Impact of pyridine-2-carboxaldehyde-derived aroylhydrazones on the copper-catalyzed oxidation of the M112A PrP 103–112 mutant fragment Abstract Misfolded prion protein (PrPSc) is known for its role in fatal neurodegenerative conditions, such as Creutzfeldt–Jakob disease. PrP fragments and their mutants represent important tools in the investigation of the neurotoxic mechanisms and in the evaluation of new compounds that can interfere with the processes involved in neuronal death. Metal-catalyzed oxidation of PrP has been implicated as a trigger for the conformational changes in protein structure, which, in turn, lead to misfolding. Targeting redox-active biometals copper and iron is relevant in the context of protection against the oxidation of biomolecules and the generation of oxidative stress, observed in several conditions and considered an event that might promote sporadic prion diseases as well as other neurodegenerative disorders. In this context, ortho-pyridine aroylhydrazones are of interest, as they can act as moderate tridentate ligands towards divalent metal ions such as copper(II). In the present work, we explore the potentiality of this chemical class as peptide protecting agents against the deleterious metal-catalyzed oxidation in the M112A mutant fragment of human PrP, which mimics relevant structural features that may play an important role in the neurotoxicity observed in prion pathologies. The compounds inhere studied, especially HPCFur, showed an improved stability in aqueous solution compared to our patented lead hydrazone INHHQ, displaying a very interesting protective effect toward the oxidation of methionine and histidine, processes that are related to both physiological and pathological aging.

Perturbation of tubulin structure by stellate gold nanoparticles retards MDA-MB-231 breast cancer cell viability Abstract Gold nanoparticles (GNPs) of different sizes and shapes have been investigated extensively for their therapeutic potential against several diseases including cancer. However, the mechanisms with which they affect the cells are yet to be fully comprehended. In this study, we report the strong antiproliferative potential of novel, star-shaped (“stellate”) GNPs that target tubulin—the building-block protein of the cytoskeletal filaments called microtubules—and disrupt microtubule network integrity. The stellate GNPs (“sGNPs”) were synthesized from tryptone-stabilized GNPs (“tGNPs”) and characterized by various spectroscopy methods combined with high-resolution transmission electron microscopy. Among a panel of cancer cell lines tested, they showed strong antiproliferative and anti-clonogenic efficacy against MDA-MB-231 cells. The antiproliferative mechanism of the sGNPs involves perturbation of the secondary and tertiary conformation of tubulin as evidenced by far-UV circular dichroism and anilinonaphthalene sulphate-binding assays. The structural perturbation of tubulin retarded its assembly competence as evidenced by polymer mass analysis and electron microscopy imaging of tubulin assembled in vitro and by immunofluorescence visualization of the cellular microtubules. The treated cells also induced cell cycle arrest at G1 phase. Taken together, our data suggest that sGNPs are potent, tubulin-targeted antiproliferative particles that can be evaluated further for their anticancer potential.

New dinuclear palladium(II) complexes with benzodiazines as bridging ligands: interactions with CT-DNA and BSA, and cytotoxic activity Abstract Three new dinuclear Pd(II) complexes with general formula [{Pd(en)Cl}2(μ-L)](NO3)2 [L is bridging ligand quinoxaline (Pd1), quinazoline (Pd2) and phthalazine (Pd3)] were synthesized and characterized by elemental microanalyses, UV–Vis, IR and NMR (1H and 13C) spectroscopy. The interaction of dinuclear Pd1–Pd3 complexes with calf thymus DNA (CT-DNA) has been monitored by viscosity measurements, UV–Vis and fluorescence emission spectroscopy in aqueous phosphate buffer solution (PBS) at pH 7.40 and 37 °C. In addition, these experimental conditions have been applied to investigate the binding affinities of Pd1–Pd3 complexes to the bovine serum albumin (BSA) by fluorescence emission spectroscopy. In vitro antiproliferative and apoptotic activities of the dinuclear Pd(II) complexes have been tested on colorectal and lung cancer cell lines. All tested Pd(II) complexes had lower cytotoxic effect than cisplatin against colorectal cancer cells, but also had similar or even higher cytotoxicity than cisplatin against lung cancer cells. All complexes induced apoptosis of colorectal and lung cancer cells, while the highest antiproliferative effect exerted Pd2 complex. Graphic abstract

