Cytotoxicity and mechanism of action of metal complexes: An overview

The Antimicrobial Efficacy of Copper Complexes: A Review

The alarming increase in antimicrobial resistance has intensified the search for novel therapeutic agents capable of combating resistant microbial strains. Copper complexes have emerged as promising antimicrobial agents due to their intrinsic redox activity, ability to disrupt microbial membranes, and interactions with vital biomolecules such as DNA and proteins. This review critically evaluates the antimicrobial potential of copper complexes reported between 2018 and 2025, emphasizing their structural diversity, mechanisms of action, and biological performance against a wide range of bacterial and fungal pathogens. Key findings reveal that Schiff base copper complexes, amino acid derivatives, heterocyclic ligands, and mixed-ligand systems exhibit potent antimicrobial activities, often surpassing standard antibiotics. Mechanistically, copper complexes induce reactive oxygen species (ROS) generation, inhibit enzyme function, cause DNA cleavage, and compromise cell membrane integrity. Furthermore, structure-activity relationship (SAR) analyses indicate that ligand type, coordination geometry, and lipophilicity significantly influence antimicrobial efficacy. Overall, the reviewed studies support the development of copper-based compounds as viable candidates for antimicrobial drug development. This review also identifies current challenges and gaps in knowledge, such as limited in vivo studies and toxicity assessments, which must be addressed to advance these compounds toward clinical application.

Cytotoxicity, Cell Line Selectivity and Proapoptotic Activity of New Anticancer Agents Derived From N,N'-Functionalised Benzimidazolium Salts and Their Silver(I)-N-Heterocyclic Carbene Complexes

A new series of N-decyl-N'-benzylbenzimidazolium N-heterocyclic carbene (NHC) precursors and their mononuclear silver(I)-NHC complexes were synthesised and characterised. The benzyl group was functionalised with various para substituents (H, CH3, F, Cl, Br, CN, NO2). The effect of these substituents on cytotoxicity and cell line selectivity against human cervical cancer (HeLa), oestrogen-positive human breast cancer (MCF-7), and normal skin fibroblasts (Hs-27) was investigated. All compounds exhibited significant growth inhibition against the tested cell lines. The activity and selectivity of the compounds were influenced by the para substituents and the type of cell line. The electron-donating methylated NHC precursor and its silver complex generally demonstrated higher growth inhibition potentials than the analogues with electron-withdrawing groups, except in two cases where the fluorinated compounds were more potent against Hs-27 and HeLa, while the chlorinated NHC precursor was more active against MCF-7. Notably, all compounds, particularly the silver(I)-NHC complexes, were more active towards MCF-7 but less toxic towards Hs-27. The methyl-, bromo-, and cyano-containing silver(I)-NHC complexes broadened the safety windows against MCF-7 (selectivity indices ≥ 3). The most selective (against MCF-7) chlorinated NHC precursor and its silver(I)-NHC exhibited ROS-mediated proapoptotic activity, which indicated that these compounds promoted cell death by inducing intracellular ROS formation and accumulation. Our findings highlight the potential use of silver(I)-NHC complexes in the design and development of safe and selective anticancer agents.

Metal-based immunogenic cell death inducers for cancer immunotherapy

Immunogenic cell death (ICD) has attracted enormous attention over the past decade due to its unique characteristics in cancer cell death and its role in activating innate and adaptive immune responses against tumours. Many efforts have been dedicated to screening, identifying and discovering ICD inducers, resulting in the validation of several based on metal complexes. In this review, we provide a comprehensive summary of current metal-based ICD inducers, their molecular mechanisms for triggering ICD initiation and subsequent protective antitumour immune responses, along with considerations for validating ICD both in vitro and in vivo. We also aim to offer insights into the future development of metal complexes with enhanced ICD-inducing properties and their applications in potentiating antitumour immunity.

