Mitochondria-Targeting Click-Derived Pyridinyltriazolylmethylquinoxaline-Based Y-Shaped Binuclear Luminescent Ruthenium(II) and Iridium(III) Complexes as Cancer Theranostic Agents

Developing an Arene Binuclear Ruthenium(II) Complex to Induce Ferroptosis and Activate the cGAS-STING Pathway: Targeted Inhibiting Growth and Metastasis of Triple Negative Breast Cancer

To effectively inhibit the growth and metastasis of triple-negative breast cancer (TNBC), we developed a high-efficiency and low-toxicity arene ruthenium (Ru) complex based on apoferritin (AFt). To achieve this, we optimized a series of Ru(II) 1,10-phenanthroline-2,9-diformaldehyde thiosemicarbazone complexes by studying their structure-activity relationships to obtain an arene binuclear Ru(II) complex (C5) with significant cytotoxicity and high accumulation in the mitochondria of tumor cells. Subsequently, a C5-AFt nanoparticle (NPs) delivery system was constructed. We found that the C5/C5-AFt NPs effectively inhibited TNBC growth and metastasis with few side effects. The C5-AFt NPs improved the anticancer and targeting abilities of C5 in vivo. Moreover, we confirmed the mechanism by which C5/C5-AFt NPs inhibit tumor growth and metastasis via mitochondrial damage-mediated ferroptosis and activation of the cGAS-STING pathway.

Exploring the binding properties of DNA/BSA and cytotoxicity studies with new terpyridine-ester-based metal complexes (M = Fe(III), Ni(II), Cu(II) and Ru(III)) - A comparative analysis

Many terpyridines and their metal complexes are known to exhibit remarkable potential for the interaction of biological targets. Notably, a subtle change in the structure of the ligand can influence these interactions significantly. In this regard, it would be very interesting to assess the binding affinity of functionalized molecules with DNA/BSA. In this work, a novel ester-based terpyridine (L) and the corresponding four metal complexes with Ni(II) (MC1), Cu(II) (MC2), Fe(III) (MC3) and Ru(III) (MC4) were prepared and structurally characterized using various spectroscopic and analytical techniques including the validation of molecular structures of ligand (L) and Ni(II)-Tpy complex (MC1). The EPR data demonstrate that MC1 is diamagnetic and other complexes (MC2-MC4) exhibit paramagnetic behavior. Additionally, the structures of ligands and metal complexes were determined using DFT studies and the same were utilized for the docking studies. Interestingly, MC3 and MC4 exhibit a predominant lowest binding energy of -9.62 Kcal/mol (with DNA) and -10.05 Kcal/mol (with BSA) respectively. The binding affinity of the ligand and its complexes with protein and DNA was evaluated by spectroscopic techniques. Notably, the cytotoxicity studies of L and MC1-MC4 were performed against the MCF-7 (human breast cancer) cell lines. The complex MC4 displayed great activity with an IC50 of 3.5 ± 1.75 μM among all synthesized compounds and comparable with cisplatin.

2-Aryl-1H-imidazo[4,5-f][1,10]phenanthroline-Based Binuclear Ru(II)/Ir(III)/Re(I) Complexes as Mitochondria Targeting Cancer Stem Cell Therapeutic Agents

A series of novel Ru(II)/Ir(III)/Re(I)-based organometallic complexes [Ru2L1, Ru2L2, Ir2L1, Ir2L2, Re2L1, and Re2L2] have been synthesized to assess their potency and selectivity against multiple cancer cells A549, HCT-116, and HCT-116 colon CSCs. The cytotoxic screening of the synthesized complexes has revealed that complex Ru2L1 and Ir2L2 are two proficient complexes among all, but Ru2L1 is the most potent complex. A significant binding constant value was observed for DNA and BSA in all complexes. Significant lipophilic properties allow them to penetrate cancer cell membranes, and substantial quantum yield (ϕf) values support bioimaging potential. Again, these complexes are particular for mitochondrial localization and produce a profuse amount of ROS to damage the mitochondrial DNA and then G1 phase cell-cycle arrest. Protein expression analysis unveiled that pro-apoptotic Bax protein overexpressed in Ru2L1-treated cells, whereas antiapoptotic Bcl-2 protein was expressed twofold in Ir2L2-treated cells, which correlated with autophagy reticence.

