📚 BiometalDB

An iridium (III) complex [Ir(ppy)₂(BDPIP)]PF₆ (Ir-1) was reported to show high anticancer activity and may be used as a potent anticancer drug. In the current study, we designed and synthesized a novel iridium (III) complex and evaluated its potential inhibitory effect on the cancer cell growth in vitro and in vivo. This complex was found to display high cytotoxic activity in vitro and in vivo against A549 cell with a low IC₅₀ value of 3.6 ± 0.3 μM and inhibiting percentage of tumor growth is 63.84% compared with the control. The complex also exhibited potencies superior to that of cisplatin toward A549 cell in vitro and in vivo. Further studies revealed that the complex can induce apoptosis and autophagy, enhance the ROS level, cause a decrease in the mitochondrial membrane potential and inhibit the cell invasion. Our findings indicated that the complex induced apoptosis in A549 through mitochondria dysfunction and PI3K/AKT/mTOR signaling pathways. Show less

PDT is a well-established therapeutic modality for many types of cancer. Photoluminescent cyclometalated iridium(III) complexes are one of the most commonly used classes of organometallic compounds with potential beneficial applications in bioimaging and as promising anticancer agents. In the present study, three new cyclometalated iridium(III) complexes (Ir1-Ir3) containing guanidinium ligands were found to exert excellent cytotoxic effects on different types of cancer cells upon light irradiation at 425 nm. Notably, Ir1 conferred almost no dark toxicity (IC₅₀ > 100 μM) to HepG2 cells, but the value decreased by 387-fold to 0.36 μM following 10 min of light irradiation (425 nm). Further mechanistic investigation revealed that complex Ir1 could induce apoptosis via the activation of reactive oxygen species (ROS)-mediated mitochondrial signaling pathways in the presence or absence of light irradiation. In vivo studies demonstrated that Ir1 significantly inhibited tumor growth in HepG2 xenograft-bearing mice under light irradiation at 425 nm. Taken together, these findings indicate that designing PDT-based Ir(III) complexes may hold a great deal of promise for anticancer drug development. Show less

The effective design of metal complexes to manipulate their lipid-water distribution coefficient is an appealing strategy for improving their cellular penetration and treatment efficacy. Here, we conveniently synthesized three iridium (Ir) complexes with red fluorescence via the simple non-conjugate modification of the side arm of the ligand. Bio-evaluation revealed that upon adding non-conjugate selenium (Se) arene derivatives, the lipid-water distribution coefficient of Ir-Se was found to be suitable, not only decreasing the toxic side effects of complexes to normal cells, but also effectively improving their anticancer activity via enhancing their penetration into tumor cells. Moreover, mechanistic investigations demonstrated that Ir-Se entered R-HeLa cells through endocytosis, and triggered apoptosis via the down-regulation of the mitochondrial membrane potential and excessive production of singlet oxygen, thereby possessing a highly effective cytotoxicity to antagonize cisplatin resistance. Therefore, we developed a convenient strategy to derive functional metal complexes and revealed that the introduction of Se on the side arm of the ligand provided the complexes with the capacity to reverse multidrug resistance. Show less

