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Title: Designing novel tridentate iridium(III) complexes comprising functionalized benzothiazole ligands to improve anticancer activity by targeting mitochondria. Abstract: In recent years, organo‑iridium anticancer agents have shown promising antitumor activity toward cancer cells. In this paper, two benzothiazole-based tridentate ligands, 2,2'-(5-(tert-butyl)-1,3-phenylene)bis(benzo[d]thiazole) (L1) and 2,2'-(5-(methyl)-1,3-phenylene)bis(benzo[d]thiazole) (L2), have been designed and synthesized, and then combined with 2,2'-bipyridine (bipy) and 1,10-phenanthroline (phen) ancillary ligands to form a series of novel [Ir(N^C^N)(N^N)Cl]+-type iridium(III) complexes (Ir1-Ir4). The phosphorescence properties of these complexes facilitate the visualization of their subcellular localization and interactions with other biomolecules. Among them, complex Ir2 has the best cytotoxicity activity toward A549 cells and its antitumor activity was further evaluated. Laser confocal assay reveals that Ir2 followed an energy-dependent cellular uptake mechanism and specifically accumulates in mitochondria (Pearson colocalization coefficient: 0.89). The anticancer mechanism has been explored through apoptosis, cell cycle arrest, western blotting (WB), reactive oxygen species (ROS) levels and mitochondrial membrane potential (MMP) changes. The antitumor activity in vivo confirms that Ir2 could effectively inhibit tumor growth with an inhibitory rate of 71.60 %, which is superior to cisplatin. To the best of our knowledge, Ir2 is a rare example of [Ir(N^C^N)(N^N)Cl]+-type complexes as potential anticancer agents. Show less

In recent years, photodynamic therapy (PDT) has emerged as a promising alternative to classical chemotherapy for treating cancer. PDT is based on a nontoxic prodrug called photosensitizer (PS) activated by light at the desired location. Upon irradiation, the PS reacts with the oxygen present in the tumor, producing cytotoxic reactive oxygen species (ROS). Compounds with highly conjugated π-bond systems, such as porphyrins and chlorins, have proven to be excellent light scavengers, and introducing a metal atom in their structure improved the generation of ROS. In this work, a series of tetrapyrrole-ruthenium(II) complexes derived from protoporphyrin IX and the commercial drug verteporfin were designed as photosensitizers for PDT. The complexes were almost nontoxic on human gastric cancer cells under dark conditions, revealing remarkable cytotoxicity upon irradiation with light. The ruthenium atom in the central cavity of the chlorin ligand allowed combined mechanisms in photodynamic therapy, as both singlet oxygen and superoxide radicals were detected. Additionally, one complex produced large amounts of singlet oxygen under hypoxic conditions. Biological assays demonstrated that the ruthenium derivatives caused cell death through a caspase 3 mediated apoptotic pathway and via CHOP, an endoplasmic reticulum stress-inducible transcription factor involved in apoptosis and growth arrest. Show less

Two new Ru(II) complexes, mononuclear [RuCl₂(η⁶-p-cymene)(3,4-dmph-κN)] (1) and the binuclear complex [{RuCl(η⁶-p-cymene)}₂(μ-Cl)(μ-3,4-dmph-κ²N,N')]Cl (2; 3,4-dmph = 3,4-dimethylphenylhydrazine), are synthesized and experimentally and theoretically structurally characterized utilizing ¹H and ¹³C NMR and FTIR spectroscopy, as well as DFT calculations. Degradation product of 2, thus ([{RuCl(η⁶-p-cymene)}₂(μ-Cl)(μ-3,4-dmph-κ²N,N')][RuCl₃(η⁶-p-cymene)] (2b) was characterized with SC-XRD. In the crystals of 2b, the cationic and anionic parts interact through N-H^...Cl hydrogen bridges. The spectrofluorimetric measurements proved the spontaneity of the binding processes of both complexes and HSA. Spin probing EPR measurements implied that 1 and 2 decreased the amount of bound 16-doxylstearate and implicated their potential to bind to HSA more strongly than the spin probe. The cytotoxicity assessment of both complexes against the MDA-MB-231 and MIA PaCa-2 cancer cell lines demonstrated a clear dose-dependent decrease in cell viability and no effect on healthy HS-5 cells. Determination of the malondialdehyde and protein carbonyl concentrations indicated that new complexes could offer protective antioxidant benefits in specific cancer contexts. Gel electrophoresis measurements showed the reduction in MMP9 activity and indicated the potential of 1 in limiting the cancer cells' invasion. The annexin V/PI apoptotic assay results showed that 1 and 2 exhibit different selectivity towards MIA PaCa-2 and MDA-MB-231 cancer cells. A comparative molecular docking analysis of protein binding, specifically targeting acetylcholinesterase (ACHE), matrix metalloproteinase-9 (MMP-9), and human serum albumin (HSA), demonstrated distinct binding interactions for each complex. Show less

Title: Triphenylphosphine-modified cyclometalated iridium Abstract: This study presents the development and evaluation of triphenylphosphine-modified cyclometalated iridiumIII complexes as selective anticancer agents targeting mitochondria. By leveraging the mitochondrial localization capability of the triphenylphosphine group, these complexes displayed promising cytotoxicity in the micromolar range (3.12-7.24 μM) against A549 and HeLa cancer cells, these complexes exhibit significantly higher activity compared to their unmodified counterparts lacking the triphenylphosphine moiety. Moreover, they demonstrate improved specificity for cancer cells over normal cells, achieving selectivity index in the range of 5.46-14.83. Mechanistic studies confirmed that these complexes selectively target mitochondria rather than DNA, as shown by confocal microscopy and flow cytometry, where they accumulate to induce mitochondrial dysfunction. This disruption leads to mitochondrial membrane depolarization (MMP), elevated reactive oxygen species (ROS) levels, and activation of intrinsic apoptosis pathways. Furthermore, the complexes induce cell cycle arrest at the G2/M phase and suppress the migration of A549 cells. Show less

