KP1019, a new redox-active anticancer agent--preclinical development and results of a clinical phase I study in tumor patients

Ruthenium(II)-mercapto complexes induce cell damage via apoptosis pathway on ovarian cancer cells

Ovarian cancer represents a leading cause of cancer-related deaths in women worldwide. Chemotherapeutic agents are usually employed to treat the patients, and Ruthenium(II)-based compounds have been investigated as possible substitutes for platinum drugs. In this work, we studied three different Ru(II)-phosphine-mercapto complexes (1-3) as potential cytotoxic agents against A2780 and A2780-cisR ovarian cancer cells. A time-dependent cytotoxicity was observed for 2, which also exhibited better selectivity than cisplatin control. A similar cytotoxic behavior was observed on 3D tumor spheroids. Although no changes were observed in cell cycle distribution, compound 2 affected the mitochondrial membrane potential on A2780 cells, and caused cell death via apoptotic pathway, which was confirmed by flow cytometry assay. Western blotting experiments revealed that 2 affected the expression of p53, PCNA, γH2AX and cleaved caspase-3, making it a promising anticancer agent for ovarian cancer.

Ruthenium(II) complexes containing PEGylated N-heterocyclic carbene ligands for tunning biocompatibility in the fight against cancer

A synthetic procedure was designed for the preparation and characterization of Ag and Ru complexes containing NHC ligands functionalized with PEG fragments. Stability studies were conducted to gain insight of the species in water and other solvents like DMSO, or with reagents like imidazole as representative group for histidine amino acid. The presence of Cl atoms instead of H in the 4,5 positions of the N-heterocyclic carbene afforded higher water stability. The complexes containing PEG units must be considered inactive as anticancer agents. To enhance the anticancer activity of PEG-containing complexes, the balance between hydrophilicity and hydrophobicity was adjusted using a silane moiety, and an anionic carbosilane dendrimer as a lipophilic carrier.

Anticancer potential of benzo[b]thiophene functionalized thiosemicarbazone ligands and their organoruthenium complexes

As novel promising anticancer candidates, the piano-stool type complexes of ruthenium, [RuCl(η6-p-cymene)(N,S-Ln)]PF6, K1-4, were synthesized from the reaction of the substituted benzo[b]thiophene based thiosemicarbazone ligands (L1-4) with [{RuCl(η6-p-cymene)}2(μ-Cl)2]. All complexes were fully characterized using elemental analysis, and spectroscopic methods such as FT-IR and 1H NMR. The molecular masses of the complexes were proved by MALDI-TOF analysis. Single crystal X-ray diffraction study was employed in the structural elucidation of complex K1 which shows a distorted octahedral geometry around the Ru(II) ion. Furthermore, spectroscopic methods revealed that in all complexes the ligands are coordinated to the metal center in neutral thione form via N, S donors. In this study, the effect of all ligands, complexes and commercial drugs with a different concentration on the viability of OVCAR-3, A2780 and OSE cells were compared. In this comparison, the cytotoxicity of ruthenium (II) complexes on two ovarian cancer cell lines (human A2780 and human OVCAR-3) was evaluated. For this purpose, the resazurin assay was performed. Based on our studies, complex K2 showed the highest toxicity against OVCAR-3 and A2780 cells. The cytotoxic effect of K2 was found to be higher than that of the commercial anticancer agents Oxalpin and Carbodex, 1.8-34.7-fold for OVCAR-3 cells and 1.9-11.8-fold for A2780 cells, respectively. These results provide insight into the potential of ruthenium (II) complexes as a cytotoxic agent for the treatment of ovarian cancer, particularly for primary tumors.

Triphenylphosphine-Modified IridiumIII, RhodiumIII, and RutheniumII Complexes to Achieve Enhanced Anticancer Selectivity by Targeting Mitochondria

The incorporation of an organelle-targeting moiety into compounds has proven to be an effective strategy in the development of targeted anticancer drugs. We herein report the synthesis, characterization, and biological evaluation of novel triphenylphosphine-modified half-sandwich iridiumIII, rhodiumIII, and rutheniumII complexes. The primary goal was to enhance anticancer selectivity through mitochondrial targeting. All these triphenylphosphine-modified complexes exhibited promising cytotoxicity in the micromolar range (5.13-23.22) against A549 and HeLa cancer cell lines, surpassing the activity of comparative complexes that lack the triphenylphosphine moiety. Noteworthy is their good selectivity toward cancer cells compared to normal BEAS-2B cells, underscored by selectivity index ranging from 7.3 to >19.5. Mechanistically, these complexes primarily target mitochondria rather than interacting with DNA. The targeting of mitochondria and triggering mitochondrial dysfunction were confirmed using both confocal microscopy and flow cytometry. Their ability to depolarize mitochondrial membrane potential (MMP) and enhance reactive oxygen species (ROS) was observed, thereby leading to intrinsic apoptotic pathways. Moreover, these complexes lead to cell cycle arrest in the G2/M phase and demonstrated antimigration effects, significantly inhibiting the migration of A549 cells in wound-healing assays.

Novel tris-bipyridine based Ru(II) complexes as type-I/-II photosensitizers for antitumor photodynamic therapy through ferroptosis and immunogenic cell death

Ru(II) complexes have attracted attention as photosensitizers for their promising photodynamic properties. Herein, novel tris-bipyridine based Ru(II) complexes (6a-e) were synthesized by introducing saturated heterocycles to improve photodynamic properties and lipid-water partition coefficients. Among them, 6d demonstrated significant phototoxicity towards three cancer cells, with IC50 values of 5.66-7.17 μM, exceeding values in dark (IC50s > 100 μM). Under hypoxic conditions, 6d maintained excellent photodynamic activity in A549 cells, with PI values exceeding 24, highlighting its potential for highly effective type-I/-II photodynamic therapy by inducing ROS generation, oxidative stress, and mitochondrial damage. Additionally, it induced ferroptosis and immunogenic cell death of A549 cells by regulating the expression of relevant markers. Finally, 6d remarkably inhibited the growth of A549 transplanted tumor growth by 95.4 %. This Ru(II) complex shows great potential for cancer treatment with its potent photodynamic activity and diverse mechanisms of tumor cell death.

The Elusive Biological Activity of Scorpionates: A Useful Scaffold for Cancer Therapy?

Cancer remains a formidable challenge, requiring the constant pursuit of novel therapeutic agents and strategies. Scorpionates, known for their unique coordination properties, have recently gained attention for their anticancer potential. Traditionally applied in catalysis, these compounds have demonstrated notable cytotoxicity across various cancer cell lines, often surpassing the efficacy of conventional chemotherapeutics. This review addresses recent findings on scorpionate complexes, emphasizing the impact of metal choice and ligand design on biological activity. Copper and ruthenium scorpionates show promise, leveraging redox activity and mitochondrial disruption mechanisms to selectively induce cancer cell death. Ligand modifications, including sulfur-containing heterocycles and unsubstituted pyrazoles, have proven effective in enhancing cytotoxicity and selectivity. Furthermore, dipodal ligands show unique potential, with selective binding sites that improve stability and facilitate specific cellular interactions, such as targeting metastatic pathways. These findings highlight the largely unexplored potential of scorpionate complexes, positioning them as candidates for next-generation anticancer therapies. Continued research into structure-activity relationships and precise mechanisms of action could pave the way for developing highly potent and selective anticancer agents based on scorpionate chemistry.

Tailored Metal-Based Catalysts: A New Platform for Targeted Anticancer Therapies

Innovative strategies for targeted anticancer therapies have gained significant momentum, with metal complexes emerging as tunable catalysts for more effective and safer treatments. Rational design and engineering of metal complexes enable the development of tailored molecular structures optimized for precision oncology. The strategic incorporation of metal complex catalysts within combinatorial therapies amplifies their anticancer properties. This perspective highlights the advancements in synthetic strategies and rational design since 2019, showing how tailored metal catalysts are optimized by designing structures to release or in situ synthesize active drugs, leveraging the target-specific characteristics to develop more precise cancer therapies. This review explores metal-based catalysts, including those conjugated with biomolecules, nanostructures, and metal-organic frameworks (MOFs), highlighting their catalytic activity in biological environments and their in vitro/in vivo performance. To sum up, the potential of metal complexes as catalysts to reshape the landscape of anticancer therapies and foster novel avenues for therapeutic advancement is emphasized.

