Next-Generation Metal Anticancer Complexes: Multitargeting via Redox Modulation

Well designed iridium-phosphinite complexes: Biological assays, electrochemical behavior and density functional theory calculations

Mononuclear phosphinite Iridium complexes based on ferrocene group have been prepared and characterized by various spectroscopic techniques. The complexes were subjected to cyclic voltammetry studies in order to determine the energies of HOMO and LUMO levels and to estimate their electrochemical and some electronic properties. Organic complex-based memory substrates were immobilized using TiO2-modified ITO electrodes, and the memory functions of phosphinite-based organic complexes were verified by chronoamperometry (CA) and open-circuit potential amperometry (OCPA). Extensive theoretical and experimental investigations were directed to gain a more profound understanding of the chemical descriptors and the diverse electronic transitions taking place within the iridium complexes, as well as their electrochemical characteristics. The quantum chemical calculations were carried out for the iridium complexes at the DFT/CAM-B3LYP level of theory in the gas phase. Furthermore, the antioxidant, antimicrobial, DNA binding, and DNA cleavage activities of the complexes were tested. Complex 2 exhibited the highest radical scavenging activity (67.5 ± 2.24 %) at 200.0 mg/L concentration. It was observed that the complexes formed an inhibition zone in the range of 8-15 mm against Gram + bacteria and in the range of 0-13 mm against Gram - bacteria. The agarose gel electrophoresis method was used to determine the DNA binding and DNA cleavage activities of the complexes. All of the tested complexes had DNA binding activity; however, complexes 1, 2, and 8 showed better binding activity than the others.

Iminoamido chelated iridium(III) and ruthenium(II) anticancer complexes with mitochondria-targeting ability and potential to overcome cisplatin resistance

A diverse set of neutral half-sandwich iminoamido iridium and ruthenium organometallic complexes is synthesized through the utilization of Schiff base pro-ligands with N˄N donors. Notably, these metal complexes with varying leaving groups (Cl- or OAc-) are formed by employing different quantities of the deprotonating agent NaOAc, and exhibit promising cytotoxicity against various cancer cell lines such as A549 and cisplatin-resistant A549/DDP lung cancer cells, as well as HeLa cells, with IC50 values spanning from 9.26 to 15.98 μM. Cytotoxicity and anticancer selectivity (SI: 1.9-2.4) of these metal complexes remain unaffected by variations in the metal center, leaving group, and ligand substitution. Further investigations reveal that these metal complexes specifically target mitochondria, leading to the depolarization of the mitochondrial membrane and instigating the production of intracellular reactive oxygen species. Furthermore, the metal complexes are found to induce late apoptosis and disrupt the cell cycle, leading to G2/M cell cycle arrest specifically in A549 cancer cells. In light of these findings, it is evident that the primary mechanism contributing to the anticancer effectiveness of these metal complexes is the redox pathway.

Silver(I) Complexes with Mefenamic Acid and Nitrogen Heterocyclic Ligands: Synthesis, Characterization, and Biological Evaluation

Four Ag(I) complexes with mefenamato and nitrogen heterocyclic ligands, [Ag(2-apy)(mef)]2 (1), [Ag(3-apy)(mef)] (2), [Ag2(tmpyz)(mef)2] (3), and {[Ag(4,4'-bipy)(mef)]2(CH3CN)1.5(H2O)2}n (4), (mef = mefenamato, 2-apy = 2-aminopyridine, 3-apy = 3-aminopyridine, tmpyz = 2,3,5,6-tetramethylpyrazine, 4,4'-bipy = 4,4'-bipyridine), were synthesized and characterized. The interactions of these complexes with BSA were investigated by fluorescence spectroscopy, which indicated that these complexes quench the fluorescence of BSA by a static mechanism. The fluorescence data also indicated that the complexes showed good affinity for BSA, and one binding site on BSA was suitable for the complexes. The in vitro cytotoxicity of the four complexes against human cancer cell lines (MCF-7, HepG-2, A549, and MDA-MB-468) and one normal cell line (HTR-8) was evaluated by the MTT assay. Complex 1 displayed high cytotoxic activity against A549 cells. Further studies revealed that complex 1 could enhance the intracellular levels of ROS (reactive oxygen species) in A549 cells, cause cell cycle arrest in the G0/G1 phase, and induce apoptosis in A549 cells in a dose-dependent manner.

Redox modulator iron complexes trigger intrinsic apoptosis pathway in cancer cells

The emergence of multidrug resistance in cancer cells necessitates the development of new therapeutic modalities. One way cancer cells orchestrate energy metabolism and redox homeostasis is through overloaded iron pools directed by iron regulatory proteins, including transferrin. Here, we demonstrate that targeting redox homeostasis using nitrogen-based heterocyclic iron chelators and their iron complexes efficiently prevents the proliferation of liver cancer cells (EC50: 340 nM for IITK4003) and liver cancer 3D spheroids. These iron complexes generate highly reactive Fe(IV)=O species and accumulate lipid peroxides to promote oxidative stress in cells that impair mitochondrial function. Subsequent leakage of mitochondrial cytochrome c activates the caspase cascade to trigger the intrinsic apoptosis pathway in cancer cells. This strategy could be applied to leverage the inherent iron overload in cancer cells to selectively promote intrinsic cellular apoptosis for the development of unique iron-complex-based anticancer therapeutics.

Exploring copper (II) porphyrin complexes and their derivatives for electrochemical analysis and biological assessment in the study of breast cancer (MCF-7) cell lines

In this study, several derivatives of tetraphenylporphyrin were synthesized, each with unique meso-substituent groups including phenyl, methoxyphenyl, butyloxyphenyl, octyloxyphenyl, and dectyloxyphenyl. Additionally, their corresponding copper complexes were prepared and thoroughly characterized. The structural confirmation of all compounds was established through CHN elemental analysis, mass spectrometry, and FT-IR spectroscopy. As the number of carbon atoms in the alkyl long-chain increased, a slight red shift in the electronic absorption band was observed, which was attributed to the electronic influence of the alkyl group. DFT analysis indicated that electron density predominantly localized on the porphyrin ring of both the metal free porphyrins and copper (II) porphyrin complexes, with relatively low electron density in the p orbital of the meso-aryl long-chain substituent group. EPR spectroscopy of the Copper (II) ion complexes revealed signals, indicating their paramagnetic properties. Additionally, the Copper (II) tetraphenylporphyrin (CuTPP) complexes displayed two reversible oxidation peaks at +0.97 V and +1.35 V, whereas other derivatives exhibited lower oxidation potentials. The cytotoxicity of these compounds against MCF-7 cell lines was assessed using MTT assay, revealing cytotoxic effects in all cases. Among them, Copper (II) tetrakis (4-methyloxyphenyl)porphyrin (CuTOMPP) demonstrated the highest potential, with an IC50 value of 32.07 μg/mL.

