Click ferrocenyl-erlotinib conjugates active against erlotinib-resistant non-small cell lung cancer cells in vitro

Thanks to development of erlotinib and other target therapy drugs the lung cancer treatment have improved a lot in recent years. However, erlotinib-resistant lung cancer remains an unsolved clinical problem which demands for new therapeutics to be developed. Herein we report the synthesis of a library of 1,4- and 1,5-triazole ferrocenyl derivatives of erlotinib together with their anticancer activity studies against erlotinib-sensitive A549 and H1395 as well as erlotinib-resistant H1650 and H1975 cells. Studies showed that extend of anticancer activity is mainly related to the length of the spacer between the triazole and the ferrocenyl entity. Among the series of investigated compounds two isomers commonly bearing C(O)CH₂CH₂ spacer have shown superior to erlotinib activity against erlotinib-resistant H1650 and H1975 cells whereas compound with short methylene spacer devoid of any activity. In-depth biological studies for the most active compound showed differences in its mechanism of action in compare to erlotinib. The latter is known EGFR inhibitor whereas their ferrocenyl congener exerts anticancer activity mainly as ROS-inducer which activates mitochondrial pathway of apoptosis in cancer cells. However, docking studies suggested that the most active compound can also binds to the active site of EGFR TK in a similar way as erlotinib.

The chemistry of ferrocenesulfonyl fluoride revealed

The first general route toward polysubstituted ferrocenesulfonyl fluorides is described. Merging deprotometallations, 'halogen dance' reaction, Sonogashira, Suzuki-Miyaura and Negishi cross-couplings with SuFEx chemistry allowed original ferrocenes of an unprecedented diversity to be obtained.

Impact of the ferrocenyl group on cytotoxicity and KSP inhibitory activity of ferrocenyl monastrol conjugates

The incorporation of the ferrocenyl moiety into a bioactive molecule may significantly alter the activity of the resulting conjugate. By applying this strategy, we designed ferrocenyl analogs of monastrol - the first low molecular weight kinesin spindle protein (KSP) inhibitor. The obtained compounds showed low micromolar antiproliferative activity towards a panel of sensitive and ABC-overexpressing cancer cells. Most cytotoxic compounds exhibited also higher KSP modulatory activity and ability for ROS generation compared to monastrol. The increased bioactivity of the studied compounds can be attributed to the presence of the ferrocenyl group.

Group VIII Metal Carbonyl Cluster-Boronic Acid Conjugates: Cytotoxicity and Mode of Action Studies

A set of metal carbonyl cluster-boronic acid conjugates of the group VIII metals (Fe, Ru, and Os) were synthesized and their antiproliferative effects measured against two breast cancer cell lines (MCF-7 and MDA-MB-231) and a noncancerous breast epithelial (MCF-10A) cell line. The cytotoxicity followed the order Ru > Os > Fe for the MDA-MB-231 cells, although the latter two exhibited similar cytotoxicity against MCF-7 and MCF-10A cells. The osmium species {Os₃(CO)₁₀(μ-H)[μ-SC₆H₄-p-B(OH)₂]} (2) could be chemically oxidized to its hydroxy analogue [Os₃(CO)₁₀(μ-H)(μ-SC₆H₄ -p-OH)] (2-OH), which showed comparable cytotoxicity. Mode of action studies pointed to an apoptotic pathway for cell death.

NMR studies of group 8 metallodrugs: 187Os-enriched organo-osmium half-sandwich anticancer complex

We report the synthesis of the organo-osmium anticancer complex [Os(η⁶-p-cym)(N,N-azpy-NMe₂)Br]PF₆ (1) containing natural abundance ¹⁸⁷Os (1.96%), and isotopically-enriched (98%) [¹⁸⁷Os]-1. Complex 1 and [¹⁸⁷Os]-1 contain a π-bonded para-cymene (p-cym), a chelated 4-(2-pyridylazo)-N,N-dimethylaniline (azpy-NMe₂), and a monodentate bromide as ligands. The X-ray crystal structure of 1 confirmed its half-sandwich 'piano-stool' configuration. Complex 1 is a member of a family of potent anticancer complexes, and exhibits sub-micromolar activity against A2780 human ovarian cancer cells (IC₅₀ = 0.40 μM). Complex [¹⁸⁷Os]-1 was analysed by high-resolution ESI-MS, 1D ¹H and ¹³C NMR, and 2D ¹H COSY, ¹³C-¹H HMQC, and ¹H-¹⁸⁷Os HMBC NMR spectroscopy. Couplings of ¹H and ¹³C nuclei from the azpy/p-cym ligands to ¹⁸⁷Os were observed with J-couplings (¹J to ⁴J) ranging between 0.6-8.0 Hz. The ¹⁸⁷Os chemical shift of [¹⁸⁷Os]-1 (-4671.3 ppm, determined by 2D ¹H-¹⁸⁷Os HMBC NMR) is discussed in relation to the range of values reported for related Os(II) arene and cyclopentadienyl complexes (-2000 to -5200 ppm).