Modulating mitochondrial activity to regulate cancer cell homeostatic recycling presents a promising approach to overcome tumor resistance. Consequently, there is an urgent need for novel mitochondria-targeting agents and innovative strategies. We have developed [((η⁵-Cp∗)Ir(rhod)]²⁺2PF₆^- (Ir-rhod), a new mitochondria-targeted iridium complex that exhibits greater cytotoxicity towards A549R (cisplatin-resistant human lung cancer) cells compared to the ligand rhod. Ir-rhod's mitochondrial targeting ability stems from both rhodamine's inherent mitochondrial affinity and the complex's positive bivalent nature. The positively charged Ir-rhod enters cells and is drawn to mitochondria due to the high transmembrane potential in tumor cells. Notably, rhodamine enables real-time observation of Ir-rhod's dynamic distribution in vivo. Ir-rhod influences mitochondrial function, triggering tumor cell ferroptosis and apoptosis by modulating ACSL4 and GPX4. The targeting effect of Ir-rhod reduces its systemic toxicity in vivo, enhancing its biosafety profile. To our knowledge, Ir-rhod is an effective mitochondria-targeted Ir complex capable of inducing tumor cell death by disrupting mitochondrial function, offering a potent strategy to suppress cisplatin resistance in non-small cell lung cancer. Show less

Title: Highly effective Ru(II) and Os(II) half-sandwich complexes induce cytotoxicity in cancer cells through combined mitochondrial and endoplasmic reticulum stress. Abstract: A series of ruthenium(II) and osmium(II) half-sandwich complexes was synthesized and characterized for its potential as a new class of anticancer agents. The complexes feature polycyclic aromatic hydrocarbon (PAH)-substituted Schiff bases and were rationally designed to combine the redox-modulating MoA of half-sandwich Ru, Rh, Os and Ir complexes, connected with their ability to induce the formation of various reactive oxygen species (ROS), with the ability of PAH-substituents to target and disrupt DNA. The complexes [Ru(η6-pcym)Cl(L)]PF6 (1-4) and [Os(η6-pcym)Cl(L)]PF6 (5-8) were stable in aqueous environments, in contrast to the rapid degradation observed for the co-studied rhodium(III) (9-12) and iridium(III) (13-16) [M(η5-Cp∗)Cl(L)]PF6 complexes; L = ethane-1,2-diamine-based Schiff bases (L1-L4) bearing two terminal PAH substituents 2-naphtyl (for L1), 9-anthracenyl (for L2), 9-phenanthrenyl (L3) or 1-pyrenyl (L4); pcym = 1-methyl-4-(propan-2-yl)benzene (p-cymene), Cp∗ = pentamethylcyclopentadienyl. Biological testing demonstrated that 1-8 possess significant antiproliferative activity against various lung cancer cell lines, including those resistant to cisplatin, with Os(II) complex 5 showing the highest cytotoxicity. Treatment with these complexes led to the activation of stress-related gene pathways, including unconventional endoplasmic reticulum stress, apoptotic signalling, and mitochondrial membrane depolarization. Activation of p21/GADD45A pathway indicates DNA-damage response, as well. Notably, these complexes did not induce significant inflammatory responses, a notable advantage over cisplatin. The results highlight the potential of Ru and Os half-sandwich complexes as alternative metallodrugs, capable of overcoming platinum resistance and minimizing inflammatory side effects. This study suggests that these compounds could serve as a promising class of anticancer agents for future clinical development. Show less

Background/objectives

Breast cancer (BC) remains one of the most prevalent and deadly cancers worldwide, with limited access to advanced treatments in developing regions. There is a critical need for novel therapies with unique mechanisms of action, especially to overcome resistance to conventional platinum-based drugs. This study investigates the anticancer potential of the ruthenium complex Bis(quinolin-8-olato)bis(triphenylphosphine)ruthenium(II) (Ru(quin)₂) in ER-positive (T47D) and triple-negative (MDA-MB-231) BC cell lines.

Results

Ru(quin)₂ demonstrated dose-dependent cytotoxicity, with IC50 values of 48.3 μM in T47D cells and 45.5 μM in MDA-MB-231 cells. Its cytotoxic effects are primarily driven by apoptosis, as shown by increased BAX expression, enhanced caspase-3 activity, reduced Aurora B kinase levels, and elevated histone release. Ru(quin)₂ also induced autophagy, evidenced by LC3-I to LC3-II conversion and reduced SQSTM1, partially mediated through MAPK signaling. Furthermore, Ru(quin)₂ induced G0/G1 cell cycle arrest by downregulating cyclin D1, CDK4, and CDK6, alongside upregulation of the CDK inhibitor p21.

Conclusions

Ru(quin)₂ emerges as a potent candidate for BC treatment, with multiple mechanisms of action involving apoptosis, autophagy, and cell cycle arrest. Further studies are warranted to elucidate its detailed molecular mechanisms and evaluate its therapeutic potential in vivo, moving toward clinical applications for both ER-positive and triple-negative BC management. Show less

Title: Systematic Investigation of Coordination Chemistry in Iridium(III) and Ruthenium(II) Complexes Derived from Pyridyl-Amine Ligands and Their Anticancer Evaluation. Abstract: A systematic investigation of the coordination chemistry of iridium(III) and ruthenium(II) complexes synthesized from pyridyl-amine ligands was performed, focusing on how ligand steric hindrance and metal centers affect oxidation behavior, coordination modes, and biological activities. The study revealed that steric hindrance at the ligand's bridge carbon strongly influenced both oxidation behavior and coordination modes. Smaller substituents (e.g., H and Me) facilitated oxidation to form pyridyl-imine species under adventitious oxygen, whereas bulky substituents (e.g., i-Bu and mesityl) suppressed oxidation, yielding stable pyridyl-amine or 16-electron pyridyl-amido complexes. Moreover, iridium(III) complexes were more prone to oxidation than the corresponding ruthenium(II) complexes under similar conditions. The aqueous stability of the newly synthesized complexes was confirmed. Cytotoxicity assays demonstrated that most of the complexes exhibited notable anticancer potency against A549, HeLa and cisplatin-resistant A549/DDP cancer cells. Mechanistic studies suggested a redox-driven pathway involving the catalytic oxidation of NADH to NAD+, the elevation of ROS levels and depolarization of the mitochondrial membrane. Notably, pyridyl-amine complexes induced apoptosis, while 16-electron pyridyl-amido complexes did not, though both caused S phase cell cycle arrest. Additionally these complexes can inhibit A549 cell migration, suggesting their potential to reduce cancer metastasis. Show less