Promoting the Anticancer Activity with Multidentate Furan-2-Carboxamide Functionalized Aroyl Thiourea Chelation in Binuclear Half-Sandwich Ruthenium(II) Complexes

A new set of binuclear arene ruthenium complexes [Ru2(p-cymene)2(k4-N2OS)(L1-L3)Cl2] (Ru2L1-Ru2L3) encompassing furan-2-carboxamide-based aroylthiourea derivatives (H2L1-H2L3) was synthesized and characterized by various spectral and analytical techniques. Single-crystal XRD analysis unveils the N^O and N^S mixed monobasic bidentate coordination of the ligands constructing N, S, Cl/N, O, and Cl legged piano stool octahedral geometry. DFT analysis demonstrates the predilection for the formation of stable arene ruthenium complexes. In vitro antiproliferative activity of the complexes was examined against human cervical (HeLa), breast (MCF-7), and lung (A549) cancerous and noncancerous monkey kidney epithelial (Vero) cells. All the complexes are more efficacious against HeLa and MCF-7 cells with low inhibitory doses (3.86-11.02 μM). Specifically, Ru2L3 incorporating p-cymene and -OCH3 fragments exhibits high lipophilicity, significant cytotoxicity against cancer cells, and lower toxicity on noncancerous cells. Staining analysis indicates the apoptosis-associated cell morphological changes expressively in MCF-7 cells. Mitochondrial membrane potential (MMP) and reactive oxygen species (ROS) analyses reveal that Ru2L3 can raise ROS levels, reduce MMP, and trigger mitochondrial dysfunction-mediated apoptosis. The catalytic oxidation of glutathione (GSH) to its disulfide form (GSSG) by the complexes may simultaneously increase the ROS levels, alluding to their observed cytotoxicity and apoptosis induction. Flow cytometry determined the quantitative classification of late apoptosis and S-phase arrest in MCF-7 and HeLa cells. Western blotting analysis confirmed that the complexes promote apoptosis by upregulating Caspase-3 and Caspase-9 and downregulating BCL-2. Molecular docking studies unfolded the strong binding affinities of the complexes with VEGFR2, an angiogenic signaling receptor, and BCL2, Cyclin D1, and HER2 proteins typically overexpressed on tumor cells.

Bioactive O^N^O^ Schiff base appended homoleptic titanium(iv) complexes: DFT, BSA/CT-DNA interactions, molecular docking and antitumor activity against HeLa and A549 cell lines

Five new homoleptic derivatives of titanium(iv) have been developed and characterized by physicochemical techniques. Metal complexes, TiH2L1 [(C38H26N6O4)Ti], TiH2L2 [(C38H24F2N6O4)Ti], TiH2L3 [(C38H24Cl2N6O4)Ti], TiH2L4 [(C38H24Br2N6O4)Ti] and TiH2L5 [(C38H24N8O8)Ti], were obtained by treating Ti(OPri)4 with appropriate ONO ligands (H2L1-H2L5) in anhydrous THF as solvent. The electronic structures and properties of titanium(iv) complexes (TiH2L1-TiH2L5) and ligands (H2L1-H2L5) were examined by DFT studies. The stability of all synthesized derivatives was assessed by a UV-visible technique using 10% DMSO, GSH medium and n-octanol/water systems. The binding interactions of BSA and CT-DNA with respective titanium(iv) complexes were successfully evaluated by employing UV-visible absorption, fluorescence, circular dichroism (CD) techniques and docking studies. The in vitro cytotoxicity of TiH2L2, TiH2L3 and TiH2L4 complexes was assessed against HeLa (human epithelioid cervical cancer cells) and A549 (lung carcinoma) cell lines. The IC50 values of TiH2L2, TiH2L3 and TiH2L4 were observed to be 28.8, 14.7 and 31.2 μg mL-1 for the HeLa cell line and 38.2, 32.9 and 67.78 μg mL-1 for A549 cells, respectively. Complex TiH2L3 exhibited remarkably induced cell cycle arrest in the G1 phase and 77.99% ROS production selectivity in the HeLa cell line.