Heterogeneity of Response to Iron-Based Metallodrugs in Glioblastoma Is Associated with Differences in Chemical Structures and Driven by FAS Expression Dynamics and Transcriptomic Subtypes

Glioblastoma (GBM) is the most frequent and deadliest primary brain cancer in adults, justifying the search for new treatments. Some members of the iron-based ferrocifen family have demonstrated a high cytotoxic effect on various cancer cell lines via innovative mechanisms of action. Here, we evaluated the antiproliferative activity by wst-1 assay of six ferrocifens in 15 molecularly diverse GBM patient-derived cell lines (PDCLs). In five out of six compounds, the half maximal inhibitory concentration (IC₅₀) values varied significantly (10 nM < IC₅₀ < 29.8 µM) while the remaining one (the tamoxifen-like complex) was highly cytotoxic against all PDCLs (mean IC₅₀ = 1.28 µM). The pattern of response was comparable for the four ferrocifens bearing at least one phenol group and differed widely from those of the tamoxifen-like complex and the complex with no phenol group. An RNA sequencing differential analysis showed that response to the diphenol ferrocifen relied on the activation of the Death Receptor signaling pathway and the modulation of FAS expression. Response to this complex was greater in PDCLs from the Mesenchymal or Proneural transcriptomic subtypes compared to the ones from the Classical subtype. These results provide new information on the mechanisms of action of ferrocifens and highlight a broader diversity of behavior than previously suspected among members of this family. They also support the case for a molecular-based personalized approach to future use of ferrocifens in the treatment of GBM.

Co(II) complexes of curcumin and a ferrocene-based curcuminoid: a study on photo-induced antitumor activity

Co(II) complexes having a ferrocene-based curcuminoid (Fc-curH) ligand viz. [Co(L)₂(Fc-cur)]ClO₄ (1, 2), where L is phenanthroline base, namely, 1,10-phenanthroline (phen in 1) and dipyrido[3,2-a:2',3'-c]phenazine (dppz in 2) have been synthesized, characterized and evaluated as photochemotherapeutic agents in vitro. The corresponding Co(II) complexes of the naturally occurring polyphenol curcumin (curH), namely, [Co(L)₂(cur)]ClO₄ (3, 4), where L is phen (in 3) and dppz (in 4) were synthesized and their photo-induced anticancer activities compared with their ferrocene containing counterparts 1 and 2. The Co(II) acetylacetonato complex viz. [Co(phen)₂(acac)]ClO₄ (5) was structurally characterized through X-ray crystallography and used as control for cellular experiments. The Co(II) complexes having ferrocene-based curcuminoid are remarkably stable at physiological condition with higher lipophilicity compared to their curcumin analogues. The complexes display significant binding propensity to calf thymus (ct) DNA and human serum albumin (HSA). The complexes 1-4 display remarkable visible light induced cytotoxicity with the ferrocenyl analogues showing more phototoxic index (PI). The Co(II) curcumin complexes localize in the nucleus and mitochondria of A549 cells. The primary cell death mechanism is believed to be apoptotic in nature induced by light assisted generation of reactive oxygen species (ROS).Graphic abstract.

Transition metal-catalyzed synthesis of new 3-substituted coumarin derivatives as antibacterial and cytostatic agents

Aim: The aim of this study was to synthesize new coumarin-based compounds and evaluate their antibacterial and antitumor potential. Results: Using transition metal-catalyzed reactions, a series of 7-hydroxycoumarin derivatives were synthesized with aliphatic and aryl moiety attached directly at C-3 of the coumarin ring and through the ethynyl or 1,2,3-triazole linker. The 3-substituted coumarin derivative bearing bistrifluoromethylphenyl at the C-4 position of 1,2,3-triazole (33) showed strong and selective antiproliferative activity against cervical carcinoma cells. The 7-hydroxy-4-methylcoumarin with a phenyl ring directly attached to coumarin at C-3 (10) showed good potency against the methicillin-resistant Staphylococcus aureus and vancomycin-resistant strains. Conclusion: The most active coumarin derivatives owe their antiproliferative potential to the 3,5-ditrifluoromethylphenyl substituent (in 33) and antibacterial activity to the aromatic moiety (in 10); their structure can be optimized further for improved effect.