Diruthenium Paddlewheel Complexes Attacking Proteins: Axial versus Equatorial Coordination

Metallodrugs are an important group of medicinal agents used for the treatment of various diseases ranging from cancers to viral, bacterial, and parasitic diseases. Their distinctive features include the availability of a metal centre, redox activity, as well as the ability to multitarget. Diruthenium paddlewheel complexes are an intensely developing group of metal scaffolds, which can securely coordinate bidentate xenobiotics and transport them to target tissues, releasing them by means of substitution reactions with biomolecular nucleophiles. It is of the utmost importance to gain a complete comprehension of which chemical reactions happen with them in physiological milieu to design novel drugs based on these bimetallic scaffolds. This review presents the data obtained in experiments and calculations, which clarify the chemistry these complexes undergo once administered in the proteic environment. This study demonstrates how diruthenium paddlewheel complexes may indeed embody a new paradigm in the design of metal-based drugs of dual-action by presenting and discussing the protein metalation by these complexes.

Synthesis, characterization, and cancer cell-selective cytotoxicity of mixed-ligand cobalt(III) complexes of 8-hydroxyquinolines and phenanthroline bases

Transition metal complexes exhibiting selective toxicity towards a broad range of cancer types are highly desirable as potential anticancer agents. Herein, we report the synthesis, characterization, and cytotoxicity studies of six new mixed-ligand cobalt(III) complexes of general formula [Co(B)2(L)](ClO4)2 (1-6), where B is a N,N-donor phenanthroline base, namely, 1,10-phenanthroline (phen in 1, 2), dipyrido[3,2-d:2',3'-f]quinoxaline (dpq in 3, 4), and dipyrido[3,2-a:2',3'-c]phenazine (dppz in 5, 6), and L is the monoanion of 8-hydroxyquinoline (HQ in 1, 3, 5) and 5-chloro-7-iodo-8-hydroxyquinoline (CQ in 2, 4, 6). The X-ray single crystal structures of complexes 1 and 2 as PF6- salts revealed a distorted octahedral CoN5O coordination environment. Complexes demonstrated good stability in an aqueous buffer medium and in the presence of ascorbic acid as a reductant. Cytotoxicity studies using a panel of nine cancer cell lines showed that complex 6, with the dppz and CQ ligands, was significantly toxic against most cancer cell types, yielding IC50 values in the range of 2 to 14 μM. Complexes 1, 3, and 5, containing the HQ ligand, displayed lower toxicity compared to their CQ counterparts. The phenanthroline complexes demonstrated marginal toxicity towards the tested cell lines, while the dpq complexes exhibited moderate toxicity. Interestingly, all complexes demonstrated negligible toxicity towards normal HEK-293 kidney cells (IC50 > 100 μM). The observed cytotoxicity of the complexes correlated well with their lipophilicities (dppz > dpq > phen). The cytotoxicity of complex 6 was comparable to that of the clinical drug cisplatin under similar conditions. Notably, neither the HQ nor the CQ ligands alone demonstrated noticeable toxicity against any of the tested cell lines. The Annexin-V-FITC and DCFDA assays revealed that the cell death mechanism induced by the complexes involved apoptosis, which could be attributed to the metal-assisted generation of reactive oxygen species. Overall, the dppz complex 6, with its remarkable cytotoxicity against a broad range of cancer cells and negligible toxicity toward normal cells, holds significant potential for cancer chemotherapeutic applications.

Phenanthroline and Schiff Base associated Cu(II)-coordinated compounds containing N, O as donor atoms for potent anticancer activity

As an inherent metal ion, copper has been the subject of investigation for developing a novel antitumoral compound that exhibits fewer adverse effects. Copper serves as a cofactor in multiple enzymes, generates reactive oxygen species (ROS), facilitates tumour evolution, metastasis and angiogenesis and has been detected at elevated concentrations in the serum and tissues of various human cancer types. In the given setting, utilising two methodologies in developing novel Copper-based pharmaceuticals for anti-cancer applications is standard practice. These approaches involve either the sequestration of unbound Copper ions or the synthesis of Copper complexes that induce cellular apoptosis. In the past four decades, the latter system has been used, leading to numerous reviews that have examined the anticancer characteristics of a wide range of Copper complexes. These analyses have consistently demonstrated that multiple factors frequently influence the efficacy of these compounds. This review examines the possible anticancer properties of copper and Cu(II) complexes that incorporate Schiff base ligands containing 1,10-phenanthroline. The present study will comprehensively analyse the examined cell lines and mechanistic research associated with each complex.

Potent Half-Sandwich 16-/18-Electron Iridium(III) and Ruthenium(II) Anticancer Complexes with Readily Available Amine-Imine Ligands

The synthesis and biological evaluation of stable 16-electron half-sandwich complexes have remained scarce. We herein present the different coordination modes (16-electron or 18-electron) between half-sandwich iridium(III) complexes and ruthenium(II) complexes derived from the same amine-imine ligands chelating hybrid sp3-N/sp2-N donors. The 16-electron iridium(III) and 18-electron ruthenium(II) complexes with different counteranions were obtained and identified by various techniques. The promising cytotoxicity of these complexes against A549 lung cancer cells, cisplatin-resistant A549/DPP cells, cervical carcinoma HeLa cells, and human hepatocellular liver carcinoma HepG2 cells was observed with IC50 values ranging from 5.4 to 16.3 μM. Moreover, these complexes showed a certain selectivity (selectivity index: 2.1-3.7) toward A549 cells and BEAS-2B normal cells. The variation of metal center, counteranion, 16/18-electron coordination mode, and ligand substituents showed little influence on the cytotoxicity and selectivity of these complexes. The mechanism of action study showed that these complexes could target mitochondria, induce the depolarization of the mitochondrial membrane, and promote the generation of intracellular reactive oxygen species (ROS). Further, the induction of cell apoptosis and the perturbation of the cell cycle in the G0/G1 phase were also observed for these complexes. Overall, it seems that the redox mechanism dominated the anticancer efficacy of these complexes.

