Ru(ii)arene(N^N bpy/phen)-based RAPTA complexes for in vitro anti-tumour activity in human glioblastoma cancer cell lines and in vivo toxicity studies in a zebrafish model

Intracellular Photocatalytic NADH/NAD(P)H Oxidation for Cancer Drug Development

Photocatalytic cancer therapy (PCT) has emerged as a cutting-edge anticancer mechanism of action, harnessing light energy to mediate the catalytic oxidation of intracellular substrates. PCT is of significant current importance due to its potential to address the limitations of conventional chemotherapy, particularly drug resistance and side effects. This approach offers a noninvasive, targeted cancer treatment option by utilizing metal-based photocatalysts to induce redox and metabolic disorders within cancer cells. The photocatalysts disrupt the cancer cell metabolism by converting NADH/NAD(P)H to NAD+/NAD(P)+ via catalytic photoredox processes, altering intracellular NAD+/NADH or NAD(P)+/NAD(P)H ratios, which are crucial for cellular metabolism. Ir(III), Ru(II), Re(I), and Os(II) photocatalysts demonstrated promising PCT efficacy. Despite these developments, gaps remain in the literature for translating this new anticancer mechanism into clinical trials. This Perspective critically examines the developments in this research area and provides future directions for designing efficient photocatalysts for PCT.

RuIII-Morpholine-Derived Thiosemicarbazone-Based Metallodrugs: Lysosome-Targeted Anticancer Agents

The idea of coordinating biologically active ligand systems to metal centers to exploit their synergistic effects has gained momentum. Therefore, in this report, three RuIII complexes 1-3 of morpholine-derived thiosemicarbazone ligands have been prepared and characterized by spectroscopy and HRMS along with the structure of 2 through a single-crystal X-ray diffraction study. The solution stability of 1-3 was tested using conventional techniques such as UV-vis and HRMS. Further, the anticancer activity of 1-3 was tested in HT-29 and HeLa cancer cell lines. To gain insight into their mechanism of action, the cytotoxicity, hydrophobicity, and the interaction of 1-3 with DNA and HSA were evaluated by different conventional methods such as absorption, fluorescence, and circular dichroism studies. Along with favorable biomolecule interaction, 1-3 revealed potent selectivity toward cancer cells, which is a prerequisite for the generation of an anticancer drug. According to cell viability results, 1 has the highest cytotoxicity among all in the group, against both cells, respectively. Additionally, the fluorescence-active ruthenium complexes selectively target lysosomes, which is evaluated by live-cell imaging. 1-3 disrupt the lysosome membrane potential by generating an excessive amount of reactive oxygen species, which results in an apoptotic mode of cell death.

Discovery of Arene Ruthenium(II) Complexes as Potential VEGF Inhibitors for Glioblastoma Metastasis Suppression

Developing drugs for treating glioblastoma has been a significant challenge. Herein, a series of arene ruthenium(II) complexes have been synthesized and investigated as potential candidates to suppress the proliferation and metastasis of glioblastoma. It is found that para-substituent-modified molecules, especially 6, exhibit higher antitumor activity than ortho-substituents. Further studies show that 6 can trigger tumor cell autophagy by regulating the PI3K/AKT/mTOR pathway. Moreover, it is also found that 6 can induce DNA damage in glioblastoma cells through binding and stabilizing VEGF G-quadruplex DNA. Furthermore, it is confirmed that 6 can inhibit the proliferation and metastasis of U87-MG glioblastoma cell in situ xenograft in the zebrafish model. Hence, arene ruthenium(II) complexes can be developed as promising therapeutic agents for glioblastoma treatment in the future.

Exploring the phototoxicity of GSH-resistant 2-(5,6-dichloro-1H-benzo[d]imidazol-2-yl)quinoline-based Ir(III)-PTA complexes in MDA-MB-231 cancer cells

Metal complexes play a crucial role in photo-activated chemotherapy (PACT), which has recently been used to treat specific disorders. Triple-negative breast cancer has an enormously high rate of relapse due to the existence and survival of cancer stem cells (CSCs) characterized by increased amounts of glutathione (GSH). Hence, designing a phototoxic molecule is an enticing area of research to combat triple-negative breast cancer (TNBC) via GSH depletion and DNA photocleavage. Herein, we focus on the application of PTA and non-PTA Ir(III) complexes for phototoxicity in the absence and presence of GSH against MDA-MB-231 TNBC cells. Between these two complexes, [Cp*IrIII(DD)PTA]·2Cl (DDIRP) exhibited better phototoxicity (IC50 ∼ 2.80 ± 0.52 μM) compared to the non-PTA complex [Cp*IrIII(DD)Cl]·Cl (DDIR) against TNBC cells because of the high GSH resistance power of the complex DDIRP. The significant potency of the complex DDIRP under photo irradiation in both normoxia and hypoxia conditions can be attributed to selective transportation, high cellular permeability and uptake towards the nucleus, GSH depletion by GSH-GSSG conversion, the ability of strong DNA binding including intercalation, and oxidative stress. The strong affinity to serum albumin, which serves as a carrier protein, aids in the transport of the complex to its target site while preventing glutathione (GSH) deactivation. Consequently, the complex DDIRP was developed as a suitable phototoxic complex in selective cancer therapy, ruling over the usual chemotherapeutic drug cisplatin and the PDT drug Photofrin. The ability of ROS generation under hypoxic conditions delivers this complex as a hypoxia-efficient selective metallodrug for the treatment of TNBC.