N-Heterocyclic Carbene Iron Complexes as Anticancer Agents: In Vitro and In Vivo Biological Studies

Cisplatin and its derivatives are commonly used in chemotherapeutic treatments of cancer, even though they suffer from many toxic side effects. The problems that emerge from the use of these metal compounds led to the search for new complexes capable to overcome the toxic side effects. Here, we report the evaluation of the antiproliferative activity of Fe(II) cyclopentadienyl complexes bearing n-heterocyclic carbene ligands in tumour cells and their in vivo toxicological profile. The in vitro antiproliferative assays demonstrated that complex Fe1 displays the highest cytotoxic activity both in human colorectal carcinoma cells (HCT116) and ovarian carcinoma cells (A2780) with IC₅₀ values in the low micromolar range. The antiproliferative effect of Fe1 was even higher than cisplatin. Interestingly, Fe1 showed low in vivo toxicity, and in vivo analyses of Fe1 and Fe2 compounds using colorectal HCT116 zebrafish xenograft showed that both reduce the proliferation of human HCT116 colorectal cancer cells in vivo.

Synthesis of Platinum(II) N-Heterocyclic Carbenes Based on Adenosine

Organometallic derivatization of nucleosides is a highly promising strategy for the improvement of the therapeutic profile of nucleosides. Herein, a methodology for the synthesis of metalated adenosine with a deprotected ribose moiety is described. Platinum(II) N-heterocyclic carbene complexes based on adenosine were synthesized, namely N-heterocyclic carbenes bearing a protected and unprotected ribose ring. Reaction of the 8-bromo-2′,3′,5′-tri-O-acetyladenosine with Pt(PPh₃)₄ by C8−Br oxidative addition yielded complex 1, with a Pt^II centre bonded to C-8 and an unprotonated N7. Complex 1 reacted at N7 with HBF₄ or methyl iodide, yielding protic carbene 2 or methyl carbene 3, respectively. Deprotection of 1 to yield 4 was achieved with NH₄OH. Deprotected compound 4 reacted at N7 with HCl solutions to yield protic NHC 5 or with methyl iodide yielding methyl carbene 6. Protic N-heterocyclic carbene 5 is not stable in DMSO solutions leading to the formation of compound 7, in which a bromide was replaced by chloride. The cis-influence of complexes 1–7 was examined by ³¹P{¹H} and ¹⁹⁵Pt NMR. Complexes 2, 3, 5, 6 and 7 induce a decrease of ¹J_Pt,P of more than 300 Hz, as result of the higher cis-influence of the N-heterocyclic carbene when compared to the azolato ligand in 1 and 4.

A Strategy to Conjugate Bioactive Fragments to Cytotoxic Diiron Bis(cyclopentadienyl) Complexes

A series of bioactive molecules were synthesized from the condensation of aspirin or chlorambucil with terminal alkynes bearing alcohol or amine substituents. Insertion of the resulting alkynes into the iron–carbyne bond of readily accessible diiron bis(cyclopentadienyl) μ-aminocarbyne complexes, [1a,b]CF₃SO₃, afforded novel diiron complexes with a bridging vinyliminium ligand, [2–10]CF₃SO₃, functionalized with a bioactive moiety. All compounds were characterized by elemental analysis and IR and multinuclear NMR spectroscopy and in three cases by single-crystal X-ray diffraction. Moreover, the D₂O solubility, stability in D₂O and cell culture media, and octanol–water partition coefficients of diiron complexes were determined spectroscopically. The cytotoxicity of the complexes was assessed in the tumorigenic A2780 and A2780cisR and the nontumorigenic HEK 293T cell lines. Some complexes exhibit high potency and the ability to overcome resistance in A2780cisR cells (aspirin complexes) or high selectivity relative to HEK 293T cells (chlorambucil complexes). Further studies indicate that the complexes significantly trigger intracellular ROS production, irrespective of the nature of the bioactive fragment. DNA alkylation and protein binding studies were also undertaken.

