Chiral Iridium-Based TLD-1433 Analogues: Exploration of Enantiomer-Dependent Behavior in Photodynamic Cancer Therapy

Metallodrug-based photodynamic therapy (PDT) agents have demonstrated significant superiority against cancers, while their different chirality-induced biological activities remain largely unexplored. In this work, we successfully developed a pair of enantiopure mononuclear Ir(III)-based TLD-1433 analogues, Δ-Ir-3T and Λ-Ir-3T, and their enantiomer-dependent anticancer behaviors were investigated. Photophysical measurements revealed that they display high photostability and chemical stability, strong absorption at 400 nm with high molar extinction coefficients (ε = 5.03 × 104 M-1 cm-1), and good 1O2 relative quantum yields (ΦΔ ≈ 47%). Δ- and Λ-Ir-3T showed potent efficacy against MCF-7 cancer cells, with a photocytotoxicity index of ≤44 238. This impressive result, to the best of our knowledge, represents the highest value among reported mononuclear Ir(III)-based PDT agents. Remarkably, Λ-Ir-3T tended to be more potent than Δ-Ir-3T when tested against SK-MEL-28, HepG2, and LO2 cells, with consistent results across multiple test repetitions.

A monoadduct generating Ru(ii) complex induces ribosome biogenesis stress and is a molecular mimic of phenanthriplatin

Ruthenium complexes are often investigated as potential replacements for platinum-based chemotherapeutics in hopes of identifying systems with improved tolerability in vivo and reduced susceptibility to cellular resistance mechanisms. Inspired by phenanthriplatin, a non-traditional platinum agent that contains only one labile ligand, monofunctional ruthenium polypyridyl agents have been developed, but until now, few demonstrated promising anticancer activity. Here we introduce a potent new scaffold, based on [Ru(tpy)(dip)Cl]Cl (tpy = 2,2':6',2''-terpyridine and dip = 4,7-diphenyl-1,10-phenanthroline) in pursuit of effective Ru(ii)-based monofunctional agents. Notably, the extension of the terpyridine at the 4' position with an aromatic ring resulted in a molecule that was cytotoxic in several cancer cell lines with sub-micromolar IC50 values, induced ribosome biogenesis stress, and exhibited minimal zebrafish embryo toxicity. This study demonstrates the successful design of a Ru(ii) agent that mimics many of the biological effects and phenotypes seen with phenanthriplatin, despite numerous differences in both the ligands and metal center structure.

Platinum Complexes as Inhibitors of DNA Repair Protein Ku70 and Topoisomerase IIα in Cancer Cells

Ku70 protein and topoisomerase IIα (Topo IIα) are promising targets of anticancer drugs, which play critical roles in DNA repair and replication processes. Three platinum(II) complexes, [PtCl(NH3)2(9-(pyridin-2-ylmethyl)-9H-carbazole)]NO3 (OPPC), [PtCl(NH3)2(9-(pyridin-3-ylmethyl)-9H-carbazole)]NO3 (MPPC),...

Metal complexes as optical probes for DNA sensing and imaging

Transition and lanthanide metal complexes have rich photophysical properties that can be used for cellular imaging, biosensing and phototherapy. One of the applications of such luminescent compounds is the detection and visualisation of nucleic acids. In this brief review, we survey the recent literature on the use of luminescent metal complexes (including Re^I, Ru^II, Os^II, Ir^III, Pt^II, Eu^III and Tb^III) as DNA optical probes, including examples of compounds that bind selectively to non-duplex DNA topologies such as quadruplex, i-motif and DNA mismatches. We discuss the applications of metal-based luminescent complexes in cellular imaging, including time-resolved microscopy and super-resolution techniques. Their applications in biosensing and phototherapy are briefly mentioned in the relevant sections.

DNA topoisomerases as additional targets for anticancer monofunctional platinum(ii) complexes