Title: Mitochondrial-targeted iridium(III) complexes suppress tumor growth through inducting immunogenic cell death to activate immune response. Abstract: A new ligand, 2-(2-hydroxyl-4-methyl)phenyl-1H-imidazo[4,5-f][1,10]phenanthroline (IPMP), and [Ir(ppy)2(IPMP)]PF6 (7a), [Ir(bzq)2(IPMP)]PF6 (7b), and [Ir(piq)2(IPMP)]PF6 (7c) have been prepared and characterized by HRMS, NMR spectra. The 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assays revealed that 7b exhibited excellent activity (IC50 = 4.5 ± 0.4 μM), while 7a and 7c showed good cytotoxicity (IC50 = 8.5 ± 0.9 μM and 8.9 ± 2.2 μM) against non-small cell lung cancer A549 cells. The experiments of cellular uptake and mitochondrial localization demonstrate that these new iridium(III) complexes are readily taken up by A549 cells and accumulate in the mitochondria and damage the structure of the mitochondria, which results in the loss of mitochondrial membrane potential (MMP), elevated lipid peroxidation, as well as DNA damage, the inhibition of microtubule polymerization, hindrance of the cell cycle in the G0/G1 phase, and release of cytochrome c, collectively leading to apoptosis. Furthermore, upregulation of Beclin-1, overexpression of NF-κB and downregulation of GPX4 protein were observed, which resulted in the activation of autophagy, pyroptosis and ferroptosis, respectively. In the C57BL/6 mouse model, the 7b demonstrated promising in vivo antitumor efficacy, with a tumor inhibitory rate of 66.9 %. Additionally, the complexes induce an immunogenic cell death to activate immune response, further enhance CD8+ T cells and efficiently inhibit tumor growth. Collectively, we consider that the complexes may be utilized as potential candidate agents for the treatment of A549 cancer. Show less

A series of iridium(iii) complexes (Ir1-Ir3) with the formula [Ir(F₂ppy)₂(L)] (F₂ppy = 2-(2,4-difluoro-phenyl)pyridine, L = pyridine-2-aldoxime, 2-pyridylamidoxime and di-2-pyridylketoxime) were synthesized through the reaction of [(F₂ppy)₂Ir(μ-Cl)₂Ir(F₂ppy)₂] (SM1) and the respective ancillary ligands (L). All the complexes were characterised by FT-IR, ¹H & ¹⁹F-NMR analysis, electronic absorption-emission spectroscopy and cyclic voltammetric studies. Molecular structures of complexes Ir1 and Ir3 were determined by interpreting single crystal X-ray data. All the complexes were found to be luminescent with low quantum yields. Anticancer studies on cancer cell lines MDAMB, HT-29 and LN-229 revealed their effectiveness as antiproliferative agents. The cytotoxicity of the complexes was evaluated using the MTT assay and complex Ir2 showed activity similar to that of cisplatin towards the three cancer cells. The elevated level of reactive oxygen species (ROS) in the iridium complex-treated cancer cells further supported the antiproliferation efficacy of Ir1-Ir3. Further, the effectiveness of Ir1-Ir3 on cancer cells was established through a cell migration study and apoptotic induction assay on LN-229 and a colony formation assay on HT-29 cancer cells. Immunocytochemistry analysis of LN-229 cancer cells revealed apoptosis through the p53-dependent pathway. Show less

Title: New rhodium(III)-triphenylphosphine complexes with 5-halogenate-8-hydroxyquinoline as ligands: synthesis, characterization, cytotoxicity, and mechanism of action. Abstract: The incorporation of triphenylphosphine (PPh3) can enhance the antiproliferative activity of complexes. Herein, four Rh(III) complexes GUPT1-GUPT4 were synthesized. GUPT4 exhibited stronger anticancer activity than HGU, cisplatin, and GUPT1-GUPT3 against human non-small cell lung A549 and its cisplatin-resistant A549 cell line (CR-A549), with IC50 values of 6.73 ± 0.41 and 5.11 ± 0.16 μM, respectively. The antiproliferative activity of the four RhIII complexes increased with different 5-substituted ligands in the following order: H (GUPT1) < Br (GUPT2) < Cl (GUPT3) < F (GUPT4). GUPT3 and GUPT4 induce CR-A549 mitochondrial autophagy and ATP blockade, leading to apoptosis. In addition, the inhibition rate of GUPT4 on A549 was 39.1 %, showing potential antitumor efficacy. Thus, GUPT3 and GUPT4 can be considered as promising non-Pt drug candidates for lung cancer treatment. Show less

