy assay shows that the complexes can cause autophagy and up-regulate the expression of Beclin-1 protein. Additionally, the complexes inhibit the cell growth in HepG2 cells at G0/G1 phase, and the complexes can regulate the expression of caspase 3 and Bcl-2 family proteins. The studies demonstrate that the complexes induce apoptosis in HepG2 cells through DNA damage and ROS-mediated mitochondrial dysfunction pathways. Show less

Background

Photodynamic therapy (PDT) is a promising anti-tumor treatment strategy. Photosensitizer is one of the most important components of PDT. In this work, the anticancer activities of PDT mediated by six new ruthenium porphyrin complexes were screened. The mechanisms of the most efficacious candidate were investigated.

Methods

Photocytotoxicity of the six porphyrins was tested. The most promising complex, Rup-03, was further investigated using Geimsa staining, which indirectly detects reactive oxygen species (ROS) and subcellular localization. Mitochondrial membrane potential (MMP), cell apoptosis, DNA fragmentation, c-Myc gene expression, and telomerase activities were also assayed.

Results

Rup-03 and Rup-04 had the lowest IC₅₀ values. Rup-03 had an IC₅₀ value of 29.5±2.3μM in HepG2 cells and 59.0±6.1μM in RAW264.7 cells, while Rup-04 had an IC₅₀ value of 40.0±3.8μM in SGC-7901 cells. The complexes also induced cellular morphological changes and impaired cellular ability to scavenge ROS, and accumulated preferentially in mitochondria and endoplasmic reticulum. Rup-03 reduced MMP levels, induced apoptosis, and repressed both c-Myc mRNA expression and telomerase activity in HepG2 cells.

Conclusions

Among six candidates, Rup-03-mediated PDT is most effective against HepG2 and RAW264.7, with a similar efficacy as that of Rup-04-mediated PDT against SGC-7901 cells. Repression of ROS scavenging activities and c-Myc expression, which mediated DNA damage-induced cell apoptosis and repression of telomerase activity, respectively, were found to be involved in the anticancer mechanisms of Rup-03. Show less

Chemotherapy is limited by its poor selectivity towards cancer cells over normal cells. Herein, we designed half-sandwich ruthenium imino-pyridyl complexes [(η⁶-bz)Ru(N^N)Cl]PF₆ to achieve selective cytotoxicity to cancer cells. This kind of ruthenium complex has unique characteristics and is worthy of further exploration in the design of new anticancer drugs. Show less

A photochemically dissociating ligand in Ru(bpy)₂(dmphen)Cl₂ [bpy = 2,2'-bipyridine; dmphen = 2,9-dimethyl-1,10-phenanthroline] was found to be more cytotoxic on the ML-2 Acute Myeloid Leukemia cell line than Ru(bpy)₂(H₂O)₂²⁺ and prototypical cisplatin. Our findings illustrate the potential potency of diimine ligands in photoactivatable Ru(ii) complexes. Show less

Ruthenium coordination complexes have the potential to serve as novel theranostic agents for cancer. However, a major limitation in their clinical implementation is effective tumor accumulation. In this study, we have developed a liposome-based theranostic nanodelivery system for [Ru(phen)₂dppz](ClO₄)₂ (Lipo-Ru). This ruthenium polypyridine complex emits a strong fluorescent signal when incorporated in the hydrophobic lipid bilayer of the delivery vehicle or in the DNA helix, enabling visualization of the therapeutic agent in tumor tissues. Incubation of MDA-MB-231 breast cancer cells with Lipo-Ru induced double-strand DNA breaks and triggers apoptosis. In a mouse model of triple-negative breast cancer, treatment with Lipo-Ru dramatically reduced tumor growth. Biodistribution studies of Lipo-Ru revealed that more than 20% of the injected dose accumulated in the tumor. These results suggest that Lipo-Ru could serve as a promising theranostic platform for cancer. Show less