In vivo active organometallic-containing antimycotic agents

Fungal infections represent a global problem, notably for immunocompromised patients in hospital, COVID-19 patient wards and care home settings, and the ever-increasing emergence of multidrug resistant fungal strains is a sword of Damocles hanging over many healthcare systems. Azoles represent the mainstay of antifungal drugs, and their mode of action involves the binding mode of these molecules to the fungal lanosterol 14α-demethylase target enzyme. In this study, we have prepared and characterized four novel organometallic derivatives of the frontline antifungal drug fluconazole (1a-4a). Very importantly, enzyme inhibition and chemogenomic profiling demonstrated that lanosterol 14α-demethylase, as for fluconazole, was the main target of the most active compound of the series, (N-(ferrocenylmethyl)-2-(2,4-difluorophenyl)-2-hydroxy-N-methyl-3-(1H-1,2,4-triazol-1-yl)propan-1-aminium chloride, 2a). Transmission electron microscopy (TEM) studies suggested that 2a induced a loss in cell wall integrity as well as intracellular features ascribable to late apoptosis or necrosis. The impressive activity of 2a was further confirmed on clinical isolates, where antimycotic potency up to 400 times higher than fluconazole was observed. Also, 2a showed activity towards azole-resistant strains. This finding is very interesting since the primary target of 2a is the same as that of fluconazole, emphasizing the role played by the organometallic moiety. In vivo experiments in a mice model of Candida infections revealed that 2a reduced the fungal growth and dissemination but also ameliorated immunopathology, a finding suggesting that 2a is active in vivo with added activity on the host innate immune response.

Redox-dependent cytotoxicity of ferrocene derivatives and ROS-activated prodrugs based on ferrocenyliminoboronates

Four ferrocene derivatives - ferrocenecarboxylic acid, ferrocenium salt, ferroceneboronic acid, and aminoferrocene - were characterized electrochemically, and their cytotoxicity was probed using cancer cells (line MG-63). We related the observed cytotoxicity with the determined redox potentials of these four ferrocenes - aminoferrocene with its lowest redox potential exhibited the highest cytotoxicity. Thus, we synthesized four derivatives consisting of aminoferrocene and phenylboronic acid residue with the intent to employ them as ROS-activated prodrugs (ROS - reactive oxygen species). We characterized them and studied their time-dependent stability in aqueous environments. Then, we performed electrochemical measurements at oxidative conditions to confirm ROS-responsivity of the synthesized molecules. Finally, the cytotoxicity of the synthesized molecules was tested using cancer MG-63 cells and noncancerous NIH-3T3 cells. The experiments revealed sought behaviour, especially for para-regioisomers of synthesized ferrocenyliminoboronates.

Recent developments of metal-based compounds against fungal pathogens

This review provides insight into the rapidly expanding field of metal-based antifungal agents. In recent decades, the antibacterial resistance crisis has caused reflection on many aspects of public health where weaknesses in our medicinal arsenal may potentially be present - including in the treatment of fungal infections, particularly in the immunocompromised and those with underlying health conditions where mortality rates can exceed 50%. Combination of organic moieties with known antifungal properties and metal ions can lead to increased bioavailability, uptake and efficacy. Development of such organometallic drugs may alleviate pressure on existing antifungal medications. Prodigious antimicrobial moieties such as azoles, Schiff bases, thiosemicarbazones and others reported herein lend themselves easily to the coordination of a host of metal ions, which can vastly improve the biocidal activity of the parent ligand, thereby extending the library of antifungal drugs available to medical professionals for treatment of an increasing incidence of fungal infections. Overall, this review shows the impressive but somewhat unexploited potential of metal-based compounds to treat fungal infections.

Anticancer Diiron Vinyliminium Complexes: A Structure-Activity Relationship Study

A series of 16 novel diiron complexes of general formula [Fe2Cp2(CO)(μ-CO){μ-η1:η3-C(R')C(R″)CN(R)(Y)}]CF3SO3 (2-7), bearing different substituents on the bridging vinyliminium ligand, was synthesized in 69-95% yields from the reactions of diiron μ-aminocarbyne precursors with various alkynes. The products were characterized by elemental analysis, IR, 1H and 13C NMR spectroscopy; moreover the X-ray structures of 2c (R = Y = CH2Ph, R' = R″ = Me) and 3a (R = CH2CH=CH2, Y = R' = Me, R″ = H) were ascertained by single-crystal X-ray diffraction studies. NMR and UV-Vis methods were used to assess the D2O solubility, the stability in aqueous solution at 37 °C and the octanol-water partition coefficients of the complexes. A screening study evidenced a potent cytotoxicity of 2-7 against the A2780 cancer cell line, with a remarkable selectivity compared to the nontumoral Balb/3T3 cell line; complex 4c (R = Cy, Y = R' = R″ = Me) revealed as the most performant of the series. The antiproliferative activity of a selection of complexes was also assessed on the cisplatin-resistant A2780cisR cancer cell line, and these complexes were capable of inducing a significant ROS production. Moreover, ESI-MS experiments indicated the absence of interaction of selected complexes with cytochrome c and the potentiality to inhibit the thioredoxin reductase enzyme (TrxR).