Title: Radiosensitization effect of iridium (III) complex on lung cancer cells via mitochondria apoptosis pathway. Abstract: BACKGROUND: Lung cancer is the leading cause of cancer-related death in the worldwide. Although cisplatin and other platinum-based drugs are widely used as radiosensitizers in radiotherapy and considered the first-line treatment for advanced lung cancer, their clinical utility is often limited by drug resistance and severe cytotoxic side effects. In recent years, iridium-based complexes and other transition metal cation complexes with similar structural properties have garnered increasing research interest due to their potential anticancer properties. METHODS: Recently, we synthesized a novel iridium (III) complex (Ir-1) and evaluated its safety and stability. The present study aimed to identify Ir-1 with potent anticancer activity by assessing its cytotoxic effects on lung cancer cells in vitro. Additionally, it investigated Ir-1's radiosensitizing efficacy and the underlying mechanisms. RESULTS: The results demonstrated that Ir-1 exhibited significant radiosensitizing effects on lung cancer cells. Ir-1 effectively reduced cell viability and colony formation, arrested the cell cycle at the G2/M phase, inhibited cell migration and invasion, decreased mitochondrial membrane potential, and increased reactive oxygen species (ROS) generation in lung cancer cells. Importantly, these cytotoxic effects were selective, with minimal impact on normal cells. Mechanistic studies showed that Ir-1 enhanced radiation-induced cancer cell death by disrupting mitochondrial function and activating the mitochondrial apoptotic pathway. This was evidenced by upregulated expression levels of Bax, Cytochrome c (Cyt-C), and Caspase9 proteins, along with reduced level of Bcl-2 protein. Notably, the addition of a Cyt-C inhibitor significantly reduced the expression of Cyt-C and Caspase9 proteins. Similarly, treatment with the Caspase9 inhibitor Z-LEHD-FMK also reduced Caspase9 protein level. CONCLUSION: This study provides robust evidence that Ir-1 is a promising and safe radiosensitizer for lung cancer therapy. Its ability to enhance radiation-induced cytotoxicity through mitochondrial dysfunction and activation of apoptotic pathways highlights its potential for clinical application. Show less

Title: Synthesis, characterization and irradiation enhances anticancer activity of liposome-loaded iridium(III) complexes. Abstract: Herein, we synthesized and characterized two novel iridium (III) complexes: [Ir(bzq)2(PPD)](PF6) (4a, with bzq = deprotonated benzo[h]quinoline and PPD = pteridino[6,7-f][1,10]phenanthroline-11,13-diamine) and [Ir(piq)2(PPD)](PF6) (4b, with piq = deprotonated 1-phenylisoquinoline). The anticancer efficacy of these complexes, 4a and 4b, was investigated using 3-(4,5-dimethylthiazole)-2,5-diphenltetraazolium bromide (MTT). Complex 4a exhibited no cytotoxic activity, while 4b demonstrated moderate efficacy against SGC-7901, A549, and HepG2 cancer cells. To enhance their anticancer potential, we explored two strategies: (I) light irradiation and (II) encapsulation of the complexes in liposomes, resulting in the formation of 4alip and 4blip. Both strategies significantly increased the ability of 4a, 4b to kill cancer cells. The cellular studies indicated that both the free complexes 4a, 4b and their liposomal forms 4alip and 4blip effectively inhibited cell proliferation. The cell cycle arrest analysis uncovered 4alip and 4blip arresting cell growth in the S period. Additionally, we investigated apoptosis and ferroptosis pathways, observing an increase in malondialdehyde (MDA) levels, a reduction of glutathione (GSH), a down-regulation of GPX4 (glutathione peroxidase) expression, and lipid peroxidation. The effects on mitochondrial membrane potential and intracellular Ca2+ concentrations were also examined, revealing that both light-activated and liposomal forms of 4alip and 4blip caused a decline in mitochondrial membrane potential and an enhancement in intracellular Ca2+ levels. In conclusion, these complexes and them encapsulated liposomes induce cell death through apoptosis and ferroptosis. Show less

Title: Anticancer activity of 8-hydroxyquinoline-triphenylphosphine rhodium(III) complexes targeting mitophagy pathways. Abstract: Metallodrugs exhibiting distinct mechanisms of action compared with cisplatin hold promise for overcoming cisplatin resistance and improving the efficacy of anticancer drugs. In this study, a new series of rhodium (Rh)(III) complexes containing tris(triphenylphosphine)rhodium(I) chloride [(TPP)3RhCl] (TPP = triphenylphosphine, TPP=O = triphenylphosphine oxide) and 8-hydroxyquinoline derivatives (H-XR1-H-XR4), namely [Rh(XR1)2(TPP)Cl]·(TPP=O) (Yulin Normal University-1a [YNU-1a]), [Rh(XR2)2(TPP)Cl] (YNU-1b), [Rh(XR3)2(TPP)Cl] (YNU-1c), and [Rh(XR4)2(TPP)Cl] (YNU-1d), was synthesized and characterized via X-ray diffraction, mass spectrometry and IR. The cytotoxicity of the compounds YNU-1a-YNU-1d in Hep-G2 and HCC1806 human cancer cell lines and normal HL-7702 cell line was evaluated. YNU-1c exhibited cytotoxicity and selectivity in HCC1806 cells (IC50 = 0.13 ± 0.06 μM, selectivity factor (SF) = 384.6). The compounds YNU-1b and YNU-1c, which were selected for mechanistic studies, induced the activation of apoptotic pathways and mitophagy. In addition, these compounds released cytochrome c, cleaved caspase-3/pro-caspase-3 and downregulated the levels of mitochondrial respiratory chain complexes I/IV (M1 and M4) and ATP. The compound YNU-1c, which was selected for in vivo experiments, exhibited tumor growth inhibition (58.9 %). Importantly, hematoxylin and eosin staining and TUNEL revealed that HCC1806 tumor tissues exhibited significant apoptotic characteristics. YNU-1a-YNU-1d compounds are promising drug candidates that can be used to overcome cisplatin resistance. Show less

Sorafenib, a multiple kinase inhibitor, is widely used as a first-line treatment for hepatocellular carcinoma. However, there is a need for more effective alternatives when sorafenib proves insufficient. In this study, we aimed to design a structure that surpasses sorafenib's efficacy, leading us to synthesize sorafenib-ruthenium complexes for the first time and investigate their properties. Our results indicate that the sorafenib-ruthenium complexes exhibit superior epidermal growth factor receptor (EGFR) inhibition compared to sorafenib alone. Interestingly, among these complexes, Ru3S demonstrated high activity against various cancer cell lines including sorafenib-resistant HepG2 cells while exhibiting significantly lower cytotoxicity than sorafenib in healthy cell lines. Further evaluation of cell cycle, cell apoptosis, and antiangiogenic effects, molecular docking, and molecular dynamics studies revealed that Ru3S holds great potential as a drug candidate. Additionally, when free Ru3S was encapsulated into polymeric micelles M1, enhanced cytotoxicity on HepG2 cells was observed. Collectively, these findings position Ru3S as a promising candidate for EGFR inhibition and warrant further exploration for drug development purposes. Show less