Topoisomerases are ubiquitous enzymes and important targets for DNA-oriented anticancer drugs. Two mitochondrion-targeted monofunctional platinum(ii) complexes, [Pt(ortho-PPh₃CH₂Py)(NH₃)₂Cl](NO₃)₂ (OPT) and [Pt(para-PPh₃CH₂Py)(NH₃)₂Cl](NO₃)₂ (PPT; PPh₃ = triphenylphosphonium, Py = pyridine), show significant inhibition towards the activity of DNA topoisomerases in addition to their DNA binding and mitochondrial targeting capabilities. OPT exhibits strong cytotoxicity toward the human renal clear cell carcinoma 786-O and the murine prostate cancer RM-1 cell lines. The complex could bind to the minor groove of DNA, as well as DNA topoisomerases I and IIα, thereby acting as an inhibitor of topoisomerase I/IIα and causing DNA damage. The damage was evidenced by the enhanced expression of γ-H2AX, Chk1/2 phosphorylation, p53 and cell cycle arrest in the G2/M phase. In contrast, the inhibitory effect of PPT on DNA topoisomerases was largely limited to the isolated enzymes. The results demonstrate that the cellular inhibition of the complex towards the DNA topoisomerases positively correlated with its mitochondrial accumulation. Molecular docking provided more detailed structural insights into the interactions of OPT or PPT with DNA and topoisomerase I/IIα. The binding sites of OPT and PPT in topoisomerase-DNA complexes are different from each other. Aside from previously revealed DNA and mitochondrial targets, this study discovered new evidence that DNA topoisomerases may also serve as targets of monofunctional platinum(ii) complexes. For a multispecific platinum complex, strong DNA binding ability does not necessarily lead to potent cytotoxicity as other factors including the cell types, mitochondrial accumulation, and activity of DNA topoisomerases also affect the outcome of DNA damage.

Tris-heteroleptic ruthenium(II) polypyridyl complexes: Synthesis, structural characterization, photophysical, electrochemistry and biological properties

Three water-soluble tris-heteroleptic ruthenium(II) polypyridyl complexes [Ru(bpy)(phen)(bpg)]²⁺ (1), [Ru(bpy)(dppz)(bpg)]²⁺ (2), and [Ru(phen)(dppz)(bpg)]²⁺ (3) (where bpy = 2,2'-bipyridine, phen = 1,10-phenanthroline, dppz = dipyrido[3,2-a:2',3'-c] phenazine, bpg = 4b,5,7,7a-tetrahydro-4b,7a-epiminomethanoimino-6H-imidazo[4,5-f] [1,10] phenanthroline-6,13-dione) have been synthesized and characterized. Molecular structures of complexes 1 and 3 are confirmed by single crystal X-ray structure determination. Interaction of complexes 1-3 with DNA is explored by various spectroscopic techniques. The complexes 1-3 show solvent dependent photophysical properties. Complexes 2 and 3 show extensive "molecular light switch" effect for DNA. The complexes 1-3 are low toxic towards HeLa (human cervical cancer) and HL-60 (human promyelocytic leukemia) cell lines. Further, the cellular uptake of complexes 2 and 3 by cells shows that complexes mainly localised on the nucleus of the cells.

DNA interaction of ruthenium(ii) complexes with imidazo[4,5-f][1,10]phenanthroline derivatives

The DNA interaction properties of four Ru(ii) complexes with imidazo[4,5-f][1,10]phenanthroline derivatives were investigated by spectral titration, gel electrophoresis (GAR), dynamic light scattering (DLS), zeta potential, atomic force microscopy (AFM), and transmission electron microscopy (TEM).

Chirality in metal-based anticancer agents

Chiral metal-based drugs are currently an interesting and rapidly growing field in anticancer research. Here the different chiral metal-based anticancer agents and the extent to which the chiral resolution affects their biological properties are discussed. This review will aid the design of new potent and efficient chiral metal-based anticancer drugs that exploit the unique properties combined with their potential selectivity toward targeted chiral biomolecules.

Recent developments in the nanostructured materials functionalized with ruthenium complexes for targeted drug delivery to tumors

In recent years, the field of metal-based drugs has been dominated by other existing precious metal drugs, and many researchers have focused their attention on the synthesis of various ruthenium (Ru) complexes due to their potential medical and pharmaceutical applications. The beneficial properties of Ru, which make it a highly promising therapeutic agent, include its variable oxidation states, low toxicity, high selectivity for diseased cells, ligand exchange properties, and the ability to mimic iron binding to biomolecules. In addition, Ru complexes have favorable adsorption properties, along with excellent photochemical and photophysical properties, which make them promising tools for photodynamic therapy. At present, nanostructured materials functionalized with Ru complexes have become an efficient way to administer Ru-based anticancer drugs for cancer treatment. In this review, the recent developments in the nanostructured materials functionalized with Ru complexes for targeted drug delivery to tumors are discussed. In addition, information on "traditional" (ie, non-nanostructured) Ru-based cancer therapies is included in a precise manner.

Luminescent ruthenium polypyridyl complexes with extended ‘dppz’ like ligands as DNA targeting binders and cellular agents

DNA-binding and phototoxicity of Ru(ii) complexes with ligands derived from pyrazinodipyridophenazine and either phen or TAP as ancillary ligands are reported.