Pancreatic ductal adenocarcinoma (PDAC), the most common pancreatic malignancy, has a dismal 5-year survival rate, making palliative chemotherapy the only treatment option. Targeted therapy has limited efficacy in PDAC, underscoring the need for novel therapeutic approaches. The inducible stress-response protein, haem oxygenase-1 (HMOX1), has been implicated in treatment failure in PDAC. Copper coordination complexes have shown promise as anticancer agents against various cancers, and are associated with apoptotic cell death. The different ligands to which copper is complexed, determine the specificity and efficacy of each complex. Three different classes of copper complexes were evaluated for anti-cancer activity against AsPC-1 and MIA PaCa-2 pancreatic cancer cell lines. A copper-phenanthroline-theophylline complex (CuPhTh), a copper-8-aminoquinoline-naphthyl complex (Cu8AqN), and two copper-aromatic-isoindoline complexes (CuAIsI) were effective inhibitors of cell proliferation with clinically relevant IC values below 5 μM. The copper complexes caused reactive oxygen species (ROS) formation, promoted annexin-V binding, disrupted the mitochondrial membrane potential (MMP) and activated caspase-9 and caspase-3/7, confirming apoptotic cell death. Expression of nuclear HMOX1 was increased in both cell lines, with the CuPhTh complex being the most active. Inhibition of HMOX1 activity significantly decreased the IC values of these copper complexes suggesting that HMOX1 inhibition may alter treatment outcomes in PDAC.

In this study, [Ir(ppy)(DMHBT)](PF) (ppy = deprotonated 1-phenylpyridine, DMHBT = 10,12-dimethylpteridino[6,7-f][1,10]phenanthroline-11,13-(10,12H)-dione, 8a), [Ir(bzq)(DMHBT)](PF) (bzq = deprotonated benzo[h]quinoline, 8b) and [Ir(piq)(DMHBT)](PF) (piq = deprotonated 1-phenylisoquinoline, 8c) were synthesized and characterized by HRMS, C NMR and H NMR. In vitro cytotoxicity experiments showed that 8a, 8b, 8c show moderate cytotoxicity against B16 cells, while the cytotoxicity of the complexes 8a, 8b and 8c toward B16 cells was greatly improved upon light irradiation, which can be used as photosensitizers to exert anticancer efficacy in photodynamic therapy (PDT). After being taken up by cells, 8a, 8b, 8c were localized in the mitochondria, resulting in a large amount of Ca in-flux, a burst release of ROS, a sustained opening of mitochondrial permeability transition pore, and a decrease of the mitochondrial membrane potential, which led to mitochondrial dysfunction and further activation of caspase 3 and Bcl-2 family proteins to induce apoptosis. Overloaded ROS reacted with polyunsaturated fatty acids on the cell membrane, and initiated lipid peroxidation, inhibited the x-system-glutathione (GSH)-glutathione peroxidase 4 (GPX4) antioxidant defense system, and upregulated the expression of the damage-associated molecules, HMGB1, CRT, and HSP70. The presence of Fer-1 was effective on increasing the cell survival, which demonstrates that the complexes possess the potential to induce ferroptosis and immunogenic cell death. In addition, 8a, 8b and 8c induced autophagy by inhibiting the AKT/PI3K/mTOR signaling pathway, downregulating p62 and promoting Beclin-1 expression upon light irradiation.

This study deals with the unprecedented reactivity of a [(cyclam)Mn(OTf)] (3-cis; OTf = CFSO) with O, which, depending on the presence or absence of a hydrogen atom donor like 1-hydroxy-2,2,6,6-tetramethyl-piperidine (TEMPO-H), selectively generates di-μ-oxo Mn(III)Mn(IV) (1) or Mn (2) complexes, respectively. Both dimers have been characterized by different techniques including single-crystal X-ray diffraction, X-ray absorption spectroscopy, and electron paramagnetic resonance. Oxygenation reactions carried out with labeled O and Resonance Raman spectroscopy unambiguously show that the oxygen atoms present in the MnMn dimer originate from O. Experimental evidences are provided for a novel method of dioxygen activation involving three Mn ions or two Mn ions and TEMPO-H to generate the bis(μ-oxo)dimanganese(IV) or bis(μ-oxo) dimanganese(III, IV) cores, respectively.