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.

GSH resistant, luminescent 2-(pyren-1-yl)-1H-imidazo[4,5-f][1,10]phenanthroline-based Ru(II)/Ir(III)/Re(I) complexes for phototoxicity in triple-negative breast cancer cells

Selective chemotherapeutic strategies necessitate the emergence of a photosensitive scaffold to abate the nuisance of cancer. In the current context, photo-activated chemotherapy (PACT) has, therefore, appeared to be very effective to vanquish the vehemence of triple-negative breast cancer (TNBC). Metal complexes have been identified to act well against cancer cell microenvironment (high GSH content, low pH, and hypoxia), and thus they have been employed in the treatment of various types of cancer. As TNBC is very challenging to treat owing to its poor prognosis, lack of a specific target, high chance of relapse, and strong metastatic ability, herein we have aspired to design GSH-resistant phototoxic Ru(II)/Ir(III)/Re(I) based pyrene imidazophenathroline complexes to selectively avert the triple-negative breast cancer. The application of complexes, [RuL], [IrL], and [ReL] in the absence and in the presence of GSH against MDA-MB-231TNBC cells, has revealed that they are very active upon irradiation of visible light compared to dark due to the creation of copious singlet oxygen (1O2) as reactive oxygen species (ROS). Among three synthesized complexes, [IrL] has shown outstanding potency (IC50 = 3.70 in the absence of GSH and IC50 = 3.90 in the presence of GSH). Also, the complex, [IrL] is capable of interacting with DNA with the highest binding constant (Kb = 0.023 × 106 M-1) along with higher protein binding affinity (KBSA = 0.0321 × 106 M-1). Here, it has been unveiled that all the complexes have been entitled to involve DNA covalent interaction through the available sites of both adenine and guanine bases.

Synthesis, characterization, photophysical and electrochemical properties, and biomolecular interaction of 2,2'-biquinoline based phototoxic Ru(II)/Ir(II) complexes

The phototoxic nature of drugs has been seen to convey immense importance in photo activated chemotherapy (PACT) for the selective treatment of disease. Rationally, in order to eradicate the vehemence of cancer in a living body, the design of phototoxic molecules has been of growing interest in research to establish a selective strategy for cancer therapy. Therefore, the present work portrays the synthesis of a phototoxic anticancer agent by incorporating ruthenium(II) and iridium(III) metals into a biologically active 2,2'-biquinoline moiety, BQ. The complexes, RuBQ and IrBQ, have been revealed as effective anticancer agents with remarkable toxicity in the presence of light compared to the dark towards HeLa and MCF-7 cancer cell lines due to the production of a profuse amount of singlet oxygen (1O2) upon irradiation by visible light (400-700 nm). Complex IrBQ exhibited the best toxicity (IC50 = 8.75 μM in MCF-7 and 7.23 μM in HeLa) in comparison to the RuBQ complex under visible light. RuBQ and IrBQ displayed considerable quantum yields (Φf) along with a good lipophilic property, indicating the cellular imaging capability of both complexes upon significant accumulation in cancer cells. Also, the complexes have shown significant binding propensity with biomolecules, viz. deoxyribonucleic acid (DNA) as well as serum albumin (BSA, HSA).