Protective effect of adenosine triphosphate against cisplatin-induced necrotic and degenerative oral mucositis in rats

BACKGROUND

Inflammation, oxidative damage, and adenosine triphosphate (ATP) depletion play a role in the pathogenesis of cisplatin (CIS)-induced oral mucositis.

OBJECTIVE

The purpose of this research is to examine the impact of ATP against potential oral mucositis development in cisplatin-treated rats. Methodology All rats were randomly assigned to four groups, namely healthy control group (HG), ATP group (ATPG), Cisplatin group (CISG), and ATP + Cisplatin group (ATCS). Firstly, ATP 4 mg/kg was administered via intraperitoneal injection (IP) to both ATPG and ATCS groups. The same volume of normal saline was injected into HG and CISG groups. After 1 h, cisplatin 5 mg/kg was administered via IP to CISG and ATCS groups. The drugs were taken 1x1 for 7 d. Later, tongue tissues were collected from all groups. Biochemical, macroscopic, and histopathological examinations were performed on all tissues.

RESULTS

ATP inhibited cisplatin-induced oxidative damage and pro-inflammatory cytokines levels in tongue tissue. In the CIS group, a significant number of distinct sulcus formations were found in the apex and corpus, as well as a few ulcer foci in the corpus, significant papilla loss, and bleeding. Meanwhile, in the ATP group, a similar appearance to healthy tissue was observed. Histopathologically, it was determined that in cisplatin-aggravated tongue tissue damage, filiform papillae decreased when ATP was administered, and the arrangement and structures of the epithelium, blood capillaries, muscle groups, and adipose cell groups were normal.

CONCLUSIONS

Oral mucositis caused by cisplatin is alleviated by ATP. These findings may be useful for developing new therapeutic approaches to prevent or treat mucositis, a side effect so severe that can lead to treatment discontinuation.

The Elusive Biological Activity of Scorpionates: A Useful Scaffold for Cancer Therapy?

Cancer remains a formidable challenge, requiring the constant pursuit of novel therapeutic agents and strategies. Scorpionates, known for their unique coordination properties, have recently gained attention for their anticancer potential. Traditionally applied in catalysis, these compounds have demonstrated notable cytotoxicity across various cancer cell lines, often surpassing the efficacy of conventional chemotherapeutics. This review addresses recent findings on scorpionate complexes, emphasizing the impact of metal choice and ligand design on biological activity. Copper and ruthenium scorpionates show promise, leveraging redox activity and mitochondrial disruption mechanisms to selectively induce cancer cell death. Ligand modifications, including sulfur-containing heterocycles and unsubstituted pyrazoles, have proven effective in enhancing cytotoxicity and selectivity. Furthermore, dipodal ligands show unique potential, with selective binding sites that improve stability and facilitate specific cellular interactions, such as targeting metastatic pathways. These findings highlight the largely unexplored potential of scorpionate complexes, positioning them as candidates for next-generation anticancer therapies. Continued research into structure-activity relationships and precise mechanisms of action could pave the way for developing highly potent and selective anticancer agents based on scorpionate chemistry.

Diosmetin Promotes Early Embryonic Development in Pigs by Alleviating Oxidative Stress

Diosmetin (DIOS), a natural flavonoid monomer derived from lemons and present in various plants such as spearmint and spider moss, exhibits antioxidant, anti-inflammatory, and antiaging properties. Nonetheless, its impact on early embryonic development in pigs remains unexplored. This study aimed to determine the influence of DIOS supplementation in an in vitro culture (IVC) medium on porcine embryo development and to elucidate the underlying mechanisms. Findings revealed that embryos cultured in IVC medium with 0.1 μM DIOS demonstrated an increased blastocyst formation rate, higher total cell number, reduced LC3B and CASPASE3 levels, elevated Nrf2 levels, decreased ROS, and enhanced GSH and mitochondrial membrane potential at the 4-cell embryonic stage. Additionally, the expression of proapoptotic genes (CAS3, CAS8, and BAX) and autophagy-related genes (BECLIN1, ATG5, LC3B, and P62) was downregulated, whereas the expression of embryonic development-related genes (CDK1 and CDK2), antioxidant-related genes (SOD1 and SOD2), and mitochondrial biogenesis-related genes (NRF2) was upregulated. These findings suggest that DIOS promotes early embryonic development in pigs by mitigating oxidative stress and enhancing mitochondrial function, thereby reducing autophagy and apoptosis levels.