Complexes of Ruthenium(II) as Promising Dual-Active Agents against Cancer and Viral Infections

Poor responses to medical care and the failure of pharmacological treatment for many high-frequency diseases, such as cancer and viral infections, have been widely documented. In this context, numerous metal-based substances, including cisplatin, auranofin, various gold metallodrugs, and ruthenium complexes, are under study as possible anticancer and antiviral agents. The two Ru(III) and Ru(II) complexes, namely, BOLD-100 and RAPTA-C, are presently being studied in a clinical trial and preclinical studies evaluation, respectively, as anticancer agents. Interestingly, BOLD-100 has also recently demonstrated antiviral activity against SARS-CoV-2, which is the virus responsible for the COVID-19 pandemic. Over the last years, much effort has been dedicated to discovering new dual anticancer-antiviral agents. Ru-based complexes could be very suitable in this respect. Thus, this review focuses on the most recent studies regarding newly synthesized Ru(II) complexes for use as anticancer and/or antiviral agents.

GSH resistant, luminescent 2-(pyren-1-yl)-1H-imidazo[4,5-f][1,10]phenanthroline-based Ru(II)/Ir(III)/Re(I) complexes for phototoxicity in triple-negative breast cancer cells

Selective chemotherapeutic strategies necessitate the emergence of a photosensitive scaffold to abate the nuisance of cancer. In the current context, photo-activated chemotherapy (PACT) has, therefore, appeared to be very effective to vanquish the vehemence of triple-negative breast cancer (TNBC). Metal complexes have been identified to act well against cancer cell microenvironment (high GSH content, low pH, and hypoxia), and thus they have been employed in the treatment of various types of cancer. As TNBC is very challenging to treat owing to its poor prognosis, lack of a specific target, high chance of relapse, and strong metastatic ability, herein we have aspired to design GSH-resistant phototoxic Ru(II)/Ir(III)/Re(I) based pyrene imidazophenathroline complexes to selectively avert the triple-negative breast cancer. The application of complexes, [RuL], [IrL], and [ReL] in the absence and in the presence of GSH against MDA-MB-231TNBC cells, has revealed that they are very active upon irradiation of visible light compared to dark due to the creation of copious singlet oxygen (1O2) as reactive oxygen species (ROS). Among three synthesized complexes, [IrL] has shown outstanding potency (IC50 = 3.70 in the absence of GSH and IC50 = 3.90 in the presence of GSH). Also, the complex, [IrL] is capable of interacting with DNA with the highest binding constant (Kb = 0.023 × 106 M-1) along with higher protein binding affinity (KBSA = 0.0321 × 106 M-1). Here, it has been unveiled that all the complexes have been entitled to involve DNA covalent interaction through the available sites of both adenine and guanine bases.

Half-Sandwich Iridium(III), Rhodium(III), and Ruthenium(II) Complexes Chelating Hybrid sp2-N/sp3-N Donor Ligands to Achieve Improved Anticancer Selectivity

The biological efficacy of half-sandwich platinum group organometallic complexes of the formula [(η5-Cpx)/(η6-arene)M(XY)Cl]0/+ (XY = bidentate ligands; Cpx = functionalized cyclopentadienyl; M = Ir, Rh, Ru, Os) has received considerable attention due to the significance of the metal center, chelating ligand, and Cpx/arene moieties in defining their anticancer potency and selectivity. With a facile access to the BIAN-derived imine-amine ligands using alkylaluminum as the reductant, we herein described the preparation and characterization of 16 half-sandwich Ir(III), Rh(III), and Ru(II) complexes chelating the hybrid sp2-N/sp3-N donor ligand. A nonplanar five-member metallacycle was confirmed by X-ray single-crystal structures of Ir1-Ir3, Ir7, Rh1, Ru1, and Ru4. The attempt to prepare imine-amido complexes using a base as the deprotonating agent led to the mixture of imine-amine complexes, within which the leaving group Cl- was displaced, and 16-electron imine-amido complexes without Cl-. The half-sandwich imine-amine complexes in this system underwent rapid hydrolysis in aqueous solution, exhibited weak photoluminescence, and showed the ability of binding to CT-DNA and BSA. The cytotoxicity of all imine-amine complexes against A549 lung cancer cell lines, HeLa cervical cancer cell lines, and 4T1 mouse breast cancer cells was determined by an MTT assay. The IC50 values of these complexes were in a range of 5.71-67.28 μM. Notably, most of these complexes displayed improved selectivity toward A549 cancer cells versus noncancerous BEAS-2B cells in comparison with the corresponding α-diimine complexes chelating the sp2-N/sp2-N donor ligand, which have been shown no selectivity in our previous report. The anticancer selectivity of these complexes appeared to be related to the redox-based mechanism including the catalytic oxidation of NADH to NAD+, reactive oxygen species (ROS) generation, and depolarization of the mitochondrial membrane. Further, inducing apoptosis of these complexes in A549 cancer cells and BEAS-2B normal cells also correlated with their anticancer selectivity, indicating the apoptosis mode of cell death in this system. In addition, these complexes could enter A549 cells via energy-dependent pathway and were able to impede the in vitro migration of A549 cells.

Regulating tumor glycometabolism and the immune microenvironment by inhibiting lactate dehydrogenase with platinum(iv) complexes

Lactate dehydrogenase (LDH) is a key enzyme involved in the process of glycolysis, assisting cancer cells to take in glucose and generate lactate, as well as to suppress and evade the immune system by altering the tumor microenvironment (TME). Platinum(iv) complexes MDP and DDP were prepared by modifying cisplatin with diclofenac at the axial position(s). These complexes exhibited potent antiproliferative activity against a panel of human cancer cell lines. In particular, DDP downregulated the expression of LDHA, LDHB, and MCTs to inhibit the production and influx/efflux of lactate in cancer cells, impeding both glycolysis and glucose oxidation. MDP and DDP also reduced the expression of HIF-1α, ARG1 and VEGF, thereby disrupting the formation of tumor vasculature. Furthermore, they promoted the repolarization of macrophages from the tumor-supportive M2 phenotype to the tumor-suppressive M1 phenotype in the TME, thus enhancing the antitumor immune response. The antitumor mechanism involves reprogramming the energy metabolism of tumor cells and relieving the immunosuppressive TME.

Medicinal applications of vanadium complexes with Schiff bases

Many transition metal complexes have been explored for their therapeutic properties after the discovery of cisplatin. Schiff bases have an efficient complexation tendency with the transition metals and several medicinal properties have been reported. However, fewer studies have reported the medicinal utility of vanadium and its Schiff base complexes. This paper provides a comprehensive overview of vanadium complexes with Schiff bases along with their mechanistic insight. Vanadium complexes in + 4 and + 5 oxidation states have exhibited well-defined geometry and found to be thermodynamically stable. The studies have reported the G0/G1 phase cell cycle arrest and decreased delta psi m, inducing mitochondrial membrane depolarization in cancer cell lines along with the alterations in the metabolism of the cancer cells upon dosing with the vanadium complexes. Cancer cell invasion and growth are also found to be markedly reduced by peroxo complexes of vanadium. The studies included in the review paper have been taken from leading indexing databases and focus was laid on recent reports in literature. The biological potential of vanadium complexes of Schiff bases opens new horizons for future interdisciplinary studies and investigation focussed on understanding the biochemistry of these complexes, along with designing new complexes which have better bioavailability, solubility and low or non-toxicity.