Our study demonstrates that four novel kinetically inert C,N-cyclometalated Ru^II complexes of the type [Ru(C^N)(N^N)₂ ][PF₆ ] containing a handle for functionalization on the C^N ligand are very potent cytotoxic agents against several different human cancer cell lines and are up to 400-fold more potent than clinically used cisplatin. In addition, the investigated ruthenium complexes are less cytotoxic in noncancerous cells, and exhibit higher selectivity for cancer cells than conventional platinum anticancer drugs. The high potency of the investigated ruthenium compounds can be attributed to several factors, including enhanced internalization and their capability to change mitochondrial transmembrane potential in cells. The new ruthenium complexes also interfere with protein synthesis with a markedly higher potency than conventional inhibitors of DNA translation. Notably, the latter mechanism has not been hitherto described for other cytotoxic Ru compounds and cisplatin. Show less

Six cyclometalated iridium(iii) complexes bearing different numbers of fluorine atoms were synthesized. These complexes demonstrated much better anti-proliferation activities towards five tumour cell lines than the widely used clinical chemotherapeutic agent cisplatin. Moreover, the anti-proliferation activities were correlated to the number of substituted fluorine atoms. Colocalization and inductively coupled plasma-mass spectrometry (ICP-MS) indicated that this series of complexes could penetrate cell membranes rapidly and preferentially target mitochondria. Manifesting high selectivity between tumour cells and normal cells and remarkable sensitivity to a cisplatin-resistant cell line (A549R), complex Ir6 was successfully developed as a novel anticancer agent (with IC₅₀ values of 0.5 ± 0.1 μM for HeLa, 1.1 ± 0.2 μM for HepG2, 1.5 ± 0.3 μM for BEL-7402, 0.8 ± 0.1 μM for A549, and 0.7 ± 0.2 μM for A549R cell lines). Further mechanism studies including mitochondrial membrane potential depolarization and caspase 3/7 activation revealed that Ir6 induced apoptosis via mitochondrial pathways. These results demonstrated that complex Ir6 might be a promising candidate as a mitochondria-targeted theranostic anticancer agent. Show less

Four phosphorescent cyclometalated iridium(III) complexes containing benzimidazole moiety have been designed and synthesized. These Ir(III) complexes can effectively inhibit several cancerous processes, including cell migration, invasion, colony formation, and angiogenesis. Interestingly, they show a much higher singlet oxygen quantum yield in an acidic solution than in a neutral solution. Upon irradiation at 425 nm with low energy (1.2 J cm^-2), they can induce apoptosis through lysosomal damage, evaluation of reactive oxygen species level, and activation of caspase-3/7. The highest phototoxicity index is >476, with almost no dark cytotoxicity observed for Ir4. Ir4 can also inhibit tumor growth effectively in nude mice in vivo after photodynamic therapy. An in vitro assay against 70 kinases indicates that maternal embryonic leucine zipper kinase (MELK), PIK3CA, and AMPK are the possible molecular targets. The half maximal inhibitory concentration of Ir4 toward MELK is 1.27 μM. Our study demonstrates that these Ir(III) complexes are promising anticancer agents with dual functions, including metastasis inhibition and lysosome-damaged photodynamic therapy. Show less

In this article, we report on the development of new metal-based anticancer agents with imaging, chemotherapeutic and photosensitizing properties. Hence, a new heterobimetallic complex (Pt-LQ-Re) was prepared by connecting a non-conventional trans-chlorido Pt(ii) complex to a photoactive Re tricarbonyl unit (LQ-Re), which can be replaced by ^99mTc to allow for in vivo imaging. We describe the photophysical and biological properties of the new complexes, in the dark and upon light irradiation (DNA interaction, cellular localization and uptake, and cytotoxicity). Furthermore, planar scintigraphic images of mice injected with Pt-LQ-Tc clearly showed that the radioactive compound is taken up by the excretory system organs, namely liver and kidneys, without significant retention in other tissues. All in all, the strategy of conjugating a chemotherapeutic compound with a PDT photosensitizer endows the resulting complexes with an intrinsic cytotoxic activity in the dark, driven by the non-classical platinum core, and a selective activity upon light irradiation. Most importantly, the possibility of integrating a SPECT imaging radiometal (^99mTc) in the structure of these new heterobimetallic complexes might allow for in vivo non-invasive visualization of their tumoral accumulation, a crucial issue to predict therapeutic outcomes. Show less

Identifying drug-target interactions is an important task in drug discovery. To reduce heavy time and financial cost in experimental way, many computational approaches have been proposed. Although these approaches have used many different principles, their performance is far from satisfactory, especially in predicting drug-target interactions of new candidate drugs or targets. Show less