Title: Design and anticancer behaviour of cationic/neutral half-sandwich iridium(III) imidazole-phenanthroline/phenanthrene complexes. Abstract: Considerable attention has been devoted to the exploration of organometallic iridium(III) (IrIII) complexes for their potential as metallic anticancer drugs. In this study, twelve half-sandwich IrIII imidazole-phenanthroline/phenanthrene complexes were prepared and characterized. Complexes exhibited promising in-vitro anti-proliferative activity, and some are obviously superior to cisplatin towards A549 cells. These complexes possessed suitable fluorescence, and a non-energy-dependent uptake pathway was identified, subsequently leading to their accumulation in the lysosome and the lysosomal damage. Additionally, complexes could inhibit the cell cycle (G1-phase) and catalyze intracellular NADH oxidation, thus substantiating the elevation of intracellular reactive oxygen species (ROS) level, which confirming the oxidative mechanism. Western blotting further confirmed that complexes could induce A549 cell apoptosis through the lysosomal-mitochondrial anticancer pathway, which was inconsistent with cisplatin. In summary, these complexes offer fresh concepts for the development of organometallic non‑platinum anticancer drugs. Show less

Title: Mitochondria-targeted neutral and cationic iridium(III) anticancer complexes chelating simple hybrid sp Abstract: Most platinum group-based cyclometalated neutral and cationic anticancer complexes with the general formula [(C^N)2Ir(XY)]0/+ (neutral complex: XY = bidentate anionic ligand; cationic complex: XY = bidentate neutral ligand) are notable owing to their intrinsic luminescence properties, good cell permeability, interaction with some biomolecular targets and unique mechanisms of action (MoAs). We herein synthesized a series of neutral and cationic amine-imine cyclometalated iridium(III) complexes using Schiff base ligands with sp2-N/sp3-N N^NH2 chelating donors. The cyclometalated iridium(III) complexes were identified by various techniques. They were stable in aqueous media, displayed moderate fluorescence and exhibited affinity toward bovine serum albumin (BSA). The complexes demonstrated promising cytotoxicity against lung cancer A549 cells, cisplatin-resistant lung cancer A549/DDP cells, cervical carcinoma HeLa cells and human liver carcinoma HepG2 cells, with IC50 values ranging from 9.98 to 19.63 μM. Unfortunately, these complexes had a low selectivity (selectivity index: 1.62-1.98) towards A549 cells and BEAS-2B normal cells. The charge pattern of the metal center (neutral or cationic) and ligand substituents showed little influence on the cytotoxicity and selectivity of these complexes. The study revealed that these complexes could target mitochondria, cause depolarization of the mitochondrial membrane, and trigger the production of intracellular ROS. Additionally, the complexes were observed to induce late apoptosis and perturb the cell cycle in the G2/M or S phase in A549 cells. Based on these results, it appears that the anticancer efficacy of these complexes was predominantly attributed to the redox mechanism. Show less

Title: Anticancer activity and mechanism studies of photoactivated iridium(III) complexes toward lung cancer A549 cells. Abstract: Cyclometalated iridium(III) compounds have been widely explored due to their outstanding photo-physical properties and multiple anticancer activities. In this paper, three cyclometalated iridium(III) compounds [Ir(ppy)2(DBDIP)]PF6 (5a), [Ir(bzq)2(DBDIP)]PF6 (5b), and [Ir(piq)2(DBDIP)]PF6 (5c) (ppy: 2-phenylpyridine; bzq: benzo[h]quinoline; piq: 1-phenylisoquinoline, and DBDIP: 2-(2,3-dihydrobenzo[b][1,4]dioxin-6-yl)-1H-imidazo[4,5-f][1,10]phenanthroline) were synthesized and the mechanism of antitumor activity was investigated. Compounds photoactivated by visible light show strong cytotoxicity against tumor cells, especially toward A549 cells. Biological experiments such as migration, cellular localization, mitochondrial membrane potential and permeability, reactive oxygen species (ROS) and calcium ion level detection were performed, and they demonstrated that the compounds induced the apoptosis of A549 cells through a mitochondrial pathway. At the same time, oxidative stress caused by ROS production increases the release of damage-related molecules and the expression of porogen gasdermin D (GSDMD), and the content of LDH released from damaged cell membranes also increased. Besides, the content of the lipid peroxidation product, malondialdehyde (MDA), increased and the expression of GPX4 decreased. These indicate that the compounds promote cell death by combining ferroptosis and pyroptosis. The results reveal that cyclometalated iridium(III) compounds 5a-5c may be a potential chemotherapeutic agent for photodynamic therapy of cancers. Show less

Title: pH-Responsive, Self-Assembled Ruthenium Nanodrug: Dual Impact on Lysosomes and DNA for Synergistic Chemotherapy and Immunogenic Cell Death. Abstract: Several DNA-damaging antitumor agents, including ruthenium complexes, induce immunogenic cell death (ICD). In this study, an arginyl-glycyl-aspartic acid (RGD) peptide-modified carboline ruthenium complex (KS-Ru) is synthesized as a chemotherapeutic nanodrug and an ICD inducer. The RGD peptide, an integrin ligand, provides tumor-specific targeting and promotes self-assembly of the KS-Ru complex. The pH-responsive self-assembly is assessed through transmission and scanning electron microscopy. Additionally, in vitro cytotoxic activity and anti-metastasis ability are evaluated using MTT and Transwell assays, respectively, along with cellular immunofluorescence staining and imaging flow cytometry. The ability of the complex to inhibit primary tumor formation and lung metastasis in vivo is evaluated using Lewis lung cancer and A549 xenograft models. Furthermore, the tumor immune microenvironment is evaluated using single-cell flow mass cytometry. KS-Ru translocates to the nucleus, causing DNA damage and inducing ICD. Within the lysosomes, KS-Ru self-assembled into nanoflowers, leading to lysosomal swelling and apoptosis. Notably, the as-synthesized pH-dependent ruthenium nanomedicine achieves dual functionality-chemotherapy and immunotherapy. Moreover, the pH-responsive self-assembly of KS-Ru enables simultaneous mechanisms in the lysosome and nucleus, thereby lowering the likelihood of drug resistance. This study provides valuable insight for the design of novel ruthenium-based nanoantitumor drugs. Show less