Iminoamido chelated iridium(III) and ruthenium(II) anticancer complexes with mitochondria-targeting ability and potential to overcome cisplatin resistance

A diverse set of neutral half-sandwich iminoamido iridium and ruthenium organometallic complexes is synthesized through the utilization of Schiff base pro-ligands with N˄N donors. Notably, these metal complexes with varying leaving groups (Cl- or OAc-) are formed by employing different quantities of the deprotonating agent NaOAc, and exhibit promising cytotoxicity against various cancer cell lines such as A549 and cisplatin-resistant A549/DDP lung cancer cells, as well as HeLa cells, with IC50 values spanning from 9.26 to 15.98 μM. Cytotoxicity and anticancer selectivity (SI: 1.9-2.4) of these metal complexes remain unaffected by variations in the metal center, leaving group, and ligand substitution. Further investigations reveal that these metal complexes specifically target mitochondria, leading to the depolarization of the mitochondrial membrane and instigating the production of intracellular reactive oxygen species. Furthermore, the metal complexes are found to induce late apoptosis and disrupt the cell cycle, leading to G2/M cell cycle arrest specifically in A549 cancer cells. In light of these findings, it is evident that the primary mechanism contributing to the anticancer effectiveness of these metal complexes is the redox pathway.

Ru(II)-arene azole complexes as anti-amyloid-β agents

With the recent clinical success of anti-amyloid-β (Aβ) monoclonal antibodies, there is a renewed interest in agents which target the Aβ peptide of Alzheimer's disease (AD). Metal complexes are particularly well-suited for this development, given their structural versatility and ability to form stabile interactions with soluble Aβ. In this report, a small series of ruthenium-arene complexes were evaluated for their respective ability to modulate both the aggregation and cytotoxicity of Aβ. First, the stability of the complexes was evaluated in a variety of aqueous media where the complexes demonstrated exceptional stability. Next, the ability to coordinate and modulate the Aβ peptide was evaluated using several spectroscopic methods, including thioflavin T (ThT) fluorescence, dynamic light scattering (DLS), and transmission electron microscopy (TEM). Overall, the complex RuBO consistently gave the greatest inhibitory action towards Aβ aggregation, which correlated with its ability to coordinate to Aβ in solution. Furthermore, RuBO also had the lowest affinity for serum albumin, which is a key consideration for a neurotherapeutic, as this protein does not cross the blood brain barrier. Lastly, RuBO also displayed promising neuroprotective properties, as it had the greatest inhibition of Aβ-inducted cytotoxicity.

Analysis of antiproliferative activity of new half-sandwich arene Ru(II) thiophene based aroylhydrazone complexes

Efforts in researching the efficient anti-tumor properties of three novel arene ruthenium(II) complexes incorporating thiophene-based aroylhydrazone ligands have been undertaken. The complexes' elemental composition was [(η6-p-cymene)Ru(L)Cl]. They were comprehensively characterized through elemental and spectroscopic analyses (FT-IR, UV-vis, NMR, and HR-MS). Single crystal X-ray diffraction studies revealed a pseudo-octahedral geometry with bidentate coordination of the ligands in a representative complex. The in vitro assessment of the complexes' cancer cell growth inhibition was conducted using the MTT assay against A549 (human lung carcinoma), HeLa (human cervical carcinoma), HuH-7 (hepatocellular carcinoma), and NIH-3T3 (mouse fibroblast non-cancerous cell line). Results indicated significant cytotoxicity across all cancer cell lines, with IC50 concentrations of complex 2 being 6.8 μM for A549, 11.6 μM for HeLa, and 9.4 μM for HuH-7, compared to cisplatin with IC50 values of 18.9 μM, 17.68 μM, and 24 μM respectively. Notably, complex 2 demonstrated particularly promising cytotoxicity against all tested cancerous cell lines. Fluorescent staining analysis such as acridine orange/ethidium bromide (AO-EB) and HOECHST 33342 revealed cell death mechanisms involving membrane disintegration and nuclear condensation following treatment with complex 2. Further studies were conducted to measure reactive oxygen species (ROS) levels using the dichlorodihydrofluorescein diacetate (DCFH-DA) assay, and mitochondrial membrane potential (MMP) was assessed using the JC-1 dye assay. These studies demonstrated that complex 2 increased ROS levels, decreased membrane potential, and promoted mitochondrial dysfunction-mediated cell death pathways. Additionally, flow cytometry analysis, utilizing dual staining of Annexin V-FITC and propidium iodide (PI), was employed to quantitatively study apoptosis induction.

Ligand Characterization and DNA Intercalation of Ru(II) Polypyridyl Complexes: A Local Vibrational Mode Study

We investigated in this work ruthenium-ligand bonding across the RuN framework in 12 Ru(II) polypyridyl complexes in the gas phase and solution for both singlet and triplet states, in addition to their affinity for DNA binding through π-π stacking interactions with DNA nucleobases. As a tool to assess the intrinsic strength of the ruthenium-ligand bonds, we determined local vibrational force constants via our local vibrational mode analysis software. We introduced a novel local force constant that directly accounts for the intrinsic strength of the π-π stacking interaction between DNA and the intercalated Ru(II) complex. According to our findings, [Ru(phen)2(dppz)]2+ and [Ru(phen)2(11-CN-dppz)]2+ provide an intriguing trade-off between photoinduced complex excitation and the strength of the subsequent π-π stacking interaction with DNA. [Ru(phen)2(dppz)]2+ displays a small singlet-triplet splitting and a strong π-π stacking interaction in its singlet state, suggesting a favorable photoexcitation but potentially weaker interaction with DNA in the excited state. Conversely, [Ru(phen)2(11-CN-dppz)]2+ exhibits a larger singlet-triplet splitting and a stronger π-π stacking interaction with DNA in its triplet state, indicating a less favorable photoinduced transition but a stronger interaction with DNA postexcitation. We hope our study will inspire future experimental and computational work aimed at the design of novel Ru-polypyridyl drug candidates and that our new quantitative measure of π-π stacking interactions in DNA will find a general application in the field.

Recent Development of Transition Metal Complexes as Chemotherapeutic Hypoxia Activated Prodrug (HAP)

Hypoxia is a state characterized by low concentration of Oxygen. Hypoxic state is often found in the central region of solid tumors. Hypoxia is associated with abnormal neovascularization resulted in poor blood flow in tissues and increased proliferation of tumor cells, imbalance between O2 supply and O2 consumption in tumor cells, high concentration of proton and strong reducibility. And, these abnormalities enhance the survival potency of the hypoxic tumours and increase the resistance towards chemotherapy and radiotherapy. One of the approach for treating hypoxic region of tumour is to use reducing environment of hypoxic tumours for reducing a molecule (hypoxia activated prodrug, HAP) and as a result the active drug will be released in hypoxic region in a controlled manner from the prodrug and kill the hypoxic tumour. Co(III) and Pt(IV) complexes with monodentate active drug molecule in the axial position can be reduced to Co(II) and Pt(II) moieties and as a result, the axial ligands (active drug) could come out from the metal center and could show its anticancer activity. In this review we have highlighted the research articles where transition metal-based complexes are used as chemotherapeutic hypoxia activated prodrug molecules which are reported in last 5 years.

