Bioinorganic supramolecular coordination complexes and their biomedical applications

The field of Bioinorganic Supramolecular Chemistry is an emerging research area including metal-based supramolecules resulting from coordination-driven self-assembly (CDSA), whereby metal ions and organic ligands can be easily linked by metal-ligand bonds via Lewis' acid/base interactions. The focus of this 'In a Nutshell' review will be on the family of supramolecular coordination complexes, discrete entities formed by CDSA, which have recently captured widespread attention as a new class of versatile multifunctional materials with broad biological applications including molecular recognition, biosensing, therapy, imaging and drug delivery. Herein, we provide a summary of the state-of-the-art use of these systems in biomedicine, with some selected representative examples, as well as our visions of the challenges and possible directions in the field.

BODIPY based Metal-Organic Macrocycles and Frameworks: Recent Therapeutic Developments

Boron dipyrromethene, commonly known as BODIPY, based metal-organic macrocycles (MOCs) and metal-organic frameworks (MOFs) represent an interesting part of materials due to their versatile tunability of structure and functionality as well as significant physicochemical properties, thus broadening their applications in various scientific domains, especially in biomedical sciences. With increasing concern over the efficacy of cancer drugs versus quality of patient's life dilemma, scientists have been trying to fabricate novel comprehensive therapeutic strategies along with the discovery of novel safer drugs where research with BODIPY metal complexes has shown vital advancements. In this review, we have exclusively examined the articles involving studies related to light harvesting and photophysical properties of BODIPY based MOCs and MOFs, synthesized through self-assembly process, with a special focus on biomolecular interaction and its importance in anti-cancer drug research. In the end, we also emphasized the possible practical challenges involved during the synthetic process, based on our experience on dealing with BODIPY molecules and steps to overcome them along with their future potentials. This review will significantly help our fellow research groups, especially the budding researchers, to quickly and comprehensively get the near to wholesome picture of BODIPY based MOCs and MOFs and their present status in anti-cancer drug discovery.

Pyrene and porphyrin-based Zn metal 1-D-polymer: synthesis, molecular structure, and photocatalytic property

A zinc-based pyrene-porphyrin hybrid linear 1-D coordination polymer ZnPyrPorp with general formula [Zn(Pyr)(Porp)]n (Pyr = pyrene, Porp = tetraphenylporphyrin) was synthesized using a facile one-pot solvothermal method and fully characterized...

Anticancer Half-Sandwich Rhodium(III) Complexes

Platinum-based anticancer drugs are most likely the most successful group of bioinorganic compounds. Their apparent disadvantages have led to the development of anticancer compounds of other noble metals, resulting in several ruthenium-based drugs which have entered clinical trials on oncological patients. Besides ruthenium, numerous rhodium complexes have been recently reported as highly potent antiproliferative agents against various human cancer cells, making them potential alternatives to Pt- and Ru-based metallodrugs. In this review, half-sandwich Rh(III) complexes are overviewed. Many representatives show higher in vitro potency than and different mechanisms of action (MoA) from the conventional anticancer metallodrugs (cisplatin in most cases) or clinically studied Ru drug candidates. Furthermore, some of the reviewed Rh(III) arenyl complexes are also anticancer in vivo. Pioneer anticancer organorhodium compounds as well as the recent advances in the field are discussed properly, and adequate attention is paid to their anticancer activity, solution behaviour and various processes connected with their MoA. In summary, this work summarizes the types of compounds and the most important biological results obtained in the field of anticancer half-sandwich Rh complexes.

Unmasking Arene Ruthenium Building Blocks

We have, like many others, contributed to the development and to the popularity of arene ruthenium assemblies. From early on, our research was driven by applications, mainly biological (therapeutic, drug delivery, DNA interactions, photodynamic therapy, imaging). For nearly 15 years, we have focused on the use of arene ruthenium building block as a tool to construct added-value objects. In this account, we want to give the basic reasons behind our choice, and uncover our most successful examples, with an emphasis on the foreseen applications.

Flavonoids from Brazilian Cerrado: Biosynthesis, Chemical and Biological Profile

Flavonoids are highly bioactive compounds with very low toxicity, which makes them attractive starting points in drug discovery. This study aims to provide information on plant species containing flavonoids, which are found in the Brazilian Cerrado. First, we present the characterization and plant diversity with emphasis on the families of flavonoid-producing plants, and then we describe the phenylpropanoid pathway which represents the flavonoids’ main route biosynthesis—generally conserved in all species. Chemical structures and biological activities of flavonoids isolated from the Cerrado’s plant species are also described based on examples from the relevant literature studies. Finally, research on the biodiversity of the Cerrado biome should be encouraged, due to the discovery of new sources of flavonoids which can provide several benefits to human health and the possibility of developing new drugs by the pharmaceutical industry.

Polynuclear ruthenium organometallic compounds induce DNA damage in human cells identified by the nucleotide excision repair factor XPC

Ruthenium organometallic compounds represent an attractive avenue in developing alternatives to platinum-based chemotherapeutic agents. While evidence has been presented indicating ruthenium-based compounds interact with isolated DNA in vitro, it is unclear what effect these compounds exert in cells. Moreover, the antibiotic efficacy of polynuclear ruthenium organometallic compounds remains uncertain. In the present study, we report that exposure to polynuclear ruthenium organometallic compounds induces recruitment of damaged DNA sensing protein Xeroderma pigmentosum Group C into chromatin-immobilized foci. Additionally, we observed one of the tested polynuclear ruthenium organometallic compounds displayed increased cytotoxicity against human cells deficient in nucleotide excision repair (NER). Taken together, these results suggest that polynuclear ruthenium organometallic compounds induce DNA damage in cells, and that cellular resistance to these compounds may be influenced by the NER DNA repair phenotype of the cells.