Synthesis, DNA binding and biological evaluation of benzimidazole Schiff base ligands and their metal(ii) complexes

Two novel benzimidazole ligands (E)-2-((4-(1H-benzo[d]imidazole-2-yl)phenylimino)methyl)-6-bromo-4-chlorophenol (L₁) and (E)-1-((4-(1H-benzo[d]imidazole-2-yl)phenylimino)methyl)naphthalene-2-ol (L₂) with their corresponding Cu(ii), Ni(ii), Pd(ii) and Zn(ii) complexes were designed and synthesized. The compounds were characterized by elemental, IR, and NMR (¹H & ¹³C) spectral analyses. Molecular masses were determined by ESI-mass spectrometry, and the structure of ligand L₁ was confirmed by single crystal X-ray diffraction analysis. Molecular docking was carried out for the theoretical investigation of DNA binding interactions. The results obtained were verified experimentally by UV/Visible absorption spectroscopy in conjunction with DNA thermal denaturation studies. It was observed that ligands (L₁ and L₂) and complexes (1-8) were moderate to strong DNA binders, as evident from the binding constants (K _b). The value was found to be highest for complex 2 (3.27 × 10⁵ M^-1) and lowest for 5 (6.40 × 10³ M^-1). A cell line study revealed that breast cancer cells were less viable to the synthesized compounds compared to that of standard drugs, cisplatin and doxorubicin, at the same concentration. The compounds were also screened for in vitro antibacterial activity for which complex 2 showed a promising broad-spectrum effect against all tested strains of bacteria, almost in the proximity of the reference drug kanamycin, while the rest of the compounds displayed activity against selected strains.

A comparative study on the metal complexes of an anticancer estradiol-hydroxamate conjugate and salicylhydroxamic acid

Hydroxamic acids bearing an (O,O) donor set are well-known metal-chelating compounds with diverse biological activities including anticancer activity. Since steroid conjugation with a pharmacophoric moiety may have the potential to improve this effect, a salicylhydroxamic acid-estradiol hybrid molecule (E2HA) was synthesized. Only minimal effect of the conjugation on the proton dissociation constants was observed in comparison to salicylhydroxamic acid (SHA). The complexation with essential metal ions (iron, copper) was characterized, since E2HA may exert its cytotoxicity through the binding of these ions in cells. UV-visible spectrophotometric and pH-potentiometric titrations revealed the formation of high-stability complexes, while the Fe(III) preference over Fe(II) was proved by cyclic voltammetry and spectroelectrochemical measurements. Complex formation with half-sandwich Rh(III)(η⁵-Cp*) and Ru(II)(η⁶-p-cymene) organometallic cations was also studied as it may improve the anticancer effect and the pharmacokinetic profile of the ligand. At equimolar concentration the speciation is complicated because of the presence of mononuclear and binuclear complexes. The complexes readily react with small molecules e.g. glutathione, 1-methylimidazole and nucleosides, having major effect on solution speciation, namely mixed-ligand complex formation and ligand displacement occur. These processes serve as models for the interactions with biomolecules in the body. E2HA exerted moderate anticancer activity (IC₅₀ = 25-59 μM) in the tested three human cancer cell lines (Colo205, Colo320 and MCF-7), while being non-toxic on non-cancerous MRC-5 cells. Meanwhile, SHA was inactive in the same cells. Complexation with half-sandwich Rh(III) and Ru(II) cations had only a minor improvement on the cytotoxic effect of E2HA.

Reactivity of non-organometallic ruthenium(II) polypyridyl complexes and their application as catalysts for hydride transfer reactions

Recently, we investigated the substitution behavior of a series of ruthenium(II) complexes of the general formula [RuII(terpy)(N∧N)Cl]Cl, where terpy = 2,2′:6′,2″-terpyridine, N∧N = bidentate ligand, in aqueous solutions. We have shown that the most and least reactive complexes of the series are [RuII(terpy)(en)Cl]Cl (en = ethylenediamine) and [RuII(terpy)(phen)Cl]Cl (phen = 1, 10-phenantroline), respectively, as a result of different electronic effects provided by the bidentate spectator chelates. Polypyridyl amine Ru(II) complex, viz. [Ru(terpy)(en)Cl]Cl and [Ru(terpy)(ampy)Cl]Cl (where ampy = 2-(aminomethyl)pyridine), in which the terpy chelate labilizes the metal center, are able to catalyze the conversion of NAD+ to 1,4-NADH using sodium formate as a source of hydride. We showed that this complex can control the [NAD+]/[NADH] ratio and potentially induce reductive stress in living cells, which is accepted as an effective method to kill cancer cells. Polypyridyl Ru(II) complexes, characterized in terms of the behavior in aqueous solutions, can be used as model systems to monitor heterogeneous multiphase ligand substitution reactions at the solid-liquid interface. Colloidal coordination compounds in the submicron range were synthesized from Ru(II)-aqua derivatives of starting chlorido complexes via the anti-solvent procedure and stabilized by a surfactant shell layer.

Exploring pta Alternatives in the Development of Ruthenium-Arene Anticancer Compounds

Organoruthenium pyrithione (1-hydroxypyridine-2-thione) complexes have been shown in our recent studies to be a promising family of compounds for development of new anticancer drugs. The complex [(η⁶-p-cymene)Ru(pyrithionato)(pta)]PF₆ contains phosphine ligand pta (1,3,5-triaza-7-phosphaadamantane) as a functionality that improves the stability of the complex and its aqueous solubility. Here, we report our efforts to find pta alternatives and discover new structural elements to improve the biological properties of ruthenium anticancer drugs. The pta ligand was replaced by a selection of phosphine, phosphite, and arsine ligands to identify new functionalities, leading to improvement in inhibitory potency towards enzyme glutathione S-transferase. In addition, cytotoxicity in breast, bone, and colon cancers was investigated.