Ruthenium p-Cymene Complexes Incorporating Substituted Pyridine-Quinoline-Based Ligands: Synthesis, Characterization, and Cytotoxic Properties

Organometallic complexes of the formula [Ru(N^N)(p-cymene)Cl][X] (N^N = bidentate polypyridyl ligands, p-cymene = 1-methyl-4-(1-methylethyl)-benzene, X = counter anion), are currently studied as possible candidates for the potential treatment of cancer. Searching for new organometallic compounds with good to moderate cytotoxic activities, a series of mononuclear water-soluble ruthenium(II)-arene complexes incorporating substituted pyridine-quinoline ligands, with pending -CH2OH, -CO2H and -CO2Me groups in the 4-position of quinoline ring, were synthesized, for the first time, to study their possible effect to modulate the activity of the ruthenium p-cymene complexes. These include the [Ru(η6-p-cymene)(pqhyme)Cl][X] (X = Cl- (1-Cl), PF6- (1-PF6), pqhyme = 4-hydroxymethyl-2-(pyridin-2-yl)quinoline), [Ru(η6-p-cymene)(pqca)Cl][Cl] ((2-Cl), pqca = 4-carboxy-2-(pyridin-2-yl)quinoline), and [Ru(η6-p-cymene)(pqcame)Cl][X] (X = Cl- (3-Cl), PF6- (3-PF6), pqcame = 4-carboxymethyl-2-(pyridin-2-yl)quinoline) complexes, respectively. Identification of the complexes was based on multinuclear NMR and ATR-IR spectroscopic methods, elemental analysis, conductivity measurements, UV-Vis spectroscopic, and ESI-HRMS techniques. The solid-state structures of 1-PF6 and 3-PF6 have been elucidated by single-crystal X-ray diffraction revealing a three-legged piano stool geometry. This is the first time that the in vitro cytotoxic activities of these complexes are studied. These were conducted in HEK293T (human embryonic kidney cells) and HeLa cells (cervical cancer cells) via the MTT assay. The results show poor in vitro anticancer activities for the HeLa cancer cell lines and 3-Cl proved to be the most potent (IC50 > 80 μΜ). In both cell lines, the cytotoxicity of the ligand precursor pqhyme is significantly higher than that of cisplatin.

Anticancer Activity of Metallodrugs and Metallizing Host Defense Peptides-Current Developments in Structure-Activity Relationship

This article provides an overview of the development, structure and activity of various metal complexes with anti-cancer activity. Chemical researchers continue to work on the development and synthesis of new molecules that could act as anti-tumor drugs to achieve more favorable therapies. It is therefore important to have information about the various chemotherapeutic substances and their mode of action. This review focuses on metallodrugs that contain a metal as a key structural fragment, with cisplatin paving the way for their chemotherapeutic application. The text also looks at ruthenium complexes, including the therapeutic applications of phosphorescent ruthenium(II) complexes, emphasizing their dual role in therapy and diagnostics. In addition, the antitumor activities of titanium and gold derivatives, their side effects, and ongoing research to improve their efficacy and reduce adverse effects are discussed. Metallization of host defense peptides (HDPs) with various metal ions is also highlighted as a strategy that significantly enhances their anticancer activity by broadening their mechanisms of action.

Exploring the potential of ruthenium(II)-phosphine-mercapto complexes as new anticancer agents

The search for new metal-based anticancer drug candidates is a fundamental task in medicinal inorganic chemistry. In this work, we assessed the potential of two new Ru(II)-phosphine-mercapto complexes as potential anticancer agents. The complexes, with the formula [Ru(bipy)(dppen)(Lx)]PF6 [(1), HL1 = 2-mercapto-pyridine and (2), HL2 = 2-mercapto-pyrimidine, bipy = 2,2'-bipyridine, dppen = cis-1,2-bis(diphenylphosphino)-ethylene] were synthesized and characterized by nuclear magnetic resonance (NMR) [1H, 31P(1H), and 13C], high resolution mass spectrometry (HR-MS), cyclic voltammetry, infrared and UV-Vis spectroscopies. Complex 2 was obtained as a mixture of two isomers, 2a and 2b, respectively. The composition of these metal complexes was confirmed by elemental analysis and liquid chromatography-mass spectrometry (LC-MS). To obtain insights into their lipophilicity, their distribution coefficients between n-octanol/PBS were determined. Both complexes showed affinity mainly for the organic phase, presenting positive log P values. Also, their stability was confirmed over 48 h in different media (i.e., DMSO, PBS and cell culture medium) via HPLC, UV-Vis and 31P{1H} NMR spectroscopies. Since enzymes from the P-450 system play a crucial role in cellular detoxification and metabolism, the microsomal stability of 1, which was found to be the most interesting compound of this study, was investigated using human microsomes to verify its potential oxidation in the liver. The analyses by LC-MS and ESI-MS reveal three main metabolites, obtained by oxidation in the dppen and bipy moieties. Moreover, 1 was able to interact with human serum albumin (HSA). The cytotoxicity of the metal complexes was tested in different cancerous and non-cancerous cell lines. Complex 1 was found to be more selective than cisplatin against MDA-MB-231 breast cancer cells when compared to MCF-10A non-cancerous cells. In addition, complex 1 affects cell morphology and migration, and inhibits colony formation in MDA-MB-231 cells, making it a promising cytotoxic agent against breast cancer.

Glutathione Depletion and Stalwart Anticancer Activity of Metallotherapeutics Inducing Programmed Cell Death: Opening a New Window for Cancer Therapy

The cellular defense system against exogenous substances makes therapeutics inefficient as intracellular glutathione (GSH) exhibits an astounding antioxidant activity in scavenging reactive oxygen species (ROS) or reactive nitrogen species (RNS) or other free radicals produced by the therapeutics. In the cancer cell microenvironment, the intracellular GSH level becomes exceptionally high to fight against oxidative stress created by the production of ROS/RNS or any free radicals, which are the byproducts of intracellular redox reactions or cellular respiration processes. Thus, in order to maintain redox homeostasis for survival of cancer cells and their rapid proliferation, the GSH level starts to escalate. In this circumstance, the administration of anticancer therapeutics is in vain, as the elevated GSH level reduces their potential by reduction or by scavenging the ROS/RNS they produce. Therefore, in order to augment the therapeutic potential of anticancer agents against elevated GSH condition, the GSH level must be depleted by hook or by crook. Hence, this Review aims to compile precisely the role of GSH in cancer cells, the importance of its depletion for cancer therapy and examples of anticancer activity of a few selected metal complexes which are able to trigger cancer cell death by depleting the GSH level.

Mechanisms of Ligand Hyperfine Coupling in Transition-Metal Complexes: σ and π Transmission Pathways

Theoretical interpretation of hyperfine interactions was pioneered in the 1950s-1960s by the seminal works of McConnell, Karplus, and others for organic radicals and by Watson and Freeman for transition-metal (TM) complexes. In this work, we investigate a series of octahedral Ru(III) complexes with aromatic ligands to understand the mechanism of transmission of the spin density from the d-orbital of the metal to the s-orbitals of the ligand atoms. Spin densities and spin populations underlying ligand hyperfine couplings are analyzed in terms of π-conjugative or σ-hyperconjugative delocalization vs spin polarization based on symmetry considerations and restricted open-shell vs unrestricted wave function analysis. The transmission of spin density is shown to be most efficient in the case of symmetry-allowed π-conjugative delocalization, but when the π-conjugation is partially or fully symmetry-forbidden, it can be surpassed by σ-hyperconjugative delocalization. Despite a lower spin population of the ligand in σ-hyperconjugative transmission, the hyperfine couplings can be larger because of the direct involvement of the ligand s-orbitals in this delocalization pathway. We demonstrate a quantitative correlation between the hyperfine couplings of aromatic ligand atoms and the characteristics of the metal-ligand bond modulated by the trans substituent, a hyperfine trans effect.

Mitochondrial Calcium Uniporter (MCU) is Involved in an Ischemic Postconditioning Effect Against Ischemic Reperfusion Brain Injury in Mice

The phenomenon of ischemic postconditioning (PostC) is known to be neuroprotective against ischemic reperfusion (I/R) injury. One of the key processes in PostC is the opening of the mitochondrial ATP-dependent potassium (mito-KATP) channel and depolarization of the mitochondrial membrane, triggering the release of calcium ions from mitochondria through low-conductance opening of the mitochondrial permeability transition pore. Mitochondrial calcium uniporter (MCU) is known as a highly sensitive transporter for the uptake of Ca2+ present on the inner mitochondrial membrane. The MCU has attracted attention as a new target for treatment in diseases, such as neurodegenerative diseases, cancer, and ischemic stroke. We considered that the MCU may be involved in PostC and trigger its mechanisms. This research used the whole-cell patch-clamp technique on hippocampal CA1 pyramidal cells from C57BL mice and measured changes in spontaneous excitatory post-synaptic currents (sEPSCs), intracellular Ca2+ concentration, mitochondrial membrane potential, and N-methyl-D-aspartate receptor (NMDAR) currents under inhibition of MCU by ruthenium red 265 (Ru265) in PostC. Inhibition of MCU increased the occurrence of sEPSCs (p = 0.014), NMDAR currents (p < 0.001), intracellular Ca2+ concentration (p < 0.001), and dead cells (p < 0.001) significantly after reperfusion, reflecting removal of the neuroprotective effects in PostC. Moreover, mitochondrial depolarization in PostC with Ru265 was weakened, compared to PostC (p = 0.004). These results suggest that MCU affects mitochondrial depolarization in PostC to suppress NMDAR over-activation and prevent elevation of intracellular Ca2+ concentrations against I/R injury.