A new ligand THPDP (THPDP = 11-(6,7,8,9-tetrahydrophenazin-2-yl)dipyrido[3,2-a:2',3'-c]phenazine) and its iridium(III) complex [Ir(ppy)₂(THPDP)]PF₆ (Ir-1) was synthesized and characterized by elemental analysis, IR, ESI-MS, ¹H NMR and ¹³C NMR. The cytotoxicity in vitro of the complex against cancer cells B16, A549, Eca-109, SGC-7901, BEL-7402 and normal NIH 3T3 cell lines was evaluated using MTT method. The IC₅₀ values of the complex toward B16, A549 and Eca-109 cells are 1.0 ± 0.02, 1.4 ± 0.03 and 1.6 ± 0.06 μM, respectively. The apoptosis was investigated with AO/EB and DAPI staining methods. The complex shows strong ability to inhibit the cell growth in B16, A549 and Eca-109 cells. Ir-1 can induce apoptosis, increase the intracellular ROS level, and cause a decrease in the mitochondrial membrane potential. The intracellular Ca²⁺ level and the release of cytochrome c were studied under a fluorescent microscope. The cell invasion and autophagy were also performed, and the cell cycle arrest was assayed by flow cytometry. The expression of Bcl-2 family proteins, PI3K, AKT, mTOR, P-mTOR was investigated by western blot. The results show that the complex induces apoptosis through ROS-mediated mitochondria dysfunction and inhibition of AKT/mTOR pathways. These findings are helpful for design and synthesis of iridium(III) complexes as potent anticancer drugs. Show less

This work mainly introduces the synthesis and characterization of three iridium(III) complexes [Ir(ppy)₂(adppz)](PF₆) (Ir-1), [Ir(bzq)₂(addpz)](PF₆) (Ir-2) and [Ir(piq)₂(adppz)](PF₆) (Ir-3). The complexes are more cytotoxic than cisplatin against tumor cell lines such as SGC-7901, A549, HeLa, Eca-109, HepG2 and BEL-7402. The toxicity test results indicated that complexes Ir-1, Ir-2 and Ir-3 can effectively inhibit the cell growth of SGC-7901 cells, and the measured IC₅₀ values are 1.8 ± 0.4, 1.6 ± 0.3 and 0.8 ± 0.1 μM, respectively. AO/EB staining and flow apoptosis confirmed that SGC-7901 cells were caused apoptosis after being treated with the complexes. Along with the increase of endogenous ROS and Ca²⁺ levels, mitochondrial membrane potential collapse and massive release of cytochrome c, it is fully demonstrated that these complexes induce apoptosis through ROS-mediated mitochondrial pathway. At the same time, the complex Ir-3 is outstanding in the inhibition of tumor growth in vivo. Combined with the above results, it provides a favorable foundation for the future development of more effective anti-tumor drugs. Show less

Three new iridium (III) complexes [Ir (ppy)₂ (ipbc)](PF₆) (1), [Ir (bzq)₂ (ipbc)](PF₆) (2) and [Ir (piq)₂ (ipbc)](PF₆) (3) were designed and synthesized. All the complexes were tested for anticancer activity using 3-(4,5-dimethylthiazole)-2,5-diphenyltetraazolium bromide (MTT) method. The complexes show no cytotoxic activity toward cancer BEL-7402, SGC-7901, Eca-109, A549, HeLa and HepG2 cells. However, upon irradiation with white light, the complexes display high cytotoxicity against BEL-7402 cells with an IC₅₀ value of 5.5 ± 0.8, 7.3 ± 1.3 and 11.5 ± 1.6 μM for 1, 2 and 3, respectively. AO/EB staining and comet assay show that the complexes can induce apoptosis in BEL-7402 cells. The complexes can increase intracellular ROS and Ca²⁺ levels and cause a decrease in the mitochondrial membrane potential. Autophagic assays exhibit that the complexes can induce autophagy and regulate the expression of Beclin-1 and LC3 proteins. The cell cycle distribution in BEL-7402 cells was carried out by flow cytometry. The expression of Bcl-2 family proteins was studied by western blot. Additionally, the complexes can release cytochrome c and inhibit the polymerization of α-tubulin. Our study reveals that the complexes inhibit the cell growth in BEL-7402 cells through an ROS-mediated mitochondria dysfunction and targeting tubules pathways. These complexes are a promising new entity for the development of multi-target anticancer drugs. Show less