Luminescent 11-{Naphthalen-1-yl}dipyrido[3,2-a:2',3'-c]phenazine-Based Ru(II)/Ir(III)/Re(I) Complexes for HCT-116 Colorectal Cancer Stem Cell Therapy

Due to a number of unpleasant considerations, marketed drugs have steadily lost their importance in the treatment of cancer. In order to find a viable cancer cell diagnostic agent, we therefore focused on metal complexes that displayed target adequacy, permeability to cancer cells, high standard water solubility, cytoselectivity, and luminescent behavior. In this aspect, luminescent 11-{naphthalen-1-yl} dipyrido [3,2-a:2',3'-c] phenazine based Ru(II)/Ir(III)/Re(I) complexes have been prepared for HCT-116 colorectal cancer stem cell therapy. Our study successfully established the possible cytotoxicity of IrL complex at different doses on HCT-116 colorectal cancer stem cells (CRCSCs). Additionally, an immunochemistry analysis of the complex IrL showed that the molecule was subcellularly localized in the nucleus and other regions of the cytoplasm, where it caused nuclear DNA damage and mitochondrial dysfunction. The level of BAX and Bcl-2 was further quantified by qRT-PCR. The expression of proapoptotic BAX showed increased expression in the complex IrL-treated cell compared to the control, indicating the potential of complex IrL for apoptotic induction. Upon further validation, complex IrL was developed as an inhibitor of autophagy for the eradication of cancer stem cells.

Platinum(II)-Metallaclip-Based Theranostics for Cell Imaging and Synergetic Chemotherapy-Photodynamic Therapy

Supramolecular coordination complexes formed by coordination-induced assembly not only avoid the loss of activity of precursors but also provide an efficient way for controlled release, which can be further used in various fields of biology such as drug delivery, cell imaging, and tumor treatment. In this work, a Pt^II metallaclip (4) was prepared from 4-[4-(1,2,2-triphenylvinyl)phenyl]pyridine (1), 5,10,15-triphenyl-20-(pyridin-4-yl)porphyrin (2), 90^o Pt, and glycol-chain-modified isophthalic acid (3) in an acetone/water mixture through the "coordination-driven self-assembly" method. ³¹P and ¹H NMR spectroscopy and high-resolution mass spectrometry were used to characterize the obtained metallaclip 4. 4 can self-assemble into fluorescent nanostructures in aqueous solution because of the tetraphenylethylene unit and its amphiphilic nature. Importantly, the fluorescent nanoparticles not only can be employed for cell imaging but also can generate singlet oxygen (¹O₂) under 660 nm laser irradiation and the release of Pt drug in the tumor issue for cancer therapy. The work may provide a new way for scientists to construct functional biomaterials with multiple applications via molecular self-assembly.

Ruthenium(II)-Dithiocarbazates as Anticancer Agents: Synthesis, Solution Behavior, and Mitochondria-Targeted Apoptotic Cell Death

The reaction of the Ru(PPh₃ )₃ Cl₂ with HL^1-3 -OH (-OH stands for the oxime hydroxyl group; HL¹ -OH=diacetylmonoxime-S-benzyldithiocarbazonate; HL² -OH=diacetylmonoxime-S-(4-methyl)benzyldithiocarbazonate; and HL³ -OH=diacetylmonoxime-S-(4-chloro)benzyl-dithiocarbazonate) gives three new ruthenium complexes [Ru^II (L^1-3 -H)(PPh₃ )₂ Cl] (1-3) (-H stands for imine hydrogen) coordinated with dithiocarbazate imine as the final products. All ruthenium(II) complexes (1-3) have been characterized by elemental (CHNS) analyses, IR, UV-vis, NMR (¹ H, ¹³ C, and ³¹ P) spectroscopy, HR-ESI-MS spectrometry and also, the structure of 1-2 was further confirmed by single crystal X-ray crystallography. The solution/aqueous stability, hydrophobicity, DNA interactions, and cell viability studies of 1-3 against HeLa, HT-29, and NIH-3T3 cell lines were performed. Cell viability results suggested 3 being the most cytotoxic of the series with IC₅₀ 6.9±0.2 μM against HeLa cells. Further, an apoptotic mechanism of cell death was confirmed by cell cycle analysis and Annexin V-FITC/PI double staining techniques. In this regard, the live cell confocal microscopy results revealed that compounds primarily target the mitochondria against HeLa, and HT-29 cell lines. Moreover, these ruthenium complexes elevate the ROS level by inducing mitochondria targeting apoptotic cell death.