The specific autophagic elimination of mitochondria (mitophagy) plays the role of quality control for this organelle. Deregulation of mitophagy leads to an increased number of damaged mitochondria and triggers cell death. The deterioration of mitophagy has been hypothesized to underlie the pathogenesis of several neurodegenerative diseases, most notably Parkinson disease. Although some of the biochemical and molecular mechanisms of mitochondrial quality control are described in detail, physiological or pathological triggers of mitophagy are still not fully characterized. Here we show that the induction of mitophagy by the mitochondrial uncoupler FCCP is independent of the effect of mitochondrial membrane potential but dependent on acidification of the cytosol by FCCP. The ionophore nigericin also reduces cytosolic pH and induces PINK1/PARKIN-dependent and -independent mitophagy. The increase of intracellular pH with monensin suppresses the effects of FCCP and nigericin on mitochondrial degradation. Thus, a change in intracellular pH is a regulator of mitochondrial quality control. Show less

DNA binding and DNA transcription inhibition is regarded as a promising strategy for cancer chemotherapy. Herein, chloro terpyridyl Ru(ii) complexes, [Ru(tpy)(N^N)Cl](+) (Ru1, N^N = 2,2'-bipyridine; Ru2, N^N = 3-(pyrazin-2-yl)-as-triazino[5,6-f]acenaphthylene; Ru3, N^N = 3-(pyrazin-2-yl)-as-triazino[5,6-f]phenanthrene; Ru4, N^N = 3-(pyrazin-2-yl)-as-triazino[5,6-f]pyrene) were prepared as DNA intercalative and covalent binding anticancer agents. The chloro ligand hydrolysis slowly and the octanol and water partition coefficient of Ru2-Ru4 were between 0.6 and 1.2. MALDI-TOF mass, DNA gel electrophoresis confirmed covalent and intercalative DNA binding modes of Ru2-Ru4, while Ru1 can only bind DNA covalently. As a result, Ru2-Ru4 exhibited stronger DNA transcription inhibition activity, higher cell uptake efficiency and better anticancer activity than Ru1. Ru4 was the most toxic complex toward all cancer cells which inhibited DNA replication and transcription. AO/EB, Annexin V/PI, nuclear staining, JC-1 assays further confirmed that Ru2-Ru4 induced cancer cell death by an apoptosis mechanism. Show less

Lactate dehydrogenase (LDH) is a redox enzyme often overexpressed in cancer cells allowing their survival in stressful metabolic tumor environment. Ruthenium(II) complexes have been shown to impact on the activity of purified horseradish peroxidase and glucose oxidase but the physiological relevance remains unclear. In this study we investigated how ruthenium complexes impact on the activity of LDH in vitro and in cancer cells and performed a comparative study using polypyridine ruthenium(II) complex [Ru(bpy)₃]²⁺ (1) and its structurally related cyclometalated 2-phenylpyridinato counterpart [Ru(phpy)(bpy)₂]⁺ (2) (bpy=2,2'-bipyridine, phpyH=2-phenylpyridine). We show that the cytotoxicity in gastric and colon cancer cells induced by 2 is significantly higher compared to 1. The kinetic inhibition mechanisms on purified LDH and the corresponding inhibition constants K_i or i_0.5 values were calculated. Though complexes 1 and 2 are structurally very similar (one Ru-C bond in 2 replaces one Ru-N bond in 1), their inhibition modes are different. Cyclometalated complex 2 behaves exclusively as a non-competitive inhibitor of LDH from rabbit muscle (LDH_rm), strongly suggesting that 2 does not interact with LDH in the vicinities of either lactate/pyruvate or NAD⁺/NADH binding sites. Sites of interaction of 1 and 2 with LDH_rm were revealed theoretically through computational molecular docking. Inhibition of LDH activity by 2 was confirmed in cancer cells. Altogether, these results revealed an inhibition of LDH activity by ruthenium complex through a direct interaction structurally tuned by a Ru-C bond. Show less