Antitumor activity of copper(II) complexes with Schiff bases derived from N'-tosylbenzene-1,2-diamine

The electrochemical oxidation of anodic metal copper in a solution of the ligands N-[(5-tert-butyl-2-hydroxyphenyl)methylidine]-N'-tosylbenzene-1,2-diamine [H₂L¹] and N-[(3,5-di-tert-butyl-2-hydroxyphenyl)methylidine]-N'-tosylbenzene-1,2-diamine, [H₂L²] afforded homoleptic [CuL] compounds or solvate [CuLS] complexes. The addition to the electrochemical cell of coligands (L') such as 2,2'-bipyridine (2-bpy), 4,4'-bipyridine(4-bpy) or 1,10-phenanthroline (phen) allowed the synthesis, in one step, of heteroleptic [CuLL'] compounds, namely [CuL¹(H₂O)] (1), [CuL¹(2,2'-bpy)]⋅CH₃CN (2), [CuL¹(phen)]·H₂O (3), [Cu₂L¹₂(4,4'-bpy)] (4), [CuL²(CH₃OH)] (5), [CuL²(2,2'-bpy)] (6), [CuL²(phen)] (7) and [Cu₂L²₂(4,4'-bpy)] (8). The crystal structures of both ligands, H₂L¹, H₂L², and those of the complexes (2), (4), (5), (6) and (7) have been determined by X-ray diffraction techniques. Coordination polyhedron around metal atom is square planar for [CuL²(CH₃OH)] (5) and [Cu₂L¹₂(4,4'-bpy)] (4) and square pyramid for the other complexes with additional chelating ligands. The cytotoxic activity of this new series of copper(II) complexes against the SH-SY5Y neuroblastoma cell line and U87-MG and U373-MG glioblastoma cell lines has been investigated. Most of the test compounds showed higher activity than cisplatin in the three cell lines. Among this series, compound [CuL¹(phen)] (3) displayed the highest activity with IC₅₀ equal to 1.77 μM on SH-SY5Y whereas compound [Cu₂L¹₂(4.4'-bpy)] (4) resulted the most potent compounds on U87 MG and U373 MG glioblastoma cell lines. Studies on the cytotoxic activity of these derivatives suggest that these compounds induce cell death by a mechanism other than apoptosis.

Stimuli-responsive platinum and ruthenium complexes for lung cancer therapy

Lung cancer is the most common cause of cancer-related deaths worldwide. More efficient treatments are desperately needed. For decades, the success of platinum-based anticancer drugs has promoted the exploration of metal-based agents. Four ruthenium-based complexes have also entered clinical trials as candidates of anticancer metallodrugs. However, systemic toxicity, severe side effects and drug-resistance impeded their applications and efficacy. Stimuli-responsiveness of Pt- and Ru-based complexes provide a great chance to weaken the side effects and strengthen the clinical efficacy in drug design. This review provides an overview on the stimuli-responsive Pt- and Ru-based metallic anticancer drugs for lung cancer. They are categorized as endo-stimuli-responsive, exo-stimuli-responsive, and dual-stimuli-responsive prodrugs based on the nature of stimuli. We describe various representative examples of structure, response mechanism, and potential medical applications in lung cancer. In the end, we discuss the future opportunities and challenges in this field.

Metal complexes of benzimidazole-derived as potential anti-cancer agents: synthesis, characterization, combined experimental and computational studies

In this study, a series of 14 Cu (II), Zn (II), Ni (II) and Ag (I) complexes containing bis-benzimidazole derivatives were successfully designed and synthesized from 2-(1H-benzimidazole-2-yl)-phenol derivatives and corresponding metal salt solutions. The compound structures were identified by FT-IR, ¹H-NMR, powder X-ray diffraction and ESI-MS analyses, and the presence of the metal in the complexes was confirmed by ultraviolet-visible spectroscopy and ICP optical emission spectrometry. Electronic structure calculations were also carried out to describe the detailed structures in addition to the electronic absorption spectra of the ligands. The cytotoxic activity of the complexes was evaluated against three human cancer cell lines: lung (A549), breast (MDA-MB-231) and prostate (PC3) cancer cells. All complexes inhibited anti-proliferative cancer cells better than free ligands, especially Zn (II) and Ag (I) complexes, which are most sensitive to MDA-MB-231 cells. In addition, showing the growth inhibition of three cancer cell lines with IC₅₀ < 10.4 µM, complexes C₁ , C₃ and C₁₄ could be considered potential multi-targeted anti-cancer agents.

Metal complexes of benzimidazole-derived as potential anti-cancer agents: synthesis, characterization, combined experimental and computational studies

In this study, a series of 14 Cu (II), Zn (II), Ni (II) and Ag (I) complexes containing bis-benzimidazole derivatives were successfully designed and synthesized from 2-(1H-benzimidazole-2-yl)-phenol derivatives and corresponding metal salt solutions. The compound structures were identified by FT-IR, ¹H-NMR, powder X-ray diffraction and ESI-MS analyses, and the presence of the metal in the complexes was confirmed by ultraviolet-visible spectroscopy and ICP optical emission spectrometry. Electronic structure calculations were also carried out to describe the detailed structures in addition to the electronic absorption spectra of the ligands. The cytotoxic activity of the complexes was evaluated against three human cancer cell lines: lung (A549), breast (MDA-MB-231) and prostate (PC3) cancer cells. All complexes inhibited anti-proliferative cancer cells better than free ligands, especially Zn (II) and Ag (I) complexes, which are most sensitive to MDA-MB-231 cells. In addition, showing the growth inhibition of three cancer cell lines with IC₅₀ < 10.4 µM, complexes C₁ , C₃ and C₁₄ could be considered potential multi-targeted anti-cancer agents.

Cytotoxic effects of halogenated tin phosphinoyldithioformate complexes against several cancer cell lines

Organotin complexes are studied as promising alternatives to the anticancer drug cisplatin. We report two monoorganotin(IV) complexes based on a dibenzyl phosphinoyldithioformate (H-DBPTF) ligand, containing either bromide (Sn-DBPTF-1) or chloride (Sn-DBPTF-2) anions. The complexes were characterized by standard analytical techniques and the structural details of these complexes were elucidated by single crystal X-ray diffraction. Sn-DBPTF-1 was cytotoxic at IC50 <10 μg mL-1 against cancer cell lines A549 (lung cancer), Aspc-1 (pancreatic cancer), OVCAR-3 (ovarian cancer), T-47D (breast cancer) and HCT116 (colon cancer), and breast epithelial stem cell line D492. The non-tumorigenic breast epithelial cell line MCF-10 was less sensitive at IC50 = 22 μg mL-1. Sn-DBPTF-2 had limited cytotoxic effect at IC50 13-37 μg mL-1. Sn-DBPTF-1 induced apoptosis and double-strand DNA breaks. Cell cycle arrest in G2 occurred in HCT116 and accumulation in G1 in Aspc-1. The results indicate that the basic effect of Sn-DBPTF-1 is to induce DNA damage, leading to apoptosis and cell cycle arrest depending on the cell line.