A novel series of mixed-ligand M(II) complexes containing 2,2′-bipyridyl as potent α-glucosidase inhibitor: synthesis, crystal structure, DFT calculations, and molecular docking Abstract Diabetes mellitus (DM) is a common degenerative disease and characterized by high blood glucose levels. Since the effective antidiabetic treatments attempt to decrease blood glucose levels, keeping glucose under control is very important. Recent studies have demonstrated that α-glucosidase inhibitor improves postprandial hyperglycemia and then reduces the risk of developing type 2 diabetes in patients. Therefore, the design and synthesis of high affinity glucosidase inhibitors are of great importance. In this regard, novel series of mixed-ligand M(II) complexes containing 2,2′-bipyridyl {[Hg(6-mpa)2(bpy)(OAc)]·2H2O, (1), [Co(6-mpa)2(bpy)2], (2), [Cu(6-mpa)(bpy)(NO3)]·3H2O, (3), [Mn(6-mpa)(bpy)(H2O)2], (4), [Ni(6-mpa)(bpy)(H2O)2]·H2O, (5), [Fe(6-mpa)(bpy)(H2O)2]·2H2O, (6), [Fe(3-mpa)(bpy)(H2O)2]·H2O, (7)} were synthesized as potential α-glucosidase inhibitors. Their effects on α-glucosidase activity were evaluated. All synthesized complexes displayed α-glucosidase inhibitory activity with IC50 values ranging from 0.184 ± 0.015 to > 600 μM. The experimental spectral analyses were carried out using FT–IR and UV–Vis spectroscopic techniques for these complexes characterized by XRD and LC–MS/MS. Moreover, the calculations at density functional theory approximation were used to obtain optimal molecular geometries, vibrational wavenumbers, electronic spectral behaviors, and major contributions to the electronic transitions for the complexes 1–7. Finally, to display interactions between the synthesized complexes and target protein (the template structure Saccharomyces cerevisiae isomaltase), the molecular docking study was carried out.

A new 4-(pyridinyl)-4 H -benzo[ g ]chromene-5,10-dione ruthenium(II) complex inducing senescence in 518A2 melanoma cells Abstract 2-Amino-5,10-dihydro-5,10-dioxo-4(pyridine-3-yl)-4H-benzo[g]chromene-3-carbonitrile 5, a cytotoxic lawsone derivative, was reacted with [Ru(p-cymene)Cl2]2 to afford a new Ru(II) ‘piano-stool’ complex 6 which differed from its ligand 5 by a greater selectivity for highly invasive 518A2 melanoma cells over human dermal fibroblasts in MTT cytotoxicity assays, and by inducing senescence rather than apoptosis in the former. DNA is a likely cellular target of complex 6 as it bound, presumably non-covalently, to linear and circular double-stranded DNA in vitro and as ruthenium was found in the lysate of nuclei of treated 518A2 melanoma cells. It also caused a fivefold increase of reactive oxygen species in these cells, originating from a more persistent redox cycling as visualised by cyclic voltammetry.

Activity and electrochemical properties: iron complexes of the anticancer drug triapine and its analogs Abstract Triapine (3-AP), is an iron-binding ligand and anticancer drug that is an inhibitor of human ribonucleotide reductase (RNR). Inhibition of RNR by 3-AP results in the depletion of dNTP precursors of DNA, thereby selectively starving fast-replicating cancer cells of nucleotides for survival. The redox-active form of 3-AP directly responsible for inhibition of RNR is the Fe(II)(3-AP)2 complex. In this work, we synthesize 12 analogs of 3-AP, test their inhibition of RNR in vitro, and study the electronic properties of their iron complexes. The reduction and oxidation events of 3-AP iron complexes that are crucial for the inhibition of RNR are modeled with solution studies. We monitor the pH necessary to induce reduction in iron complexes of 3-AP analogs in a reducing environment, as well as the kinetics of oxidation in an oxidizing environment. The oxidation state of the complex is monitored using UV–Vis spectroscopy. Isoquinoline analogs of 3-AP favor the maintenance of the biologically active reduced complex and possess oxidation kinetics that allow redox cycling, consistent with their effective inhibition of RNR seen in our in vitro experiments. In contrast, methylation on the thiosemicarbazone secondary amine moiety of 3-AP produces analogs that form iron complexes with much higher redox potentials, that do not redox cycle, and are inactive against RNR in vitro. Graphic abstract The catalytic subunit of human Ribonucleotide Reductase (RNR), contains a tyrosyl radical in the enzyme active site. Fe(II) complexes of 3-AP and its analogs can quench the radical and, subsequently, inactivate RNR. The potency of RNR inhibitors is highly dependent on the redox properties of the iron complexes, which can be tuned by ligand modifications. Complexes are found to be active within a narrow redox window imposed by the cellular environment.