Two iridium(III) polypyridyl complexes [Ir(ppy)₂(HPIP)](PF₆) (Ir-1), [Ir(ppy)₂(BHPIP)](PF₆) (Ir-2) and their liposomes Ir-1-Lipo and Ir-2-Lipo were synthesized and characterized by elemental analysis, IR, ¹H NMR and ¹³C NMR. The anticancer activity in vitro and in vivo was evaluated. The cytotoxic activity in vitro of the complexes and their liposomes Ir-1-Lipo and Ir-2-Lipo against cancer cells was investigated by MTT methods. Ir-1 and Ir-2 show no cytotoxic activity, while Ir-1-Lipo and Ir-2-Lipo exhibit high cytotoxic effect. The IC₅₀ values range from 5.2 ± 0.8 to 22.3 ± 1.8 μM. The apoptosis, reactive oxygen species, the change of mitochondrial membrane potential, intracellular Ca²⁺ levels and a release of cytochrome c were investigated. The effect of Ir-1-Lipo and Ir-2-Lipo on microtubules was also explored. In the C57BL/6 mice model, Ir-1 only displays a tumor inhibitory rate of 23.21%, while lr-1-Lipo exhibits satisfactory in vivo antitumor efficacy with tumor inhibitory rate of 72.55%. This study demonstrates that complexes encapsulated in liposomes induce apoptosis in B16 through ROS-mediated lysosomal-mitochondria dysfunction, inhibition of polymerization of microtubules and induce cell cycle arrest at S phase. Show less

Two pairs of Rh(III) and Ir(III) biscyclometallated complexes with thiabendazole (L¹), named [Ir-a]Cl and [Rh-a]Cl, and N-benzyl-thiabendazole (L²), named [Ir-b]Cl and [Rh-b]Cl, have been designed and synthesized to explore the photophysical and biological effects that arise from changing both the metal center and the ancillary ligand. In the dark, the four metal complexes exhibit greater cytotoxicity than cisplatin against human colon (SW480) and human lung (A549) adenocarcinoma cell lines. Moreover, the pair of complexes bearing the ligand L² is markedly more cytotoxic and present higher uptake values than complexes with L¹, thereby their biological properties were studied further to determine their mechanism of action. Interestingly, in spite of the different metal center both the [Ir-b]Cl and [Rh-b]Cl complexes are responsible for the loss of mitochondrial functionality and the activation of apoptotic cell death pathways. Moreover, the photodynamic activity of the four complexes, [Ir-a,b]Cl and [Rh-a,b]Cl, was tested using visible blue light (460 nm) under soft irradiation conditions (20 min, 5.5 mW cm^-2). While the Rh complexes are not photopotentiated, the phototoxicity index (IC₅₀ non-irradiated/IC₅₀ irradiated) of [Ir-a]Cl and [Ir-b]Cl complexes was 15.8 and 3.6, respectively. We also demonstrate that only the Ir derivatives are capable of photocatalyzing the oxidation of S-containing l-amino acids under blue light irradiation, [Ir-a]Cl being more active than [Ir-b]Cl, which provides a reasonable mechanism for their biological action (oxidative stress could be selectively promoted through a photocatalytic action) upon irradiation. This different PDT behaviour depending on the metal center and the ancillary substituent may be useful for future rational design of metal-based photosensitizers. Show less

The endoplasmic reticulum (ER) is an indispensable organelle that undertakes the synthesis and export of proteins and membrane lipids. Subtle interferences of the ER redox signaling pathway are very likely to cause ER-stress induced apoptosis. In view of this, we herein present a series of ER-targeted Ir(iii) complexes (Ir1-Ir3) as photodynamic therapy (PDT) photosensitizers with a gradually extended conjugation area in the main ligand, and study the correlation between the conjugation area and PDT performance. The results showed that all of these complexes can accumulate in the ER and effectively induce cell apoptosis after PDT therapeutics (405 nm, 6 J cm-2) by an ER stress mechanism, and both their singlet oxygen quantum yields and cytotoxicities increase as the conjugation area extends. All complexes showed PDT efficacy towards different cancer cell lines. Among them, Ir2 exhibited the highest PI value (94.3) against A549 cells with an IC50 down to 0.65 μM. In addition, the post PDT ER-stress induced apoptosis along with the efflux of Ca2+ from the ER system in A549 cells in a short period of time (45-90 min) with the pretreatment of Ir2 was demonstrated. All of these results indicate the promising potential of Ir2 as an effective PDT photosensitizer. Show less

