Superoxide Dismutase Mimetic Activity Research Articles

Synthesis, crystal structure, DNA cleavage and antitumor activity of two copper(II) complexes with N-sulfonamide ligand

Two Cu(II) complexes, [Cu(L1)2(py)2(H2O] (C1) (HL1 = N-(5-(4-methylphenyl)-[1,3,4]-thiadiazole-2-yl)-naphtalenesulfonamide) and [Cu(HL2)4](OH)2 (C2) (HL2 = N-(5-(4-methoxyphenyl)-[1,3,4]-thiadiazole-2-yl)-toluenesulfonamide) with two new obtained ligands were synthesized. The X-ray crystal structures of the complexes have been determined. In the complex C1, the Cu(II) ion is five-coordinated, forming a CuN4O chromophore and in the complex C2, the Cu(II) ion is four-coordinated, forming a CuN4 chromophore. The ligands act as monodentate, coordinating the metal ion through a single Nthiadiazole atom. For the complex C1, the molecules from the reaction medium (pyridine and water) are also involved in the coordination of the Cu(II) ion. The complexes have a slightly distorted square pyramidal square-planar (C1) and a square-planar (C2) geometry. The compounds were characterized by FT-IR, electronic, EPR spectroscopic and magnetic methods. The nuclease activity studies of the synthesized complexes confirm their capacity to cleavage the DNA molecule. The results of in vitro cell cytotoxicity on three carcinoma cell lines (HeLa, A2780 and A2780cisR) are in concordance with the DNA cleavage study and with the SOD-mimetic activity and indicate that both complexes have antitumor activity. The antitumor activity was compared with Cisplatin and C1 complex demonstrated a higher activity. Both complexes overcame the Cisplatin resistance tence in A2789cisR cells whitout enhanced toxicity on normal fibroblastic cells.

Albumin coated copper-cysteine nanozyme for reducing oxidative stress induced during sperm cryopreservation

In the present work, SOD mimetic nanozyme (NACu-Cys) consisting of Cu-Cys complex and nano-albumin (NA) were synthesized. After characterizing the nanozyme, its superoxide dismutase (SOD) behavior was evaluated by inhibition of the pyrogallol autoxidation method. The results revealed that NACu-Cys exhibited SOD mimetic activity with a half inhibition concentration (IC50) value of 7.0 × 10−3 µM and a turnover number (kcat) of 5.4 × 107 s−1. In the next step, this nanozyme was applied as a protective agent against oxidative stress induced by sperm cryopreservation. Increasing the motility, raising the viability and reducing the apoptosis occurred as a result of NACu-Cys additions to human sperm freezing medium. Comparison between the natural SOD and SOD mimic behavior of NACu-Cys revealed that this nanoparticle has the ability to be used as oxidative stress decrescent during cryopreservation process.

Two versatile salicylatocopper(II) complexes: Structure, spectral, magnetic, electrochemical properties and SOD mimetic activity

Two new salicylatocopper(II) complexes of formula [Cu(3-Mesal)2(inia)2]21 and [Cu(4-MeOsal)2(H2O)]·H2O 2, (where 3-Mesal = 3-methylsalicylate, inia = isonicotinamide, 4-MeOsal = 4-methoxylsalicylate) have been studied in solid state or in solutions. The coordination environment of compound 1 differs from complex 2, but both compounds build up 2-D supramolecular framework. The spectral and magnetic properties are in good agreement to their structure. Moreover, the cyclic voltammetric study, as well as the superoxide dismutase activity of prepared complexes has been studied in solution by NBT assay, and compared with the activity of the parent ligand, copper acetate and native SOD enzyme. SOD mimetic activity of the prepared compounds exhibited rather different IC50 values for compound 1 and 2. The SOD activity together with the redox stability is related to the composition and structure of the complexes.

Superoxide Dismutase Mimetic GC4419 Enhances the Oxidation of Pharmacological Ascorbate and Its Anticancer Effects in an H₂O₂-Dependent Manner.