A ruthenium(II) complex [Ru(p-cymene)(NHC)Cl2] (NHC=1,3-bis(4-(tert-butyl)benzylimidazol-2-ylidene), referred to as L-4, has been designed and synthesized recently in order to look for new anticancer drugs with high efficacy and low side effects. The anticancer activity and mechanism of action of L-4 in human esophageal squamous carcinoma EC109 cells were systematically investigated. The results revealed that L-4 exerted strong inhibitory effect on the proliferation of EC109 cells, and it arrested EC109 cells at G2/M phase, accompanied with the up-regulation of p53 and p21 and the down-regulation of cyclin D1. The results also showed that the reactive oxygen species (ROS)-dependent apoptosis of EC109 can be induced by L-4 via inhibiting the activity of glutathione reductase (GR), decreasing the ratio of glutathione to oxidized glutathione (GSH/GSSG), and leading to the generation of reactive oxygen species. The mitochondria-mediated apoptosis of EC109 induced by L-4 was also observed from the increase of Bax/Bcl-2 ratio, overload of Ca(2+), disruption of mitochondrial membrane potential (MMP), redistribution of cytochrome c, and activation of caspase-3/-9. However, the effects of L-4 on the cell viability, GR activity, GSH/GSSG ratio, reactive oxygen species level, mitochondria dysfunction and apoptosis induction were remarkably attenuated by adding the reactive oxygen species scavenger, NAC. Therefore, it was concluded that L-4 can inhibit the proliferation of EC109 cells via blocking cell cycle progression and inducing reactive oxygen species-dependent and mitochondria-mediated apoptosis. These findings suggested that the ruthenium(II) complex might be a potential effective chemotherapeutic agent for human esophageal squamous carcinoma (ESCC) and worthy of further investigation. Show less

Four new ruthenium(II) polypyridyl complexes [Ru(N-N)2(bddp)](ClO4)21-4 (N-N=dmb: 4,4'-dimethyl-2,2'-bipyridine 1, bpy: 2,2'-bipyridine 2, phen: 1,10-phenanthroline 3 and dmp: 2,9-dimethyl-1,10-phenanthroline 4, bddp=benzilo[2,3-b]-1,4-diazabenzo[i]dipyrido[3,2-a:2',3'-c]phenazine) were synthesized and characterized by elemental analysis, ESI-MS and (1)H NMR. The cytotoxicity in vitro of the complexes against BEL-7402, HeLa, MG-63 and A549 cell lines was investigated by MTT method. The complexes show high cytotoxic activity toward the selected cell lines with an IC50 value ranging from 5.3±0.6 to 15.7±3.6μM. The apoptosis was studied with acridine orange (AO)/ethdium bromide (EB) and Hoechst 33258 staining methods. The cellular uptake was investigated with DAPI staining method. The reactive oxygen species (ROS) and mitochondrial membrane potential were performed under fluorescent microscope and flow cytometry. The complexes can induce an increase in the ROS levels and a decrease in the mitochondrial membrane potential. The comet assay was studied with fluorescent microscope. The percentage in apoptotic and necrotic cells and cell cycle arrest were assayed by flow cytometry. The effects of the complexes on the expression of caspases and Bcl-2 family proteins were studied by western blot analysis. The results show that the complexes induce apoptosis in A549 cells through an ROS-mediated mitochondrial dysfunction pathway, which was accompanied by regulating the expression of Bcl-2 family proteins. Show less

As one of the major cell regulated center, mitochondria are closely associated with cell proliferation, apoptosis of tumor cell. In this work, four new ruthenium (II) polypyridyl complexes [Ru(bpy)₂(FTTP)](ClO₄)₂ (1) (FTTP=11-(3-fluoro-naphthalen-2-yloxy)-4,5,9,14-tetraaza-benzo[b]triphenylene, bpy=2,2'-bipyridine), [Ru(phen)₂(FTTP)](ClO₄)₂ (2) (phen=1,10-phenanthroline), [Ru(bpy)₂(PTTP)](ClO₄)₂ (3) (PTTP=2-phenoxy-1,4,8,9-tetraazatriphenylene) and [Ru(phen)₂(PTTP)](ClO₄)₂ (4) were synthesized and characterized by elemental analysis, ESI-MS, ¹H NMR and ¹³C NMR. The cytotoxic activity, ability of inhibiting cell invasion, cell cycle arrest and apoptosis-inducing mechanism of these Ru(II) complexes have been investigated in detail by MTT (3-(4,5-dimethylthiazole)-2,5-diphenyltetrazolium bromide) method, invasion assay, comet assay as well as western blotting techniques. Notably, complexes 1-4 displayed high cytotoxic activity against liver carcinoma HepG2 cells and the IC₅₀ values of complexes 1-4 against HepG2 cells are 10.4±1.2, 9.3±0.6, 29.1±1.5 and 5.6±1.2μM, respectively. The comet assay showed that the complexes can induce DNA damage. The acridine orange (AO) and ethidium bromide (EB) staining method indicated that the complexes can cause apoptosis in HepG2 cells. Further studies showed that complexes 1-4 caused cell cycle arrest at G0/G1 phase and induced HepG2 cells apoptosis through a ROS-mediated mitochondrial dysfunction pathway, which involved an increase in the levels of reactive oxygen species (ROS), a decrease in the mitochondrial membrane potential, activation of caspases and Bcl-2 family proteins. Show less