Schiff bases derived from aminoguanidine are extensively investigated for their structural versatility. The tridentate 2-formylpyridine guanylhydrazones act as analogues of 2-formyl or 2-acetylpyridine thiosemicarbazones, where the thioamide unit is replaced by the guanidyl group. Six derivatives of 2-formylpyridine guanylhydrazone were synthesized and their proton dissociation and complex formation processes with Cu(II), Fe(II) and Fe(III) ions were studied using pH-potentiometry, UV-visible, NMR and electron paramagnetic resonance spectroscopic methods. The ligands have substituents such as amine, morpholine, N-methyl-piperazine at different positions of the pyridine ring. The influence of the different structural elements on the solution chemical properties and cytotoxicity has been disclosed. The solid state structure of four ligands was determined by X-ray crystallography. The ligands bind to Cu(II) in a tridentate fashion via an (N,N,N) donor set, forming mono-ligand complexes. However, for ligands with heterocyclic morpholine and piperazine nitrogen atoms in coordination position a tetradentate binding was observed. Despite the additional coordinating donor atom, the stability of these Cu(II) complexes showed little or no increase. The Cu(II), Fe(II) and Fe(III) complexes of the studied 2-formylpyridine guanylhydrazones exhibited significantly lower stability compared to their corresponding 2-formyl or 2-acetylpyridine thiosemicarbazone analogues. The ligands underwent slow partial hydrolysis (and oxidation) in the presence of Cu(II) ions, leading to the formation of new ligands through the reorganization of structural components around the metal ion. Additionally, the studied Cu(II) complexes demonstrated a great propensity for reduction by glutathione. All these features contributed to the finding that these 2-formylpyridine guanylhydrazones and their Cu(II) complexes did not display measurable cytotoxic activity.

Here, we show that the replacement of the distal residues Asp and/or Arg of the DyP peroxidases from Bacillus subtilis and Pseudomonas putida results in functional enzymes, albeit with spectroscopically perturbed active sites. All the enzymes can be activated either by the addition of exogenous HO or by in situ electrochemical generation of the reactive oxygen species (ROS) OH, O and HO. The latter method leads to broader and upshifted pH-activity profiles. Both WT enzymes exhibit a differential predominance of ROS involved in their electrochemical activation, which follows the order OH > O > HO for BsDyP and O > HO > OH for PpDyP. This ROS selectivity is preserved in mutants with unperturbed sites but is blurred out for distorted sites. The underlying molecular basis of the selectivity mechanisms is analysed through molecular dynamics simulations, which reveal distorted hydrogen bonding networks and higher throughput of the access tunnels in the variants exhibiting no selectivity. The electrochemical activation method provides superior performance for protein variants with a high prevalence of the alternative OH and O species. These results constitute a promising advance towards engineering DyPs for electrocatalytic applications.

Mimosine, a non-essential amino acid derived from plants, has a strong affinity for binding divalent and trivalent metal cations, including Zn, Ni, Fe, and Al. This ability endows mimosine with significant antimicrobial and anti-cancer properties, making it a promising candidate for therapeutic applications. Previous research has demonstrated the effectiveness of mimosine-containing peptides as metal chelators, offering a safer alternative to conventional chelation agents. However, optimizing the design of these peptides necessitates a thorough understanding of their conformational ensembles in both free and metal-bound states. Here, we perform an in-depth analysis of mimosine-containing peptides using long-time MD simulations and quantum calculations to identify key factors critical for peptide design. Our results show that these peptides can achieve metal-binding affinities comparable to established aluminum chelators like deferiprone and citrate. Additionally, we underscore the crucial role of the peptide backbone in reducing the entropic penalty associated with metal binding. We propose strategies to modulate this entropic penalty-a challenging thermodynamic property to evaluate but essential in complexes between short peptides and metals-by incorporating proline residues and optimizing sequence length. These approaches offer promising pathways for developing efficient peptide chelators.

Lysosomal labile Zn levels have been unclear. By targeting a small-molecule fluorescent Zn probe, ZnDA-3H, to lysosomes via VAMP7-Halo, the lysosomal labile Zn concentration was determined to be 1.9 nM in HeLa cells. Furthermore, ZnDA-3H enabled direct visualization of the Zn efflux from the lysosomes to cytosol upon TRPMLs activation.

Three stable oxidovanadium(IV) [VOL] complexes (1-3) were synthesized through the incorporation of unsymmetrical salen ligands (HL). All the ligands are synthesized, and their vanadium compounds were thoroughly characterized by CHNS analysis, various spectroscopy methods (IR, UV-Vis, NMR spectroscopy), and HR-ESI-MS. The structures of 1-3 were validated through the single-crystal X-ray analysis. UV-Vis and HR-ESI-MS were used to determine the solution stability of the complexes in the aqueous phase, revealing their stability in aqueous/biological medium. Various spectroscopy techniques were used to study the DNA/BSA binding abilities, and the results indicate that 1-3 shows effective biomolecular interactions. The partition coefficient result indicates that 1-3 are highly hydrophobic and may easily permeate the cells. Finally, the in vitro anticancer properties of 1-3 were determined with two cancerous (HT-29 and A549), and the NIH-3T3 normal cell lines. Among the series, 3 is the most cytotoxic, with IC values of 6.2 ± 0.2 and 5.3 ± 0.4 μM against HT-29 and A549 cell lines respectively. Moreover, the apoptotic cell death mechanism of 1-3 was assessed through DAPI, AO/EB, and double staining apoptosis experiments.