Targeting of the intracellular redox balance by metal complexes towards anticancer therapy

The development of cancers is often linked to the alteration of essential redox processes, and therefore, oxidoreductases involved in such mechanisms can be considered as attractive molecular targets for the development of new therapeutic strategies. On the other hand, for more than two decades, transition metals derivatives have been leading the research on drugs as alternatives to platinum-based treatments. The success of such compounds is particularly due to their attractive redox kinetics properties, favorable oxidation states, as well as routes of action different to interactions with DNA, in which redox interactions are crucial. For instance, the activity of oxidoreductases such as PHD2 (prolyl hydroxylase domain-containing protein) which can regulate angiogenesis in tumors, LDH (lactate dehydrogenase) related to glycolysis, and enzymes, such as catalases, SOD (superoxide dismutase), TRX (thioredoxin) or GSH (glutathione) involved in controlling oxidative stress, can be altered by metal effectors. In this review, we wish to discuss recent results on how transition metal complexes have been rationally designed to impact on redox processes, in search for effective and more specific cancer treatments.

Degradable polyprodrugs: design and therapeutic efficiency

Prodrugs are developed to increase the therapeutic properties of drugs and reduce their side effects. Polyprodrugs emerged as highly efficient prodrugs produced by the polymerization of one or several drug monomers. Polyprodrugs can be gradually degraded to release therapeutic agents. The complete degradation of polyprodrugs is an important factor to guarantee the successful disposal of the drug delivery system from the body. The degradation of polyprodrugs and release rate of the drugs can be controlled by the type of covalent bonds linking the monomer drug units in the polymer structure. Therefore, various types of polyprodrugs have been developed based on polyesters, polyanhydrides, polycarbonates, polyurethanes, polyamides, polyketals, polymetallodrugs, polyphosphazenes, and polyimines. Furthermore, the presence of stimuli-responsive groups, such as redox-responsive linkages (disulfide, boronate ester, metal-complex, and oxalate), pH-responsive linkages (ester, imine, hydrazone, acetal, orthoester, P-O and P-N), light-responsive (metal-complex, o-nitrophenyl groups) and enzyme-responsive linkages (ester, peptides) allow for a selective degradation of the polymer backbone in targeted tumors. We envision that new strategies providing a more efficient synergistic therapy will be developed by combining polyprodrugs with gene delivery segments and targeting moieties.

Formation of Iridium(III) and Rhodium(III) Amine, Imine, and Amido Complexes Based on Pyridine-Amine Ligands: Structural Diversity Arising from Reaction Conditions, Substituent Variation, and Metal Centers

Herein, we present the different coordination modes of half-sandwich iridium(III) and rhodium(III) complexes based on pyridine-amine ligands. The pyridyl-amine iridium(III) and rhodium(III) complexes, the corresponding oxidation pyridyl-imine products, and 16-electron pyridyl-amido complexes can be obtained through the change in reaction conditions (nitrogen/adventitious oxygen atmosphere, reaction time, and solvents) and structural variations in the metal and ligand. Overall, the reaction of pyridine-amine ligands with [(η⁵-C₅(CH₃)₅)MCl₂]₂ (M = Ir or Rh) in the presence of adventitious oxygen afforded the oxidized pyridyl-imine complexes. The possible mechanism for the oxidation of iridium(III) and rhodium(III) amine complexes was confirmed by the detection of the byproduct hydrogen peroxide. Moreover, the formation of pyridyl-amine complexes was favored when nonpolar solvent CH₂Cl₂ was used instead of CH₃OH. The rarely reported complex with [(η⁵-Cp*)IrCl₃] anions can also be obtained without the addition of NH₄PF₆. The introduction of the sterically bulky i-Bu group on the bridge carbon of the ligand led to the formation of stable 16-electron pyridyl-amido complexes. The pyridyl-amine iridium(III) and rhodium(III) complexes were also synthesized under a N₂ atmosphere, and no H₂O₂ was detected in the whole process. In particular, the aqueous solution stability and in vitro cytotoxicity toward A549 and HeLa human cancer cells of these complexes were also evaluated. No obvious selectivity was observed for cancer cells versus normal cells with these complexes. Notably, the represented complex 5a can promote an increase in the reactive oxygen species level and induce cell death via apoptosis.

Novel Nickel(II), Palladium(II), and Platinum(II) Complexes with O,S Bidendate Cinnamic Acid Ester Derivatives: An In Vitro Cytotoxic Comparison to Ruthenium(II) and Osmium(II) Analogues

(1) Background: Since the discovery of cisplatin’s cytotoxic properties, platinum(II) compounds have attracted much interest in the field of anticancer drug development. Over the last few years, classical structure−activity relationships (SAR) have been broken by some promising new compounds based on platinum or other metals. We focus on the synthesis and characterization of 17 different complexes with β-hydroxydithiocinnamic acid esters as O,S bidendate ligands for nickel(II), palladium(II), and platinum(II) complexes. (2) Methods: The bidendate compounds were synthesized and characterized using classical methods including NMR spectroscopy, MS spectrometry, elemental analysis, and X-ray crystallography, and their cytotoxic potential was assessed using in vitro cell culture assays. Data were compared with other recently reported platinum(II), ruthenium(II), and osmium(II) complexes based on the same main ligand system. (3) Results: SAR analyses regarding the metal ion (M), and the alkyl-chain position (P) and length (L), revealed the following order of the effect strength for in vitro activity: M > P > L. The highest activities have Pd complexes and ortho-substituted compounds. Specific palladium(II) complexes show lower IC50 values compared to cisplatin, are able to elude cisplatin resistance mechanisms, and show a higher cancer cell specificity. (4) Conclusion: A promising new palladium(II) candidate (Pd3) should be evaluated in further studies using in vivo model systems, and the identified SARs may help to target platinum-resistant tumors.

Current Developments of N-Heterocyclic Carbene Au(I)/Au(III) Complexes toward Cancer Treatment

Since their first discovery, N-heterocyclic carbenes have had a significant impact on organometallic chemistry. Due to their nature as strong σ-donor and π-acceptor ligands, they are exceptionally well suited to stabilize Au(I) and Au(III) complexes in biological environments. Over the last decade, the development of rationally designed NHCAu(I/III) complexes to specifically target DNA has led to a new “gold rush” in bioinorganic chemistry. This review aims to summarize the latest advances of NHCAu(I/III) complexes that are able to interact with DNA. Furthermore, the latest advancements on acyclic diamino carbene gold complexes with anticancer activity are presented as these typically overlooked NHC alternatives offer great additional design possibilities in the toolbox of carbene-stabilized gold complexes for targeted therapy.

