Cyclometalated iridium(III) complexes as anti-breast cancer and anti-metastasis agents via STAT3 inhibition.

Breast cancer is the most commonly diagnosed cancer and second­leading cause of cancer deaths in women. Signal transducer and activator of transcription 3 (STAT3) plays a critical role in promoting breast cancer cell proliferation, invasion, angiogenesis, and metastasis, and the high expression of STAT3 is related to the occurrence and poor chemotherapy sensitivity of breast cancer. Iridium(III) complexes Ir-PTS-1- 4 containing a pterostilbene-derived ligand were synthesized to inhibit the STAT3 pathway in breast cancer. Ir-PTS-4 inhibited the proliferation of breast cancer cells by suppressing the expression of phosphorylated STAT3 and STAT3-related cyclin D1, arresting cell cycle in the S-phase, inducing DNA damage and reactive oxygen species (ROS) generation, eventually leading to autophagic cell death. The cell metastasis and invasion were also inhibited after Ir-PTS-4 treatment. Besides, Ir-PTS-4 exhibited excellent anti-proliferation activity in 3D multicellular tumor spheroids, showing potential for the treatment of solid tumors. This work presents the rational design of metal-based anticancer agents to block the STAT3 pathway for simultaneously inhibiting breast cancer proliferation and metastasis.

Iridium nanozyme-mediated photoacoustic imaging-guided NIR-II photothermal therapy and tumor microenvironment regulation for targeted eradication of cancer stem cells.

Cancer stem cells (CSCs) are found in many solid tumors, which play decisive roles in the occurrence, recurrence and metastasis of tumors. However, drugs are difficult to kill CSCs due to their limited number and location in oxygen-deprived tissue far from the blood vessels. Meanwhile, the survival and stemness maintenance of CSCs strongly depend on the tumor microenvironment (TME). Herein, we developed a CD44 antibody modified iridium nanosheet with enzyme-like activity (defined as Ir Nts-Ab) that effectively eradicates CSCs for cancer therapy. We observe that Ir Nts-Ab can enrich tumor tissues to remove excessive reactive oxygen species and produce oxygen, thus alleviating hypoxia and the inflammatory TME to reduce the proportion of CSCs and inhibit metastasis. In addition, Ir Nts-Ab targets CSCs and normal cancer cells with near infrared II-region photothermal therapy (NIR-II PTT), and is easily taken up by CSCs due to recognition of the CD44 proteins. Moreover, photoacoustic imaging helps monitor drug accumulation and hypoxic TME improvement in tumor tissue. Importantly, Ir Nts-Ab has good biological safety, making it suitable for biomedical applications. This iridium nanozyme based on TME regulation as well as NIR-II PTT will be a promising strategy for the treatment of cancer. STATEMENT OF SIGNIFICANCE: Cancer stem cells (CSCs) are key factors that make tumors difficult to eradicate, and strongly depend on the hypoxic tumor microenvironment (TME), which plays a crucial role in the occurrence and metastasis of tumors. Herein, an antibody modified iridium nanosheet (definition as Ir Nts-Ab) was developed for targeted eradication of CSCs by photoacoustic imaging guided photothermal therapy (PTT) and TME regulation. Ir Nts-Ab with catalase-like activity could inhibit HIF-1α by producing oxygen, thus effectively reducing the proportion of CSCs and inhibiting tumor metastasis. Additionally, Ir Nts-Ab achieved the eradication of CSCs by PTT, and eliminated reactive oxygen species to decrease the inflammatory response, resulting in reduced tumor metastasis, which was promising for the cure of solid tumors in the clinics.

Iridium metal complex targeting oxidation resistance 1 protein attenuates spinal cord injury by inhibiting oxidative stress-associated reactive oxygen species.