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

Acacetin (AC) is a natural polyphenol from the group of flavonoids. It is well established that the behavior of flavonoids depends on the presence of redox-active substances; therefore, we aim to investigate their biological activity following the interaction with Cu(II) ion. Our study demonstrates that AC can effectively bind Cu(II) ions, as confirmed by UV-Vis and EPR spectroscopy as well as DFT calculations. AC appears as a potent scavenger against the model ABTS radical cation by itself, but this ability is significantly limited upon Cu(II) coordination. The possible mild synergistic effect of AC in the presence of vitamin C and glutathione was also shown by the ABTS test. In contrast, an inhibitory effect was observed in the presence of Cu(II) ions. The equimolar addition of AC to the model Fenton-like system containing Cu(II) did not have a noticeable effect on the concentration of hydroxyl radicals produced, but in its excess the formation of OH decreased, as proved by EPR spin trapping. Absorption titrations and gel electrophoresis revealed effective binding to calf thymus (CT)-DNA with a stronger interaction for the Cu(II)-AC complex. The detailed mode of binding to biomolecules was described using molecular docking and molecular dynamics. Obtained results indicate that the double helix of DNA unwinds after interaction with the Cu(II)-AC complex. Fluorescence spectroscopy, employing human serum albumin (HSA), suggested a potential transport capacity for both AC and its Cu(II) complex.

The design of protein-metal complexes is rapidly advancing, with applications spanning catalysis, sensing, and bioremediation. We report a comprehensive investigation of METPsc1, a Miniaturized Electron Transfer Protein, in complex with cadmium. This study elucidates the impact of metal coordination on protein folding and structural dynamics across temperatures from 100 K to 300 K. Our findings reveal that METPsc1, composed of two similar halves stabilized by intramolecular hydrogen bonds, exhibits a unique "clothespin-like" recoil mechanism. This allows it to adapt to metal ions of varying radii, mirroring the flexibility observed in natural rubredoxins. High-resolution crystallography and molecular dynamics simulations unveil concerted backbone motions and subtle temperature-dependent shifts in side-chain conformations, particularly for residues involved in crystal packing. Notably, CdS bond lengths increase with temperature, correlating with anisotropic motions of the sulfur atoms involved in second-shell hydrogen bonding. This suggests a dynamic role of protein matrix upon redox cycling. These insights into METPsc1 highlight its potential for catalysis and contribute to the designing of artificial metalloproteins with functional plasticity.

Nitrite (NO) interacts with myoglobin (Mb) and hemoglobin (Hb) behaving as a ligand of both the ferrous (i.e., Mb(II) and Hb(II)) and ferric (i.e., Mb(III) and Hb(III)) forms. However, while the binding to the Fe(III) species corresponds to the formation of a stable complex (i.e., Mb(III)-NO and Hb(III)-NO), in the case of the ferrous forms the reaction proceeds with a nitrite reductase redox process, leading to the oxidation of the heme-protein with the reduction of NO to NO. This event is of the utmost importance for the rapid production of NO in vivo in the blood stream and in striated muscles, being crucial for the regulation of the blood flow, and thus for O supply to poorly oxygenated tissues, such as the eye's retina. Further, NO interacts with Mb(II)-O and Hb(II)-O, inducing their oxidation with a complex mechanism, which has been only partially elucidated. Mb and Hb form the complex with NO through the O-nitrito binding mode (i.e., Fe-ONO), which is regulated by residues paving the heme distal side; thus, in a site-directed mutant, where HisE7 is substituted by Val, the interaction occurs in the N-nitro binding mode (i.e., Fe-N(O)O), like in most other heme-proteins. The structure-function relationships of the interaction of NO with both ferric and ferrous forms of Mb and Hb are discussed here.