Lung cancer, together with head and neck cancer, accounts for more than one-fourth of cancer deaths worldwide. New, non-toxic therapeutic approaches are needed. High-dose IV vitamin C (aka, pharmacological ascorbate; P-AscH−) represents a promising adjuvant to radiochemotherapy that exerts its anti-cancer effects via metal-catalyzed oxidation to form H2O2. Mn(III)-porphyrins possessing superoxide dismutase (SOD) mimetic activity have been shown to increase the rate of oxidation of AscH−, enhancing the anti-tumor effects of AscH− in several cancer types. The current study demonstrates that the Mn(II)-containing pentaazamacrocyclic selective SOD mimetic GC4419 may serve as an AscH−/O2•− oxidoreductase as evidenced by the increased rate of oxygen consumption, steady-state concentrations of ascorbate radical, and H2O2 production in complete cell culture media. GC4419, but not CuZnSOD, was shown to significantly enhance the toxicity of AscH− in H1299, SCC25, SQ20B, and Cal27 cancer cell lines. This enhanced cancer cell killing was dependent upon the catalytic activity of the SOD mimetic and the generation of H2O2, as determined using conditional overexpression of catalase in H1299T cells. GC4419 combined with AscH− was also capable of enhancing radiation-induced cancer cell killing. Currently, AscH− and GC4419 are each being tested separately in clinical trials in combination with radiation therapy. Data presented here support the hypothesis that the combination of GC4419 and AscH− may provide an effective means by which to further enhance radiation therapy responses.

Antioxidative study of Cerium Oxide nanoparticle functionalised PCL-Gelatin electrospun fibers for wound healing application

Skin wound healing involves a coordinated cellular response to achieve complete reepithelialisation. Elevated levels of reactive oxygen species (ROS) in the wound environment often pose a hindrance in wound healing resulting in impaired wound healing process. Cerium oxide nanoparticles (CeNPs) have the ability to protect the cells from oxidative damage by actively scavenging the ROS. Furthermore, matrices like nanofibers have also been explored for enhancing wound healing. In the current study CeNP functionalised polycaprolactone (PCL)-gelatin nanofiber (PGNPNF) mesh was fabricated by electrospinning and evaluated for its antioxidative potential. Wide angle XRD analysis of randomly oriented nanofibers revealed ∼2.6 times reduced crystallinity than pristine PCL which aided in rapid degradation of nanofibers and release of CeNP. However, bioactive composite made between nanoparticles and PCL-gelatin maintained the fibrous morphology of PGNPNF upto 14 days. The PGNPNF mesh exhibited a superoxide dismutase (SOD) mimetic activity due to the incorporated CeNPs. The PGNPNF mesh enhanced proliferation of 3T3-L1 cells by ∼48% as confirmed by alamar blue assay and SEM micrographs of cells grown on the nanofibrous mesh. Furthermore, the PGNPNF mesh scavenged ROS, which was measured by relative DCF intensity and fluorescence microscopy; and subsequently increased the viability and proliferation of cells by three folds as it alleviated the oxidative stress. Overall, the results of this study suggest the potential of CeNP functionalised PCL-gelatin nanofibrous mesh for wound healing applications.

Modulating the Catalytic Activity of Cerium Oxide Nanoparticles with the Anion of the Precursor Salt.