Redox proteome analysis of auranofin exposed ovarian cancer cells (A2780)

The effects of Auranofin (AF) on protein expression and protein oxidation in A2780 cancer cells were investigated through a strategy based on simultaneous expression proteomics and redox proteomics determinations. Bioinformatics analysis of the proteomics data supports the view that the most critical cellular changes elicited by AF treatment consist of thioredoxin reductase inhibition, alteration of the cell redox state, impairment of the mitochondrial functions, metabolic changes associated with conversion to a glycolytic phenotype, induction of ER stress. The occurrence of the above cellular changes was extensively validated by performing direct biochemical assays. Our data are consistent with the concept that AF produces its effects through a multitarget mechanism that mainly affects the redox metabolism and the mitochondrial functions and results into severe ER stress. Results are discussed in the context of the current mechanistic knowledge existing on AF.

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Redox proteomics allows to underline cell adaptation mechanisms in response to Auranofin treatment in ovarian cancer cells.

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BRCA1 is one of the major candidates of the ovarian cancer cell adaptation to Auranofin treatment.

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Auranofin alters the oxidative phosphorylation and mitochondrial protein import machinery.

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TRAP1 C501 modulates Auranofin toxicity.

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Auranofin induces severe stress of the endoplasmic reticulum.

Highly Cytotoxic Osmium(II) Compounds and Their Ruthenium(II) Analogues Targeting Ovarian Carcinoma Cell Lines and Evading Cisplatin Resistance Mechanisms

(1) Background: Ruthenium and osmium complexes attract increasing interest as next generation anticancer drugs. Focusing on structure-activity-relationships of this class of compounds, we report on 17 different ruthenium(II) complexes and four promising osmium(II) analogues with cinnamic acid derivatives as O,S bidentate ligands. The aim of this study was to determine the anticancer activity and the ability to evade platin resistance mechanisms for these compounds. (2) Methods: Structural characterizations and stability determinations have been carried out with standard techniques, including NMR spectroscopy and X-ray crystallography. All complexes and single ligands have been tested for cytotoxic activity on two ovarian cancer cell lines (A2780, SKOV3) and their cisplatin-resistant isogenic cell cultures, a lung carcinoma cell line (A549) as well as selected compounds on three non-cancerous cell cultures in vitro. FACS analyses and histone γH2AX staining were carried out for cell cycle distribution and cell death or DNA damage analyses, respectively. (3) Results: IC50 values show promising results, specifically a high cancer selective cytotoxicity and evasion of resistance mechanisms for Ru(II) and Os(II) compounds. Histone γH2AX foci and FACS experiments validated the high cytotoxicity but revealed diminished DNA damage-inducing activity and an absence of cell cycle disturbance thus pointing to another mode of action. (4) Conclusion: Ru(II) and Os(II) compounds with O,S-bidentate ligands show high cytotoxicity without strong effects on DNA damage and cell cycle, and this seems to be the basis to circumvent resistance mechanisms and for the high cancer cell specificity.

Effect of cysteine thiols on the catalytic and anticancer activity of Ru(II) sulfonyl-ethylenediamine complexes

We have synthesized a series of novel substituted sulfonyl ethylenediamine (en) Ru^II arene complexes 1-8 of [(η⁶-arene)Ru(R¹-SO₂-EnBz)X], where the arene is benzene, HO(CH₂)₂O-phenyl or biphenyl (biph), X = Cl or I, and R¹ is phenyl, 4-Me-phenyl, 4-NO₂-phenyl or dansyl. The 'piano-stool' structure of complex 3, [(η⁶-biph)Ru(4-Me-phenyl-SO₂-EnBz)I], was confirmed by X-ray crystallography. The values of their aqua adducts were determined to be high (9.1 to 9.7). Complexes 1-8 have antiproliferative activity against human A2780 ovarian, and A549 lung cancer cells with IC₅₀ values ranging from 4.1 to >50 μM, although, remarkably, complex 7 [(η⁶-biph)Ru(phenyl-SO₂-EnBz)Cl] was inactive towards A2780 cells, but as potent as the clinical drug cisplatin towards A549 cells. All these complexes also showed catalytic activity in transfer hydrogenation (TH) of NAD⁺ to NADH with sodium formate as hydride donor, with TOFs in the range of 2.5-9.7 h^-1. The complexes reacted rapidly with the thiols glutathione (GSH) and N-acetyl-L-cysteine (NAC), forming dinuclear bridged complexes [(η⁶-biph)₂Ru₂(GS)₃]^2- or [(η⁶-biph)₂Ru₂(NAC-H)₃]^2-, with the liberation of the diamine ligand which was detected by LC-MS. In addition, the switching on of fluorescence for complex 8 in aqueous solution confirmed release of the chelated DsEnBz ligand in reactions with these thiols. Reactions with GSH hampered the catalytic TH of NAD⁺ to NADH due to the decomposition of the complexes. Co-administration to cells of complex 2 [(η⁶-biph)Ru(4-Me-phenyl-SO₂-EnBz)Cl] with L-buthionine sulfoximine (L-BSO), an inhibitor of GSH synthesis, partially restored the anticancer activity towards A2780 ovarian cancer cells. Complex 2 caused a concentration-dependent G1 phase cell cycle arrest, and induced a significant level of reactive oxygen species (ROS) in A2780 human ovarian cancer cells. The amount of induced ROS decreased with increase in GSH concentration, perhaps due to the formation of the dinuclear Ru-SG complex.

Self-Assembling Metallocomplexes of the Amphiphilic 1,4-Diazabicyclo[2.2.2]octane Derivative as a Platform for the Development of Nonplatinum Anticancer Drugs

New 1-cetyl-4-aza-1-azoniabicyclo[2.2.2]octane bromide complexes with copper(II) bromide and lanthanum(III) nitrate were characterized using dynamic light scattering and transmission electron microscopy, with self-assembly and the morphological behavior elucidated. For the lanthanum(III) nitrate complex, the 3D crystal structure was characterized using X-ray diffractometry. These metallosurfactants were tested as antitumor agents, and a high cytotoxic effect comparable with doxorubicin was revealed against the M-HeLa and A-549 cell lines. Both complexes were 2 times more active toward the MCF-7 cell line than the breast cancer drug tamoxifen. The cytotoxic mechanism of complexes is assumed to be related to the induction of apoptosis through the mitochondrial pathway.