To evaluate the anticancer activity of the cyclometalated ruthenium(II) complexes [Ru(bpy)2(C^N)]Cl, we have studied the interaction of these complexes using calf thymus DNA (CT-DNA) and cytotoxicity assays with two tumor (L1210 and HeLa) and a non-tumor (BALB/3T3 clone A31) cell lines. It is suggested that the complexes act as intercalators and/or DNA minor groove binders. Moreover, the complexes display favorable cytotoxicity activities with L1210 and HeLa, which in all cases were significantly more favorable than cisplatin. In contrast, the complexes exhibit appreciably lower cytotoxicity toward BALB/3T3 clone A31. Show less

Four new ruthenium(II) polypyridyl complexes [Ru(N-N)2(dhbn)](ClO4)2 (N-N = dmb: 4,4'-dimethyl-2,2'-bipyridine 1; bpy = 2,2'-bipyridine 2; phen = 1,10-phenanthroline 3; dmp = 2,9-dimethyl-1,10-phenanthroline 4) were synthesized and characterized. The cytotoxicity in vitro of the ligand and complexes toward HepG-2, HeLa, MG-63 and A549 were assayed by MTT method. The IC50 values of the complexes against the above cells range from 17.7 ± 1.1 to 45.1 ± 2.8 μM. The cytotoxic activity of the complexes against HepG-2 cells follows the order of 4 > 2 > 3 > 1. Ligand shows no cytotoxic activity against the selected cell lines. Cellular uptake, apoptosis, comet assay, reactive oxygen species, mitochondrial membrane potential, cell cycle arrest, and the expression of proteins involved in apoptosis pathway induced by the complexes were investigated. The results indicate that complexes 1-4 induce apoptosis in HepG-2 cells through an intrinsic ROS-mediated mitochondrial dysfunction pathway. Show less

Ruthenium (Ru) complexes are currently the focus of substantial interest because of their potential application as chemotherapeutic agents with broad anticancer activities. This study investigated the in vitro and in vivo anticancer activities and mechanisms of two Ru complexes-2,3,7,8,12,13,17,18-Octaethyl-21H,23H-porphine Ru(II) carbonyl (Ru1) and 5,10,15,20-Tetraphenyl-21H,23H-porphine Ru(II) carbonyl (Ru2)-against human hepatocellular carcinoma (HCC) cells. These Ru complexes effectively inhibited the cellular growth of three human hepatocellular carcinoma (HCC) cells, with IC50 values ranging from 2.7-7.3 μM. In contrast, the complexes exhibited lower toxicity towards L02 human liver normal cells with IC50 values of 20.4 and 24.8 μM, respectively. Moreover, Ru2 significantly inhibited HepG2 cell migration and invasion, and these effects were dose-dependent. The mechanistic studies demonstrated that Ru2 induced HCC cell apoptosis, as evidenced by DNA fragmentation and nuclear condensation, which was predominately triggered via caspase family member activation. Furthermore, HCC cell treatment significantly decreased the expression levels of Nrf2 and its downstream effectors,

Nad(p)h

quinone oxidoreductase 1 (NQO1) and heme oxygenase 1 (HO1). Ru2 also exhibited potent in vivo anticancer efficacy in a tumor-bearing nude mouse model, as demonstrated by a time- and dose-dependent inhibition on tumor growth. The results demonstrate the therapeutic potential of Ru complexes against HCC via Nrf2 pathway regulation. Show less