Synthesis of novel rapanone derivatives via organocatalytic reductive C-alkylation: biological evaluation of antioxidant properties, in vivo zebrafish embryo toxicity, and docking studies

A biologically crucial natural product rapanone 1 was isolated from Embelia ribes at the gram scale with excellent purity. Semi-synthetic analogs of 1 semi-synthesized through reductive C-alkylation could increase the therapeutic value of the compounds. Herein, a new synthetic methodology was developed as a single-step reductive C-alkylation protocol using a metal-free, room-temperature-based reaction condition that can be scaled up to gram-scale synthesis with an excellent yield of up to 93%. A straightforward purification protocol was employed for the product obtained by this method. The derivatives of 1 showed antioxidant activity, which was evaluated using DPPH and ABTS scavenging assays. Compounds 5a-5ze showed an IC50 value of 2.48-3.37 μM and 1.81-3.12 μM. Substitution by electron-donating groups on the quinone moiety seems to play an essential role in the increased antioxidant activity of compounds 5a-5i, 5v, 5w, 5zc, and 5z. Further, the in vivo embryotoxicity of 1 and its derivatives was analyzed in a zebrafish-based aquatic toxicology model. Zebrafish embryos were exposed to 1 and 5a-5ze at 20 to 160 μM concentrations. They showed reduced toxicity and a survival rate of 90-98% after 96 hpf of treatment; similarly, the compounds 5a-5i, 5v, 5w, 5zc, and 5zd did not significantly affect the hatching rates of 75.66-85.33% or developmental abnormalities of the embryos after 48 hpf of treatment. In silico molecular docking studies for the parent compound, along with its derivatives 5a-5i, 5v-5w, 5zc-5zd, and standard l-ascorbic acid (l-Aa) indicated favorable interactions with the active site of the crystal structure, coupled with the assay protein PDB:1ZB6, which was responsible for the observed biological understanding and potential.

Design of an anticancer organoruthenium complex as the guest and polydiacetylene-coated fluorogenic nanocarrier as the host: engineering nanocarrier using ene-yne conjugation for sustained guest release, enhanced anticancer activity and reduced in vivo toxicity

Despite the enormous efforts made over the past two decades to develop metallodrugs and nanocarriers for metallodrug delivery, there are still few precise strategies that aim to optimize the design of both metallodrugs and metallodrug carriers jointly in a concerted effort. In this work, three half-sandwich ruthenium(II) complexes with pyridylimidazo[1,5-a]pyridine ligand functionalized with polycyclic aromatic moiety (Ru(nap), Ru(ant), Ru(pyr)) are evaluated as possible anticancer candidates and polydiacetylene (PDA)-coated amino-functionalized mesoporous silica nanoparticles (AMSNs) are designed as a functional nanocarrier for drug delivery. Ru(pyr) exhibits higher cytotoxicity in HT-29 colorectal cancer cells compared to other complexes and cis-platin, but it does not exhibit better cellular uptake. Ru(pyr) is found to be preferentially accumulated in plasma, mitochondria, and ER-Golgi membrane. The complex induces cell cycle arrest in the G0/G1 phase, while higher concentrations cause programmed cell death via apoptosis. Ru(pyr) influences cancer cell adhesion property and acts as an antioxidant in HT-29 cells. In order to modulate the anticancer potency of Ru(pyr), AMSNs are used to encapsulate the complex, and then diacetylene self-assembly is allowed to deposit on the surface of the nanoparticles. Subsequently, the nanoparticles undergo topopolymerization, which results in π-conjugated PDA-Ru(pyr)@AMSNs. Owing to the ene-yne polymeric skeleton in the backbone, the non-fluorescent AMSNs turn into red-emissive particles, which are exploited for cell imaging applications. The release profile analysis reveals that such a π-conjugated polymer prevents the premature release of the complex from porous silica nanoparticles with the accelerated release of the complex in an acidic medium compared to physiological conditions. The PDA gatekeepers have also been proven to enhance the cellular internalization of Ru(pyr) with slow continuous release from the nanoformulation. Zebrafish embryo toxicity analysis suggests that the PDA-coated nanocarriers could be suitable candidates for in vivo investigations.