Ligand Regulation Strategy to Modulate ROS Nature in a Rhodamine-Iridium(III) Hybrid System for Phototherapy

The efficacy of photodynamic therapy (PDT) is highly dependent on the photosensitizer features. The reactive oxygen species (ROS) generated by photosensitizers is proven to be associated with immunotherapy by triggering immunogenic cell death (ICD) as well. In this work, we establish a rhodamine-iridium(III) hybrid model functioning as a photosensitizer to comprehensively understand its performance and potential applications in photodynamic immunotherapy. Especially, the correlation between the ROS generation efficiency and the energy level of the Ir(III)-based excited state (T1'), modulated by the cyclometalating (C∧N) ligand, is systematically investigated and correlated. We prove that in addition to the direct population of the rhodamine triplet state (T1) formed through the intersystem crossing process with the assistance of a heavy Ir(III) metal center, the fine-tuned T1' state could act as a relay to provide an additional pathway for promoting the cascade energy transfer process that leads to enhanced ROS generation ability. Moreover, type I ROS can be effectively produced by introducing sulfur-containing thiophene units in C∧N ligands, providing a stronger M1 macrophage-activation efficiency under hypoxia to evoke in vivo antitumor immunity. Overall, our work provides a fundamental guideline for the molecular design and exploration of advanced transition-metal-based photosensitizers for biomedical applications.

Evaluation of heteroscorpionate ligands as scaffolds for the generation of Ruthenium(II) metallodrugs in breast cancer therapy

The modular synthesis of the heteroscorpionate core is explored as a tool for the rapid development of ruthenium-based therapeutic agents. Starting with a series of structurally diverse alcohol-NN ligands, a family of heteroscorpionate-based ruthenium derivatives was synthesized, characterized, and evaluated as an alternative to platinum therapy for breast cancer therapy. In vitro, the antitumoral activity of the novel derivatives was assessed in a series of breast cancer cell lines using UNICAM-1 and cisplatin as metallodrug control. Through this approach, a bimetallic heteroscorpionate-based metallodrug (RUSCO-2) was identified as the lead compound of the series with an IC50 value range as low as 3-5 μM. Notably, RUSCO-2 was found to be highly cytotoxic in TNBC cell lines, suggesting a mode of action independent of the receptor status of the cells. As a proof of concept and taking advantage of the luminescent properties of one of the complexes obtained, uptake was monitored in human breast cancer MCF7 cell lines by fluorescence lifetime imaging microscopy (FLIM) to reveal that the compound is evenly distributed in the cytoplasm and that the incorporation of the heteroscorpionate ligand protects it from aqueous processes, conversion in another entity, or the loss of the chloride group. Finally, ROS studies were conducted, lipophilicity was estimated, the chloride/water exchange was studied, and stability studies in simulated biological media were carried out to propose structure-activity relationships.

Effect of Cu(II) compound containing dipicolinic acid on DNA damage: a study of antiproliferative activity and DNA interaction properties by spectroscopic, molecular docking and molecular dynamics approaches

A polymeric compound formulized as [Cu(µ-dipic)2{Na2(µ-H2O)4]n.2nH2O (I), where dipic is 2,6-pyridine dicarboxylic acid (dipicolinic acid, H2dipic), was synthesized by sonochemical irradiation. The initial in-vitro cytotoxic activity of this complex compared with renowned anticancer drugs like cisplatin, versus HCT116 colon cell lines, shows promising results. This study investigated the interaction mode between compound (I) and calf-thymus DNA utilizing a range of analytical techniques including spectrophotometry, fluorimetry, partition coefficient analysis, viscometry, gel electrophoresis and molecular docking technique. The results obtained from experimental methods reveal complex (I) could bind to CT-DNA via hydrogen bonding and van der Waals forces and the theoretical methods support it. Also, complex (I) indicates nuclease activity in the attendance of H2O2 and can act as an artificial nuclease to cleave DNA with high efficiency.Communicated by Ramaswamy H. Sarma.

Exploring the cytotoxicity of dinuclear Ru(II) p-cymene complexes appended N,N'-bis(4-substituted benzoyl)hydrazines: insights into the mechanism of apoptotic cell death

Cancer is a perilous life-threatening disease, and attempts are constantly being made to create multinuclear transition metal complexes that could lead to the development of potential anticancer medications and administration procedures. Hence, this work aims to design, synthesize, characterize, and assess the anticancer efficacy of ruthenium p-cymene complexes incorporating N,N'-bis(4-substituted benzoyl)hydrazine ligands. The formation of the new complexes (Ru2H1-Ru2H3) has been thoroughly established by elemental analysis, and FT-IR, UV-vis, NMR, and HR-MS spectral techniques. The solid-state molecular structures of the complexes Ru2H1 and Ru2H3 have been determined using the SC-XRD study, which confirms the N, O, and Cl-legged piano stool pseudo-octahedral geometry of each ruthenium(II) ion. The stability of these complexes in the solution state and their lipophilicity profile have been determined. Furthermore, the title complexes were tested for their in vitro anticancer activity against cancerous H460 (lung cancer cells), SkBr3 (breast cancer cells), HepG2 (liver cancer cells), and HeLa (cervical cancer cells) along with non-cancerous (HEK-293) cells. The IC50 results revealed that complex Ru2H3 exhibits potent activity against the proliferation of all four cancer cells and outscored the effect of the standard metallodrug cisplatin. This may be attributed to the presence of a couple of lipophilic electron-donating methoxy groups in the ligand scaffold and also the ruthenium(II) p-cymene motifs. Advantageously, all the complexes (Ru2H1-Ru2H3) displayed cytotoxic specificity only towards cancerous cells by leaving the off-target non-cancerous cells undamaged. Acridine orange/ethidium bromide (AO/EB) staining, Hoechst 33342, mitochondrial membrane potential (MMP), and reactive oxygen species (ROS) staining assays were used to investigate the apoptotic pathway and ROS levels in mitochondria. The results of western blot analysis confirmed that the complexes triggered apoptosis through an intrinsic mitochondrial pathway by upregulating Bax and downregulating Bcl-2 proteins. Finally, the extent of apoptosis triggered by the complex Ru2H3 was quantified with the aid of flow cytometry using the Annexin V-FITC/propidium iodide (PI) double-staining technique.

Synthesis, anticancer activity, and molecular docking of half-sandwich iron(II) cyclopentadienyl complexes with maleimide and phosphine or phosphite ligands

In these studies, we designed and investigated the potential anticancer activity of five iron(II) cyclopentadienyl complexes bearing different phosphine and phosphite ligands. All complexes were characterized with spectroscopic analysis viz. NMR, FT-IR, ESI-MS, UV-Vis, fluorescence, XRD (for four complexes) and elemental analyses. For biological studies, we used three types of cells-normal peripheral blood mononuclear (PBM) cells, leukemic HL-60 cells and non-small-cell lung cancer A549 cells. We evaluated cell viability and DNA damage after cell incubation with these complexes. We observed that all iron(II) complexes were more cytotoxic for HL-60 cells than for A549 cells. The complex CpFe(CO)(P(OPh)3)(η1-N-maleimidato) 3b was the most cytotoxic with IC50 = 9.09 µM in HL-60 cells, IC50 = 19.16 µM in A549 and IC50 = 5.80 µM in PBM cells. The complex CpFe(CO)(P(Fu)3)(η1-N-maleimidato) 2b was cytotoxic only for both cancer cell lines, with IC50 = 10.03 µM in HL-60 cells and IC50 = 73.54 µM in A549 cells. We also found the genotoxic potential of the complex 2b in both types of cancer cells. However, the complex CpFe(CO)2(η1-N-maleimidato) 1 which we studied previously, was much more genotoxic than complex 2b, especially for A549 cells. The plasmid relaxation assay showed that iron(II) complexes do not induce strand breaks in fully paired ds-DNA. The DNA titration experiment showed no intercalation of complex 2b into DNA. Molecular docking revealed however that complexes CpFe(CO)(PPh3) (η1-N-maleimidato) 2a, 2b, 3b and CpFe(CO)(P(OiPr)3)(η1-N-maleimidato) 3c have the greatest potential to bind to mismatched DNA. Our studies demonstrated that the iron(II) complex 1 and 2b are the most interesting compounds in terms of selective cytotoxic action against cancer cells. However, the cellular mechanism of their anticancer activity requires further research.