Theranostic anticancer agents incorporating anticancer properties with capabilities for real-time treatment assessment are appealing candidates for chemotherapy. The design of mitochondria-targeted cytotoxic drugs represents a promising approach to target tumors selectively and overcome resistance to current anticancer therapies. In this work, three coumarin-appended phosphorescent cyclometalated iridium(iii) complexes 1-3 have been explored as mitochondria-targeted theranostic anticancer agents. These complexes display rich photophysical properties, which facilitate the study of their intracellular fate. All three complexes can specifically target mitochondria and show much higher antiproliferative activities than cisplatin against various cancer cells including cisplatin-resistant cells. 1-3 can penetrate into human cervical carcinoma (HeLa) cells quickly and efficiently, and they can carry out theranostic functions by simultaneously inducing and monitoring the morphological changes in mitochondria. Mechanism studies show that 1-3 exert their anticancer efficacy by initiating a cascade of events related to mitochondrial dysfunction. Genome-wide transcriptional and Connectivity Map analyses reveal that the cytotoxicity of complex 3 is associated with pathways involved in mitochondrial dysfunction and apoptosis. Show less

Many phosphorescent iridium complexes are potent candidates as photodynamic therapeutic agents. In this work, a series of mixed-ligand phosphorescent iridium complexes (Ir1: [Ir(L₁)(bpy)Cl](PF₆)₂; Ir2: [Ir(L₁)(ppy)Cl](PF₆); Ir3: [Ir(L₂)(bpy)Cl](PF₆)₂; Ir4: [Ir(L₂)(ppy)Cl](PF₆). L₁ = 2,6-bis(2-benzimidazolyl)pyridine; bpy = 2,2'-bipyridine; L₂ = 2,6-bis(1-methyl-benzimidazol-2-yl)pyridine; ppy = 2-phenylpyridine) have been synthesized and characterized. These complexes display high luminescence quantum yields and long phosphorescence lifetimes. All the complexes are resistant to hydrolysis in aqueous solutions, and can produce singlet oxygen (¹O₂) effectively upon irradiation. Ir1 and Ir2 show pH-sensitive emission properties. Interestingly, higher cellular uptake efficiency is observed for Ir2 and Ir4 with the cyclometalated ppy ligand in human lung adenocarcinoma A549 cells. Ir2 with pH-sensitive emission properties can selectively image lysosomes, and Ir4 can specifically target mitochondria. Both Ir2 and Ir4 exhibit potent photodynamic therapy (PDT) effects, with Ir2 displaying a higher phototoxicity index (PI) especially in A549 cells (PI > 54). Mechanism studies indicate that Ir2 and Ir4 can induce apoptosis through reactive oxygen species (ROS) generation and caspase activation upon visible light (425 nm) irradiation. As expected, Ir2 can damage lysosomes more effectively with a pH-sensitive singlet oxygen (¹O₂) yield, while Ir4 tends to impair mitochondrial function. Nevertheless, the practical application of Ir2 and Ir4 for PDT may be limited to superficial tumors due to the short excitation wavelength (425 nm). Our study gives insights into the design and anticancer mechanisms of new metal-based PDT anticancer agents. Show less

Twelve novel half-sandwich IrIII-NHC complexes [(η5-Cpx)Ir(C^O)Cl] were synthesized and characterized. These complexes showed higher cytotoxic activity toward A549 cells and HeLa cells than cisplatin. An increase in the number of contained phenyl groups was related to better anticancer activity. The reaction of complexes with nucleobases 9-MeA, nucleobases 9-EtG, plasmid DNA and CT-DNA showed no significant effects. These complexes captured hydrogen from NADH and converted it to NAD+, which produced the reactive oxygen species (ROS). ROS led to a decrease in the mitochondrial membrane potential and lysosomal damage, finally inducing apoptosis. Show less