Cisplatin was the first metal-based therapeutic agent approved for the treatment of human cancers, but its clinical activity is greatly limited by tumor drug resistance. This work utilized the parent complex [Ru(phen)2(PIP)](2+) (1) to develop three Ru(II) complexes (2-4) with different positional modifications. These compounds exhibited similar or superior cytotoxicities compared to cisplatin in HeLa, A549 and multidrug-resistant (A549R) tumor cell lines. Complex 4, the most potent member of the series, was highly active against A549R cancer cells (IC50 = 0.8 μM). This complex exhibited 178-fold better activity than cisplatin (IC50 = 142.5 μM) in A549R cells. 3D multicellular A549R tumor spheroids were also used to confirm the high proliferative and cytotoxic activity of complex 4. Complex 4 had the greatest cellular uptake and had a tendency to accumulate in the mitochondria of A549R cells. Further mechanistic studies showed that complex 4 induced A549R cell apoptosis via inhibition of thioredoxin reductase (TrxR), elevated intracellular ROS levels, mitochondrial dysfunction and cell cycle arrest, making it an outstanding candidate for overcoming cisplatin resistance. Show less

Ruthenium(II) polypyridyl complexes can intercalate DNA with high affinity and prevent cell proliferation; however, the direct impact of ruthenium-based intercalation on cellular DNA replication remains unknown. Here we show the multi-intercalator [Ru(dppz)2(PIP)](2+) (dppz = dipyridophenazine, PIP = 2-(phenyl)imidazo[4,5-f][1,10]phenanthroline) immediately stalls replication fork progression in HeLa human cervical cancer cells. In response to this replication blockade, the DNA damage response (DDR) cell signalling network is activated, with checkpoint kinase 1 (Chk1) activation indicating prolonged replication-associated DNA damage, and cell proliferation is inhibited by G1-S cell-cycle arrest. Co-incubation with a Chk1 inhibitor achieves synergistic apoptosis in cancer cells, with a significant increase in phospho(Ser139) histone H2AX (γ-H2AX) levels and foci indicating increased conversion of stalled replication forks to double-strand breaks (DSBs). Normal human epithelial cells remain unaffected by this concurrent treatment. Furthermore, pre-treatment of HeLa cells with [Ru(dppz)2(PIP)](2+) before external beam ionising radiation results in a supra-additive decrease in cell survival accompanied by increased γ-H2AX expression, indicating the compound functions as a radiosensitizer. Together, these results indicate ruthenium-based intercalation can block replication fork progression and demonstrate how these DNA-binding agents may be combined with DDR inhibitors or ionising radiation to achieve more efficient cancer cell killing. Show less

A new pseudo-octahedral π-arene ruthenium(ii) piano-stool compound, containing an O,S-bidentate ligand (compound 1) and showing significant cytotoxic activity in vitro, was synthesized and characterized. In solution stability and interaction with the model protein bovine pancreatic ribonuclease (RNase A) were investigated by using UV-Vis absorption spectroscopy. Its crystal structure and that of the adduct formed upon reaction with RNase A were obtained by X-ray crystallography. The comparison between the structure of purified compound 1 and that of the fragment bound to RNase A reveals an unusual mode of protein binding that includes ligand exchange and alteration of coordination sphere geometry. Show less

Organelle-targeted photosensitizers have been reported to be effective photodynamic therapy (PDT) agents. In this work, we designed and synthesized two iridium(III) complexes that specifically stain the mitochondria and lysosomes of living cells, respectively. Both complexes exhibited long-lived phosphorescence, which is sensitive to oxygen quenching. The photocytotoxicity of the complexes was evaluated under normoxic and hypoxic conditions. The results showed that HeLa cells treated with the mitochondria-targeted complex maintained a slower respiration rate, leading to a higher intracellular oxygen level under hypoxia. As a result, this complex exhibited an improved PDT effect compared to the lysosome-targeted complex, especially under hypoxia conditions, suggestive of a higher practicable potential of mitochondria-targeted PDT agents in cancer therapy. Show less

