Selection of Ruthenium Polypyridyl Complex-Modified Aptamers for Photodynamic Therapy against Streptococcus Pneumonia.

Design and synthesis of new ruthenium polypyridyl complexes with potent antitumor activity in vitro.

A series of ruthenium(II) polypyridyl complexes were synthesized and evaluated for their in vitro anticancer activities. The results showed that ruthenium polypyridyl complexes, especially [Ru(bpy)2 (p-tFPIP)](2+) (2 a; bpy=bipyridine, tFPIP=2-(2-trifluoromethane phenyl)imidazole[4,5-f][1,10]phenanthroline), exhibited novel anticancer activity against human cancer cell lines, but with less toxicity to a human normal cell line. The results of flow cytometry and caspase activities analysis indicated that the 2 a-induced growth inhibition against MG-63 osteosarcoma cells was mainly caused by mitochondria-mediated apoptosis. DNA fragmentation and nuclear condensation as detected by TUNEL-DAPI co-staining further confirmed 2 a-induced apoptotic cell death. Further, fluorescence imaging revealed that ruthenium(II) polypyridyl complexes could target mitochondria to induce mitochondrial fragmentation, accompanied by depletion of mitochondrial membrane potential. Taken together, these findings suggest a potential application of theses ruthenium(II) complexes in the treatment of cancers.

Ruthenium complexes, and especially ruthenium(II) polypyridyl complexes, have attracted a lot of attention as potential photosensitizers for photodynamic therapy. However, some are unsuitable due to their low cellular uptake, potentially due to their relatively low degree of lipophilicity, which prevents them from penetrating tumor cells. Here, we report the conjugation of a non-cell-penetrating ruthenium polypyridyl complex, [Ru(bipy)2-dppz-7-hydroxymethyl][PF6]2 (bipy = 2,2’-bipyridine, dppz = dipyrido[3,2-a:2;2’,3’-c]phenazine) (RuOH), to a highly hydrophobic biodegradable and biocompatible polylactide to enhance its cellular uptake. The ruthenium-polylactide conjugates were prepared by drug-initiated ring-opening polymerization of lactide through the formation of a zinc alkoxide initiator and formulated into nanoparticles by nanoprecipitation. They were characterized by means of nuclear magnetic resonance spectroscopy (NMR), matrix-assisted laser desorption/ionization – time of flight mass spectrometry (MALDI-TOF MS) and dynamic light scattering (DLS). Finally, their photo-therapeutic activity (λexc = 480 nm, 3.21 J cm-2) in cancerous human cervical carcinoma (HeLa) and non-cancerous retinal pigment epithelium (RPE-1) cells was tested alongside that of RuOH and their cellular uptake in HeLa cells was assessed by confocal microscopy and inductively coupled plasma - mass spectrometry (ICP-MS). All nanoparticles showed improved photophysical properties including luminescence and singlet oxygen generation, enhanced cellular uptake and, capitalizing on this, an improved photo-toxicity.