Heterocyclic (pyrazine)carboxamide Ru(ii) complexes: structural, experimental and theoretical studies of interactions with biomolecules and cytotoxicity

Treatments of N-(1H-benzo[d]imidazol-2-yl)pyrazine-2-carboxamide (HL1) and N-(benzo[d]thiazol-2-yl)pyrazine-2-carboxamide carboxamide ligands (HL2) with [Ru(p-cymene)Cl2]2 and [Ru(PPh3)3Cl2] precursors afforded the respective Ru(ii) complexes [Ru(L1)(p-cymene)Cl] (Ru1), [Ru(L2)(p-cymene)Cl] (Ru2), [Ru(L1)(PPh3)2Cl] (Ru3), and [Ru(L2)(PPh3)2Cl] (Ru4). These complexes were characterized by NMR, FT-IR spectroscopies, mass spectrometry, elemental analyses, and crystal X-ray crystallography for Ru2. The molecular structure of complex Ru2 contains one mono-anionic bidentate bound ligand and display pseudo-octahedral piano stool geometry around the Ru(ii) atom. The interactions with calf thymus DNA (CT-DNA) and bovine serum albumin (BSA) were investigated by spectroscopic techniques. The experimental binding studies suggest that complexes Ru1-Ru4 interact with DNA, primarily through minor groove binding, as supported by molecular docking results. Additionally, these complexes exhibit strong quenching of the fluorescence of tryptophan residues in BSA, displaying static quenching. The in vitro cytotoxicity studies of compounds Ru1-Ru4 were assessed in cancer cell lines (A549, PC-3, HT-29, Caco-2, and HeLa), as well as a non-cancer line (KMST-6). Compounds Ru1 and Ru2 exhibited superior cytotoxicity compared to Ru3 and Ru4. The in vitro cytotoxicity and selectivity of compounds Ru1 and Ru2 against A549, PC-3, and Caco-2 cell lines surpassed that of cisplatin.

Preparation of new organo-ruthenium(II) complexes and their nucleic acid/albumin binding efficiency and in vitro cytotoxicity studies

Hetero-bimetallic ruthenium(II) complexes (PRAFIZ and PRBFIZ) containing acetyl ferrocene (AFIZ)/benzoyl ferrocene isonicotinic hydrazone ligands (BFIZ) were synthesized and characterized by various spectral and analytical techniques. The structure of acetyl ferrocene isonicotinic hydrazone (AFIZ) and the complex PRBFIZ was confirmed by X-ray crystallography. The hydrazide ligands coordinated in a bidentate monobasic fashion using their N1 hydrazinic nitrogen and enolic oxygen atoms. The binding interactions of the ligands and complexes were examined using Calf-Thymus DNA (CT-DNA) and bovine serum albumin (BSA). Scanning Electron Microscopic (SEM) experiments clarified the efficient binding interaction of the ligands and complexes with BSA. The results of in vitro cytotoxicity studies on MDA-MB-261 breast cancer cells and A549 human lung cancer cells and cell morphological analysis results through staining assays clearly indicated the cytotoxic nature of the complexes.

A bis-quinoline ruthenium(II) arene complex with submicromolar cytotoxicity in castration-resistant prostate cancer cells

A new Ru(II) arene chlorido organometallic complex [(η6-p-cymene)(L)RuCl]PF6 (named as pCYRuL) using 2-bis(quinolin-2-ylmethylene) hydrazine (L) was developed that exhibits potent anticancer activity against castration-resistant prostate cancer (CRPC) (IC50 = 0.71 μM), and it is 45 times more effective than the standard drug cisplatin (IC50 = 31.3 μM) in a castration-resistant human prostatic adenocarcinoma cell line (PC-3) but non-toxic in normal human kidney cells (HK2) as well as normal breast cells (MCF10A) and found that pCYRuL exerted anticancer activity via apoptosis induction and cell cycle arrest in the G2/M phase of PC-3 cells.

Red-Light Activation of a Microtubule Polymerization Inhibitor via Amide Functionalization of the Ruthenium Photocage

Photoactivated chemotherapy (PACT) is a promising cancer treatment modality that kills cancer cells via photochemical uncaging of a cytotoxic drug. Most ruthenium-based photocages used for PACT are activated with blue or green light, which penetrates sub-optimally into tumor tissues. Here, we report amide functionalization as a tool to fine-tune the toxicity and excited states of a terpyridine-based ruthenium photocage. Due to conjugation of the amide group with the terpyridine π system in the excited state, the absorption of red light (630 nm) increased 8-fold, and the photosubstitution rate rose 5-fold. In vitro, red light activation triggered inhibition of tubulin polymerization, which led to apoptotic cell death both in normoxic (21 % O2 ) and hypoxic (1 % O2 ) cancer cells. In vivo, red light irradiation of tumor-bearing mice demonstrated significant tumor volume reduction (45 %) with improved biosafety, thereby demonstrating the clinical potential of this compound.

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.

Cyclometalated ruthenium complexes overcome cisplatin resistance through PI3K/mTOR/Nrf2 signaling pathway

Currently, cisplatin resistance remains a primary clinical obstacle in the successful treatment of non-small cell lung cancer. Here, we designed, synthesized, and characterized two novel cyclometalated Ru(II) complexes, [Ru(bpy)2(1-Ph-7-OCH3-IQ)] (PF6) (bpy = 2,2'-bipyridine, IQ = isoquinoline, RuIQ7)and [Ru(bpy)2(1-Ph-6,7-(OCH3)2-IQ)] (PF6) (RuIQ8). As experimental controls, we prepared complex [Ru(bpy)2(1-Ph-IQ)](PF6) (RuIQ6) lacking a methoxy group in the main ligand. Significantly, complexes RuIQ6-8 displayed higher in vitro cytotoxicity when compared to ligands, precursor cis-[Ru(bpy)2Cl2], and clinical cisplatin. Mechanistic investigations revealed that RuIQ6-8 could inhibit cell proliferation by downregulating the phosphorylation levels of Akt and mTOR proteins, consequently affecting the rapid growth of human lung adenocarcinoma cisplatin-resistant cells A549/DDP. Moreover, the results from qRT-PCR demonstrated that these complexes could directly suppress the transcription of the NF-E2-related factor 2 gene, leading to the inhibition of downstream multidrug resistance-associated protein 1 expression and effectively overcoming cisplatin resistance. Furthermore, the relationship between the chemical structures of these three complexes and their anticancer activity, ability to induce cell apoptosis, and their efficacy in overcoming cisplatin resistance has been thoroughly examined and discussed. Notably, the toxicity test conducted on zebrafish embryos indicated that the three Ru-IQ complexes displayed favorable safety profiles. Consequently, the potential of these developed compounds as innovative therapeutic agents for the efficient and low-toxic treatment of NSCLC appears highly promising.

