Challenges and opportunities in the development of metal-based anticancer theranostic agents

Real-time visualization of epileptic seizures using photoacoustic imaging with a peroxynitrite-responsive manganese(ii) texaphyrin

Real-time visualization and tracking of epileptic seizures are important for studying epilepsy pathogenesis and treating epilepsy; however, the requisite sensing is extremely challenging, primarily due to the transient and intricate nature of neural activity associated with epilepsy. The onset of epilepsy is closely correlated with increases in peroxynitrite (ONOO-) levels, a reactive nitrogen species that can serve as a biomarker for epilepsy. However, the fleeting biological half-life and high reactivity of ONOO- has historically impeded its direct visualization within the epileptic brain. This study explores the efficacy of manganese(ii) texaphyrin (MMn), a water-soluble and stable expanded porphyrin, in dynamically sensing ONOO- and providing real-time tracking of epileptic seizures using a custom-built photoacoustic imaging (PAI) setup. UV-vis spectral analyses established the preferential sensitivity of MMn to ONOO- over other reactive oxygen species (ROS), as well as its effectiveness through multiple usage cycles when rejuvenated via reaction with suitable reducing agents. This selectivity was recapitulated in vitro as determined through PAI experiments. In vivo application of this technique revealed that MMn administered intravenously crosses the blood-brain barrier (BBB) in a pentylenetetrazole (PTZ)-induced epilepsy mouse model and provides an observable 14.1 ± 3.7% reduction in photoacoustic (PA) signal intensity within the hippocampal region during epileptic seizures. Multiple decreasing-increasing cycles of PA signal intensity could be detected in the hippocampal region in this model; the observed effect thus mirrors closely the course of epileptic seizures inferred from mouse tail curling. Similar cyclical patterns were also seen in the motor cortex, a finding consistent with the extensive spread of epileptic activity throughout the brain. To the best of our knowledge, the present investigation represents the first real-time visualization and tracking of epileptic seizures using a peroxynitrite-specific sensing probe in combination with photoacoustic imaging (PAI). This approach enables deeper brain imaging while simultaneously capturing dynamic ONOO- fluctuations, offering biochemical insights into epilepsy pathogenesis. By integrating deep-tissue imaging with neurochemical monitoring, this method lays the foundation for potential advances in epilepsy management and treatment.

A critical analysis of the potential of iron heterobimetallic complexes in anticancer research

Due to their diverse chemical properties and high ability to interact with biological molecules and cellular processes, transition metal-based compounds have emerged as promising candidates for cancer therapy. Iron complexes are among them, however, there is a gap in the comprehensive analysis of heterometallic iron complexes in the anticancer field. This review aims to fill this gap by summarizing recent progress in the study of Fe(II) and Fe(III) heterobimetallic complexes for anticancer applications and to gather important insights and future perspectives, with special emphasis on their theranostic capabilities. Works published between 2014 and 2024 were considered in this critical survey, that covers a range of complex types, including ferrocene in bimetallic complexes with Pt, Pd, Au, Ag, Ru, Rh, Ir, Cu, Re, Sn and Co; organometallic Fe-complexes with Ru and Ag; photoactive metal complexes with Pt and Co; and magnetic resonance imaging contrast agents with Gd and Mn. Studies conducted to determine the modes of action are highlighted and suggest the involvement of the metal species in reactive oxygen species generation within cells, the impact on apoptosis and cell cycle arrest, and many others. By pursuing interdisciplinary research, innovative theranostic platforms with enhanced efficacy, specificity, and clinical relevance can be developed for cancer management.