Highly Stable Silica-Coated Bismuth Nanoparticles Deliver Tumor Microenvironment-Responsive Prodrugs to Enhance Tumor-Specific Photoradiotherapy

Radiosensitizers are agents capable of amplifying injury to tumor tissues by enhancing DNA damage and fortifying production of radical oxygen species (ROS). The use of such radiosensitizers in the clinic, however, remains limited by an insufficient ability to differentiate between cancer and normal cells and by the presence of a reversible glutathione system that can diminish the amount of ROS generated. Here, to address these limitations, we design an H₂O₂-responsive prodrug which can be premixed with lauric acid (melting point ∼43 °C) and loaded around the surface of silica-coated bismuth nanoparticles (BSNPs) for cancer-specific photoradiotherapy. Particularly, silica coating confers BSNPs with improved chemical stability against both near-infrared light and X-rays. Upon photothermal heating, lauric acid is melted to trigger prodrug release, followed by its transformation into p-quinone methide via H₂O₂ stimulation to irreversibly alkylate glutathione. Concurrently, this heat boosts tumor oxygenation and helps relieve the hypoxic microenvironment. Following sequential irradiation by X-rays, BSNPs generate plentiful ROS, which act in combination with these events to synergistically induce cell death via DNA breakage and mitochondria-mediated apoptosis pathways, ultimately enabling effective inhibition of tumor growth in vivo with high tumor specificity and reduced side effects. Collectively, this work presents a promising approach for the improvement of other ROS-responsive proalkylating agents, while simultaneously highlighting a robust nanosystem for combining these prodrugs with photoradiosensitizers to realize precision photoradiotherapy.

Design of ferrocenylseleno-dopamine derivatives to optimize the Fenton-like reaction efficiency and antitumor efficacy

In the current study, six ferrocenylseleno-dopamine derivatives with different structural parameters were designed. Among these derivatives, F4b, containing two ferrocene units and a tertiary amine, showed in vitro anticancer activity with IC50 = 2.4 ± 0.4 μM for MGC-803 cells, and its in vivo studies suggested effective antitumor activity in mice bearing an MGC-803 tumor xenograft. Mechanistic study revealed that the cytotoxicity of these ferrocenylseleno-dopamine derivatives is mainly related to the Fenton-like reaction under physiological conditions, and the tertiary amine in F4b can facilitate the H2O2 decomposition to generate toxic ˙OH which induces apoptosis through CDK-2 inactivation.

Rational approaches towards inorganic and organometallic antibacterials

The occurrence of drug-resistant bacteria is drastically rising and new and effective antibiotic classes are urgently needed. However, most of the compounds in development are minor modifications of previously used drugs to which bacteria can easily develop resistance. The investigation of inorganic and organometallic compounds as antibiotics is an alternative approach that holds great promises due to the ability of such molecules to trigger metal-specific mechanisms of action, which results in lethal consequences for pathogens. In this review, a selection of concepts to rationally design inorganic and organometallic antibiotics is discussed, highlighting their advantages by comparing them to classical drug discovery programmes. The review concludes with a short perspective for the future of antibiotic drug development and the role metal-based compounds will play in the field.

Easily Available, Amphiphilic Diiron Cyclopentadienyl Complexes Exhibit in Vitro Anticancer Activity in 2D and 3D Human Cancer Cells through Redox Modulation Triggered by CO Release

A straightforward two-step procedure via single CO removal allows the conversion of commercial [Fe2 Cp2 (CO)4 ] into a range of amphiphilic and robust ionic complexes based on a hybrid aminocarbyne/iminium ligand, [Fe2 Cp2 (CO)3 {CN(R)(R')}]X (R, R'=alkyl or aryl; X=CF3 SO3 or BF4 ), on up to multigram scales. Their physicochemical properties can be modulated by an appropriate choice of N-substituents and counteranion. Tested against a panel of human cancer cell lines, the complexes were shown to possess promising antiproliferative activity and to circumvent multidrug resistance. Interestingly, most derivatives also retained a significant cytotoxic activity against human cancer 3D cell cultures. Among them, the complex with R=4-C6 H4 OMe and R'=Me emerged as the best performer of the series, being on average about six times more active against cancer cells than a noncancerous cell line, and displayed IC50 values comparable to those of cisplatin in 3D cell cultures. Mechanistic studies revealed the ability of the complexes to release carbon monoxide and to act as oxidative stress inducers in cancer cells.