Oxidative stress is a key factor leading to profound neurological deficits following spinal cord injury (SCI). In this study, we present the development and potential application of an iridium (iii) complex, (CpxbiPh) Ir (N^N) Cl, where CpxbiPh represents 1-biphenyl-2,3,4,5-tetramethyl cyclopentadienyl, and N^N denotes 2-(3-(4-nitrophenyl)-1H-1,2,4-triazol-5-yl) pyridine chelating agents, to address this challenge through a mechanism governed by the regulation of an antioxidant protein. This iridium complex, IrPHtz, can modulate the Oxidation Resistance 1 (OXR1) protein levels within spinal cord tissues, thus showcasing its antioxidative potential. By eliminating reactive oxygen species (ROS) and preventing apoptosis, the IrPHtz demonstrated neuroprotective and neural healing characteristics on injured neurons. Our molecular docking analysis unveiled the presence of π stacking within the IrPHtz-OXR1 complex, an interaction that enhanced OXR1 expression, subsequently diminishing oxidative stress, thwarting neuroinflammation, and averting neuronal apoptosis. Furthermore, in in vivo experimentation with SCI-afflicted mice, IrPHtz was efficacious in shielding spinal cord neurons, promoting their regrowth, restoring electrical signaling, and improving motor performance. Collectively, these findings underscore the potential of employing the iridium metal complex in a novel, protein-regulated antioxidant strategy, presenting a promising avenue for therapeutic intervention in SCI.

Transferrin-targeted iridium nanoagglomerates with multi-enzyme activities for cerebral ischemia-reperfusion injury therapy.

Cerebral ischemia-reperfusion injury (CIRI) is a complex pathological condition with high mortality. In particular, reperfusion can stimulate overproduction of reactive oxygen species (ROS) and activation of inflammation, causing severe secondary injuries to the brain. Despite tremendous efforts, it remains urgent to rationally design antioxidative agents with straightforward and efficient ROS scavenging capability. Herein, a potent antioxidative agent was explored based on iridium oxide nano-agglomerates (Tf-IrO2 NAs) via the facile transferrin (Tf)-templated biomineralization approach, and innovatively applied to treat CIRI. Containing some small-size IrO2 aggregates, these NAs possess intrinsic hydroxyl radicals (•OH)-scavenging ability and multifarious enzyme activities, such as catalase (CAT), superoxide dismutase (SOD) and glutathione peroxidase (GPx). Moreover, they also showed improved blood-brain barrier (BBB) penetration and enhanced accumulation in the ischemic brain via Tf receptor-mediated transcytosis. Therefore, Tf-IrO2 NAs achieved robust in vitro anti-inflammatory and cytoprotection effects against oxidative stress. Importantly, mice were effectively protected against CIRI by enhanced ROS scavenging activity in vivo, and the therapeutic mechanism was systematically verified. These findings broaden the idea of expanding Ir-based NAs as potent antioxidative agents to treat CIRI and other ROS-mediated diseases. STATEMENT OF SIGNIFICANCE: (1) The ROS-scavenging activities of IrO2 are demonstrated comprehensively, which enriched the family of nano-antioxidants. (2) The engineering Tf-IrO2 nano-agglomerates present unique multifarious enzyme activities and simultaneous transferrin targeting and BBB crossing ability for cerebral ischemia-reperfusion injury therapy. (3) This work may open an avenue to enable the use of IrO2 to alleviate ROS-mediated inflammatory and brain injury diseases.

Efficacy of once-daily, single-inhaler, fixed-dose combination of mometasone/indacaterol/glycopyrronium in patients with asthma with or without persistent airflow limitation: Post hoc analysis from the IRIDIUM study.

BACKGROUND: A novel, once-daily, fixed-dose combination of mometasone furoate/indacaterol acetate/glycopyrronium bromide (MF/IND/GLY) delivered via Breezhaler® is the first inhaled corticosteroid/long-acting ꞵ2-agonist/long-acting muscarinic antagonist (ICS/LABA/LAMA) therapy approved for the maintenance treatment of asthma in adults inadequately controlled on ICS/LABA combination. In patients with asthma and persistent airflow limitation (PAL), maximal treatment, especially with combination is suggested. This post hoc analysis of data from the IRIDIUM study assessed the efficacy of MF/IND/GLY in asthma patients with and without PAL. METHODS: Patients with post-bronchodilator FEV1 ≤80% of predicted and FEV1/FVC ratio of ≤0.7 were categorised as PAL subgroup and the remaining as the non-PAL subgroup. Lung function parameters (FEV1, PEF, and FEF25%-75%) and annualised asthma exacerbations rates were evaluated in both subgroups across the treatment arms: once-daily high-dose MF/IND/GLY (160/150/50 µg), high-dose MF/IND (320/150 µg) and twice-daily high-dose fluticasone/salmeterol (FLU/SAL; 500/50 µg). RESULTS: Of the 3092 randomised patients, 64% (n = 1981) met the criteria for PAL. Overall, there was no evidence of treatment difference between PAL and non-PAL subgroups (interaction P-value for FEV1, FEF25%-75%, PEF, moderate or severe exacerbations, severe exacerbations and all exacerbations were 0.42, 0.08, 0.43 0.29, 0.35 and 0.12, respectively). In the PAL subgroup, high-dose MF/IND/GLY versus high-dose MF/IND and high-dose FLU/SAL improved trough FEV1 (mean difference: 102 mL [P < 0.0001] and 137 mL [P < 0.0001]) and reduced moderate or severe (16% and 32%), severe (25% and 39%) and all exacerbations (19% and 38%), respectively. CONCLUSIONS: Once-daily fixed-dose MF/IND/GLY was efficacious in asthma patients with and without persistent airflow limitation.