Anthelmintic activity of 1,10-phenanthroline-5,6-dione-based metallodrugs

Parasitic worm infections impose a significant public health burden, affecting over 2 billion people, particularly in low-income regions. The limited efficacy of current treatments highlights the urgent need for new anthelmintic agents. This study investigates the potential antiparasitic activity of 1,10-phenanthroline-5,6-dione (phendione) and its metal complexes, [Cu(phendione)3](ClO4)2.8H2O and [Ag(phendione)2](ClO4), against Schistosoma mansoni, the causative agent of intestinal schistosomiasis, and Angiostrongylus cantonensis, responsible for eosinophilic meningitis in humans. Additionally, the compounds were tested on Caenorhabditis elegans, a model organism for drug discovery. All compounds exhibited strong antiparasitic activity, with Cu-phendione showing the greatest potency (EC50 = 2.3 µM for S. mansoni and 6.4 µM for A. cantonensis). Ag-phendione also demonstrated significant activity, achieving EC₅₀ values of 6.5 µM against S. mansoni and 12.7 µM against A. cantonensis. The lethal dose (LD50) values in C. elegans were over 40 times higher, indicating selective antiparasitic effects. Cytotoxicity assays using Vero cells revealed a low toxicity profile and a high selectivity index. Given the promising biological properties of phendione and its metal complexes, these findings contribute to the growing body of research seeking to address the urgent need for new anthelmintic therapies.

Quantum Chemical and Biological Insights into Redox Activity of Metallacarborane Complexes in Cancer Cells

A relationship between the electronic properties of metal ions in metallacarboranes and their ability to modulate mitochondrial oxidase activity and membrane hyperpolarization in cancer cells was demonstrated. Quantum chemistry methods, including DFT and molecular dynamics simulations, were used to understand the oxidized and reduced forms of metallacarboranes and their intramolecular rotatory behavior. According to the low-spin assumption for metal ions, the intramolecular oscillations of cluster ligands in metallacarboranes are significantly influenced by the type of metal and correspond to the cellular uptake of these complexes in vitro. In particular, the low-spin iron compound may be a new xenogeneic booster of redox homeostasis in cancer cells resistant to cisplatin, which induces metabolic 'exhaustion' of cancer cells and their death.

Recent Advances on Pt-Based Compounds for Theranostic Applications

Since the discovery of cisplatin's antitumoral activity and its approval as an anticancer drug, significant efforts have been made to enhance its physiological stability and anticancer efficacy and to reduce its side effects. With the rapid development of targeted and personalized therapies, and the promising theranostic approach, platinum drugs have found new opportunities in more sophisticated systems. Theranostic agents combine diagnostic and therapeutic moieties in one scaffold, enabling simultaneous disease monitoring, therapy delivery, response tracking, and treatment efficacy evaluation. In these systems, the platinum core serves as the therapeutic agent, while the functionalized ligand provides diagnostic tools using various imaging techniques. This review aims to highlight the significant role of platinum-based complexes in theranostic applications, and, to the best of our knowledge, this is the first focused contribution on this type of platinum compounds. This review presents a brief introduction to the development of platinum chemotherapeutic drugs, their limitations, and resistance mechanisms. It then describes recent advancements in integrating platinum complexes with diagnostic agents for both tumor treatment and monitoring. The main body is organized into three categories based on imaging techniques: fluorescence, positron emission tomography (PET), single-photon emission computed tomography (SPECT), and magnetic resonance imaging (MRI). Finally, this review outlines promising strategies and future perspectives in this evolving field.

Nanoformulations in Pharmaceutical and Biomedical Applications: Green Perspectives

This study provides a brief discussion of the major nanopharmaceuticals formulations as well as the impact of nanotechnology on the future of pharmaceuticals. Effective and eco-friendly strategies of biofabrication are also highlighted. Modern approaches to designing pharmaceutical nanoformulations (e.g., 3D printing, Phyto-Nanotechnology, Biomimetics/Bioinspiration, etc.) are outlined. This paper discusses the need to use natural resources for the "green" design of new nanoformulations with therapeutic efficiency. Nanopharmaceuticals research is still in its early stages, and the preparation of nanomaterials must be carefully considered. Therefore, safety and long-term effects of pharmaceutical nanoformulations must not be overlooked. The testing of nanopharmaceuticals represents an essential point in their further applications. Vegetal scaffolds obtained by decellularizing plant leaves represent a valuable, bioinspired model for nanopharmaceutical testing that avoids using animals. Nanoformulations are critical in various fields, especially in pharmacy, medicine, agriculture, and material science, due to their unique properties and advantages over conventional formulations that allows improved solubility, bioavailability, targeted drug delivery, controlled release, and reduced toxicity. Nanopharmaceuticals have transitioned from experimental stages to being a vital component of clinical practice, significantly improving outcomes in medical fields for cancer treatment, infectious diseases, neurological disorders, personalized medicine, and advanced diagnostics. Here are the key points highlighting their importance. The significant challenges, opportunities, and future directions are mentioned in the final section.