Due to its commercial availability and well-defined structure, the interaction between bovine protein β-lactoglobulin (βLG) and a wide variety of non-native ligands - including transition metal complexes - has been explored, but its application as an artificial metalloenzyme scaffold is limited. This protein is hypothesized to transport fatty acids and other nutrients during juvenile development, and it binds hydrophobic ligands inside a binding pocket constructed upon an 8-stranded β-barrel, called the 'calyx'. Herein, we compare the binding behavior of two rhenium(anthracene-bispyridine) ('Anth-py') tricarbonyl complexes, one with a 12‑carbon chain appended to the ligand scaffold ('Anth-py') to βLG. We investigate (i) how calyx-binding specificity is affected by pH (which controls βLG structure at the entrance to the calyx) and (ii) modification of a free cysteine residue located in a putative second binding site of βLG (SMe-βLG). The binding affinities of [Re(Anth-py)(CO)(solv)] (ReC) and [Re(Anth-py)(CO)(solv)] (ReCH) for βLG at pH 7.3 were similar at 36 ± 2 μM and 43 ± 1 μM, respectively. The K of ReC decreased by ∼13 μM at pH 6.1 due to a well-known conformational change (Tanford transition) at the entrance to the calyx; the K value was not significantly affected by Cys121 modification, indicating β-barrel calyx binding specificity. In contrast, ReCH experienced a decrease in K in response to blocking the second binding (SMe-βLG), but was also unaffected by pH. The results show an increase in binding affinity and specificity as a result of targeted ligand design and utilization of native protein characteristics. The findings will inform and improve the design of future βLG-derived ArMs.

By introducing new-to-nature transformations, artificial metalloenzymes hold great potential for expanding the biosynthetic toolbox. The chemistry of an active cofactor in these enzymes is highly dependent on how the holoprotein is assembled, potentially limiting the choice of organometallic complexes amenable to incorporation and ability of the protein structure to influence the metal centre. We have previously reported a method utilising ligand exchange as a means to introduce ruthenium-arene fragments into a four-helix bundle protein. In this work we expand the scope of this method to incorporate an iridium pentamethylcyclopentadienyl fragment into a four-helix bundle, yielding an artificial metalloenzyme with improved transfer hydrogenation properties, highlighting that understanding ligand exchange reactions is important for speciation control.

A series of new Pd(II) complexes were synthesized from the reaction of andrographolide appended hydrazide derivatives with potassium tetrachloropalladate K[PdCl]. The formation of the complexes was confirmed through structural assessments conducted using various spectroscopic techniques. From the spectral studies we confirmed that the ligands coordinated to Pd(II) ion via amine nitrogen and enone oxygen. The complexes were assessed for their antioxidant properties, demonstrating significant radical scavenging activity with a series of free radicals such as 1,1-diphenyl-2-picrylhydrazyl (DPPH), 2,2'-azinobis-(3-ethylbenzothiazoline-6-sulphonic acid diammonium salt (ABTS), Super oxide (O) and Nitric oxide (NO) radicals compared with standard antioxidants. Moreover, in vitro antiproliferative investigations conducted on A549 (human lung cancer) and HeLa (human cervical cancer) cell lines revealed significant cytotoxicity of the complexes, with lower IC values compared to the standard metallo-drug cisplatin. Morphological alterations observed in HeLa and A549 cells when treated with IC concentrations of the complexes, as examined through Acridine Orange-Ethidium Bromide (AO-EB) and 4',6-diamidino-2-phenylindole (DAPI) staining techniques, indicated cell death via apoptosis. Biological studies indicated that AGC-Pd exhibited superior activity among others, further the percentages of the apoptotic and necrotic cells were determined by flow cytometric technique.

Nitric oxide (NO) is a small, short-lived gas molecule that influences various critical functions in living organisms. It involves multiple physiological processes, including cardiovascular function, metabolism, neurotransmission, immunity, and aberrant NO signaling leads to various disorders such as cardiovascular diseases, diabetes, and cancers. In this study, we explored the potential application of copper-nitrite complexes in treating oral precancer and cancer. The copper-nitrite complexes, LCu(NO) and LCu(NO), were shown to release NO into cells and selectively induce cytotoxicity to oral precancer and cancer cells. Notably, LCu(NO) inhibited oral cancer cell proliferation by causing G0/G1 phase cell cycle arrest. Furthermore, LCu(NO) induced cell apoptosis and upregulated the expression of p-PRAS40 (proline-rich Akt substrate of 40 kDa) in oral cancer cells. All these results reveal the therapeutic potential of copper-nitrite complexes, especially LCu(NO), to be developed as a targeted therapy against oral precancer and cancer.