Potent Half-Sandwich 16-/18-Electron Iridium(III) and Ruthenium(II) Anticancer Complexes with Readily Available Amine-Imine Ligands

The synthesis and biological evaluation of stable 16-electron half-sandwich complexes have remained scarce. We herein present the different coordination modes (16-electron or 18-electron) between half-sandwich iridium(III) complexes and ruthenium(II) complexes derived from the same amine-imine ligands chelating hybrid sp3-N/sp2-N donors. The 16-electron iridium(III) and 18-electron ruthenium(II) complexes with different counteranions were obtained and identified by various techniques. The promising cytotoxicity of these complexes against A549 lung cancer cells, cisplatin-resistant A549/DPP cells, cervical carcinoma HeLa cells, and human hepatocellular liver carcinoma HepG2 cells was observed with IC50 values ranging from 5.4 to 16.3 μM. Moreover, these complexes showed a certain selectivity (selectivity index: 2.1-3.7) toward A549 cells and BEAS-2B normal cells. The variation of metal center, counteranion, 16/18-electron coordination mode, and ligand substituents showed little influence on the cytotoxicity and selectivity of these complexes. The mechanism of action study showed that these complexes could target mitochondria, induce the depolarization of the mitochondrial membrane, and promote the generation of intracellular reactive oxygen species (ROS). Further, the induction of cell apoptosis and the perturbation of the cell cycle in the G0/G1 phase were also observed for these complexes. Overall, it seems that the redox mechanism dominated the anticancer efficacy of these complexes.

Research Progress of Metal Anticancer Drugs

Cancer treatments, including traditional chemotherapy, have failed to cure human malignancies. The main reasons for the failure of these treatments are the inevitable drug resistance and serious side effects. In clinical treatment, only 5 percent of the 50 percent of cancer patients who are able to receive conventional chemotherapy survive. Because of these factors, being able to develop a drug and treatment that can target only cancer cells without affecting normal cells remains a big challenge. Since the special properties of cisplatin in the treatment of malignant tumors were accidentally discovered in the last century, metal anticancer drugs have become a research hotspot. Metal anticancer drugs have unique pharmaceutical properties, such as ruthenium metal drugs with their high selectivity, low toxicity, easy absorption by tumor tissue, excretion, and so on. In recent years, efficient and low-toxicity metal antitumor complexes have been synthesized. In this paper, the scientific literature on platinum (Pt), ruthenium (Ru), iridium (Ir), gold (Au), and other anticancer complexes was reviewed by referring to a large amount of relevant literature at home and abroad.

Synthesis and Preclinical Evaluation of Radiolabeled [103Ru]BOLD-100

The first-in-class ruthenium-based chemotherapeutic agent BOLD-100 (formerly IT-139, NKP-1339, KP1339) is currently the subject of clinical evaluation for the treatment of gastric, pancreatic, colorectal and bile duct cancer. A radiolabeled version of the compound could present a helpful diagnostic tool. Thus, this study investigated the pharmacokinetics of BOLD-100 in more detail to facilitate the stratification of patients for the therapy. The synthesis of [103Ru]BOLD-100, radiolabeled with carrier added (c.a.) ruthenium-103, was established and the product was characterized by HPLC and UV/Vis spectroscopy. In order to compare the radiolabeled and non-radioactive versions of BOLD-100, both complexes were fully evaluated in vitro and in vivo. The cytotoxicity of the compounds was determined in two colon carcinoma cell lines (HCT116 and CT26) and biodistribution studies were performed in Balb/c mice bearing CT26 allografts over a time period of 72 h post injection (p.i.). We report herein preclinical cytotoxicity and pharmacokinetic data for BOLD-100, which were found to be identical to those of its radiolabeled analog [103Ru]BOLD-100.

Naphthoyl benzhydrazine-decorated binuclear arene Ru(II) complexes as anticancer agents targeting human breast cancer cells

Breast cancer is the most dangerous type in women and its fatality rate has increased over the past decade. To develop more potent and target-specific breast cancer drugs, six arene ruthenium(II) complexes (1-6) containing naphthoyl benzhydrazine ligands (NL1-NL3) were synthesized and characterized by analytical and spectroscopic (infrared, UV-visible, NMR and HR-MS) methods. The SC-XRD analysis of 1 and 6 demonstrates the bis N^O bidentate binding nature of ligands to ruthenium ions and a pseudo-octahedral geometry around the Ru(II) ion. Solution stability studies using UV-Vis spectroscopy evidenced the instantaneous hydrolysis of the complexes to form monoaquated species in a solution of 1 : 9 (v/v) DMSO/phosphate buffer. All the complexes were screened for their in vitro antiproliferative activities against different human breast cancer cells, including MCF-7, SkBr3, MDA-MB-468, MDA-MB-231, and non-cancerous HEK-293 cells, by an MTT assay, and they displayed good cancer cell growth inhibitory capacity with low IC50 values. Notably, complexes 2 and 5 comprising methoxy and p-cymene groups exhibited excellent cytotoxicity towards SkBr3 cells compared to clinical drug cisplatin. AO-EB and HOECHST-33342 staining assays revealed apoptotic morphological changes in complex-treated cancer cells. Further, reactive oxygen species and mitochondrial membrane potential assays validated that the complexes induce apoptotic cell death via an intrinsic mitochondrial pathway with ROS production. In addition, the apoptotic induction and the quantification of late apoptosis were established with the aid of western blot and flow cytometry analysis, respectively.

Study on the Multimodal Anticancer Mechanism of Ru(II)/Ir(III) Complexes Bearing a Poly(ADP-ribose) Polymerase 1 Inhibitor

A series of novel ruthenium(II) and iridium(III) complexes (Ru1-Ru3 and Ir1-Ir3) with different ancillary ligands and a PARP-1-inhibitory chelating ligand 2-(2,3-dibromo-4,5-dimethoxybenzylidene)hydrazine-1-carbothioamide (L1) were designed and prepared. The target complexes were structurally characterized by NMR and ESI-MS techniques. Among them, the crystal and molecular structures of Ir1 and Ir2 were also determined by X-ray crystallography. These complexes retained the PARP-1 enzyme inhibitory effect of L1 and showed potent antiproliferative activity on the tested cancer cell lines. The ruthenium(II) complexes Ru1-Ru3 were found to be more cytotoxic than the iridium(III) complexes Ir1-Ir3. Further investigations revealed that the most active complex Ru3 induced apoptosis in MCF-7 cells by multiple modes, inclusive of inducing DNA damage, suppressing DNA damage repair, disturbing cell cycle distribution, decreasing the mitochondrial membrane potential, and increasing the intracellular reactive oxygen species levels.

Half-Sandwich Iridium(III), Rhodium(III), and Ruthenium(II) Complexes Chelating Hybrid sp2-N/sp3-N Donor Ligands to Achieve Improved Anticancer Selectivity

The biological efficacy of half-sandwich platinum group organometallic complexes of the formula [(η5-Cpx)/(η6-arene)M(XY)Cl]0/+ (XY = bidentate ligands; Cpx = functionalized cyclopentadienyl; M = Ir, Rh, Ru, Os) has received considerable attention due to the significance of the metal center, chelating ligand, and Cpx/arene moieties in defining their anticancer potency and selectivity. With a facile access to the BIAN-derived imine-amine ligands using alkylaluminum as the reductant, we herein described the preparation and characterization of 16 half-sandwich Ir(III), Rh(III), and Ru(II) complexes chelating the hybrid sp2-N/sp3-N donor ligand. A nonplanar five-member metallacycle was confirmed by X-ray single-crystal structures of Ir1-Ir3, Ir7, Rh1, Ru1, and Ru4. The attempt to prepare imine-amido complexes using a base as the deprotonating agent led to the mixture of imine-amine complexes, within which the leaving group Cl- was displaced, and 16-electron imine-amido complexes without Cl-. The half-sandwich imine-amine complexes in this system underwent rapid hydrolysis in aqueous solution, exhibited weak photoluminescence, and showed the ability of binding to CT-DNA and BSA. The cytotoxicity of all imine-amine complexes against A549 lung cancer cell lines, HeLa cervical cancer cell lines, and 4T1 mouse breast cancer cells was determined by an MTT assay. The IC50 values of these complexes were in a range of 5.71-67.28 μM. Notably, most of these complexes displayed improved selectivity toward A549 cancer cells versus noncancerous BEAS-2B cells in comparison with the corresponding α-diimine complexes chelating the sp2-N/sp2-N donor ligand, which have been shown no selectivity in our previous report. The anticancer selectivity of these complexes appeared to be related to the redox-based mechanism including the catalytic oxidation of NADH to NAD+, reactive oxygen species (ROS) generation, and depolarization of the mitochondrial membrane. Further, inducing apoptosis of these complexes in A549 cancer cells and BEAS-2B normal cells also correlated with their anticancer selectivity, indicating the apoptosis mode of cell death in this system. In addition, these complexes could enter A549 cells via energy-dependent pathway and were able to impede the in vitro migration of A549 cells.