The ruthenium(ii) polypyridyl complexes (RPCs), [(phen)2Ru(tatpp)]2+ (32+ ) and [(phen)2Ru(tatpp)Ru(phen)2]4+ (44+ ) are shown to cleave DNA in cell-free studies in the presence of a mild reducing agent, i.e. glutathione (GSH), in a manner that is enhanced upon lowering the [O2]. Reactive oxygen species (ROS) are involved in the cleavage process as hydroxy radical scavengers attenuate the cleavage activity. Cleavage experiments in the presence of superoxide dismutase (SOD) and catalase reveal a central role for H2O2 as the immediate precursor for hydroxy radicals. A mechanism is proposed which explains the inverse [O2] dependence and ROS data and involves redox cycling between three DNA-bound redox isomers of 32+ or 44+ . Cultured non-small cell lung cancer cells (H358) are sensitive to 32+ and 44+ with IC50 values of 13 and 15 μM, respectively, and xenograft H358 tumors in nude mice show substantial (∼80%) regression relative to untreated tumors when the mice are treated with enantiopure versions of 32+ and 44+ (Yadav et al. Mol Cancer Res, 2013, 12, 643). Fluorescence microscopy of H358 cells treated with 15 μM 44+ reveals enhanced intracellular ROS production in as little as 2 h post treatment. Detection of phosphorylated ATM via immunofluorescence within 2 h of treatment with 44+ reveals initiation of the DNA damage repair machinery due to the ROS insult and DNA double strand breaks (DSBs) in the nuclei of H358 cells and is confirmed using the γH2AX assay. The cell data for 32+ is less clear but DNA damage occurs. Notably, cells treated with [Ru(diphenylphen)3]2+ (IC50 1.7 μM) show no extra ROS production and no DNA damage by either the pATM or γH2AX even after 22 h. The enhanced DNA cleavage under low [O2] (4 μM) seen in cell-free cleavage assays of 32+ and 44+ is only partially reflected in the cytotoxicity of 32+ and 44+ in H358, HCC2998, HOP-62 and Hs766t under hypoxia (1.1% O2) relative to normoxia (18% O2). Cells treated with RPC 32+ show up to a two-fold enhancement in the IC50 under hypoxia whereas cells treated with RPC 44+ gave the same IC50 whether under hypoxia or normoxia.

The inexorable and rapid rise of antimicrobial resistance in various Gram-positive and Gram-negative bacteria strains is severely compromising our global healthcare system. Facing a diminishing quantity of effective antibiotics against the threat, alternative therapeutics and drugs such as photodynamic therapy and antibacterial photosensitisers are vital in treating bacterial infections. Multiple reports of ruthenium(II) polypyridyl complexes possessing antibacterial activities make them attractive candidates as potential antibacterial photosensitisers. The present work reports the synthesis of a series of novel ruthenium(II) polypyridyl complexes conjugated with bis-dipicolylamine derivatives and their assessments as membrane-targeting antibacterial photosensitisers. Of the four conjugated complexes synthesised, conjugated complexes 4a and 4b were foundto be bactericidal against methicillin-susceptible Staphylococcus aureus (ATCC 35923) and bacteriostatic against methicillin-resistant Staphylococcus aureus (MRSA) (ATCC 43300) strains witha minimum inhibition concentration of 64µM under irradiated conditions. Conjugated complexes 4a, 4b and 4d were active against Gram-negative bacteria, Escherichia coli (ATCC BAA-196) at 128µM in both irradiated and non-irradiated conditions. The conjugated complexes 4a and 4b were observed to have some bacterial interaction uponexcitation at 559 nm wavelength viewed under fluorescence microscope at ×600nm magnification. The findings demonstrated the capability of ruthenium(II) polypyridyl complexes conjugated with bis-dipicolylamine as possible theranostics agents due to their fluorescence properties and their antibacterial activities through photosensitisation.

To address the challenges associated with the low cellular uptake efficiency of metal-based anticancer agents and the suboptimal therapeutic efficacy of photodynamic therapy (PDT), a series of polypyridyl ruthenium(II) complexes (Ru-Cn) with tunable carbon chain lengths were rationally designed and synthesized through the incorporation of fatty acid moieties, which confer enhanced lipid solubility and membrane-targeting capabilities. Among these, the octadecanoic acid-modified ruthenium complex (Ru-C18) exhibited superior anticancer activity. Cytotoxicity assays demonstrated that Ru-C18 displayed sub-molar cytotoxic potency under light irradiation. Co-localization studies confirmed its preferential accumulation in lysosomes after cellular internalization. Upon light activation, Ru-C18 efficiently generated singlet oxygen and induced hallmark features of pyroptosis, including plasma membrane blebbing, cellular swelling, and gasdermin-dependent membrane pore formation. Consequently, Ru-C18 significantly suppressed tumor cell proliferation via activation of the pyroptotic pathway. These findings offer new insights into the rational design of highly effective and selectively targeted photodynamic anticancer agents.