Unveiling the promising anticancer effect of copper-based compounds: a comprehensive review

Copper is a necessary micronutrient for maintaining the well-being of the human body. The biological activity of organic ligands, especially their anticancer activity, is often enhanced when they coordinate with copper(I) and (II) ions. Copper and its compounds are capable of inducing tumor cell death through various mechanisms of action, including activation of apoptosis signaling pathways by reactive oxygen species (ROS), inhibition of angiogenesis, induction of cuproptosis, and paraptosis. Some of the copper complexes are currently being evaluated in clinical trials for their ability to map tumor hypoxia in various cancers, including locally advanced rectal cancer and bulky tumors. Several studies have shown that copper nanoparticles can be used as effective agents in chemodynamic therapy, phototherapy, hyperthermia, and immunotherapy. Despite the promising anticancer activity of copper-based compounds, their use in clinical trials is subject to certain limitations. Elevated copper concentrations may promote tumor growth, angiogenesis, and metastasis by affecting cellular processes.

Synthesis, in vitro antitumor evaluation and structure activity relationship of heptacoordinated amino-bis(Phenolato) Ti(IV) complexes stabilized by 2,6-dipicolinic acid

Eighteen novel Ti(IV) complexes stabilized by different chelating amino-bis(phenolato) (ONNO, ONON, ONOO) ligands and 2,6-dipicolinic acid as a second chelator were synthesized with isolated yields ranging from 79 to 93%. Complexes were characterized by 1H and 13C-NMR spectroscopy, as well as by HRMS and X-Ray diffraction analysis. The good to excellent aqueous stability of these Ti(IV) complexes can be modulated by the substitutions on the 2-position of the phenolato ligands. Most of the synthesized Ti(IV) complexes demonstrated potent inhibitory activity against Hela S3 and Hep G2 tumor cells. Among them, the naphthalenyl based Salan type 2j, 2-picolylamine based [ONON] type 2n and N-(2-hydroxyethyl) based [ONOO] type 2p demonstrated up to 40 folds enhanced cytotoxicity compared to cisplatin together with a significantly reduced activity against healthy AML12 cells. The three Ti(IV) complexes exhibited fast cellular uptake by Hela S3 cells and induced almost exclusively apoptosis. 2j could trigger higher level of ROS generation than 2p and 2n.

(Pentamethylcyclopentadienyl)chloridoiridium(III) Complex Bearing Bidentate Ph2PCH2CH2SPh-κP,κS Ligand

The (pentamethylcyclopentadienyl)chloridoiridium(III) complex bearing a κP,κS-bonded Ph2PCH2CH2SPh ligand ([Ir(η5-C5Me5)Cl(Ph2P(CH2)2SPh-κP,κS)]PF6, (1)] was synthesized and characterized. Multinuclear (1H, 13C and 31P) NMR spectroscopy was employed for the determination of the structure. Moreover, SC-XRD confirmed the proposed structure belongs to the "piano stool" type. The Hirshfeld surface analysis outlined the most important intermolecular interactions in the structure. The crystallographic structure was optimized at the B3LYP-D3BJ/6-311++G(d,p)(H,C,P,S,Cl)/LanL2DZ(Ir) level of theory. The applicability of this level was verified through a comparison of experimental and theoretical bond lengths and angles, and 1H and 13C NMR chemical shifts. The Natural Bond Orbital theory was used to identify and quantify the intramolecular stabilization interactions, especially those between donor atoms and Ir(III) ions. Complex 1 was tested on antitumor activity against five human tumor cell lines: MCF-7 breast adenocarcinoma, SW480 colon adenocarcinoma, 518A2 melanoma, 8505C human thyroid carcinoma and A253 submandibular carcinoma. Complex 1 showed superior antitumor activity against cisplatin-resistant MCF-7, SW480 and 8505C cell lines. The mechanism of tumoricidal action on 8505C cells indicates the involvement of caspase-induced apoptosis, accompanied by a considerable reduction in ROS/RNS and proliferation potential of treated cells.