Silica-Based Materials Containing Inorganic Red/NIR Emitters and Their Application in Biomedicine

The low absorption of biological substances and living tissues in the red/near-infrared region (therapeutic window) makes luminophores emitting in the range of ~650-1350 nm favorable for in vitro and in vivo imaging. In contrast to commonly used organic dyes, inorganic red/NIR emitters, including ruthenium complexes, quantum dots, lanthanide compounds, and octahedral cluster complexes of molybdenum and tungsten, not only exhibit excellent emission in the desired region but also possess additional functional properties, such as photosensitization of the singlet oxygen generation process, upconversion luminescence, photoactivated effects, and so on. However, despite their outstanding functional applicability, they share the same drawback-instability in aqueous media under physiological conditions, especially without additional modifications. One of the most effective and thus widely used types of modification is incorporation into silica, which is (1) easy to obtain, (2) biocompatible, and (3) non-toxic. In addition, the variety of morphological characteristics, along with simple surface modification, provides room for creativity in the development of various multifunctional diagnostic/therapeutic platforms. In this review, we have highlighted biomedical applications of silica-based materials containing red/NIR-emitting compounds.

Fine-tuning the cytotoxicity of ruthenium(II) arene compounds to enhance selectivity against breast cancers

Ruthenium-based complexes have been suggested as promising anticancer drugs exhibiting reduced general toxicity compared to platinum-based drugs. In particular, Ru(η6-arene)(PTA)Cl2 (PTA = 1,3,5-triaza-7-phosphaadamantane), or RAPTA, complexes have demonstrated efficacy against breast cancer by suppressing metastasis, tumorigenicity, and inhibiting the replication of the human tumor suppressor gene BRCA1. However, RAPTA compounds have limited cytotoxicity, and therefore comparatively high doses are required. This study explores the activity of a series of RAPTA-like ruthenium(II) arene compounds against MCF-7 and MDA-MB-231 breast cancer cell lines and [Ru(η6-toluene)(PPh3)2Cl]+ was identified as a promising candidate. Notably, [Ru(η6-toluene)(PPh3)2Cl]Cl was found to be remarkably stable and highly cytotoxic, and selective to breast cancer cells. The minor groove of DNA was identified as a relevant target.

Encapsulation of Ru(II) Polypyridine Complexes for Tumor-Targeted Anticancer Therapy

Ru(II) polypyridine complexes have attracted much attention as anticancer agents because of their unique photophysical, photochemical, and biological properties. Despite their promising therapeutic profile, the vast majority of compounds are associated with poor water solubility and poor cancer selectivity. Among the different strategies employed to overcome these pharmacological limitations, many research efforts have been devoted to the physical or covalent encapsulation of the Ru(II) polypyridine complexes into nanoparticles. This article highlights recent developments in the design, preparation, and physicochemical properties of Ru(II) polypyridine complex-loaded nanoparticles for their potential application in anticancer therapy.

Design, Synthesis, and Characterization of an Amphiphilic Lipoic Acid-Based Ru(III) Complex as a Versatile Tool for the Functionalization of Different Nanosystems

Ru-based chemotherapy is emerging as an effective alternative to the well-established Pt-based one, typically associated with high toxicity. In this context, our recent efforts were devoted to the preparation of nucleolipid-based Ru(III) complexes able to form, under physiological conditions, supramolecular aggregates which can efficiently prevent metal deactivation and convey Ru(III) inside the cells where it exerts its activity. Within an interdisciplinary program for the development of multifunctional nanoparticles for theranostic applications, we here report the design, synthesis, and characterization of a novel functionalized Ru(III) salt, carrying a lipoic acid moiety in the nucleolipid-based scaffold to allow its incorporation onto metal-based nanoparticles.

The Metallodrug BOLD-100 Is a Potent Inhibitor of SARS-CoV-2 Replication and Has Broad-Acting Antiviral Activity

The COVID-19 pandemic has highlighted an urgent need to discover and test new drugs to treat patients. Metal-based drugs are known to interact with DNA and/or a variety of proteins such as enzymes and transcription factors, some of which have been shown to exhibit anticancer and antimicrobial effects. BOLD-100 (sodium trans-[tetrachlorobis(1H-indazole)ruthenate(III)]dihydrate) is a novel ruthenium-based drug currently being evaluated in a Phase 1b/2a clinical trial for the treatment of advanced gastrointestinal cancer. Given that metal-based drugs are known to exhibit antimicrobial activities, we asked if BOLD-100 exhibits antiviral activity towards SARS-CoV-2. We demonstrated that BOLD-100 potently inhibits SARS-CoV-2 replication and cytopathic effects in vitro. An RNA sequencing analysis showed that BOLD-100 inhibits virus-induced transcriptional changes in infected cells. In addition, we showed that the antiviral activity of BOLD-100 is not specific for SARS-CoV-2, but also inhibits the replication of the evolutionarily divergent viruses Human Immunodeficiency Virus type 1 and Human Adenovirus type 5. This study identifies BOLD-100 as a potentially novel broad-acting antiviral drug.

New ruthenium(II) complexes with cyclic thio- and semicarbazone: evaluation of cytotoxicity and effects on cell migration and apoptosis of lung cancer cells

We describe the synthesis, physicochemical characterization, and in vitro antitumor assays of four novel analogous ruthenium(II) complexes with general formula cis-[Ru^II(N-L)(P-P)₂]PF₆, where P-P = bis(diphenylphosphine)methane (dppm, in complexes 1 and 2) or bis(diphenylphosphine)ethane (dppe, in complexes 3 and 4) and N-L = 5,6-diphenyl-4,5-dihydro-2H-[1,2,4]triazine-3-thione (Btsc, in complexes 1 and 3) or 5,6-diphenyltriazine-3-one (Bsc, in complexes 2 and 4). The data were consistent with cis arrangement of the biphosphine ligands. For the Btsc and Bsc ligands, the data pointed to monoanionic bidentate coordination to ruthenium(II) through N,S and N,O, respectively. Single-crystal X-ray diffraction showed that complex 1 crystallized in the monoclinic system, space group P2₁/c. Determination of the cytotoxicity profiles of complexes 1-4 gave SI values ranging from 1.19 to 3.50 against the human lung adenocarcinoma cell line A549 and the non-tumor lung cell line MRC-5. Although the molecular docking studies suggested that the interaction between DNA and complex 4 was energetically favorable, the experimental results showed that they interacted weakly. Overall, our results demonstrated that these novel ruthenium(II) complexes have interesting in vitro antitumor potential and this study may contribute to further studies in medicinal inorganic chemistry.

Near-infrared metal agents assisting precision medicine: from strategic design to bioimaging and therapeutic applications

Metal agents have made incredible strides in preclinical research and clinical applications in recent years, but their short emission/absorption wavelengths continue to be a barrier to their distribution, therapeutic action, visual tracking, and efficacy evaluation. Nowadays, the near-infrared window (NIR, 650-1700 nm) provides a more accurate imaging and treatment option. Thus, there has been ongoing research focusing on developing multifunctional NIR metal agents for imaging and therapy that have deeper tissue penetration. The design, characteristics, bioimaging, and therapy of NIR metal agents are covered in this overview of papers and reports published to date. To start with, we focus on describing the structure, design strategies, and photophysical properties of metal agents from the NIR-I (650-1000 nm) to NIR-II (1000-1700 nm) region, in order of molecular metal complexes (MMCs), metal-organic complexes (MOCs), and metal-organic frameworks (MOFs). Next, the biomedical applications brought by these superior photophysical and chemical properties for more accurate imaging and therapy are discussed. Finally, we explore the challenges and prospects of each type of NIR metal agent for future biomedical research and clinical translation.