Two Gd(III) complexes [GdL(HO)(NO)(CHOH)(CHCHOH)] (Gd1) and [Gd(OOCCH)L(HO)]•2(HO) (Gd2) (HL = 2-pyridylcarboxaldehyde isonicotinoylhydrazone) were synthesized with a Schiff base ligand. Crystallographic study reveals both Gd1 and Gd2 have a zero-dimensional mononuclear or binuclear structure. Magnetic investigations demonstrate that Gd1 and Gd2 exhibit potential magnetocaloric effects due to Gd(III) ions, which provide negligible magnetic anisotropy, and possess low-lying excited spin states. The antiproliferative activity of Gd1 and Gd2 to three tumor cell lines was conducted and the results showed Gd1 and Gd2 showed more pronounced antiproliferative activity to A549 cells better than cisplatin. The administration of Gd1 and Gd2 led to an increase in apoptosis among A549 cells in a concentration-dependent manner, along with a corresponding rise in the levels of reactive oxygen species (ROS) within the cells. Besides, Gd1 and Gd2 were able to significantly inhibit tumor cell migration. Cell cycle assay in A549 cells revealed that cell cycle was arrested of G0/G1 phase. Western blotting analysis showed that Gd1 and Gd2 complexes could promote apoptosis in A549 cells by modulating the expression of Bcl-2 and Bax proteins.

Developing multifunctional nanomedicines represents a frontier. We have engineered a high-capacity DNA vector basing rolling circle amplification for the delivery of copper sulfide nanoparticles (CuS NPs) and doxorubicin (DOX), coupled with multivalent aptamers (MA) that precisely target tumors, culminating in a multifunctional nanoplatform (RMALCu@DOX), which combines the chemotherapy (CT)/photothermal therapy (PTT)/chemodynamic therapy (CDT). The vector (RMAL) boasts exceptional biocompatibility and incorporates multiple copy units, enabling the precise loading of numerous CuS NPs, forming RMALCu which possesses a robust photothermal effect and superior Fenton-like catalytic activity, heralding a project of minimally invasive dual-mode (PTT/CDT) therapy. Furthermore, the abundance of G-C of RMAL enabled effective DOX encapsulation through π-π interactions to construct RMALCu@DOX. The MA integrated into RMALCu@DOX is pivotal in enhancing the targeting of tumors and in preventing non-specific release of CuS and DOX, enabling an integrated CT/PTT/CDT. Data indicate that 1 nM of RMALCu could load 270 nM of DOX with an impressive loading capacity of 77 %, and modification with MA, its tumor-targeting ability was amplified by 51-fold and significantly bolstered in vitro imaging outcomes, and the synergistic killing of B16 was as 67.3 %. This innovative nanoplatform offers a comprehensive and holistic strategy for the treatment of malignant tumors.

Crown ethers have been shown to have physiological effects ascribed to their ionophoric properties. However, high levels of toxicity precluded interest in their evaluation as therapeutic agents. We prepared new silacrown analogs of crown ethers. These initial studies focused on examples of large ring silacrown ethers having at least fourteen ring atoms with at least one lipophilic or hydrophobic substituent on the ring and/or on the silicon atom. The synthesis of silacrown ethers, ionophoric behavior, toxicity studies, and preliminary pharmacodynamic studies in cardiac myocyte cell lines are presented and compared to their carbon analogs. We report the effects of these compounds in HL-1 cells, an atrial muscle cell line with plasma membrane and sarcoplasmic reticulum Ca channels that give rise to spontaneous Ca transients driven by action potentials. Dicyclohexano-18-crown-6 and the silacrown equivalent dimethylsila-17-cyclohexanocrown-6 were both found to rapidly inhibit the Ca transients after acute treatment, and these effects were reversed when extracellular KCl was increased to cause plasma membrane depolarization. The data suggest that the silacrowns can mimic the effects of crown ethers with similar ring sizes, and this appears to be due to their effects on membrane potential and suppression of action potential firing.

Ovarian cancer represents a leading cause of cancer-related deaths in women worldwide. Chemotherapeutic agents are usually employed to treat the patients, and Ruthenium(II)-based compounds have been investigated as possible substitutes for platinum drugs. In this work, we studied three different Ru(II)-phosphine-mercapto complexes (1-3) as potential cytotoxic agents against A2780 and A2780-cisR ovarian cancer cells. A time-dependent cytotoxicity was observed for 2, which also exhibited better selectivity than cisplatin control. A similar cytotoxic behavior was observed on 3D tumor spheroids. Although no changes were observed in cell cycle distribution, compound 2 affected the mitochondrial membrane potential on A2780 cells, and caused cell death via apoptotic pathway, which was confirmed by flow cytometry assay. Western blotting experiments revealed that 2 affected the expression of p53, PCNA, γH2AX and cleaved caspase-3, making it a promising anticancer agent for ovarian cancer.