Dual Emissive Ir(III) Complexes for Photodynamic Therapy and Bioimaging

Effect of the Appended Morpholinyl Group on Photophysical Behavior of Mono- and Bis-cyclometalated Terpyridine Iridium(III) Chromophores

This paper provides extensive studies of [IrCl(Ph-py)(morph-C6H4-terpy-κ3N)]PF6 (1A), [Ir(Ph-py)2(morph-C6H4-terpy-κ2N)]PF6 (2A), [IrCl(Ph-py)(Ph-terpy-κ3N)]PF6 (1B), and [Ir(Ph-py)2(Ph-terpy-κ2N)]PF6 (2B) designed to demonstrate the possibility of controlling the photophysical properties of mono- and bis-cyclometalated complexes [IrCl(Ph-py)(R-C6H4-terpy-κ3N)]PF6 and [Ir(Ph-py)2(R-C6H4-terpy-κ2N)]PF6 through a remote electron-donating substituent introduced into the 4'-position of 2,2':6',2″-terpyridine (terpy) via the phenyl linker. The attachment of the morpholinyl (morph) group was evidenced to induce dramatic changes in the emission characteristics of the monocyclometalated Ir(III) systems with meridionally coordinated R-C6H4-terpy ligand (κ3N). In solution, the obtained complex [IrCl(Ph-py)(morph-C6H4-terpy-κ3N)]PF6 was found to be a rare example of dual-emissive Ir(III) systems. Within the series [Ir(Ph-py)2(R-C6H4-terpy-κ2N)]PF6 bearing the R-C6H4-terpy ligand bound to the central ion in a bidentate coordination mode, the appended electron-donating morpholinyl group induced a minor effect on the emission maximum, but it was found to be an effective tool for extending the excited-state lifetime, further prolonging with the increase of solvent polarity. The results of this work are of high significance for better understanding the push-pull effect and dual-emission phenomena in Ir-based luminophores, as well as developing chromophores with prolonged emission lifetimes.

Enhancing Phototoxicity in Human Colorectal Tumor Cells Through Nanoarchitectonics for Synergistic Photothermal and Photodynamic Therapies

Phototherapies are promising for noninvasive treatment of aggressive tumors, especially when combining heat induction and oxidative processes. Herein, we show enhanced phototoxicity of gold shell-isolated nanorods conjugated with toluidine blue-O (AuSHINRs@TBO) against human colorectal tumor cells (Caco-2) with synergic effects of photothermal (PTT) and photodynamic therapies (PDT). Mitochondrial metabolic activity tests (MTT) performed on Caco-2 cell cultures indicated a photothermal effect from AuSHINRs owing to enhanced light absorption from the localized surface plasmon resonance (LSPR). The phototoxicity against Caco-2 cells was further increased with AuSHINRs@TBO where oxidative processes, such as hydroperoxidation, were also present, leading to a cell viability reduction from 85.5 to 39.0%. The molecular-level mechanisms responsible for these effects were investigated on bioinspired tumor membranes using Langmuir monolayers of Caco-2 lipid extract. Polarization-modulation infrared reflection-absorption spectroscopy (PM-IRRAS) revealed that the AuSHINRs@TBO incorporation is due to attractive electrostatic interactions with negatively charged groups of the Caco-2 lipid extract, resulting in the expansion of surface pressure isotherms. Upon irradiation, Caco-2 lipid extract monolayers containing AuSHINRs@TBO (1:1 v/v) exhibited ca. 1.0% increase in surface area. This is attributed to the generation of reactive oxygen species (ROS) and their interaction with Caco-2 lipid extract monolayers, leading to hydroperoxide formation. The oxidative effects are facilitated by AuSHINRs@TBO penetration into the polar groups of the extract, allowing oxidative reactions with carbon chain unsaturations. These mechanisms are consistent with findings from confocal fluorescence microscopy, where the Caco-2 plasma membrane was the primary site of the cell death induction process.

Tuning the Organelle-Specific Imaging and Photodynamic Therapeutic Efficacy of Theranostic Mono- and Trinuclear Organometallic Iridium(III) Complexes

The organelle-specific localization of mononuclear and trinuclear iridium(III) complexes and their photodynamic behavior within the cells are described herein, emphasizing their structure-activity relationship. Both the IrA2 and IrB2 complexes possess a pair of phenyl-benzothiazole derived from the -CHO moieties of mononuclear organometallic iridium(III) complexes IrA1 and IrB1, which chelates IrCp*Cl (Cp* = 1,2,3,4,5-pentamethylcyclopentadiene) to afford trinuclear complexes IrA3 and IrB3. Insights into the photophysical and electrochemical parameters of the complexes were obtained by a time-dependent density functional theory study. The synthesized complexes IrA2, IrA3, IrB2, and IrB3 were found to be nontoxic to human MCF7 breast carcinoma cells. However, the photoexcitation of complexes using LED light could effectively trigger intracellular reactive oxygen species (ROS) generation, leading to cell death. Furthermore, to check the organelle-specific localization of IrA2 and IrB2, we observed that both complexes could selectively localize in the endoplasmic reticulum. In contrast, trinuclear IrA3 and IrB3 accumulate in the nuclei. The photoexcitation of complexes using LED light could effectively trigger intracellular reactive oxygen species (ROS) generation, leading to cell death.