Discovery of polypyridyl iridium(III) complexes as potent agents against resistant Candida albicans.

The increasing emergence and spread of drug resistant Candida albicans represent a serious challenge for effective treatment and call for the development of new therapeutic options. To address this need, we synthesized a series of polypyridyl iridium(III) complexes and studied their antimicrobial activities. Herein, one lead iridium(III) complex Ir-3 [(ptpy)2Ir(dppz)]PF6, with ptpy = 2-(p-tolyl)pyridine and dppz = dipyrido[3,2-a:2',3'-c]phenazine, exhibited potent and broad-spectrum antifungal activities against drug-resistant pathogens and low hemolytic activity toward mammalian cells. Furthermore, Ir-3 showed low tendency to induce resistance, displayed biofilm inhibition and eradication activities. Significantly, Ir-3 exhibited potent in vivo antifungal activity in a murine model of disseminated candidiasis. This study may pave the way for the development of novel antifungal agent based upon polypyridyl iridium(III) complex to combat antifungal resistance.

A Review of the Unique Drug Development Strategy of Indacaterol Acetate/Glycopyrronium Bromide/Mometasone Furoate: A First-in-Class, Once-Daily, Single-Inhaler, Fixed-Dose Combination Treatment for Asthma.

A novel, once-daily (o.d.), fixed-dose combination (FDC) of indacaterol acetate (IND), glycopyrronium bromide (GLY), and mometasone furoate (MF), delivered by the inhaler Breezhaler® device, is the first long-acting beta2-adrenergic agonist/long-acting muscarinic antagonist/inhaled corticosteroid (LABA/LAMA/ICS) therapy to be approved for maintenance treatment of asthma in adults inadequately controlled on LABA/ICS. The approval of IND/GLY/MF in the European Union (EU) also included an optional electronic sensor and smartphone (or other suitable device) application, making it the first "digital companion" that can be prescribed with an asthma medication. As a result, the European Medicines Agency included this approval as one of the "outstanding contributions to public health" (for Pneumology/Allergology) in their 2020 highlights report. Alongside IND/GLY/MF, an o.d. LABA/ICS FDC, IND/MF, was also developed and approved. This review outlines the unique strategy used in the accelerated development of IND/GLY/MF that combined various approaches: (1) selecting individual components with established efficacy/safety, (2) bridging doses to optimize efficacy/safety of IND/GLY/MF and IND/MF delivered via the Breezhaler® device, (3) developing IND/GLY/MF and IND/MF in parallel, and (4) submission for regulatory approval before formal completion of the pivotal phase III studies. IND/GLY/MF and IND/MF were combined in a single-development plan (PLATINUM program), which comprised four phase III studies: QUARTZ and PALLADIUM evaluated IND/MF while IRIDIUM and ARGON evaluated IND/GLY/MF. A unique feature was the inclusion of two LABA/ICS comparators in the pivotal IRIDIUM study-IND/MF as an internal comparator, and high-dose salmeterol xinafoate/fluticasone propionate (SAL/FLU) as a marketed comparator. In the ARGON study, IND/GLY/MF was compared against o.d. tiotropium (via Respimat®) plus twice-daily (b.i.d.) high-dose SAL/FLU (via Diskus®). As a result of this development strategy, the development and approval of IND/GLY/MF was accelerated by ca. 4 years as against what would be expected from a traditional approach, novel data were generated, and a unique optional digital companion was approved in the EU. A Video Abstract by Dr Dominic Brittain, Global Drug Development, Novartis. (MP4 228293 kb).