As an ideal scaffold for metal ion chelation, 8-hydroxyquinoline (8HQ) can chelate different metal ions, such as Fe2+, Cu2+, Zn2+, etc. Here, by integrating 8HQ with a ruthenium(II) polypyridyl moiety, two Ru(II)-8HQ complexes (Ru1 and Ru2), [Ru(N-N)2L](PF6)2 (L = 2-(1H-imidazo[4,5-f][1,10]phenanthrolin-2-yl)quinolin-8-ol; N-N: 2,2'-bipyridine (bpy, in Ru1), 1,10-phenanthroline (phen, in Ru2)) were designed and synthesized. In both complexes, ligand L is an 8HQ derivative designed to chelate the cofactor Fe2+ of jumonji C domain-containing demethylase (JMJD). As expected, Ru1 and Ru2 could inhibit the activity of JMJD by chelating the key cofactor Fe2+ of JMJD, resulting in the upregulation of histone-methylation levels in human lung cancer (A549) cells, and the upregulation was more pronounced under light conditions. In addition, MTT data showed that Ru1 and Ru2 exhibited lower dark toxicity, and light irradiation could significantly enhance their antitumor activity. The marked photodynamic activities of Ru1 and Ru2 could induce the elevation of reactive oxygen species (ROS), depolarization of mitochondrial membrane potential (MMP), and activation of caspases. These mechanistic studies indicated that Ru1 and Ru2 could induce apoptosis through the combination of JMJD inhibitory and PDT activities, thereby achieving dual antitumor effects.

Nanophotosensitive drugs for light-based cancer therapy: what does the future hold?

Synthesis, photochemistry, and electrochemistry of ruthenium(II) polypyridyl complexes anchored by dicobalt carbonyl units

In the fight against cancer, photodynamic therapy is generating great interest thanks to its ability to selectively kill cancer cells without harming healthy tissues. In this field, ruthenium(II) polypyridyl complexes, and more specifically, complexes with dipyrido[3,2-a:2',3'-c]phenazine (dppz) as a ligand are of particular interest due to their DNA-binding and photocleaving properties. However, ruthenium(II) polypyridyl complexes can sometimes suffer from low lipophilicity, which hampers cellular internalisation through passive diffusion. In this study, four new [Ru(dppz-X2 )3 ]2+ complexes (X=H, F, Cl, Br, I) were synthesized and their lipophilicity (logP), cytotoxicity and phototoxicity on cancerous and noncancerous cell lines were assessed. This study shows that, counterintuitively, the phototoxicity of these complexes decreases as their lipophilicity increases; this could be due solely to the atomic radius of the halogen substituents.

Trinuclear ruthenium(II) polypyridyl complexes: Evaluation as photosensitizers for enhanced cervical cancer treatment

Emerging Designs of Aggregation-Induced Emission Agents for Enhanced Phototherapy Applications

Synthesis, characterization and biological properties of Ruthenium(II) polypyridyl complexes containing 2(1H)-quinolinone-3(1H-imidazo[4,5f][1,10]phenanthrolin-2-yl

A lysosome-targeted ruthenium(II) polypyridyl complex as photodynamic anticancer agent

Photodynamic therapy (PDT) is a noninvasive medical technique that has received increasing attention over the last years and been applied for the treatment of certain types of cancer. However, the currently clinically used PDT agents have several limitations, such as low water solubility, poor photostability, and limited selectivity towards cancer cells, aside from having very low two‐photon cross‐sections around 800 nm, which limits their potential use in TP‐PDT. To tackle these drawbacks, three highly positively charged ruthenium(II) polypyridyl complexes were synthesized. These complexes selectively localize in the lysosomes, an ideal localization for PDT purposes. One of these complexes showed an impressive phototoxicity index upon irradiation at 800 nm in 3D HeLa multicellular tumor spheroids and thus holds great promise for applications in two‐photon photodynamic therapy.