Synthesis and Antiproliferative Insights of Lipophilic Ru(II)-Hydroxy Stearic Acid Hybrid Species

Metallodrugs represent a combination of multifunctionalities that are present concomitantly and can act differently on diverse biotargets. Their efficacy is often related to the lipophilic features exhibited both by long carbo-chains and the phosphine ligands. Three Ru(II) complexes containing hydroxy stearic acids (HSAs) were successfully synthesized in order to evaluate possible synergistic effects between the known antitumor activity of HSA bio-ligands and the metal center. HSAs were reacted with [Ru(H)₂CO(PPh₃)₃] selectively affording O,O-carboxy bidentate complexes. The organometallic species were fully characterized spectroscopically using ESI-MS, IR, UV-Vis, and NMR techniques. The structure of the compound Ru-12-HSA was also determined using single crystal X-ray diffraction. The biological potency of ruthenium complexes (Ru-7-HSA, Ru-9-HSA, and Ru-12-HSA) was studied on human primary cell lines (HT29, HeLa, and IGROV1). To obtain detailed information about anticancer properties, tests for cytotoxicity, cell proliferation, and DNA damage were performed. The results demonstrate that the new ruthenium complexes, Ru-7-HSA and Ru-9-HSA, possess biological activity. Furthermore, we observed that the Ru-9-HSA complex shows increased antitumor activity on colon cancer cells, HT29.

New Nanostructured Materials Based on Mesoporous Silica Loaded with Ru(II)/Ru(III) Complexes with Anticancer and Antimicrobial Properties

A new series of nanostructured materials was obtained by functionalization of SBA-15 mesoporous silica with Ru(II) and Ru(III) complexes bearing Schiff base ligands derived from salicylaldehyde and various amines (1,2-diaminocyclohexane, 1,2-phenylenediamine, ethylenediamine, 1,3-diamino-2-propanol, N,N-dimethylethylenediamine, 2-aminomethyl-pyridine, and 2-(2-aminoethyl)-pyridine). The incorporation of ruthenium complexes into the porous structure of SBA-15 and the structural, morphological, and textural features of the resulting nanostructured materials were investigated by FTIR, XPS, TG/DTA, zeta potential, SEM, and N₂ physisorption. The ruthenium complex-loaded SBA-15 silica samples were tested against A549 lung tumor cells and MRC-5 normal lung fibroblasts. A dose-dependent effect was observed, with the highest antitumoral efficiency being recorded for the material containing [Ru(Salen)(PPh₃)Cl] (50%/90% decrease in the A549 cells' viability at a concentration of 70 μg/mL/200 μg/mL after 24 h incubation). The other hybrid materials have also shown good cytotoxicity against cancer cells, depending on the ligand included in the ruthenium complex. The antibacterial assay revealed an inhibitory effect for all samples, the most active being those containing [Ru(Salen)(PPh₃)Cl], [Ru(Saldiam)(PPh₃)Cl], and [Ru(Salaepy)(PPh₃)Cl], especially against Staphylococcus aureus and Enterococcus faecalis Gram-positive strains. In conclusion, these nanostructured hybrid materials could represent valuable tools for the development of multi-pharmacologically active compounds with antiproliferative, antibacterial, and antibiofilm activity.

New Organometallic Ru(II) Compounds with Lonidamine Motif as Antitumor Agents

The combination of one molecule of organic and metal-based fragments that exhibit antitumor activity is a modern approach in the search for new promising drugs. In this work, biologically active ligands based on lonidamine (a selective inhibitor of aerobic glycolysis used in clinical practice) were introduced into the structure of an antitumor organometallic ruthenium scaffold. Resistant to ligand exchange reactions, compounds were prepared by replacing labile ligands with stable ones. Moreover, cationic complexes containing two lonidamine-based ligands were obtained. Antiproliferative activity was studied in vitro by MTT assays. It was shown that the increase in the stability in ligand exchange reactions does not influence cytotoxicity. At the same time, the introduction of the second lonidamine fragment approximately doubles the cytotoxicity of studied complexes. The ability to induce apoptosis and caspase activation in tumour cell MCF7 was studied by employing flow cytometry.

Tumor selective Ru(III) Schiff bases complexes with strong in vitro activity toward cisplatin-resistant MDA-MB-231 breast cancer cells

Novel ruthenium(III) complexes of general formula Na[RuCl2(L1-3-N,O)2] where L(1-3) denote deprotonated Schiff bases (HL1-HL3) derived from 5-substituted salicyladehyde and alkylamine (propyl- or butylamine) were prepared and characterized based on elemental analysis, mass spectra, infrared, electron spin/paramagnetic resonance (ESR/EPR) spectroscopy, and cyclovoltammetric study. Optimization of five isomers of complex C1 was done by DFT calculation. The interaction of C1-C3 complexes with DNA (Deoxyribonucleic acid) and BSA (Bovine serum albumin) was investigated by electron spectroscopy and fluorescence quenching. The cytotoxic activity of C1-C3 was investigated in a panel of four human cancer cell lines (K562, A549, EA.hy926, MDA-MB-231) and one human non-tumor cell line (MRC-5). Complexes displayed an apparent cytoselective profile, with IC50 values in the low micromolar range from 1.6 ± 0.3 to 23.0 ± 0.1 µM. Cisplatin-resistant triple-negative breast cancer cells MDA-MB-231 displayed the highest sensitivity to complexes, with Ru(III) compound containing two chlorides and two deprotonated N-propyl-5-chloro-salicylidenimine (hereinafter C1) as the most potent (IC50 = 1.6 µM), and approximately ten times more active than cisplatin (IC50 = 21.9 µM). MDA-MB-231 cells treated for 24 h with C1 presented with apoptotic morphology, as seen by acridine orange/ethidium bromide staining, while 48 h of treatment induced DNA fragmentation, and necrotic changes in cells, as seen by flow cytometry analysis. Drug-accumulation study by inductively coupled plasma mass spectrometry (ICP-MS) demonstrated markedly higher intracellular accumulation of C1 compared with cisplatin.

Triple Negative Breast Cancer Preclinical Therapeutic Management by a Cationic Ruthenium-Based Nucleolipid Nanosystem

Based on compelling preclinical evidence concerning the progress of our novel ruthenium-based metallotherapeutics, we are focusing research efforts on challenging indications for the treatment of invasive neoplasms such as the triple-negative breast cancer (TNBC). This malignancy mainly afflicts younger women, who are black, or who have a BRCA1 mutation. Because of faster growing and spreading, TNBC differs from other invasive breast cancers having fewer treatment options and worse prognosis, where existing therapies are mostly ineffective, resulting in a large unmet biomedical need. In this context, we benefited from an experimental model of TNBC both in vitro and in vivo to explore the effects of a biocompatible cationic liposomal nanoformulation, named HoThyRu/DOTAP, able to effectively deliver the antiproliferative ruthenium(III) complex AziRu, thus resulting in a prospective candidate drug. As part of the multitargeting mechanisms featuring metal-based therapeutics other than platinum-containing agents, we herein validate the potential of HoThyRu/DOTAP liposomes to act as a multimodal anticancer agent through inhibition of TNBC cell growth and proliferation, as well as migration and invasion. The here-obtained preclinical findings suggest a potential targeting of the complex pathways network controlling invasive and migratory cancer phenotypes. Overall, in the field of alternative chemotherapy to platinum-based drugs, these outcomes suggest prospective brand-new settings for the nanostructured AziRu complex to get promising goals for the treatment of metastatic TNBC.

Investigating the Interaction of an Anticancer Nucleolipidic Ru(III) Complex with Human Serum Proteins: A Spectroscopic Study

Ruthenium(III) complexes are very promising candidates as metal-based anticancer drugs, and several studies have supported the likely role of human serum proteins in the transport and selective delivery of Ru(III)-based compounds to tumor cells. Herein, the anticancer nanosystem composed of an amphiphilic nucleolipid incorporating a Ru(III) complex, which we named DoHuRu, embedded into the biocompatible cationic lipid DOTAP, was investigated as to its interaction with two human serum proteins thought to be involved in the mechanism of action of Ru(III)-based anticancer drugs, i.e., human serum albumin (HSA) and human transferrin (hTf). This nanosystem was studied in comparison with the simple Ru(III) complex named AziRu, a low molecular weight metal complex previously designed as an analogue of NAMI-A, decorated with the same ruthenium ligands as DoHuRu but devoid of the nucleolipid scaffold and not inserted in liposomal formulations. For this study, different spectroscopic techniques, i.e., Fluorescence Spectroscopy and Circular Dichroism (CD), were exploited, showing that DoHuRu/DOTAP liposomes can interact with both serum proteins without affecting their secondary structures.