Silver(I)-mediated base pairing in parallel-stranded DNA involving the luminescent cytosine analog 1,3-diaza-2-oxophenoxazine Abstract 1,3-Diaza-2-oxophenoxazine (X) has been introduced as a ligand in silver(I)-mediated base pairing in a parallel DNA duplex. This fluorescent cytosine analog is capable of forming stabilizing X–Ag(I)–X and X–Ag(I)–C base pairs in DNA duplexes, as confirmed by temperature-dependent UV spectroscopy and luminescence spectroscopy. DFT calculations of the silver(I)-mediated base pairs suggest the presence of a synergistic hydrogen bond. Molecular dynamics (MD) simulations of entire DNA duplexes nicely underline the geometrical flexibility of these base pairs, with the synergistic hydrogen bond facing either the major or the minor groove. Upon silver(I) binding to the X:X or X:C base pairs, the luminescence emission maximum experiences a red shift from 448 to 460 nm upon excitation at 370 nm. Importantly, the luminescence of the 1,3-diaza-2-oxophenoxazine ligand is not quenched significantly upon binding a silver(I) ion. In fact, the luminescence intensity even increases upon formation of a X–Ag(I)–C base pair, which is expected to be beneficial for the development of biosensors. As a consequence, the silver(I)-mediated phenoxazinone base pairs represent the first strongly fluorescent metal-mediated base pairs. Graphic abstract

Groove structure of porous hydroxyapatite scaffolds (HAS) modulates immune environment via regulating macrophages and subsequently enhances osteogenesis Abstract Researches have revealed the vital roles of the generated immune environment via the response of immune cells growing on biomaterial surfaces in the bone healing process. HAS and novel constructed microgrooved patterns of HAS (HAS-G) are widely used as biocompatible ceramic, especially as a mimic of the natural bone matrix. However, it is unclear whether osteoimmune response induced by HAS and HAS-G affects the osteogenic differentiation of bone marrow stromal cells (BMSCs). RAW264.7 cells were seeded on different surface of materials and cytokines released by macrophages were detected by enzyme-linked immunosorbent assay. The cell viability and mitochondrial function of macrophages seeded on different surface of materials were detected. Then, the effects of modified inflammatory microenvironment by macrophages on osteogenesis of BMSCs were measured by performing ALP staining, Alizarin Red S staining, and western blot. We confirmed that HAS-G is more favorable for RAW cell attaching and subsequently regulated the expression and release of cytokines/chemokines. Decrease in interleukin-6 (IL-6) release was further confirmed for contributing significantly to improve mitochondrial function in RAW cells. HAS-G-conditioned medium promoted osteogenic differentiation in BMSCs and was reversed by IL-6 addition. Decrease in IL-6 contributes to downregulation of miR-214 and subsequently upregulated p38/JNK pathway, which is potentially contributes to osteogenic promotion by HAS-G. This study is the first report to reveal the effects of HAS-G on osteogenesis via immune response, which could lead to a new insight into novel material for the advantage of biomaterials for tissue engineering applications.

Organometallic rhenium tricarbonyl–enrofloxacin and –levofloxacin complexes: synthesis, albumin-binding, DNA-interaction and cell viability studies Abstract Organometallic rhenium complexes have recently been considered in the development of novel antitumor agents due to their suitable properties. A series of rhenium(I) tricarbonyl complexes was synthesized with the quinolone antimicrobial agents enrofloxacin (Herx) and levofloxacin (Hlfx) and solvent (e.g., methanol), imidazole (im) or pyridine (py) as co-ligands. The complexes were characterized by spectroscopic methods. The interaction of the rhenium complexes with bovine serum albumin was investigated by fluorescence emission spectroscopy and the corresponding binding constants were determined. The binding of the rhenium complexes to calf-thymus DNA was monitored by UV–Vis spectroscopy, viscosity measurements and competitive studies with ethidium bromide. These studies indicated that intercalation is the most possible mode of action and the corresponding DNA-binding constants of the complexes were calculated. The cytotoxicity of the Re-complexes against human K-562 erythroleukemia cells was found to be moderate to high. These preliminary results are promising and warrant the design of new Re-complexes with improved properties in future studies. Graphical abstract

Ironing out pyoverdine’s chromophore structure: serendipity or design? Abstract Pyoverdines are Pseudomonas aeruginosa’s primary siderophores. These molecules, composed of a fluorescent chromophore attached to a peptide chain of 6–14 amino acids, are synthesized by the bacterium to scavenge iron (essential to its survival and growth) from its environment. Hijacking the siderophore pathway to use pyoverdine–antibiotic compounds in a Trojan horse approach has shown promise but remains very challenging because of the synthetic efforts involved. Indeed, both possible approaches (grafting an antibiotic on pyoverdine harvested from Pseudomonas or designing a total synthesis route) are costly, time-consuming and low-yield tasks. Designing comparatively simple analogs featuring the salient properties of the original siderophore is thus crucial for the conception of novel antibiotics to fight bacterial resistance. In this work, we focus on the replacement of the pyoverdine chromophore, a major roadblock on the synthetic pathway. We propose three simpler analogs and evaluate their ability to complex iron and interact with the FpvA transporter using molecular modeling techniques. Based on these results, we discuss the role of the native chromophore’s main features (polycyclicity, positive charge, flexibility) on pyoverdine’s ability to bind iron and be recognized by membrane transporter FpvA and propose guidelines for the design of effective synthetic siderophores. Graphic abstract