Metal Complexes for Therapeutic Applications

Metal complexes have been widely used for applications in the chemical and physical sciences due to their unique electronic and stereochemical properties. For decades the use of metal complexes for medicinal applications has been postulated and demonstrated. The distinct characteristics of metal complexes, including their molecular geometries (that are not readily accessed by organic molecules), as well as their ligand exchange, redox, catalytic, and photophysical reactions, give these compounds the potential to interact and react with biomolecules in unique ways and by distinct mechanisms of action. Herein, the potential of metal complexes to act as components bioactive therapeutic compounds is discussed.

A Ferrocene Derivative Reduces Cisplatin Resistance in Breast Cancer Cells through Suppression of MDR-1 Expression and Modulation of JAK2/STAT3 Signaling Pathway

BACKGROUND

Breast cancer is the most common kind of cancer among women in the world. Despite major cancer therapy successes in recent years, cancer cells usually develop mechanisms to survive chemotherapy- induced cell death. Therefore, new strategies are needed to reverse cancer chemoresistance.

OBJECTIVE

The aim of this study was to investigate the effect of a recently-synthesized ferrocene derivative named 1-ferrocenyl-3-(4-methylsulfonylphenyl)propen-1-one (FMSP) on cisplatin resistance in MCF-7 cells, focusing on its inhibitory effects on Multi-Drug Resistance-1 (MDR-1) and inflammatory-related STAT3 pathway.

METHODS

Cisplatin-resistant MCF-7 cells were developed and the effect of cisplatin and FMSP on cell viability was examined by MTT assay. RT-PCR and Western blotting analyses were performed to assess the gene and protein expression of MDR-1 as well as phosphorylation of JAK2 and STAT3.

RESULTS

Overexpression of MDR1 as well as a marked increase in the level of phosphorylated STAT3 was observed in cisplatin-resistant MCF-7 (MCF-7R) cells. FMSP successfully reduced the MCF-7R cell viability and reversed both MDR1 expression and STAT3 phosphorylation status through which sensitivity of MCF-7R cells to cisplatin treatment was regained.

CONCLUSION

Our results indicated that FMSP may be considered as a promising therapeutic agent for the prevention and management of chemoresistance in breast cancer cells.

Photodynamic activity and photoantimicrobial chemotherapy studies of ferrocene-substituted 2-thiobarbituric acid

A ferrocene-substituted thiobarbituric acid (FT) has been synthesized to explore its photophysical properties and photodynamic and photoantimicrobial chemotherapy activities. FT has an intense metal-to-ligand charge transfer (MLCT) band at ca. 575 nm. The ferrocene moiety of FT undergoes photooxidation to form a ferrocenium species which in turn produces hydroxyl radical in an aqueous environment, which was confirmed via the bleaching reaction of p-nitrosodimethylaniline (RNO). FT exhibits efficient PDT activity against MCF-7 cancer cells with an IC₅₀ value of 5.6 μM upon irradiation with 595 nm for 30 min with a Thorlabs M595L3 LED (240 mW cm^-2). Photodynamic inactivation of Staphylococcus aureus and Escherichia coli by FT shows significant activity with log reduction values of 6.62 and 6.16 respectively, under illumination for 60 min at 595 nm. These results demonstrate that ferrocene-substituted thiobarbituric acids merit further study for developing novel bioorganometallic PDT agents.

Ferrocifen Loaded Lipid Nanocapsules: A Promising Anticancer Medication against Multidrug Resistant Tumors

Resistance of cancer cells to current chemotherapeutic drugs has obliged the scientific community to seek innovative compounds. Ferrocifens, lipophilic organometallic compounds composed of a tamoxifen scaffold covalently bound to a ferrocene moiety, have shown very interesting antiproliferative, cytotoxic and immunologic effects. The formation of ferrocenyl quinone methide plays a crucial role in the multifaceted activity of ferrocifens. Lipid nanocapsules (LNCs), meanwhile, are nanoparticles obtained by a free organic solvent process. LNCs consist of an oily core surrounded by amphiphilic surfactants and are perfectly adapted to encapsulate these hydrophobic compounds. The different in vitro and in vivo experiments performed with this ferrocifen-loaded nanocarrier have revealed promising results in several multidrug-resistant cancer cell lines such as glioblastoma, breast cancer and metastatic melanoma, alone or in combination with other therapies. This review provides an exhaustive summary of the use of ferrocifen-loaded LNCs as a promising nanomedicine, outlining the ferrocifen mechanisms of action on cancer cells, the nanocarrier formulation process and the in vivo results obtained over the last two decades.