Assessment of Mononuclear/Dinuclear copper acylhydrazone complexes for lung cancer treatment

Non-platinum metal-based complexes have good potential for cancer treatment. Here, we designed and synthesized five hydrazone copper(II) complexes, [Cu2(HL)2Cl2] 1A, [Cu2(HL)2(NO3)H2O]·NO3 2A, [Cu2(HL)2Br2] 3A, [Cu(L)pyridine] 1B and [Cu(HL)(pyridine)Br] 3B, and evaluated their anti-lung cancer activities. MTT experiments revealed that these copper(II) complexes exhibit higher anticancer activity than cisplatin. Mechanism studies revealed that complex 3A induced G1 phase cell cycle arrest, and induced cell apoptosis via reactive oxygen species (ROS)-mediated mitochondrial dysfunction. Scratch wound healing assay was also performed, revealing that complex 3A have good anti-cell migration activity. Hemolysis assays showed good blood biocompatibility of complex 3A. Furthermore, complex 3A can significantly inhibit the proliferation of A549 3D tumor spheroid. An in vivo anticancer study showed that complex 3A could delays the growth of A549 tumor xenografts with lower systemic toxicity. These results highlight the great possibility of developing highly active copper complexes as anti-lung cancer agents.

Design of an anticancer organoruthenium complex as the guest and polydiacetylene-coated fluorogenic nanocarrier as the host: engineering nanocarrier using ene-yne conjugation for sustained guest release, enhanced anticancer activity and reduced in vivo toxicity

Despite the enormous efforts made over the past two decades to develop metallodrugs and nanocarriers for metallodrug delivery, there are still few precise strategies that aim to optimize the design of both metallodrugs and metallodrug carriers jointly in a concerted effort. In this work, three half-sandwich ruthenium(II) complexes with pyridylimidazo[1,5-a]pyridine ligand functionalized with polycyclic aromatic moiety (Ru(nap), Ru(ant), Ru(pyr)) are evaluated as possible anticancer candidates and polydiacetylene (PDA)-coated amino-functionalized mesoporous silica nanoparticles (AMSNs) are designed as a functional nanocarrier for drug delivery. Ru(pyr) exhibits higher cytotoxicity in HT-29 colorectal cancer cells compared to other complexes and cis-platin, but it does not exhibit better cellular uptake. Ru(pyr) is found to be preferentially accumulated in plasma, mitochondria, and ER-Golgi membrane. The complex induces cell cycle arrest in the G0/G1 phase, while higher concentrations cause programmed cell death via apoptosis. Ru(pyr) influences cancer cell adhesion property and acts as an antioxidant in HT-29 cells. In order to modulate the anticancer potency of Ru(pyr), AMSNs are used to encapsulate the complex, and then diacetylene self-assembly is allowed to deposit on the surface of the nanoparticles. Subsequently, the nanoparticles undergo topopolymerization, which results in π-conjugated PDA-Ru(pyr)@AMSNs. Owing to the ene-yne polymeric skeleton in the backbone, the non-fluorescent AMSNs turn into red-emissive particles, which are exploited for cell imaging applications. The release profile analysis reveals that such a π-conjugated polymer prevents the premature release of the complex from porous silica nanoparticles with the accelerated release of the complex in an acidic medium compared to physiological conditions. The PDA gatekeepers have also been proven to enhance the cellular internalization of Ru(pyr) with slow continuous release from the nanoformulation. Zebrafish embryo toxicity analysis suggests that the PDA-coated nanocarriers could be suitable candidates for in vivo investigations.