One approach to reduce the side effects of chemotherapy in cancer treatment is photodynamic therapy (PDT), which allows spatiotemporal control of the cytotoxicity. We have used the strategy of coordinating π-expansive ligands to increase the excited state lifetimes of Ir(III) half-sandwich complexes in order to facilitate the generation of ¹O₂. We have obtained derivatives of formulas [Cp*Ir(C^∧N)Cl] and [Cp*Ir(C^∧N)L]BF₄ with different degrees of π-expansion in the C^∧N ligands. Complexes with the more π-expansive ligand are very effective photosensitizers with phototoxic indexes PI > 2000. Furthermore, PI values of 63 were achieved with red light. Time-dependent density functional theory (TD-DFT) calculations nicely explain the effect of the π-expansion. The complexes produce reactive oxygen species (ROS) at the cellular level, causing mitochondrial membrane depolarization, cleavage of DNA, nicotinamide adenine dinucleotide (NADH) oxidation, as well as lysosomal damage. Consequently, cell death by apoptosis and secondary necrosis is activated. Thus, we describe the first class of half-sandwich iridium cyclometalated complexes active in PDT. Show less

Title: Re(I)[2-aryl-1 Abstract: Recently, achieving selective cancer therapy with trifling side effects has been a great challenge in the eradication of cancer. Thus, to amplify the cytoselective approach of complexes, herein, we developed a series of Re(I)[2-aryl-1H-imidazo[4,5-f][1,10]phenanthroline] tricarbonyl chloride complexes and screened their potency against HeLa and MCF-7 cell lines together with the evaluation of their toxicity towards a normal kidney cell line (HEK-293). On meticulous investigation, complex [ReI(CO)3Cl(K2-N,N-(2c))] (3c) was found to be the most potent anticancer entity among other complexes. Complex 3c also showed competency to induce apoptosis in MCF-7 cells through G2/M phase cell-cycle arrest in association with the generation of ample reactive oxygen species (ROS), eventually leading to DNA intercalation and internucleosomal cleavage. The order of the cytotoxicity of these complexes depended on their lipophilic character and the electron-withdrawing halogen substitution at the para-position of the phenyl ring in the imidazophenanthroline ligand. Show less

Title: Modulatory Role of Pantropic Cell Signaling Pathways in the Antimigratory and Antiproliferative Action of Triazole Chelated Iridium(III) Complexes in Cervical Cancer Cells. Abstract: In the current study, the antimigratory and antiproliferative effect of three substituted triazole-chelated iridium(III) complexes Ir-TRN, Ir-TRH, and Ir-TRF were studied with special emphasis on modulation of P53 activity, a cell cycle regulator. ERK2/MAPK, another crucial cell signaling pathway protein, was also shown to play a crucial role in cell migration and proliferation. The complexes increase the ROS generation within the cell, further supporting apoptotic induction by exerting cellular oxidative stress. These metal complexes also affect ER stress by altering ERp29, an ER-resident chaperone, further inducing the process of apoptosis. The iridium(III) complexes restrict cervical cancer cell migration and proliferation by exerting pronounced effects as P53 activators and downregulation of ERK2/MAPK activity in cervical cancer cells. The underpinning mechanism of P53 and ERK2/MAPK activity in cervical cancer cells in the presence of iridium(III) complexes was studied in detail in this study, which paves the way for developing promising avenues for cancer therapeutics. Show less

Title: Mitochondria-targeted iridium(III) complexes encapsulated in liposome induce cell death through ferroptosis and gasdermin-mediated pyroptosis. Abstract: This paper unveils a novel perspective on synthesis and characterization of the ligand 5-bromo-2-amino-2'-(phenyl-1H-imidazo[4,5-f][1,10]phenanthroline) (BAPIP), and its iridium(III) complexes [Ir(PPY-)2(BAPIP)](PF6) (1a, with PPY- as deprotonated 2-phenylpyridine), [Ir(PIQ-)2(BAPIP)](PF6) (1b, piq- denoting deprotonated 1-phenylisoquinoline), and [Ir(BZQ-)2(BAPIP)](PF6) (1c, bzq- signifying deprotonated benzo[h]quinoline). Systematic evaluation of the cytotoxicity of 1a, 1b, and 1c across diverse cell lines encompassing B16, HCT116, HepG2, A549, HeLa, and LO2 using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) method. Unexpectedly, compounds 1b and 1c demonstrated no cytotoxicity against the above cell lines. Motivated by the pursuit of heightened anti-proliferative potential, a strategic encapsulation approach yielded liposomes 1alip, 1blip, and 1clip. As expectation, 1alip, 1blip, and 1clip displayed remarkable anti-proliferative efficacy, particularly noteworthy in A549 cells, exhibiting IC50 values of 4.9 ± 1.0, 5.9 ± 0.1, and 7.6 ± 0.2 μM, respectively. Moreover, our investigation illuminated the mitochondrial accumulation of these liposomal entities, 1alip, 1blip, and 1clip, evoking apoptosis through the mitochondrial dysfunction mediated by reactive oxygen species (ROS). The ferroptosis was confirmed by decrease in glutathione (GSH) concentrations, the downregulation of glutathione peroxidase 4 (GPX4), increase of high mobility group protein 1 (HMGB1), and lipid peroxidation. Simultaneously, pyroptosis as another mode of cell death was undertaken. RNA-sequencing was employed to investigate intricate signalling pathways. In vivo examination provided tangible evidence of 1alip in effectively curbing tumor growth. Collectively, this study provides a multifaceted mode of cellular demise orchestrated by 1a, 1alip, 1blip, and 1clip, involving pathways encompassing apoptosis, ferroptosis, and pyroptosis. Show less