Two new biscyclometalated complexes [Ir(ptzR)2(dppz)]+ (dppz = dipyridophenazene; ptzRH = 4-phenyl-1-benzyl-1,2,3-triazole (1+) and 4-phenyl-1-propyl-1,2,3-triazole (2+)) have been prepared. The hexafluorophosphate salts of these complexes have been fully characterized and, in one case, the X-ray structure of a nitrate salt was obtained. The DNA binding properties of the chloride salts of the complexes were investigated, as well as their cellular uptake by A2780 and MCF7 cell lines. Both complexes display an increase in the intensity of phosphorescence upon titration with duplex DNA, indicating the intercalation of the dppz ligand and, given that they are monocations, the complexes exhibit appreciable DNA binding affinity. Optical microscopy studies reveal that both complexes are taken up by live cancer cell lines displaying cytosol based luminescence. Colocalization studies with commercial probes show high Pearson coefficients with mitotracker dyes confirming that the new complexes specifically localize on mitochondria. Show less

Six cyclometalated iridium(iii) complexes bearing different numbers of fluorine atoms were synthesized. These complexes demonstrated much better anti-proliferation activities towards five tumour cell lines than the widely used clinical chemotherapeutic agent cisplatin. Moreover, the anti-proliferation activities were correlated to the number of substituted fluorine atoms. Colocalization and inductively coupled plasma-mass spectrometry (ICP-MS) indicated that this series of complexes could penetrate cell membranes rapidly and preferentially target mitochondria. Manifesting high selectivity between tumour cells and normal cells and remarkable sensitivity to a cisplatin-resistant cell line (A549R), complex Ir6 was successfully developed as a novel anticancer agent (with IC₅₀ values of 0.5 ± 0.1 μM for HeLa, 1.1 ± 0.2 μM for HepG2, 1.5 ± 0.3 μM for BEL-7402, 0.8 ± 0.1 μM for A549, and 0.7 ± 0.2 μM for A549R cell lines). Further mechanism studies including mitochondrial membrane potential depolarization and caspase 3/7 activation revealed that Ir6 induced apoptosis via mitochondrial pathways. These results demonstrated that complex Ir6 might be a promising candidate as a mitochondria-targeted theranostic anticancer agent. Show less

The development of iridium complexes as potent anticancer agents has received increasing attention in recent years. In this study, four cyclometalated Ir(iii) complexes with good photophysical properties and potent anticancer activity have been synthesized and characterized. They are taken up by human lung adenocarcinoma A549 cells very quickly and specifically target mitochondria. Mechanism studies reveal that one of them, namely IrM2, induces paraptosis accompanied by excessive mitochondria-derived cytoplasmic vacuoles. Meanwhile, IrM2 affects the ubiquitin-proteasome system (UPS) and mitogen-activated protein kinase (MAPK) signaling pathways. Furthermore, IrM2 rapidly induces a series of mitochondria-related dysfunctional events, including the loss of mitochondrial membrane potential, cellular ATP depletion, mitochondrial respiration inhibition and reactive oxygen species (ROS) elevation. The rapid loss of mitochondrial functions, elevation of ROS and impairment of the UPS induced by IrM2 lead to the collapse of mitochondria and the subsequent cytoplasmic vacuolation before the cells are ready to start the mechanisms of apoptosis and/or autophagy. Among the ROS, superoxide anion radicals play a critical role in IrM2-mediated cell death. In vivo studies reveal that IrM2 can significantly inhibit tumor growth in a mouse model. This work gives useful insights into the design and anticancer mechanisms of new metal-based anticancer agents. Show less