Once-daily, single-inhaler indacaterol/mometasone versus twice-daily salmeterol/fluticasone in Asian patients with inadequately controlled asthma: post hoc pooled analysis from PALLADIUM and IRIDIUM studies.

OBJECTIVE: PALLADIUM and IRIDIUM studies demonstrated efficacy and safety of indacaterol/mometasone (IND/MF) versus salmeterol/fluticasone (SAL/FLU). This post hoc analysis of pooled data from PALLADIUM and IRIDIUM studies evaluated efficacy and safety of IND/MF versus SAL/FLU in Asian patients with inadequately controlled asthma. METHODS: Both studies were Phase III, 52-week, randomized, double-blind, active-controlled that included patients with predicted pre-bronchodilator FEV1 (PALLADIUM, ≥50%-<85%; IRIDIUM, <80%), ACQ-7 score ≥1.5. Patients treated with IND/MF high- (150/320 µg) or medium-dose (150/160 µg) or SAL/FLU high-dose (50/500 µg) were included. Lung function, asthma control, and asthma exacerbations were evaluated. RESULTS: In total, 323 patients (IND/MF high-dose, n = 107; IND/MF medium-dose, n = 106, SAL/FLU high-dose, n = 110) were included. IND/MF high-dose showed improvement in trough FEV1 versus SAL/FLU high-dose at Weeks 26 (Δ, 42 mL; 95% CI, -35 to 120 mL), and 52 (Δ, 41 mL; 95% CI, -37 to 120 mL). IND/MF high-dose exhibited numerically greater improvement in ACQ-7 score versus SAL/FLU high-dose at Weeks 26 (Δ, -0.215; 95% CI, -0.385 to -0.044) and 52 (Δ, -0.176; 95% CI, -0.348 to -0.005). Improvements in trough FEV1 and ACQ-7 score were comparable between IND/MF medium-dose and SAL/FLU high-dose. IND/MF high- and medium-dose showed reductions in moderate or severe (45%; 30%), severe (39%; 41%), and all (9%; 25%) exacerbations, respectively, versus SAL/FLU high-dose over 52 weeks. All treatments were well tolerated. CONCLUSIONS: Once-daily, single-inhaler IND/MF high-dose improved lung function with better asthma control, reduced asthma exacerbations with comparable safety versus twice-daily SAL/FLU high-dose. IND/MF medium-dose showed comparable outcomes to SAL/FLU high-dose at a reduced steroid dose.

Water-Soluble Iridic-Porphyrin Complex for Non-invasive Sonodynamic and Sono-oxidation Therapy of Deep Tumors.

Due to conventional photodynamic therapy encountering serious problems of phototoxicity and low tissue-penetrating depth of light, other dynamic therapy-based therapeutic methods such as sonodynamic therapy (SDT) are expected to be developed. To improve the therapeutic response to SDT, more effective sonosensitizers are imperative. In this study, a novel water-soluble iridium(III)-porphyrin sonosensitizer (IrTMPPS) was synthesized and used for SDT. IrTMPPS generated ample singlet oxygen (1O2) under US irradiation and especially showed distinguished US-activatable abilities at more than 10 cm deep-tissue depths. Interestingly, under US irradiation, IrTMPPS sonocatalytically oxidized intracellular NADH, which would enhance SDT efficiency by breaking the redox balance in the tumor. Moreover, IrTMPPS displayed great sonocytotoxicity toward various cancer cells, and in vivo experiments demonstrated efficient tumor inhibition and anti-metastasis to the lungs in the presence of IrTMPPS and US irradiation. This report gives a novel idea of metal-based sonosensitizers for sonotherapy by fully taking advantage of non-invasiveness, water solubility, and deep tumor therapy.

The design of cyclometalated iridium(iii)-metformin complexes for hypoxic cancer treatment.

Modulating the hypoxic microenvironment is the priority for tumor treatment. Cytometalated iridium(iii)-metformin conjugates were synthesized for treating hypoxic cancer cells for the first time, which alleviate hypoxia via mitochondria respiration inhibition, thus displaying 10-fold higher cytotoxicity, emerging anti-metastasis and anti-inflammatory activities than a metformin-free Ir(iii) complex and cisplatin against hypoxic cancer cells.