Title: Iridium(III) complexes conjugated with naproxen exhibit potent anti-tumor activities by inducing mitochondrial damage, modulating inflammation, and enhancing immunity. Abstract: A series of Ir(III)-naproxen (NPX) conjugates with the molecular formula [Ir(C^N)2bpy(4-CH2ONPX-4'-CH2ONPX)](PF6) (Ir-NPX-1-3) were designed and synthesized, including C^N = 2-phenylpyridine (ppy, Ir-NPX-1), 2-(2-thienyl)pyridine (thpy, Ir-NPX-2) and 2-(2,4-difluorophenyl)pyridine (dfppy, Ir-NPX-3). Cytotoxicity tests showed that Ir-NPX-1-3 exhibited excellent antitumor activity, especially in A549R cells. The cellular uptake experiment showed that the complexes were mainly localized in mitochondria, and induced apoptosis in A549R cells by damaging the structure and function of mitochondria. The main manifestations are a decrease in the mitochondrial membrane potential (MMP), an increase in reactive oxygen species (ROS) levels, and cell cycle arrest. Furthermore, Ir-NPX-1-3 could inhibit the migration and colony formation of cancer cells, demonstrating potential anti-metastatic ability. Finally, the anti-inflammatory and immunological applications of Ir-NPX-1-3 were verified. The downregulation of cyclooxygenase-2 (COX-2) and programmed death-ligand 1 (PD-L1) expression levels and the release of immunogenic cell death (ICD) related signaling molecules such as damage-associated molecular patterns (DAMPs) (cell surface calreticulin (CRT), high mobility group box 1 (HMGB1), and adenosine triphosphate (ATP)) indicate that these Ir(III) -NPX conjugates are novel ICD inducers with synergistic effects in multiple anti-tumor pathways. Show less

Title: Comparative Study of Sonodynamic and Photoactivated Cancer Therapies with Re(I)-Tricarbonyl Complexes Comprising Phenanthroline Ligands. Abstract: Herein, we have compared the effectivity of light-based photoactivated cancer therapy and ultrasound-based sonodynamic therapy with Re(I)-tricarbonyl complexes (Re1-Re3) against cancer cells. The observed photophysical and TD-DFT calculations indicated the potential of Re1-Re3 to act as good anticancer agents under visible light/ultrasound exposure. Re1 did not display any dark- or light- or ultrasound-triggered anticancer activity. However, Re2 and Re3 displayed concentration-dependent anticancer activity upon light and ultrasound exposure. Interestingly, Re3 produced 1O2 and OH• on light/ultrasound exposure. Moreover, Re3 induced NADH photo-oxidation in PBS and produced H2O2. To the best of our knowledge, NADH photo-oxidation has been achieved here with the Re(I) complex for the first time in PBS. Additionally, Re3 released CO upon light/ultrasound exposure. The cell death mechanism revealed that Re3 produced an apoptotic cell death response in HeLa cells via ROS generation. Interestingly, Re3 showed slightly better anticancer activity under light exposure compared to ultrasound exposure. Show less

Title: Mitochondrial Viscosity Probes: Iridium(III) Complexes Induce Apoptosis in HeLa Cells. Abstract: Mitochondrial viscosity has emerged as a promising biomarker for diseases such as cancer and neurodegenerative disorders, yet accurately measuring viscosity at the subcellular level remains a significant challenge. In this study, we synthesized and characterized three cyclometalated iridium(III) complexes (Ir1-Ir3) containing 5-fluorouracil derivatives as ligands. Among these, Ir1 selectively induced apoptosis in HeLa cells by increasing mitochondrial production of reactive oxygen species (ROS), which triggered a cascade of events leading to mitochondrial dysfunction. Additionally, the fluorescence lifetime of Ir1 demonstrated high sensitivity to intracellular viscosity changes, enabling real-time fluorescence lifetime imaging microscopy (FLIM) of cellular micro-viscosity during apoptosis. These findings underscore the potential of cyclometalated Ir(III) complexes for both therapeutic and diagnostic applications at the subcellular level. Show less

Title: Induction of ferroptosis of iridium(III) complexes localizing at the mitochondria and lysosome by photodynamic therapy. Abstract: In this study, [Ir(ppy)2(DMHBT)](PF6) (ppy = deprotonated 1-phenylpyridine, DMHBT = 10,12-dimethylpteridino[6,7-f][1,10]phenanthroline-11,13-(10,12H)-dione, 8a), [Ir(bzq)2(DMHBT)](PF6) (bzq = deprotonated benzo[h]quinoline, 8b) and [Ir(piq)2(DMHBT)](PF6) (piq = deprotonated 1-phenylisoquinoline, 8c) were synthesized and characterized by HRMS, 13C NMR and 1H NMR. In vitro cytotoxicity experiments showed that 8a, 8b, 8c show moderate cytotoxicity against B16 cells, while the cytotoxicity of the complexes 8a, 8b and 8c toward B16 cells was greatly improved upon light irradiation, which can be used as photosensitizers to exert anticancer efficacy in photodynamic therapy (PDT). After being taken up by cells, 8a, 8b, 8c were localized in the mitochondria, resulting in a large amount of Ca2+ in-flux, a burst release of ROS, a sustained opening of mitochondrial permeability transition pore, and a decrease of the mitochondrial membrane potential, which led to mitochondrial dysfunction and further activation of caspase 3 and Bcl-2 family proteins to induce apoptosis. Overloaded ROS reacted with polyunsaturated fatty acids on the cell membrane, and initiated lipid peroxidation, inhibited the xc--system-glutathione (GSH)-glutathione peroxidase 4 (GPX4) antioxidant defense system, and upregulated the expression of the damage-associated molecules, HMGB1, CRT, and HSP70. The presence of Fer-1 was effective on increasing the cell survival, which demonstrates that the complexes possess the potential to induce ferroptosis and immunogenic cell death. In addition, 8a, 8b and 8c induced autophagy by inhibiting the AKT/PI3K/mTOR signaling pathway, downregulating p62 and promoting Beclin-1 expression upon light irradiation. Show less