Synthesis, structural insights, and biological screening of DNA targeted Ru(ii)(η6-p-cymene) complexes containing bioactive amino-benzothiazole ligand scaffolds

Two new drug candidates [Ru(p-cymene)(C7H4ClN2S)Cl2] and [Ru(p-cymene)(C7H5FN2S)Cl2] were synthesized and characterised. The in vitro cytotoxic activity of the complexes was assessed against five human cancer cell lines and anthelmintic activity was also investigated.

Mitochondria-targeted half-sandwich iridium(iii)-Cp*-arylimidazophenanthroline complexes as antiproliferative and bioimaging agents against triple negative breast cancer cells MDA-MB-468

To reduce the side effects of marketed cancer drugs against triple negative breast cancer cells we have reported mitochondria targeting half-sandwich iridium(iii)-Cp*-arylimidazophenanthroline complexes for MDA-MB-468 cell therapy and diagnosis. Out of five Ir(iii) complexes (IrL1–IrL5), [iridium(iii)-Cp*-2-(naphthalen-1-yl)-1H-imidazo[4,5-f][1,10]phenanthroline]PF₆ (IrL1) has exhibited the best cytoselectivity against MDA-MB-468 cells compared to normal HaCaT cells along with excellent binding efficacy with DNA as well as serum albumin. The subcellular localization study of the complex revealed the localization of the compound in cytoplasm thereby pointing to a possible mitochondrial localization and consequent mitochondrial dysfunction via MMP alteration and ROS generation. Moreover, the IrL1 complex facilitated a substantial G₁ phase cell-cycle arrest of MDA-MB-468 cells at the highest tested concentration of 5 μM. The study verdicts support the prospective therapeutic potential of the IrL1 complex in the treatment and eradication of triple negative breast cancer cells. These results validate that these types of scaffolds will be fairly able to exert great potential for tumor diagnosis as well as therapy in the near future.

Mitochondria targeting half-sandwich Iridium(iii)-Cp*-arylimidazophenanthroline complexes have been developed for MDA-MB-468 cell therapy and diagnosis.

2,2'-Bipyrimidine-based luminescent Ru(ii)/Ir(iii)-arene monometallic and homo- and hetero-bimetallic complexes for therapy against MDA-MB-468 and caco-2 cells

To unearth suitable complexes that are capable of inhibiting the growth of MDA-MB-468 and Caco-2 cells, 2,2'-bipyrimidine-based luminescent Ru(ii)/Ir(iii)-arene monometallic and homo- and hetero-bimetallic complexes were synthesized. The complex [(η⁶-p-cymene)(η⁵-Cp*)Ru^IIIr^IIICl₂(K²-N,N-bipyrimidine)](PF₆)₂ [LRuIr] exhibited the best potency in both cells along with good GSH stability and strong binding efficacy with the biomolecules. The apoptotic event occurred in MDA-MB-468 cancer cells via cell cycle arrest.