Mitochondria-targeted Ir@AuNRs as bifunctional therapeutic agents for hypoxia imaging and photothermal therapy.

Ir(iii) complex modified gold nanorods, Ir@AuNRs, were developed as mitochondria-targeted theranostic nanoagents. Their hypoxia imaging and photothermal therapeutic properties were demonstrated in vitro and in vivo.

Anticancer IrIII -Aspirin Conjugates for Enhanced Metabolic Immuno-Modulation and Mitochondrial Lifetime Imaging.

The chemo-anti-inflammatory strategy is attracting ever more attention for the treatment of cancer. Here, two cyclometalated IrIII complexes Ir2 and Ir3 formed by conjugation of Ir1 with two antiphlogistics (aspirin and salicylic acid) have been designed. Ir2 and Ir3 exhibit higher antitumor and anti-inflammatory potencies than a mixture of Ir1 and aspirin/salicylic acid. We show that they can be hydrolyzed, accumulate in mitochondria, and induce mitochondrial dysfunction. Due to their intense long-lived phosphorescence, Ir2 and Ir3 can track mitochondrial morphological changes. Phosphorescence lifetime imaging shows that Ir2 and Ir3 can aggregate during mitochondrial dysfunction. As expected, Ir2 and Ir3 exhibit immunomodulatory properties by regulating the activity of immune factors. Both Ir2 and Ir3 can induce caspase-dependent apoptosis and caspase-independent paraptosis and inhibit several events related to metastasis. Moreover, Ir2 and Ir3 show potent tumor growth inhibition in vivo. Our study demonstrates that the combination of mitochondrial-targeting and immunomodulatory activities is feasible to develop multifunctional metal-based anticancer agents.

Metal-based antitumor compounds: beyond cisplatin.

Despite improvements in the 5-year survival rate to over 80% in cancers, such as Hodgkin lymphoma and testicular cancer, more aggressive tumors including pancreatic and brain cancer still have extremely low survival rates. The establishment of chemoresistance, responsible for the reduction in treatment efficiency and cancer relapse, is one possible explanation for this setback. Metal-based compounds, a class of anticancer drugs, are largely used in the treatment of cancer. Herein, we will review the use of metal-based small molecules in chemotherapy, focusing on recent studies, and we will discuss how new nonplatinum-based agents are prompting scientists to increase drug specificity to overcome chemoresistance in cancer cells.

Design, synthesis, and evaluation of fluorine and Naphthyridine-Based half-sandwich organoiridium/ruthenium complexes with bioimaging and anticancer activity.

A range of fluorine and naphthyridine-based half-sandwich iridium (III) and ruthenium (II) complexes were synthesized. The iridium complexes possessed excellent antiproliferative properties, a substantial improvement over cisplatin, especially the best 1C containing the fluorine atom and 2C containing the naphthyridine. On the contrary, the ruthenium complexes displayed much less antiproliferative activity. Two X-ray crystal structures were determined. The cytotoxicity of the complexes can be changed flexible by regulating the metal center and the ancillary ligands. The best complex 1C was chose to study further on the mechanism of action. The chemical reactivity such as hydrolysis, reaction with nucleobases, glutathione and catalytic conversion of NADH to NAD+, were investigated. Complex 1C can react with 9-ethylguanine (9-EtG) and catalyze oxidation of NADH. In addition, the self-luminescence of the complex 1C was also successfully used in confocal microscopy images for elucidating the subcellular localization. Complex 1C specifically targeted to lysosomes in A549 cancer cells and caused lysosomal damages and promote cathepsin B released. Flow cytometry studies confirmed that the biological effects of this type of complexes induced apoptosis, especially late apoptosis. Our results suggested that changes in the mitochondria membrane potential were responsible for apoptosis. The chemistry and biological studies has showed that this class of metal complexes are worthy of further exploration for the design of novel anticancer drugs.

Structure⁻Activity Relationship Study of Newly Synthesized Iridium-III Complexes as Potential Series for Treating Thrombotic Diseases.