Electron Delocalization in Spectroelectrochemically and Computationally Characterized [Pt{(p-BrC6F4)NCH═C(Cl)NEt2}Cl(py)]+ Formed by Electrochemical Oxidation of [PtII{(p-BrC6F4)NCH═C(Cl)NEt2}Cl(py)]

[Pt{(p-BrC₆F₄)NCH═C(Cl)NEt₂}Cl(py)] (1Cl) is the product of the hydrogen peroxide oxidation of the Pt^II anticancer agent [Pt{(p-BrC₆F₄)NCH₂CH₂NEt₂}Cl(py)] (1). Insights into electron delocalization and bonding in [Pt{(p-BrC₆F₄)NCH═C(Cl)NEt₂}Cl(py)]⁺ (1Cl⁺) obtained by electrochemical oxidation of 1Cl have been gained by spectroscopic and computational studies. The 1Cl/1Cl⁺ process is chemically and electrochemically reversible on the short time scale of voltammetry in dichloromethane (0.10 M [Bu₄N][PF₆]). Substantial stability is retained on longer time scales enabling a high yield of 1Cl⁺ to be generated by bulk electrolysis. In situ IR and visible spectroelectrochemical studies on the oxidation of 1Cl to 1Cl⁺ and the reduction of 1Cl⁺ back to 1Cl confirm the long-term chemical reversibility. DFT calculations indicate only a minor contribution to the electron density (13%) resides on the Pt metal center in 1Cl⁺, indicating that the 1Cl/1Cl⁺ oxidation process is extensively ligand-based. Published X-ray crystallographic data show that 1Cl is present in only one structural form, while NMR data on the dissolved crystals revealed the presence of two closely related structural forms in an almost equimolar ratio. Solution-phase EPR spectra of 1Cl⁺ are consistent with two closely related structural forms in a ratio of about 90:10. The average g value for the frozen solution spectra (2.0567 for the major species) is significantly greater than the 2.0023 expected for a free radical. Crystal field analysis of the EPR spectra leads to an estimate of the 5d(xz) character of around 10% in 1Cl⁺. Analysis of X-ray absorption fine structure derived from 1Cl⁺ also supports the presence of a delocalized singly occupied metal molecular orbital with a spin density of approximately 17% on Pt. Accordingly, the considerably larger electron density distribution on the ligand framework (diminished Pt^III character) is proposed to contribute to the increased stability of 1Cl⁺ compared to that of 1⁺.

In Vitro Anticancer Activity of Novel Co(II) and Ni(II) Complexes of Non-steroidal Anti-inflammatory Drug Niflumic Acid Against Human Breast Adenocarcinoma MCF-7 Cells

Herein, we report the synthesis, characterization and anticancer activity of six novel complexes of non-steroidal anti-inflammatory drug niflumic acid with Co(II) and Ni(II). In vitro cytotoxicity screening in MCF-7, HepG2 and HT-29 cancer cell lines showed that the complex 3 [Co(nif)2(met)(4-pic)] and complex 6 [Ni(nif)2(met)(4-pic)] among all the complexes exhibited the highest cytotoxicity against MCF-7 cells with IC50 values of 11.14 µM and, 41.47 µM, respectively. Besides, all the complexes exhibited significantly higher selectivity towards mouse fibroblast 3T3L1 cells. Further mechanistic studies with both complexes on MCF-7 cells revealed their cytotoxic action through the mitochondrial-dependent apoptotic pathway causing an increase oxidative/nitrosative stress, decrease in mitochondrial membrane potential (ΔΨm), inducing the multicaspase activation and arresting the cell cycle at S phase. q-PCR analysis resulted in an increase in the expression of the apoptotic marker proteins bax, p53 and caspase-3 and -8 in MCF-7 cells, but a decrease in the expression of antiapoptotic bcl-2 gene. Moreover, both complexes induced the apoptosis through the inhibition of PI3K/Akt signaling pathway by decreasing the expression of PI3K and increasing dephosphorylation form of Akt protein. These results provide a significant contribution to the explanation of the anticancer mechanisms of these complexes in MCF-7 cells.

Biological protein mediated ferroptotic tumor nanotherapeutics

Ferroptosis, a cell death pathway involving iron-related generation of lipid hydroperoxides for achieving incredible tumor suppression, has reignited the hope of chemotherapy in tumor treatment in the past decade. With extensive research studies, various bioactive proteins and cellular pathways have been demonstrated to regulate the occurrence and development of ferroptosis. The gradually established ferroptotic regulatory network is conducive to find effective proteins from a holistic perspective and guides better designs for future ferroptotic tumor therapies. The first section of this review summarizes the recent advances in ferroptotic regulatory mechanisms of proteins and attempts to clarify their latent function in the ferroptotic regulatory network. Second, the existing protein-mediated ferroptotic tumor nanotherapeutic strategies were reviewed, including the protein-mediated iron supplement, cell membrane transporter inhibition, glutathione peroxidase 4 interference, glutathione depletion, bioenzyme-mediated reactive oxygen species generation, heat shock protein inhibition, and tumor-overexpressed protein-triggered drug release for ferroptotic therapy. Finally, the future expectations and challenges of ferroptotic tumor nanotherapeutics for clinical cancer therapy are highlighted.

Exploring the Noncovalent Interactions of the Dinuclear Cu(II) Schiff Base Complex with Bovine Serum Albumin and Cell Viability against the SiHa Cancer Cell Line

In the present study, a dinuclear bis(μ-acetate) dicopper(II) complex [Cu₂L₂(μ_1.1-CH₃COO^-)₂] has been synthesized from a tridentate NNO Schiff Base ligand L (L = 2,4-dibromo-6-((3-(methylamino)propylimino)methyl)phenol) and characterized by elemental, ultraviolet-visible (UV-vis), Fourier transform infrared (FTIR), ¹H NMR, and electrospray ionization-mass spectrometry (ESI-MS) spectroscopic studies. The single-crystal X-ray structure, different noncovalent interactions, Hirshfeld surface analysis, and density functional theory (DFT) studies of the dinuclear complex were determined by crystallographic computational studies. The structural study exposed that the complex consists of the penta-coordinated double μ_1.1-acetato-bridged dinuclear units of Cu(II), and it is a centrosymmetric dimer in which the center of inversion lies at the midpoint of two Cu(II) ions. Hirshfeld surface and DFT studies pointed out the probable potentiality of the crystal in prospective binding with the protein. This was experimentally verified by carrying out the binding interaction studies against bovine serum albumin (BSA) protein using various spectroscopic methods. It was observed that the copper(II) complex could strongly bind to BSA and could quench the intrinsic fluorescence of BSA. Further, the studied complex was appraised for cell viability studies against SiHa cancer cells. It is observed that cell viability increases with time, demonstrating the biocompatible nature of the complex.