Ru(ii), Ir(iii), Re(i) and Rh(iii) based complexes as next generation anticancer metallopharmaceuticals

Several anticancer drugs such as cisplatin, and its analogues, epirubicin, and doxorubicin are well known for their anticancer activity but the therapeutic value of these drugs comes with certain side effects and they cannot distinguish between normal and cancer cells. Thus, a major challenge for researchers around the world is to develop an anticancer drug with the least toxicity and more target specificity. With the successful reporting of NAMI-A and KP1019, a new path has emerged in the anticancer field. Recently, several Ru(ii) complexes have been reported for their anticancer activity due to their enhanced cellular uptake and selectivity towards cancer cells. Apart from the Ru(ii) complexes, a large amount of research has been carried out with Ir(iii), Re(i), and Rh(iii) based complexes, which exhibited promising anticancer activity. The present review reports various Ru(ii), Ir(iii), Re(i), and Rh(iii) based complexes for their anticancer activity based on their cytotoxicity profiles, biological targets and mechanism of action.

Antitumor Effect of Organometallic Half-Sandwich Ru(II)-Arene Complexes Bearing a Glutathione S-Transferase Inhibitor

The facile modification of the ligands in organometallic Ru(II)-arene complexes offers more opportunities to optimize their pharmacological profiles. Herein, three Ru(II)-arene complexes containing a glutathione S-transferase (GST) inhibitor (NBDHEX) in chelate ligand have been designed and synthesized in this study. In vitro results indicated that the ligation with NBDHEX significantly increased the activities and selectivities of the organometallic Ru(II)-arene complexes against tumor cells, especially complex 3, which was the most active compound among the tested compounds. DFT calculations and hydrolysis results demonstrated that complex 3 with more alkyl groups in the arene ligand has increased electron density at the Ru(II) center as compared with complexes 1 and 2, thus resulting in the improved hydrolysis rate, which may be responsible for its higher anticancer activity. Further studies showed that complexes 1-3 can cause the loss of the mitochondrial membrane potential and upregulate the expression of Bcl-2 and Bax in A549 cells, suggesting that complexes 1-3-induced cell death may be mediated via the mitochondrial apoptotic pathway. Thus, these findings suggested that simultaneous modification of the chelate ligands and arene rings in the organometallic Ru(II)-arene complexes is an effective way to improve their pharmacological properties.

Recent progress in mitochondria-targeting-based nanotechnology for cancer treatment

Mitochondria play critical roles in the regulation of the proliferation and apoptosis of cancerous cells. Nanosystems for targeted delivery of cargos to mitochondria for cancer treatment have attracted increasing attention in the past few years. This review will summarize the state of the art of design and construction of nanosystems used for mitochondria-targeted delivery. The use of nanotechnology for cancer treatment through various pathways such as energy metabolism interference, reactive oxygen species (ROS) regulation, mitochondrial protein targeting, mitochondrial DNA (mtDNA) interference, mitophagy inducing, and combination therapy will be discussed. Finally, the major challenges and an outlook in this field will also be provided.

Expanding the Limits of Photodynamic Therapy: The Design of Organelles and Hypoxia-Targeting Nanomaterials for Enhanced Photokilling of Cancer

Photodynamic therapy (PDT) is a minimally invasive clinical protocol that combines a nontoxic photosensitizer (PS), appropriate visible light, and molecular oxygen for cancer treatment. This triad generates reactive oxygen species (ROS) in situ, leading to different cell death pathways and limiting the arrival of nutrients by irreversible destruction of the tumor vascular system. Despite the number of formulations and applications available, the advancement of therapy is hindered by some characteristics such as the hypoxic condition of solid tumors and the limited energy density (light fluence) that reaches the target. As a result, the use of PDT as a definitive monotherapy for cancer is generally restricted to pretumor lesions or neoplastic tissue of approximately 1 cm in size. To expand this limitation, researchers have synthesized functional nanoparticles (NPs) capable of carrying classical photosensitizers with self-supplying oxygen as well as targeting specific organelles such as mitochondria and lysosomes. This has improved outcomes in vitro and in vivo. This review highlights the basis of PDT, many of the most commonly used strategies of functionalization of smart NPs, and their potential to break the current limits of the classical protocol of PDT against cancer. The application and future perspectives of the multifunctional nanoparticles in PDT are also discussed in some detail.