DNA structural changes (photo)induced by tricarbonyl (pterin)rhenium(I) complex

We report on interactions of different types of DNA molecules including double-stranded and plasmid DNA as well as polynucleotides (poly[dGdC]2 and poly[dAdT]2) with fac-[ReI(CO)3(pterin)(H2O)] (or Reptr) complex. The interaction was characterized spectroscopically and changes in the plasmid structure were verified by both electrophoresis and AFM microscopy. For comparative reasons, two others related tricarbonyl rhenium(I) complexes, fac-[(4,4'-bpy)ReI(CO)3(dppz)]+ (or Redppz) and fac-[(CF3SO3)ReI(CO)3(2,2'-bpy)] (or Rebpy) were also studied to further explore the influence of the different co-ligands on the interaction and DNA (photo)damage. Data reported herein suggests that DNA molecules can be structurally modified either by direct interaction with Re(I) complexes in their ground states inducing DNA relaxation, and/or through photoinduced cross-linking processes. The chemical nature of the co-ligands modulates the extent of the damage observed.

DNA-Targeted Complexes of Tc and Re for Biomedical Applications

Due to their favorable chemical features, Re and Tc complexes have been widely used for the development of new therapeutic agents and imaging probes to solve problems of biomedical relevance. This review provides an update of the most relevant research efforts towards the development of novel cancer theranostic agents using Re and Tc-based compounds interacting with specific DNA structures. This includes a variety of homometallic complexes, namely those containing M(CO)3 (M=Re, Tc) moieties, that exhibit different modes of interaction with DNA, such as covalent binding, intercalation, groove binding or G-quadruplex DNA binding. Additionally, heterometallic complexes, designed to potentiate synergistic effects of different metal centers to improve DNA-targeting, cytotoxicity and fluorescence properties, are also reviewed. Particular attention is also given to 99m Tc- and 188 Re-labeled oligonucleotides that have been widely explored to develop imaging and therapeutic radiopharmaceuticals through the in vivo hybridization with a specific complementary DNA or RNA target sequence to provide useful molecular tools in precision medicine for cancer diagnosis and treatment. Finally, the need for further improvement of DNA-targeted Re and Tc-based compounds as potential therapeutic and diagnostic agents is highlighted, and future directions are discussed.

Research Progress of Metal Anticancer Drugs

Cancer treatments, including traditional chemotherapy, have failed to cure human malignancies. The main reasons for the failure of these treatments are the inevitable drug resistance and serious side effects. In clinical treatment, only 5 percent of the 50 percent of cancer patients who are able to receive conventional chemotherapy survive. Because of these factors, being able to develop a drug and treatment that can target only cancer cells without affecting normal cells remains a big challenge. Since the special properties of cisplatin in the treatment of malignant tumors were accidentally discovered in the last century, metal anticancer drugs have become a research hotspot. Metal anticancer drugs have unique pharmaceutical properties, such as ruthenium metal drugs with their high selectivity, low toxicity, easy absorption by tumor tissue, excretion, and so on. In recent years, efficient and low-toxicity metal antitumor complexes have been synthesized. In this paper, the scientific literature on platinum (Pt), ruthenium (Ru), iridium (Ir), gold (Au), and other anticancer complexes was reviewed by referring to a large amount of relevant literature at home and abroad.

Necrosis-Inducing High-Valent Oxo-Rhenium(V) Complexes with Potent Antitumor Activity: Synthesis, Aquation Chemistry, Cisplatin Cross-Resistance Profile, and Mechanism of Action