Improving the developmental competences of porcine parthenogenetic embryos by Notoginsenoside R1-induced enhancement of mitochondrial activity and alleviation of proapoptotic events

Notoginsenoside R1 (NGR1), derived from the Panax notoginseng root and rhizome, exhibits diverse pharmacological influences on the brain, neurons, and osteoblasts, such as antioxidant effects, mitochondrial function protection, energy metabolism regulation, and inhibition of oxygen radicals, apoptosis, and cellular autophagy. However, its effect on early porcine embryonic development remains unclear. Therefore, we investigated NGR1's effects on blastocyst quality, reactive oxygen species (ROS) levels, glutathione (GSH) levels, mitochondrial function, and embryonic development-related gene expression in porcine embryos by introducing NGR1 during the in vitro culture (IVC) of early porcine embryos. Our results indicate that an addition of 1 μM NGR1 significantly increased glutathione (GSH) levels, blastocyst formation rate, and total cell number and proliferation capacity; decreased ROS levels and apoptosis rates in orphan-activated porcine embryos; and improved intracellular mitochondrial distribution, enhanced membrane potential, and reduced autophagy. In addition, pluripotency-related factor levels were elevated (NANOG and octamer-binding transcription factor 4 [OCT4]), antioxidant-related genes were upregulated (nuclear factor-erythroid 2-related factor 2 [NRF2]), and apoptosis- (caspase 3 [CAS3]) and autophagy-related genes (light chain 3 [LC3B]) were downregulated. These results indicate that NGR1 can enhance early porcine embryonic development by protecting mitochondrial function.

Effect of the extra-nuclear cation on the cytotoxicity and mechanism of action of pyridine-2,6-dicarboxylate Ga(III) complexes

Two Ga(III) complexes (C1) and (C2) were prepared by the one-pot reaction of pyridine-2,6-dicarboxylic acid and aminopyridine derivatives with gallium(III) nitrate octahydrate. The compounds were characterized by single-crystal X-ray diffraction. The distorted octahedral geometry was confirmed by crystallographic data for both complexes. The study of the in vitro cytotoxicity of the compounds showed that the presence of different extra-nuclear cations can affect the cytotoxicity of the same anionic complexes. The most significant antiproliferative activity was observed for C1 (IC50 = 0.69 μM, MAE = 73.96%) and C2 (IC50 = 3.78 μM, MAE = 60.35%) (where MAE represents the maximal antiproliferative effect) against A431 cell line. The mechanistic study evidenced the same pathway for the death of A431 cells treated with the complexes, although the results for C2 were obtained at approximately five times the concentration of C1. According to the study, both complexes induced cell cycle arrest in G2/M phase in A431 cells by upregulating the levels of p21, p27, p-cdc25C, and p-cdc2 and downregulating the levels of cdc25C, cdc2, and cyclin B1. In addition, apoptosis via a caspase-dependent mitochondrial pathway was confirmed by a decrease in Bcl-2 family proteins and an increase in the expression of procaspase-9 and 3. Also, the complexes induced autophagic cell death by activating the RAGE /PI3KC3/Beclin 1 pathway in A431 cells. DATA AVAILABILITY: CCDC 874052 and 874055 contain the supplementary crystallographic data for C1 and C2, respectively. These data can be obtained free of charge via http://www.ccdc.cam.ac.uk/services/structures?pid=ccdc:874052,874055&sid=CCDCManual, or from the Cambridge Crystallographic Data Centre, 12 Union Road, Cambridge CB2 1EZ, UK; fax: (+44) 1223-336-033; or e-mail: deposit@ccdc.cam.ac.uk.