Adventures in Photodynamic Therapy: Location, Location, Location

In the context of photodynamic therapy, reports periodically turn up in journals where reviewers are apparently unacquainted with the essentials. Bizarre procedures and results can thereby appear. This appears to be a byproduct of the publishing industry, especially for some of the "pay to play" options.

Light activation of iridium(III) complexes driving ROS production and DNA damage enhances anticancer activity in A549 cells

The work aimed to synthesize and characterize two iridium(III) complexes [Ir(ppy)₂(IPPH)](PF₆) (Ir1, IPPH = (2S,3R,5S,6R)-2-(2-(1H-imidazo[4,5-f][1,10]phenanthrolin-2-yl)phenoxy)-6-(hydroxymethyl)tetrahydro-2H-pyran-3,4,5-triol, ppy = 2-phenylpyridine), [Ir(piq)₂(IPPH)](PF₆) (Ir2, piq = 1-phenylisoquinoline). The cytotoxicity of the complexes against BEL-7402, A549, HCT-116, B16 cancer cells and normal LO2 was evaluated through 3-(4,5-dimethylthiazole-2-yl)-2,5-biphenyl tetrazolium bromide (MTT) method. The complexes show no cytotoxic activity (IC₅₀ > 100 μM) against these cancer cells, while their cytotoxicity can significantly be elevated upon illumination. The IC₅₀ values range from 0.2 ± 0.05 to 35.5 ± 3.5 μM. The cellular uptake, endoplasmic reticulum and mitochondria localization, reactive oxygen species, the change of mitochondrial membrane potential, γ-H2AX levels, cycle arrest, apoptosis and the expression of B-cell lymphoma-2 were investigated. The calreticulin (CRT), heat shock protein 70 (HSP70), high mobility group box 1 (HMGB1) were explored. This study demonstrates that photoactivatable complexes induce cell death in A549 through ROS-mediated endoplasmic reticulum stress-mitochondrial pathway, DNA damage pathways, immunogenic cell death (ICD), activation of PI3K/AKT signaling pathway and inhibit the cell growth at S phase.

Current status of iridium-based complexes against lung cancer

Lung cancer is one of the most common malignant tumors, with the highest mortality rate in the world, and its incidence is second only to breast cancer. It has posed a serious threat to human health. Cisplatin, a metal-based drug, is one of the most widely used chemotherapeutic agents for the treatment of various cancers. However, its clinical efficacy is seriously limited by numerous side effects and drug resistance. This has led to the exploration and development of other transition metal complexes for the treatment of malignant tumors. In recent years, iridium-based complexes have attracted extensive attention due to their potent anticancer activities, limited side effects, unique antitumor mechanisms, and rich optical properties, and are expected to be potential antitumor drugs. In this review, we summarize the recent progress of iridium complexes against lung cancer and introduce their anti-tumor mechanisms, including apoptosis, cycle arrest, inhibition of lung cancer cell migration, induction of immunogenic cell death, etc.

Tunable Emissive Ir(III) Benzimidazole-quinoline Hybrids as Promising Theranostic Lead Compounds

Bioactive and luminescent cyclometallated Ir(III) complexes [Ir(ppy)₂ L1]Cl (1) and [Ir(ppy)₂ L2]Cl (2) containing a benzimidazole derivative (L1/L2) as auxiliary mimic of a nucleotide have been synthesised. The emissive properties of both complexes are conditioned by the nature of L1 and L2, rendering an orange and a green emitter respectively. Both are highly emissive with quantum yield increasing in absence of oxygen up to 0.26 (1) and 0.36 (2), suggesting their phosphorescent character. Antiproliferative activity against lung cancer A549 cells increased up to 15 times upon irradiation conditions, reaching IC₅₀ values in the nanomolar range (0.3±0.09 μM (1) and 0.26±0.14 μM (2)) and pointing them as good PSs candidates for photodynamic therapy via ¹ O₂ generation. Cellular biodistribution analysis by fluorescence microscopy suggest the lysosomes as the preferential accumulation organelle. Time-resolved studies showed a greatly increased cellular emission lifetime compared to the solution values, indicating binding to macromolecules or cellular structures and restriction of collision and vibrational quenching.

Progress of Nanomaterials in Photodynamic Therapy Against Tumor

Photodynamic therapy (PDT) is an advanced therapeutic strategy with light-triggered, minimally invasive, high spatiotemporal selective and low systemic toxicity properties, which has been widely used in the clinical treatment of many solid tumors in recent years. Any strategies that improve the three elements of PDT (light, oxygen, and photosensitizers) can improve the efficacy of PDT. However, traditional PDT is confronted some challenges of poor solubility of photosensitizers and tumor suppressive microenvironment. To overcome the related obstacles of PDT, various strategies have been investigated in terms of improving photosensitizers (PSs) delivery, penetration of excitation light sources, and hypoxic tumor microenvironment. In addition, compared with a single treatment mode, the synergistic treatment of multiple treatment modalities such as photothermal therapy, chemotherapy, and radiation therapy can improve the efficacy of PDT. This review summarizes recent advances in nanomaterials, including metal nanoparticles, liposomes, hydrogels and polymers, to enhance the efficiency of PDT against malignant tumor.