Synthesis and Biological Activity of Ferrocenyl and Ruthenocenyl Analogues of Etoposide: Discovery of a Novel Dual Inhibitor of Topoisomerase II Activity and Tubulin Polymerization

Two series of the ferrocenyl and ruthenocenyl analogues of etoposide bearing 1,2,3-triazolyl or aminoalkyl linker were synthesized and evaluated for their cytotoxic properties, influence on the cell cycle, ability to induce tubulin polymerization, and inhibition of topoisomerase II activity. We found that the replacement of the etoposide carbohydrate moiety with a metallocenyl group led to organometallic conjugates exhibiting differentiated antiproliferative activity. Biological studies demonstrated that two ferrocenylalkylamino conjugates were notably more active than etoposide, with submicromolar or low-micromolar IC₅₀ values towards SW620, etoposide-resistant SW620E, and methotrexate-resistant SW620M cancer cell lines. Moreover, the simplest ferrocenylmethylamino conjugate exerted dual inhibitory action against tubulin polymerization and topoisomerase II activity while other studied compounds affected only topoisomerase II activity.

Brief survey on organometalated antibacterial drugs and metal-based materials with antibacterial activity

Rising bacterial antibiotic resistance is a global threat. To deal with it, new antibacterial agents and antiseptic materials need to be developed. One alternative in this quest is the organometallic derivatization of well-established antibacterial drugs and also the fabrication of advanced metal-based materials having antibacterial properties. Metal-based agents and materials often show new modes of antimicrobial action which enable them to overcome drug resistance in pathogenic bacterial strains. This review summarizes recent (2017-2020) progress in the field of organometallic-derived antibacterial drugs and metal-based materials having antibacterial activity. Specifically, it covers organometallic derivatives of antibacterial drugs including β-lactams, ciprofloxacin, isoniazid, trimethoprim, sulfadoxine, sulfamethoxazole, and ethambutol as well as non-antibacterial drugs like metformin, phenformin and aspirin. Recent advances and reported clinical trials in the use of metal-based nanomaterials as antibiofouling coatings on medical devices, as photocatalytic agents in indoor air pollutant control, and also as photodynamic/photothermal antimicrobial agents are also summarized.

Replacing the Z-phenyl Ring in Tamoxifen® with a para-Connected NCN Pincer-Pt-Cl Grouping by Post-Modification †

Post-modification of a series of NCN-pincer platinum(II) complexes [PtX(NCN-R-4)] (NCN = [C₆H₂(CH₂NMe₂)₂-2,6]^–, R = C(O)H, C(O)Me and C(O)Et), X = Cl^– or Br^–) at the para-position using the McMurry reaction was studied. The synthetic route towards two new [PtCl(NCN-R-4)] (R = C(O)Me and C(O)Et) complexes used above is likewise described. The utility and limitations of the McMurry reaction involving these pincer complexes was systematically evaluated. The predicted “homo-coupling” reaction of [PtBr(NCN-C(O)H-4)] led to the unexpected formation of 3,3′,5,5′-tetra[(dimethylamino)methyl]-4,4′-bis(platinum halide)-benzophenone (halide = Br or Cl), referred to hereafter as the bispincer-benzophenone complex 13. This material was further characterized using X-ray crystal structure determination. The applicability of the pincer complexes in the McMurry reaction is shown to open a route towards the synthesis of tamoxifen-type derivatives of which one phenyl ring of Tamoxifen^® itself is replaced by an NCN arylplatinum pincer fragment. The newly synthesized derivatives can be used as potential candidates in anti-cancer drug screening protocols. Two NCN-arylpincer platinum tamoxifen type derivatives, 5 and 6, were successfully synthesized and of 5 the separation of the diastereomeric E-/Z-forms was achieved. Compound 6, which is the pivaloyl protected NCN pincer platinum hydroxy-Tamoxifen^® derivative, was obtained as a mixture of E-/Z-isomers. The new derivatives were further analyzed and characterized with ¹H-, ¹³C{¹H}- and ¹⁹⁵Pt{¹H}-NMR, IR, exact mass MS and elemental analysis.

