Synthesis, Structural and Biological Studies of Some Half-Sandwich d6-Metal Complexes with Pyrimidine-Based Ligands

Anticancer iridium(iii) cyclopentadienyl complexes

A comprehensive review of anticancer iridium(iii) cyclopentadienyl complexes, including a critical discussion of structure–activity relationships and mechanisms of action, is provided.

Mononuclear copper(II) complexes with polypyridyl ligands: synthesis, characterization, DNA interactions/cleavages and in vitro cytotoxicity towards human cancer cells

DNA being the necessary element in cell regeneration, controlled cellular apoptosis via DNA binding/cleaving is considered an approach to combat cancer cells. The widely prescribed metallodrug cisplatin has shown interactions with the guanine-N7 center, and a plethora of complexes are continually developed to enhance crosslinking properties as well as covalent and non-covalent interactions. Two pentadentate ligands, L1 (1-(6-(1H-benzo[d]imidazol-2-yl)pyridin-2-yl)-N,N-bis(pyridin-2-ylmethyl)methanamine) and L2 (1-(6-(1-methyl-1H-benzo[d]imidazol-2-yl)pyridin-2-yl)-N,N-bis(pyridin-2-ylmethyl)methanamine), were synthesized together with their respective copper(II) complexes [1](ClO4)2 and [2](ClO4)2, which crystallized in a trigonal bipyramidal fashion. Different analytical and spectroscopic methods confirmed their formation, and their redox behaviour was also examined. The interactions of salmon sperm DNA (ss-DNA) with these two complexes were explored using absorbance spectroscopy, and they both exhibited a binding affinity (Kb) of ∼104 M-1. Fluorescence quenching experiments with ethidium bromide (EB)-bound DNA (EB-DNA) were also performed, and Stern-Volmer constant (KSV) values of 6.93 × 103 and 2.34 × 104 M-1 for [1](ClO4)2 and [2](ClO4)2, respectively, were obtained. Furthermore, DNA conformational changes due to the interactions of both complexes were validated via circular dichroism. We also assessed the DNA cleavage property of these complexes, which resulted in the linearization of circular plasmid DNA. This finding was supported by studying the growth of MDA-MB-231 breast cancer cells upon treatment with both Cu(II) complexes; IC50 values of 5.34 ± 1.02 μM and 0.83 ± 0.18 μM were obtained for [1](ClO4)2 and [2](ClO4)2, respectively. This validates their affinity towards DNA, and these insights can be further utilized for non-platinum based economical metallodrug development based on first row transition metals.

Inert cationic iridium(III) complexes with phenanthroline-based ligands: application in antimicrobial inactivation of multidrug-resistant bacterial strains

The antimicrobial activity of a new series of heteroleptic iridium(III) complexes of the type [Ir(C^N)₂(N^N)][PF₆] (C^N = deprotonated 2-phenylbenzimidazole-κN, κC; N^N = phen (Ir1), dpq (Ir2), dppz (Ir3), dppn (Ir4), and dppz-idzo (Ir5)) was studied towards two Gram positive (vancomycin-resistant Enterococcus faecium and a methicillin-resistant Staphylococcus aureus) and two Gram negative (Acinetobacter baumanii and Pseudomonas aeruginosa) multidrug-resistant bacterial strains of clinical interest. Although the complexes were inactive towards Gram negative bacteria, their effectiveness against Gram positive strains was remarkable, especially for Ir1 and Ir2, the most bactericidal complexes that were even more active (10 times) than the fluoroquinolone antibiotic norfloxacin and displayed no toxicity in human kidney cells (HEK293). Mechanistic studies revealed that the cell wall and membrane of MRSA S. aureus remained intact on treatment with these compounds and that DNA was not their main target. It is important to note that the complexes were able to induce ROS generation, this being the feature key to their antimicrobial activity.

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.

Microwave assisted κ-carrageenan capped silver nanocomposites for eradication of bacterial biofilms

Maturation of bacterial biofilms and their resistance to recurrent antimicrobial agents results in convoluted infectious diseases. In the current study, kappa-Carrageenan (κ-Carrageenan/CRG), was used to formulate CRG-silver nanocomposites through a facile microwave green synthesis approach. CRG-Ag nanoparticles of size 50 ± 10 nm were obtained by using CRG as a reducing and stabilizing agent. CRG-Ag nanoparticles were highly effective against both S. aureus and P. aeruginosa mediated biofilms and acted as a broad spectrum antibacterial agent even after six months. CRG-Ag nanoparticles encapsulated in KCl cross-linked hydrogel also exhibited excellent thermal stability, and antimicrobial potency. All these results depict that CRG-Ag nanocomposites appear as a promising approach to eradicate bacterial biofilms in food packaging and biomedical applications.