Platelets play a major role in hemostatic events and are associated with various pathological events, such as arterial thrombosis and atherosclerosis. Iridium (Ir) compounds are potential alternatives to platinum compounds, since they exert promising anticancer effects without cellular toxicity. Our recent studies found that Ir compounds show potent antiplatelet properties. In this study, we evaluated the in vitro antiplatelet, in vivo antithrombotic and structure⁻activity relationship (SAR) of newly synthesized Ir complexes, Ir-1, Ir-2 and Ir-4, in agonists-induced human platelets. Among the tested compounds, Ir-1 was active in inhibiting platelet aggregation induced by collagen; however, Ir-2 and Ir-4 had no effects even at their maximum concentrations of 50 µM against collagen and 500 µM against U46619-induced aggregation. Similarly, Ir-1 was potently inhibiting of adenosine triphosphate (ATP) release, calcium mobilization ([Ca2+]i) and P-selectin expression induced by collagen-induced without cytotoxicity. Likewise, Ir-1 expressively suppressed collagen-induced Akt, PKC, p38MAPKs and JNK phosphorylation. Interestingly, Ir-2 and Ir-4 had no effect on platelet function analyzer (PFA-100) collagen-adenosine diphosphate (C-ADP) and collagen-epinephrine (C-EPI) induced closure times in mice, but Ir-1 caused a significant increase when using C-ADP stimulation. Other in vivo studies revealed that Ir-1 significantly prolonged the platelet plug formation, increased tail bleeding times and reduced the mortality of adenosine diphosphate (ADP)-induced acute pulmonary thromboembolism in mice. Ir-1 has no substitution on its phenyl group, a water molecule (like cisplatin) can replace its chloride ion and, hence, the rate of hydrolysis might be tuned by the substituent on the ligand system. These features might have played a role for the observed effects of Ir-1. These results indicate that Ir-1 may be a lead compound to design new antiplatelet drugs for the treatment of thromboembolic diseases.

Iridium (III) complex-loaded liposomes as a drug delivery system for lung cancer through mitochondrial dysfunction.

BACKGROUND AND AIM: Iridium (Ir)-based complex is a potential antitumor ingredient, but its poor physicochemical properties such as hydrophobicity and low biocompatibility hamper further application. Liposome provides a potential delivery approach for improving the poor physicochemical property and reducing the side effects of antitumor drug. In this study, we aimed at incorporating Ir ([Ir(ppy)2(BTCP)]PF6) into liposomes to enhance the biocompatibility and sustained release of Ir for intravenous administration and to elucidate the mechanism in A549 cells. MATERIALS AND METHODS: Ir-loaded PEGylated liposomes (Lipo-Ir) were formulated by thin-film dispersion and ultrasonic method. Morphology, size distribution, and zeta potential of Lipo-Ir were examined by transmission electron microscopy (TEM) and Zetasizer. The released profile and biocompatibility were investigated by dialysis method and hemolysis test, respectively. Additionally, the cytotoxic activity and mechanism of Lipo-Ir and Ir inducing apoptosis in A549 cells were evaluated. RESULTS: Lipo-Ir can keep sustained release, excellent biocompatibility, and physical stability. The average particle size, polydispersity index, zeta potential, encapsulation efficiency, and drug loading are 112.57±1.15 nm, 0.19±0.02, -10.66±0.61 mV, 94.71%±3.21%, and 4.71%±0.41%, respectively. 3-(4,5-dimethylthiazole)-2,5-diphenltetraazolium bromide (MTT) assay show that Lipo-Ir and Ir display high cytotoxicity against selected cancer cells. Furthermore, the apoptotic features of morphology, depolarization of mitochondrial membrane potential, increase in the reactive oxygen species (ROS) levels, and disorder of Ca2+ homeostasis are observed after treating A549 cells with Ir and Lipo-Ir. Besides, Lipo-Ir can arrest the cell growth in G0/G1 phase. CONCLUSION: The studies demonstrate that Lipo-Ir can trigger apoptosis in A549 cells via ROS-mediated mitochondrial dysfunctions, and the biocompatible and sustained Lipo-Ir will be a promising drug delivery system.

Recent Advances in the Design of Targeted Iridium(III) Photosensitizers for Photodynamic Therapy.

Photodynamic therapy (PDT) is a noninvasive treatment for certain types of cancer, bacterial, fungal and viral infections, and skin diseases. In recent years, adaptation of this treatment so as to achieve more specific targeted cancer therapy in particular has attracted significant attention. We focus herein on the design of novel iridium-based photosensitizers (PSs) with tunable photophysical and photobiological properties as efficient PDT agents. We highlight the ability of some IrIII photosensitizers to target specific cellular components, including their activation by one- and two-photon irradiation.