A new mononuclear rhodium(III) complex, [Rh(bzimpy)Cl₃] (bzimpy = 2,6-bis(2-benzimidazolyl)pyridine), was synthesized and characterized by elemental analysis and spectroscopic methods. The molecular structure of the complex was confirmed by single-crystal X-ray crystallography. The interaction of the complex with fish sperm DNA (FS-DNA) was investigated by UV spectroscopy, emission titration, and viscosity measurement in order to evaluate the possible DNA-binding mode and to calculate the corresponding DNA-binding constant. The results reveal that the Rh(III) complex interacts with DNA through groove binding mode with a binding affinity on the order of 10⁴. In addition, the binding of the Rh(III) complex to bovine serum albumin (BSA) was monitored by UV-Vis and fluorescence emission spectroscopy at different temperatures. The mechanism of the complex interaction was found to be static quenching. The thermodynamic parameters (ΔH, ΔS, and ΔG) obtained from the fluorescence spectroscopy data show that van der Waals interactions and hydrogen bonds play a major role in the binding of the Rh(III) complex to BSA. For the comparison of the DNA- and BSA-binding affinities of the free bzimpy ligand with its Rh(III) complex, the absorbance titration and fluorescence quenching experiments of the free bzimpy ligand with DNA and BSA were carried out. Competitive experiments using eosin Y and ibuprofen as site markers indicated that the complex was mainly located in the hydrophobic cavity of site I of the protein. These experimental results were confirmed by the results of molecular docking. Finally, the in vitro cytotoxicity properties of the Rh(III) complex against the MCF-7, K562, and HT-29 cell lines were evaluated and compared with those of the free ligand (bzimpy). It was found that the complexation process improved the anticancer activity significantly. Show less

A rhodium(iii) complex, [Rh(MQ)(DMSO)₂Cl₂] (1), with 8-hydroxy-2-methylquinoline as the ligand was synthesized and characterized. Complex 1 exhibited cytotoxicity against BEL-7404, Hep-G2, NCI-H460, T-24, and A549 cell lines with IC₅₀ values in the micromolar range (6.52-17.86 μM). Various experiments on the Hep-G2 cells showed that complex 1 caused cell cycle arrest at the S phase, downregulation of cdc25 A, cyclin A, cyclin B and CDK2, and upregulation of p21, p27 and p53. Furthermore, cytotoxicity mechanism studies suggested that complex 1-induced apoptosis was achieved via disruption of the mitochondrial function, which led to a significant loss of the mitochondrial membrane potential, an increase in the cellular levels of reactive oxygen species, cytochrome c, and apaf-1, and a fluctuation of the intracellular Ca²⁺ concentration. Taken altogether, complex 1 can trigger cancer cell death by inducing apoptosis through a mitochondrial dysfunction pathway. Show less

A new ruthenium methylimidazole complex [Ru(MeIm)4(p-cpip)](2+) (Ru1, p-cpip=2-(4-chlorophenyl)-1H-imidazo[4,5-f][1,10]phenanthroline, MeIm=1-methylimidazole) has been synthesized and characterized. The cellular uptake, in vitro cytotoxicities, cell cycle arrest and apoptosis-inducing mechanism of this Ru(II) complex have been extensively explored by Inductively Coupled Plasma Mass Spectrometry (ICP-MS), 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay, flow cytometry, Comet assay, inverted fluorescence microscope as well as Western blotting experimental techniques. Notably, Ru1 displayed relatively high cytotoxic activity against lung cancer A549 cells and had high selectivity between tumor and normal cells in comparison with cisplatin. Further studies showed that Ru1 caused cell cycle arrest at G0/G1 phase and induced apoptosis via the mitochondrial pathway, which involved reactive oxygen species (ROS) accumulation, mitochondrial dysfunction and Bcl-2 and caspase correlative family member activation. For providing more information about the possible antitumor mechanism, the in vitro DNA binding studies have been also investigated by different spectrophotometric methods, thermal denaturation and viscosity measurements. Show less

Hypoxia is the critical feature of the tumor microenvironment that is known to lead to resistance to many chemotherapeutic drugs. Six novel ruthenium(II) anthraquinone complexes were designed and synthesized; they exhibit similar or superior cytotoxicity compared to cisplatin in hypoxic HeLa, A549, and multidrug-resistant (A549R) tumor cell lines. Their anticancer activities are related to their lipophilicity and cellular uptake; therefore, these physicochemical properties of the complexes can be changed by modifying the ligands to obtain better anticancer candidates. Complex 1, the most potent member of the series, is highly active against hypoxic HeLa cancer cells (IC50 =0.53 μM). This complex likely has 46-fold better activity than cisplatin (IC50 =24.62 μM) in HeLa cells. This complex tends to accumulate in the mitochondria and the nucleus of hypoxic HeLa cells. Further mechanistic studies show that complex 1 induced cell apoptosis during hypoxia through multiple pathways, including those of DNA damage, mitochondrial dysfunction, and the inhibition of DNA replication and HIF-1α expression, making it an outstanding candidate for further in vivo studies. Show less