Title: White light increases anticancer effectiveness of iridium(III) complexes toward lung cancer A549 cells. Abstract: Anticancer activity has been extensively studies. In this article, three ligands 2-(6-bromobenzo[d][1,3]dioxol-5-yl)-1H-imidazo[4,5-f][1,10]phenanthroline (BDIP), 2-(7-methoxybenzo[d][1,3]dioxol-5-yl)-1H-imidazo[4,5-f][1,10]phenanthroline (MDIP), 2-(6-nitrobenzo[d][1,3]dioxol-5-yl)-1H-imidazo[4,5-f][1,10]phenanthroline (NDIP) and their iridium(III) complexes: [Ir(ppy)2(BDIP)](PF6) (ppy = deprotonated 2-phenylpyridine, 3a), [Ir(ppy)2(MDIP)](PF6) (3b) and [Ir(ppy)2(NDIP)](PF6) (3c) were synthesized. The cytotoxicity of 3a, 3b, 3c against Huh7, A549, BEL-7402, HepG2, HeLa, and non-cancer NIH3T3 was tested using 3-(4,5-dimethylthiazole-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) method. The results obtained from the MTT test stated clearly that these complexes demonstrated moderate or non-cytotoxicity toward Huh7, BEL-7402, HepG2 and HeLa except A549 cells. To improve the anticancer efficacy, we used white light to irradiate the mixture of cells and complexes for 30 min, the anticancer activity of the complexes was greatly enhanced. Particularly, 3a and 3b exhibited heightened capability to inhibit A549 cells proliferation with IC50 (half maximal inhibitory concentration) values of 0.7 ± 0.3 μM and 1.8 ± 0.1 μM, respectively. Cellular uptake has shown that 3a and 3b can be accumulated in the cytoplasm. Wound healing and colony forming showed that 3a and 3b significantly hinder the cell migration and growth in the S phase. The complexes open mitochondrial permeability transition pore (MPTP) channel and cause the decrease of membrane potential, release of cytochrome C, activation of caspase 3, and finally lead to apoptosis. In addition, 3a and 3b cause autophagy, increase the lipid peroxidation and lead to ferroptosis. Also, 3a and 3b increase the expression of calreticulin (CRT), high mobility group box 1 (HMGB1), heat shock protein 70 (HSP70), thereby inducing immunogenic cell death. Show less

Autophagy is a crucial quality control mechanism that degrades damaged cellular components through lysosomal fusion with autophagosomes. However, elevated autophagy levels can promote drug resistance in cancer cells, enhancing their survival. Downregulation of autophagy through oxidative stress is a clinically promising strategy to counteract drug resistance, yet precise control of oxidative stress in autophagic proteins remains challenging. Here, a molecular design strategy of biocompatible neutral Ir(III) photosensitizers is demonstrated, B2 and B4, for precise reactive oxygen species (ROS) control at lysosomes to inhibit autophagy. The underlying molecular mechanisms for the biocompatibility and lysosome selectivity of Ir(III) complexes are explored by comparing B2 with the cationic or the non-lysosome-targeting analogs. Also, the biological mechanisms for autophagy inhibition via lysosomal oxidation are explored. Proteome analyses reveal significant oxidation of proteins essential for autophagy, including lysosomal and fusion-mediator proteins. These findings are verified in vitro, using mass spectrometry, live cell imaging, and a model SNARE complex. The anti-tumor efficacy of the precise lysosomal oxidation strategy is further validated in vivo with B4, engineered for red light absorbance. This study is expected to inspire the therapeutic use of spatiotemporal ROS control for sophisticated modulation of autophagy. Show less

Title: Mitochondria Localized Anticancer Iridium(III) Prodrugs for Targeted Delivery of Myeloid Cell Leukemia-1 (Mcl-1) Inhibitors and Cytotoxic Iridium(III) Complex. Abstract: Myeloid cell leukemia-1 (Mcl-1) is an antiapoptotic oncoprotein overexpressed in several malignancies and acts as one of the promising therapeutic targets for cancer. Even though there are several small molecule based Mcl-1 inhibitors reported, the delivery of Mcl-1 inhibitor at the target site is quite challenging. In this regard, we developed a series of mitochondria targeting luminescent cyclometalated iridium(III) prodrugs bearing Mcl-1 inhibitors via ester linkage due to the presence of Mcl-1 protein in the outer mitochondrial membrane. Among the synthesized prodrugs, IrThpy@L2 was found to exhibit the potent cytotoxicity (IC50 = 30.93 nM) against HCT116 cell line when compared with bare Mcl-1 inhibitors (IC50 > 100 μM). Mechanistic studies further revealed that IrThpy@L2 quickly gets internalized inside the mitochondria of HCT116 cells and undergoes activation in the presence of overexpressed esterase which leads to the release of two cytotoxic species i.e. Mcl-1 inhibitors (I-2) and cytotoxic iridium(III) complex (IrThpy@OH). The improved cytotoxicity of IrThpy@L2 is due to the mitochondria targeting ability of iridium(III) prodrug, subsequent esterase activated release of I-2 to inhibit Mcl-1 protein and IrThpy@OH to generate reactive oxygen species (ROS). After prodrug activation, the released cytotoxic species cause mitochondrial membrane depolarization, activate a cascade of mitochondria-mediated cell death events, and arrest the cell cycle in S-phase which leads to apoptosis. The potent anticancer activity of IrThpy@L2 was further evident from the drastic morphological changes, size reduction in the solid tumor mimicking 3D multicellular tumor spheroids (MCTS) of HCT116. Show less