Phosphorescent iridium(III)-bis-N-heterocyclic carbene complexes as mitochondria-targeted theranostic and photodynamic anticancer agents.

Mitochondria-targeted compounds represent a promising approach to target tumors selectively and overcome resistance to current anticancer therapies. In this work, three cyclometalated iridium(III) complexes (1-3) containing bis-N-heterocyclic carbene (NHC) ligands have been explored as theranostic and photodynamic agents targeting mitochondria. These complexes display rich photophysical properties, which greatly facilitates the study of their intracellular fate. All three complexes are more cytotoxic than cisplatin against the cancer cells screened. 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 these complexes exert their anticancer efficacy by initiating a cascade of events related to mitochondrial dysfunction. Additionally, they display up to 3 orders of magnitude higher cytotoxicity upon irradiation at 365 nm, which is so far the highest photocytotoxic responses reported for iridium complexes.

Phosphorescent polymeric nanoparticles by coordination cross-linking as a platform for luminescence imaging and photodynamic therapy.

Water-soluble phosphorescent polymeric nanoparticles with an average diameter of approximately 100 nm were synthesized by a coordination cross-linking reaction. The pyridine blocks in poly(4-vinyl pyridine-b-ethylene oxide) (P4VP-b-PEO) were cross-linked by the iridium chloride-bridged dimer in DMF solution. Owing to the presence of an iridium complex with different ligands in the core of the polymeric nanoparticles, NP-1, NP-2, and NP-3 showed bright green, yellow, and red phosphorescence, respectively. PEG chains in the shell gave the polymeric nanoparticles solubility and biocompatibility, which was confirmed by an MTT assay using HeLa cells as a model cancer cell line. The flow cytometry and laser confocal fluorescence microscopy results revealed NP-2, as an example, could be effectively uptaken by HeLa cells. Therefore, these polymeric nanoparticles can be used as luminescent probes for living cells. In addition, (1) O2 could be effectively generated in the presence of NP-2 upon irradiation with visible light (λ>400 nm, 300 mW cm(-2) ), which was confirmed by a clear decrease in the fluorescence intensity of 9,10-dimethylanthracene (DMA). After incubation with NP-2 at a concentration of 200 µg mL(-1) for 6 h, approximately 90 % of HeLa cells were effectively ablated upon irradiation with visible light for only 10 min, indicating the potential for photodynamic therapy with polymeric nanoparticles.

A comparison of the biological effective dose of 50-kV electronic brachytherapy with (192)Ir high-dose-rate brachytherapy for vaginal cuff irradiation.

PURPOSE: Advantages for electronic brachytherapy (EBT) of the vaginal cuff include decreased physical dose to the bladder and rectum. Here we compare (192)Ir with EBT using biological effective dose (BED) to account for the different radiobiological effectiveness (RBE) predicted for low-energy x-rays. METHODS AND MATERIALS: Fifteen data sets from five consecutive postoperative endometrial cancer patients treated with EBT were analyzed. Treatment planning was performed using PLATO software. The dose was prescribed as 21Gy in three fractions to a depth of 0.5cm. Physical dose, BED(3), and BED(10) were evaluated for the mucosa, bladder, and rectum. An RBE value of 1.5 was used for BED calculations. RESULTS: Mucosal physical dose is 28.4% greater with EBT (36.6 vs. 28.5Gy, p<0.05). However, the BED(10) is increased by 79.1% (55.6 vs. 99.6Gy, p<0.05) and the BED(3) by 71.5% (118.8 vs. 203.7Gy, p<0.05). The physical dose (dose to 50% volume of the organ) to the bladder (9.3 vs. 6.6Gy, p<0.05) and rectum (7.2 vs. 4.2Gy, p<0.05) are reduced with EBT. BED(3) to the rectum and bladder are also reduced but to a lesser extent (13 vs. 8.3Gy, p<0.05; 18.9 vs. 14.7Gy, p=0.06, respectively). CONCLUSIONS: BED takes into account the higher RBE of low-energy photons generated with EBT and provides a more accurate estimate of the biological effect. When using EBT, physical dose may underestimate the biological effect on the vaginal mucosa and overestimate the benefit for the bladder and rectum. Dose adjustment for EBT based on BED should be considered.