Chemotherapy with the cytotoxic platinum (Pt) drugs cisplatin, carboplatin, and oxaliplatin is the mainstay of anticancer therapy in the clinic. The antitumor activity of Pt drugs originates from their ability to induce apoptosis via covalent adduct formation with nuclear DNA. While the phenomenal clinical success is highly encouraging, resistance and adverse toxic side effects limit the wider applicability of Pt drugs. To circumvent these limitations, we embarked on an effort to explore the antitumor potential of a new class of oxo-rhenium(V) complexes of the type [(N∧N)(EG)Re(O)Cl] (where EG = ethylene glycolate and N∧N = bipyridine, Bpy (1); phenanthroline, Phen (2); 3,4,7,8-tetramethyl-phenanthroline, Me4Phen (3)). Investigation of speciation chemistry in aqueous media revealed the formation of [(N∧N)Re(O)(OH)3] as the biologically active species. Complex 3 was found to be the most potent among the three, with IC50 values ranging from 0.1 to 0.4 μM against a panel of cancer cells, which is 5-70-fold lower when compared with cisplatin. The higher potency of 3 is attributed to its higher lipophilicity, which enhanced cellular uptake. Importantly, complex 3 efficiently overcomes cisplatin resistance in ovarian, lung, and prostate cancer cells. In addition to reporting the aquation chemistry and identifying the active species in aqueous media, we performed in-depth in vitro mechanistic studies, which revealed that complex 3 preferentially accumulates in mitochondria, depletes mitochondrial membrane potential, and upregulates intracellular reactive oxygen species (ROS), leading to ER stress-mediated necrosis-mediated cancer cell death.

The Lung Microbiome in COPD and Lung Cancer: Exploring the Potential of Metal-Based Drugs

Chronic obstructive pulmonary disease (COPD) and lung cancer 17 are two of the most prevalent and debilitating respiratory diseases worldwide, both associated with high morbidity and mortality rates. As major global health concerns, they impose a substantial burden on patients, healthcare systems, and society at large. Despite their distinct aetiologies, lung cancer and COPD share common risk factors, clinical features, and pathological pathways, which have spurred increasing research interest in their co-occurrence. One area of particular interest is the role of the lung microbiome in the development and progression of these diseases, including the transition from COPD to lung cancer. Exploring novel therapeutic strategies, such as metal-based drugs, offers a potential avenue for targeting the microbiome in these diseases to improve patient outcomes. This review aims to provide an overview of the current understanding of the lung microbiome, with a particular emphasis on COPD and lung cancer, and to discuss the potential of metal-based drugs as a therapeutic strategy for these conditions, specifically concerning targeting the microbiome.

Next Generation Gold Drugs and Probes: Chemistry and Biomedical Applications

The gold drugs, gold sodium thiomalate (Myocrisin), aurothioglucose (Solganal), and the orally administered auranofin (Ridaura), are utilized in modern medicine for the treatment of inflammatory arthritis including rheumatoid and juvenile arthritis; however, new gold agents have been slow to enter the clinic. Repurposing of auranofin in different disease indications such as cancer, parasitic, and microbial infections in the clinic has provided impetus for the development of new gold complexes for biomedical applications based on unique mechanistic insights differentiated from auranofin. Various chemical methods for the preparation of physiologically stable gold complexes and associated mechanisms have been explored in biomedicine such as therapeutics or chemical probes. In this Review, we discuss the chemistry of next generation gold drugs, which encompasses oxidation states, geometry, ligands, coordination, and organometallic compounds for infectious diseases, cancer, inflammation, and as tools for chemical biology via gold-protein interactions. We will focus on the development of gold agents in biomedicine within the past decade. The Review provides readers with an accessible overview of the utility, development, and mechanism of action of gold-based small molecules to establish context and basis for the thriving resurgence of gold in medicine.

Cytotoxicity and mechanism of action of metal complexes: An overview

After the discovery of cisplatin, many metal compounds were investigated for the therapy of diseases, especially cancer. The high therapeutic potential of metal-based compounds is related to the special properties of these compounds, such as their redox activity and ability to target vital biological sites. The overproduction of ROS and the consequent destruction of the membrane potential of mitochondria and/or the DNA helix is one of the known pathways leading to the induction of apoptosis by metal complexes. The apoptosis process can occur via the death receptor pathway and/or the mitochondrial pathway. The expression of Bcl2 proteins and the caspase family play critical roles in these pathways. In addition to apoptosis, autophagy is another process that regulates the suppression or promotion of various cancers through a dual action. On the other hand, the ability to interact with DNA is an important property found in several metal complexes with potent antiproliferative effects against cancer cells. These interactions were classified into two important categories: covalent/coordinated or subtle, and non-coordinated interactions. The anticancer activity of metal complexes is sometimes achieved by the simultaneous combination of several mechanisms. In this review, the anticancer effect of metal complexes is mechanistically discussed by different pathways, and some effective agents on their antiproliferative properties are explained.