Synthesis, DNA binding and photocleavage, and cellular uptake of an alkyl chain-linked dinuclear ruthenium(II) complex

Shining New Light on Biological Systems: Luminescent Transition Metal Complexes for Bioimaging and Biosensing Applications

Luminescence imaging is a powerful and versatile technique for investigating cell physiology and pathology in living systems, making significant contributions to life science research and clinical diagnosis. In recent years, luminescent transition metal complexes have gained significant attention for diagnostic and therapeutic applications due to their unique photophysical and photochemical properties. In this Review, we provide a comprehensive overview of the recent development of luminescent transition metal complexes for bioimaging and biosensing applications, with a focus on transition metal centers with a d6, d8, and d10 electronic configuration. We elucidate the structure-property relationships of luminescent transition metal complexes, exploring how their structural characteristics can be manipulated to control their biological behavior such as cellular uptake, localization, biocompatibility, pharmacokinetics, and biodistribution. Furthermore, we introduce the various design strategies that leverage the interesting photophysical properties of luminescent transition metal complexes for a wide variety of biological applications, including autofluorescence-free imaging, multimodal imaging, organelle imaging, biological sensing, microenvironment monitoring, bioorthogonal labeling, bacterial imaging, and cell viability assessment. Finally, we provide insights into the challenges and perspectives of luminescent transition metal complexes for bioimaging and biosensing applications, as well as their use in disease diagnosis and treatment evaluation.

In vitro biological and in silico molecular docking and ADME studies of a substituted triazine-coordinated cadmium(II) ion: efficient cytotoxicity, apoptosis, genotoxicity, and nuclease-like activity plus binding affinity towards apoptosis-related proteins

A cadmium(II) complex containing dppt ligand with the formula [CdCl₂(dppt)₂], where dppt is 5,6-diphenyl-3-(2-pyridyl)-1,2,4-triazine was synthesized, elucidated and submitted to in vitro cytotoxicity studies against human breast (MCF-7), glioblastoma (U-87), and lung (A549) cancer cell lines as well as mouse embryo normal cell line (NIH/3T3), in comparison with cisplatin employing MTT assay over 24 and 48 h. The complex exhibited the highest cytotoxic effect against MCF-7 cells among the other three cell lines with IC₅₀ values of 8.7 ± 0.5 (24 h) and 1.2 ± 0.7 µM (48 h). Significantly, flow cytometric assessment of the complex-treated MCF-7 and U-87 cells demonstrated a dose-dependent induced apoptotic cell death. The cellular morphological changes were in concord with cytotoxicity and flow cytometric results. The results of comet assay showed that the complex is able to induce DNA damage in MCF-7 cells. These observations are of importance, as sustained damage to cellular DNA could lead to apoptotic cell death. The results of DNA-binding studies indicated that the complex fits into the DNA minor groove and interacts with DNA via a partial intercalation. Moreover, the complex was able to efficiently cleave pUC19 DNA through a hydrolytic mechanism. The binding affinity between the complex and apoptosis-relevant protein targets including APAF1, Bax, Bcl-2, Cas3, Cas7, and Cas9 was evaluated through molecular docking studies. In silico virtual studies revealed the complex's strong affinity towards apoptosis-related proteins; therefore the complex can act as a potential apoptosis inducer. Physicochemical, pharmacokinetics, lipophilicity, drug-likeness, and medicinal chemistry properties of the complex were also predicted through in silico absorption, distribution, metabolism and excretion studies.

Structure, photodynamic reaction and DNA photocleavage properties of a nitrosyl iron-sulfur cluster (Me4N)2[Fe2S2(NO)4]: A DFT calculation and experimental study

Density functional theory calculations were performed on the structure of the nitrosyl iron-sulfur cluster (Me₄N)₂[Fe₂S₂(NO)₄]. The IR spectra were assigned and the electronic ground-state properties in different solvents were analyzed. Dynamic conversion of [Fe₂S₂(NO)₄]^2- was analyzed quantitatively using the time-resolved IR spectra in different solvents. Photo irradiation and polarity of solvent obviously affect the reaction rates, which are faster in CH₃CN and CH₃OH than those in DMSO and water. The calculated orbital energies of HOMOs are higher and those of LUMO-HOMO gap are smaller in CH₃CN and CH₃OH than those in DMSO and water, which is consistent with the reaction rate and explains the experimental observation. Moreover, the photo-induced nitric oxide (NO) release and cluster conversion was identified using EPR spectra. The photocleavage of pBR322 DNA was observed, both NO and oxygen related free radicals play key roles in the process. The study provides an effective method to monitor the photodynamic reactions for better understanding of the physiological activity of nitrosyl iron-sulfur clusters.