Five Ru(II)-N-heterocyclic carbenes (NHC) (1-5) were synthesized by reacting the appropriately substituted imidazolium chlorides with Ag2O, forming the NHC-silver chloride in situ followed by transmetalation with dimeric p-cymene ruthenium(II) dichloride. All the complexes were characterized by NMR and ESI-MS, and complex 1 was also characterized by single-crystal X-ray diffraction. The IC50 values of these five complexes were determined by the MTT-based assay on four human cancer cell lines, SKOV-3 (ovarian), PC-3 (prostate), MDA-MB-231 (breast) and EC109 (esophagus). The cytotoxicities of these complexes changed from a moderate effect to a fine one, corresponding to the increasing lipophilicity order of the complex of 2 < 1 < 3 < 4 < 5 (0.91, 0.88, 1.36, 1.85 and 2.62 for 1–5 respectively). Complex 5 showed the most cytotoxicity with the IC50 values 10.3 ± 0.3 μM for SKOV-3, 2.9 ± 0.1 μM for PC-3, 8.2 ± 0.6 μM for MDA-MB-231, 6.4 ± 0.2 μM for EC109 cell lines. Due to the superior cytotoxicity of complex 5 against the PC-3 cell lines, further biological evaluations were carried out to elucidate its action mechanism. The morphologic changes and cell cycle analysis showed that complex 5 can inhibit PC-3 cell lines by inducing cell cycle arrest at the G2/M phase. The DNA binding experiments further demonstrate that complex 5 has a better binding ability for DNA (Kb = 2.2 × 10(6) M(-1)) than complexes 1-4 (3.8 × 10(5), 7.0 × 10(5), 5.7 × 10(5), and 1.9 × 10(5) respectively). Show less

This study investigated the photodynamic therapy (PDT) and anticancer activity of mixed ligand Ru(ii) terpyridyl complexes (Ru1-Ru3). The photophysical and photochemical properties, hydrophobic properties, DNA binding and DNA transcription inhibition abilities, cell uptake efficiency, cellular localization and photo-cytotoxicity were investigated. Ru1-Ru3 exhibited red luminescence between 670-710 nm and functioned as photo-sensitizers (PSs) by generating both singlet oxygen and radical ions. Without light activation, Ru1-Ru3 were located at the cytoplasm and were nontoxic to cells. However, upon light activation, Ru1-Ru3 exhibited significant photocytotoxicity. After PDT treatment, mitochondria alteration and nuclear membrane disruption occurred, which resulted in relocalization of the complexes from the cytoplasm to the nucleus. Moreover, high cellular oxidative stress caused cell necrocytosis after PDT treatment. Show less

Ruthenium complexes have been considered as promising substitutes for cisplatin in cancer chemotherapy. However, novel ruthenium-based therapies are faced with some limitations, such as unimpressive cytotoxicity toward solid tumors. Herein, we designed and synthesized phenyl-substituted terpyridyl ruthenium(ii) complexes ([Ru(tpy)(bpy)Cl](+) (Ru1), [Ru(phtpy)(bpy)Cl](+) (Ru2) and [Ru(biphtpy)(bpy)Cl](+) (Ru3)) which exhibited distinctly different anticancer activity. Ru1-Ru3 all underwent moderate aquation in buffer solution and this process was significantly inhibited by high chloride concentration. Cancer cells were found to readily uptake the relatively hydrophobic Ru3, as quantified using inductively coupled plasma mass spectrometry (ICP-MS). Ru1 was found to be non-cytotoxic (IC50 > 100 μM) while Ru3 exhibited very promising cytotoxicity on both two-dimensional (2D) cancer cell monolayers and 3D MCTSs. An antiproliferative assay revealed that Ru3 significantly inhibited cellular DNA replication which ultimately induced apoptosis of cancer cells. Show less