Coordination-Driven Self-Assembly of Triazole-Based Apoptosis-Inducible Metallomacrocycles

Ru(II)-metallomacrocycles containing 4-pyridyl-1,2,3-triazole moiety were realized by coordination-driven self-assembly. All new compounds were characterized by electrospray ionisation mass spectrometry, elemental analysis, and ¹H and ¹³C NMR spectroscopic techniques. The molecular structure of metallomacrocycle 8 was determined by single-crystal X-ray crystallography. The anticancer activities of metallomacrocycles 5-8 were evaluated by cytotoxicity, cell cycle analysis, and related protein expression. Metallomacrocycle 7 showed the highest cytotoxicity in HepG2 human hepatocellular carcinoma cells. In addition, apoptotic HepG2 cells were analyzed when metallomacrocycle 7 was treated. Our results suggest that metallomacrocycle 7 induces liver cancer cell death by increasing apoptosis and cell cycle arrest and that it has potential use as an agent for the treatment of human hepatocellular carcinoma.

The Role of the Second Coordination Sphere in the Biological Activity of Arene Ruthenium Metalla-Assemblies

For nearly 15 years, the biological and biomedical applications of arene ruthenium metalla-assemblies have flourished. Today, the synthetic strategies to generate arene ruthenium assemblies are well-established, and these compounds offer tremendous possibilities in terms of structural diversities and chemical properties. However, the second coordination sphere is often poorly considered, if not ignored, when designing such arene ruthenium metalla-assemblies. These weak interactions (hydrogen bonding, hydrophobic, ionic, electrostatic, van der Waals, π-π stacking) that take place in the solid state or in solution are generally key interactions for the foreseen applications. Therefore, in this review, we want to emphasize this important property of arene ruthenium metalla-assemblies by showing examples dealing with second coordination sphere interactions and how this can be better integrated in the design of these versatile supramolecular metal-based entities.

Coordination-driven self-assembly of ruthenium(ii) architectures: synthesis, characterization and cytotoxicity studies

Coordination-driven self-assembly of organometallic η6-arene ruthenium(ii) supramolecular architectures (MA1-MA4) was carried out by employing dinuclear ruthenium acceptors [Ru2(μ-η4-C2O4)(CH3OH)2(η6-p-cymene)2](CF3SO3)2 (Rua), [Ru2(μ-η4-C6H2O4)(CH3OH)2(η6-p-cymene)2](CF3SO3)2 (Rub), [Ru2(dhnq)(H2O)2(η6-p-cymene)2](CF3SO3)2 (Ruc) and [Ru2(dhtq)(H2O)2(η6-p-cymene)2](CF3SO3)2 (Rud) separately with a new tetratopic donor (TD) in methanol at room temperature [TD = N,N,N',N'-tetra(pyridin-4-yl)-[1,1'-biphenyl]-4,4'-diamine]. All the coordination architectures were characterized by using spectroscopic techniques. The potency of these self-assembled architectures against human cervical cancer HeLa and human lung adenocarcinoma A549 cell lines is explored in vitro using MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide), annexin V-FITC/PI and 2',7'-dichlorofluorescein-diacetate assays.

Self-Assembled BODIPY-Based Iridium Metallarectangles: Cytotoxicity and Propensity to Bind Biomolecules

A new 4-ethynylpyridine 4,4-difluoro-4-bora-3a,4a-diaza-s-indacene (BODIPY)-based ligand L, which was synthesized by means of the Sonogashira coupling method, was used to obtain two new [2+2] iridium-based metallarectangles, 3 and 4. Ligand L and metallarectangles 3 and 4 were fully characterized through various analytical techniques. The structure of rectangle 4 was further confirmed by single-crystal X-ray diffraction analysis, which showed the formation of an expected [2+2] supramolecule, in which the iridium metal centers were bridged with ligand L to form the desired metallarectangle 4. In the context of the growing biological interest in metallarectangles, rectangle 4 was found to be highly active against two types of cancer cells, with IC₅₀ values almost threefold superior to those of cisplatin. Both 3 and 4 showed dose-dependent abilities to bind bovine serum albumin and salmon sperm DNA; this indicated their tendency to interact with such biomolecules as a potential mode of action.

Self-Assembly of Novel Thiophene-Based BODIPY RuII Rectangles: Potential Antiproliferative Agents Selective Against Cancer Cells

Novel Ru (2+2) rectangles were designed and synthesized by self-assembly of a new thiophene-functionalized dipyridyl BODIPY ligand, BDPS, and ruthenium(II) precursors. The complexes exhibited dose-dependent antiproliferative activities against cancer cells, in which some compounds selectively kill cancer cells. The net fluorescence due to BODIPY allowed us to visualize their location inside cancer cells. Moreover, the metalla-rectangles displayed substantial propensity to bind with biomolecules.