Kinetic and Thermodynamic Investigation of Human Serum Albumin Interaction with Anticancer Glycine Derivative of Platinum Complex by Using Spectroscopic Methods and Molecular Docking

In this paper, a new anticancer Pt (II) complex, cis-[Pt (NH₃)₂(tertpentylgly)]NO₃, was synthesized with glycine-derivative ligand and characterized. Cytotoxicity of this water-soluble Pt complex was studied against human cancer breast cell line of MCF-7. The interaction of human serum albumin (HSA) with Pt complex was studied by using UV-Vis, fluorescence spectroscopy methods, and molecular docking at 27 and 37 °C in the physiological situation (I = 10 mM, pH = 7.4). The negative [Formula: see text] and positive [Formula: see text] indicated that electrostatic force may be a major mode in the binding between Pt complex and HSA. Binding constant values were obtained through UV-Vis and fluorescence spectroscopy that reveal strong interaction. The negative Gibbs free energy that was obtained by using the UV-Vis method offers spontaneous interaction. Fluorescence quenching the intensity of HSA by adding Pt complex confirms the static mode of interaction is effective for this binding process. Hill coefficients, n_H, Hill constant, k_H, complex aggregation number around HSA, <J>, number of binding sites, g, HSA melting temperature, T_m, and Stern-Volmer constant, k_SV, were also obtained. The kinetics of the interaction was studied, which showed a second-order kinetic. The results of molecular docking demonstrate the position of binding of Pt complex on HSA is the site I in the subdomain IIA.

The development of ruthenium(ii) polypyridyl complexes and conjugates for in vitro cellular and in vivo applications

Ruthenium(ii) [Ru(ii)] polypyridyl complexes have been the focus of intense investigations since work began exploring their supramolecular interactions with DNA. In recent years, there have been considerable efforts to translate this solution-based research into a biological environment with the intention of developing new classes of probes, luminescent imaging agents, therapeutics and theranostics. In only 10 years the field has expanded with diverse applications for these complexes as imaging agents and promising candidates for therapeutics. In light of these efforts this review exclusively focuses on the developments of these complexes in biological systems, both in cells and in vivo, and hopes to communicate to readers the diversity of applications within which these complexes have found use, as well as new insights gained along the way and challenges that researchers in this field still face.

Synthesis and anticancer properties of ruthenium (II) complexes as potent apoptosis inducers through mitochondrial disruption

A new ligand MHPIP (MHPIP = 2-(1-methyl-1H-pyrazol-4-yl)-1H-imidazo[4,5-f][1,10]phenanthroline) and its three ruthenium (II) complexes [Ru(N-N)₂(MHPIP)](ClO₄)₂ (N-N = phen: 1,10-phenanthroline 1; dmp = 2,9-dimethyl-1,10-phenanthroline 2; ttbpy = 4,4'-ditertiarybutyl-2,2'-bipyridine 3) were synthesized and characterized. The cytotoxic activity in vitro was studied by MTT method. The complexes 1-3 show moderate cytotoxic effects on the cell growth in HepG2 cells with an IC₅₀ value of 25.5 ± 3.5, 35.6 ± 1.9 and 27.4 ± 2.3 μM, respectively. The apoptosis was investigated with AO/EB and Annex V/PI staining methods and comet assay. The reactive oxygen species, mitochondrial membrane potential were investigated under a fluorescent microscope. Autophagy assay shows that the complexes can cause autophagy and up-regulate the expression of Beclin-1 protein. Additionally, the complexes inhibit the cell growth in HepG2 cells at G0/G1 phase, and the complexes can regulate the expression of caspase 3 and Bcl-2 family proteins. The studies demonstrate that the complexes induce apoptosis in HepG2 cells through DNA damage and ROS-mediated mitochondrial dysfunction pathways.

Platinum, palladium, gold and ruthenium complexes as anticancer agents: Current clinical uses, cytotoxicity studies and future perspectives

Metallodrugs offer potential for unique mechanism of drug action based on the choice of the metal, its oxidation state, the types and number of coordinated ligands and the coordination geometry. This review illustrates notable recent progress in the field of medicinal bioinorganic chemistry as many new approaches to the design of innovative metal-based anticancer drugs are emerging. Current research addressing the problems associated with platinum drugs has focused on other metal-based therapeutics that have different modes of action and on prodrug and targeting strategies in an effort to diminish the side-effects of cisplatin chemotherapy. Examples of metal compounds and chelating agents currently in clinical use, clinical trials or preclinical development are highlighted.

Anthraquinone-bridged diruthenium(ii) complexes inhibit migration and invasion of human hepatocarcinoma MHCC97-H cells

Four diruthenium(ii) complexes exhibited anti-metastatic properties on MHCC97-H cells, which involved in the inhibition of migration and invasion, negative remodulation of the cytoskeleton, blocking cell cycles and regulation of relative signal pathways.

Synthesis, characterization and anticancer activity of dinuclear ruthenium(ii) complexes linked by an alkyl chain

Anticancer activity of three novel ruthenium complexes was studied and the cytotoxicity increased with the increase of the amount of methylene in the bridging ligands.