4-Oxo-7-fluoro-1,10-phenanthroline-2,9-diamides: Synthesis, Structural Features, Lanthanide Complexes, and Am(III)/Ln(III) Solvent Extraction

A highly efficient synthetic approach was developed for the synthesis of unsymmetrical 1,10-phenanthroline-2,9-diamides with two different substituents in the fourth and seventh positions of the phenanthroline core. The structures of these ligands were confirmed using various spectral methods including 2D-NMR and X-ray analysis. Quantum chemical calculations supported the presence of tautomeric forms of these ligands. Furthermore, it was discovered that these compounds exhibit polydentate ligand behavior toward lanthanide nitrates. The structural characteristics of the complexes formed between these ligands and lanthanide nitrates were investigated both in the solid state and in solution. To further understand the binding properties of these novel unsymmetrical ligands, the binding constants for potential complexes were quantitatively measured by using UV-vis spectrophotometric titration. This allowed for a comprehensive analysis of the binding affinity and stability of these complexes. Extraction experiments of f-elements were performed for symmetrical and unsymmetrical diamides. Overall, this study presents significant advancement in the synthesis and characterization of unsymmetrical 1,10-phenanthroline-2,9-diamides and provides valuable insights into their potential applications as polydentate ligands for lanthanide nitrates.

Evaluation of the Antiproliferative Properties of CpRu Complexes Containing N-Methylated Triazaphosphaadamantane Derivatives

Piano-stool-{CpRu} complexes containing 1,3,5-triaza-7-phosphaadamantane (PTA), N-methyl-1,3,5-triaza-7-phosphaadamantane (mPTA), and 3,7-dimethyl-1,3,7-triaza-5-phosphabyciclo[3.3.1]nonane (dmoPTA) were evaluated as drugs against breast cancer. The evaluated compounds include two new examples of this family, the complexes [RuCp(DMSO-κS)(HdmoPTA)(PPh3)](CF3SO3)2 (8) and [RuCp(PPh3)2-µ-dmoPTA-1κP-2κ2N,N'-PdCl2](CF3SO3) (11), which have been synthesized and characterized by NMR, IR, and single-crystal X-ray diffraction. The cytotoxic activity of compounds was evaluated against MDA-MB-231 breast cancer cells, and the three most active complexes were further tested against the hormone-dependent MCF-7 breast cancer cell line. Their cell death mechanism and ruthenium uptake were also evaluated, as well as their binding ability to human serum albumin.

Reactivity of non-organometallic ruthenium(II) polypyridyl complexes and their application as catalysts for hydride transfer reactions

Recently, we investigated the substitution behavior of a series of ruthenium(II) complexes of the general formula [RuII(terpy)(N∧N)Cl]Cl, where terpy = 2,2′:6′,2″-terpyridine, N∧N = bidentate ligand, in aqueous solutions. We have shown that the most and least reactive complexes of the series are [RuII(terpy)(en)Cl]Cl (en = ethylenediamine) and [RuII(terpy)(phen)Cl]Cl (phen = 1, 10-phenantroline), respectively, as a result of different electronic effects provided by the bidentate spectator chelates. Polypyridyl amine Ru(II) complex, viz. [Ru(terpy)(en)Cl]Cl and [Ru(terpy)(ampy)Cl]Cl (where ampy = 2-(aminomethyl)pyridine), in which the terpy chelate labilizes the metal center, are able to catalyze the conversion of NAD+ to 1,4-NADH using sodium formate as a source of hydride. We showed that this complex can control the [NAD+]/[NADH] ratio and potentially induce reductive stress in living cells, which is accepted as an effective method to kill cancer cells. Polypyridyl Ru(II) complexes, characterized in terms of the behavior in aqueous solutions, can be used as model systems to monitor heterogeneous multiphase ligand substitution reactions at the solid-liquid interface. Colloidal coordination compounds in the submicron range were synthesized from Ru(II)-aqua derivatives of starting chlorido complexes via the anti-solvent procedure and stabilized by a surfactant shell layer.

Competitive binding studies of the nucleosomal histone targeting drug, [Ru(η6-p-cymene)Cl2(pta)] (RAPTA-C), with oligonucleotide-peptide mixtures

Protein crystallography and biochemical assays reveal that the organometallic drug, [Ru(η⁶-p-cymene)Cl₂(pta)] (RAPTA-C), preferentially binds to nucleosomal histone proteins in chromatin. To better understand the binding mechanism we report here a mass spectrometric-based competitive binding study between a model peptide from the acidic patch region of the H2A histone protein (the region where RAPTA-C is known to bind) and an oligonucleotide. In contrast to the protein crystallography and biochemical assays, RAPTA-C preferentially binds to the oligonucleotide, confirming that steric factors, rather than electronic effects, primarily dictate binding of RAPTA-C to histone proteins within the nucleosome.