The organometallic ferrocene exhibits amplified anti-tumor activity by targeted delivery via highly selective ligands to αvβ3, αvβ6, or α5β1 integrins

High levels of reactive oxygen species (ROS) in tumors have been shown to exert anti-tumor activity, leading to the concept of ROS induction as therapeutic strategy. The organometallic compound ferrocene (Fc) generates ROS through a reversible one-electron oxidation. Incorporation of Fc into a tumor-targeting, bioactive molecule can enhance its therapeutic activity and enable tumor specific delivery. Therefore, we conjugated Fc to five synthetic, Arg-Gly-Asp (RGD)-based integrin binding ligands to enable targeting of the cell adhesion and signaling receptor integrin subtypes αvβ3, α5β1, or αvβ6, which are overexpressed in various, distinct tumors. We designed and synthesized a library of integrin-ligand-ferrocene (ILF) derivatives and showed that ILF conjugates maintained the high integrin affinity and selectivity of their parent ligands. A thorough biological characterization allowed us to identify the two most promising ligands, an αvβ3 (L2b) and an αvβ6 (L3b) targeting ILF, which displayed selective integrin-dependent cell uptake and pronounced ferrocene-mediated anti-tumor effects in vitro, along with increased ROS production and DNA damage. Hence, ILFs are promising candidates for the selective, tumor-targeted delivery of ferrocene to maximize its anti-cancer efficacy and minimize systemic toxicity, thereby improving the therapeutic window of ferrocene compared to currently used non-selective anti-cancer drugs.

Bioactive half-sandwich Rh and Ir bipyridyl complexes containing artemisinin

Reaction of dihydroartemisinin (DHA) with 4-methyl-4'-carboxy-2,2'-bipyridine yielded the new ester derivative L1. Six novel organometallic half-sandwich chlorido Rh(III) and Ir(III) complexes (1-6) containing pentamethylcyclopentadienyl, (Cp*), tetramethylphenylcyclopentadienyl (Cp^xph), or tetramethylbiphenylcyclopentadienyl (Cp^xbiph), and N,N-chelated bipyridyl group of L1, have been synthesized and characterized. The complexes were screened for inhibitory activity against the Plasmodium falciparum 3D7 (sensitive), Dd2 (multi-drug resistant) and NF54 late stage gametocytes (LSGNF54), the parasite strain Trichomonas vaginalis G3, as well as A2780 (human ovarian carcinoma), A549 (human alveolar adenocarcinoma), HCT116 (human colorectal carcinoma), MCF7 (human breast cancer) and PC3 (human prostate cancer) cancer cell lines. They show nanomolar antiplasmodial activity, outperforming chloroquine and artemisinin. Their activities were also comparable to dihydroartemisinin. As anticancer agents, several of the complexes showed high inhibitory effects, with Ir(III) complex 3, containing the tetramethylbiphenylcyclopentadienyl ligand, having similar IC₅₀ values (concentration for 50% of maximum inhibition of cell growth) as the clinical drug cisplatin (1.06-9.23 μM versus 0.24-7.2 μM, respectively). Overall, the iridium complexes (1-3) are more potent compared to the rhodium derivatives (4-6), and complex 3 emerges as the most promising candidate for future studies.

Coumarin-Annulated Ferrocenyl 1,3-Oxazine Derivatives Possessing In Vitro Antimalarial and Antitrypanosomal Potency

A tailored series of coumarin-based ferrocenyl 1,3-oxazine hybrid compounds was synthesized and investigated for potential antiparasitic activity, drawing inspiration from the established biological efficacy of the constituent chemical motifs. The structural identity of the synthesized compounds was confirmed by common spectroscopic techniques: NMR, HRMS and IR. Biological evaluation studies reveal that the compounds exhibit higher in vitro antiparasitic potency against the chemosensitive malarial strain (3D7 P. falciparum) over the investigated trypanosomiasis causal agent (T. b. brucei 427) with mostly single digit micromolar IC50 values. When read in tandem with the biological performance of previously reported structurally similar non-coumarin, phenyl derivatives (i.e., ferrocenyl 1,3-benzoxazines and α-aminocresols), structure-activity relationship analyses suggest that the presence of the coumarin nucleus is tolerated for biological activity though this may lead to reduced efficacy. Preliminary mechanistic studies with the most promising compound (11b) support hemozoin inhibition and DNA interaction as likely mechanistic modalities by which this class of compounds may act to produce plasmocidal and antitrypanosomal effects.

Mass spectrometry techniques for imaging and detection of metallodrugs

Undoubtedly, metallomic approaches based on mass spectrometry have evolved into essential tools supporting the drug development of novel metal-based anticancer drugs. This article will comment on the state-of-the-art instrumentation and highlight some of the recent analytical advances beyond routine, especially focusing on the latest developments in inductively coupled plasma-mass spectrometry (ICP-MS). Mass spectrometry-based bioimaging and single-cell methods will be presented, paving the way to exciting investigations of metal-based anticancer drugs in heterogeneous and structurally, as well as functionally complex solid tumor tissues.