In this work, we tested our hypothesis that surface chemistry and antioxidant properties of cerium nanoparticles (CNPs) are affected by presence of counterions. We first employed various precursor cerium (III) (Ce(III)) salts with different counterions (acetate, nitrate, chloride, sulfate) to synthesize CNPs following the same wet chemical methodology. Electron spin resonance (ESR) studies provided evidence for the formation of radicals from counterions (e.g., NO3•2- from reduction of NO3- in CNPs synthesized from Ce(III) nitrate). Physicochemical properties of these CNPs, e.g., dispersion stability, hydrodynamic size, signature surface chemistry, SOD-mimetic activity, and oxidation potentials were found to be significantly affected by the anions of the precursor salts. CNPs synthesized from Ce(III) nitrate and Ce(III) chloride exhibited higher extent of SOD-mimetic activities. Therefore, these CNPs were studied extensively employing in-situ UV-Visible spectroelectrochemistry and changing the counterion concentrations affected the oxidation potentials of these CNPs. Thus, the physicochemical and antioxidant properties of CNPs can be modulated by anions of the precursor. Furthermore, our ESR studies present evidence of the formation of guanine cation radical (G•+) in 5'-dGMP via UV-photoionization at 77 K in the presence of CNPs synthesized from Ce(III) nitrate and chloride and CNPs act as the scavenger of radiation-produced electrons.

In‐vitro Analysis of Catalase‐, Oxidase‐ and SOD‐mimetic Activity of Commercially Available and Custom‐synthesized Cerium Oxide Nanoparticles and Assessment of Neuroprotective Effects in a Hippocampal Brain Slice Model of Ischemia

Oxidative stress has been implicated in many neurological conditions, from stroke to Alzheimer's disease. Cerium oxide (CeO2) nanoparticles (nanoceria or CeNPs) are potent antioxidants that are being explored as a potential therapeutic for these and other pathologies involving oxidative stress. Nanoceria are small, capable of catalytically neutralizing multiple types of reactive oxygen species (ROS), and, due to cycling between the Ce3+ and Ce4+ oxidation states, they can continually regenerate their ROS‐neutralizing capacity depending on the redox conditions. However, both therapeutic and toxic effects of CeNPs have been reported and we hypothesize that this stems from differences in the types of CeNPs used because the method of synthesis as well as the choice of stabilizers coating the particles can lead to disparate biological effects. Understanding which physical/chemical properties correlate with biological activity is critical in order to gain insight into the conditions that promote the positive effects and to understand under what circumstances toxic properties emerge. In the present study we begin to address these issues in a systematic way. Specifically, we tested the enzyme‐mimetic properties of two commercially available (Treibacher Industries and Nanophase) and one custom‐synthesized (CeNRx) CeNP formulation using commercially available enzymatic assay kits. These particles differed in size and method of stabilization. We detected significant differences in the catalase‐ and SOD‐mimetic activities across the three formulations with the Treibacher formulation displaying low levels of catalase‐mimetic activity and undetectable levels of SOD‐mimetic activity. The Nanophase formulation displayed intermediate levels of catalase‐mimetic and low levels of SOD mimetic activity. The custom‐synthesized CeNRx formulation displayed the highest levels of both catalase and SOD‐mimetic activity of the three formulations tested. None of the nanoparticle formulations displayed significant oxidase mimetic activity, demonstrating that there is not a high level of non‐selective oxidation with these CeNPs. We then tested the effects of these CeNPs in a mouse hippocampal brain slice model of ischemia where cell death was assessed using the fluorescence indicator SYTOX green. Fluorescence levels in the slices treated with Treibacher CeNPs were not significantly different from that in untreated slices. In contrast, there was a ~23% increase in cell death in slices treated with Nanophase CeNPs, and a 34% decrease in cell death in slices treated with CeNRx CeNPs. These results demonstrate that three CeNP formulations display different enzyme‐mimetic activity in vitro which correlates with different neuroprotective profiles in brain slices. Future studies will assess further CeNP modifications in order maximize beneficial and minimize toxic effects.Support or Funding InformationSome funding for these studies was provided by CeNRx.

Albumin-Mediated Biomineralization of Shape-Controllable and Biocompatible Ceria Nanomaterials.

Although ceria-based nanostructures have emerged as fascinating materials with diverse biological activities, developing a facile, rapid, and biocompatible method of their preparation remains a major challenge. Herein we describe bovine serum albumin (BSA) protein-directed synthesis of ceria-based nanostructures, including ceria nanoclusters (CNLs), nanoparticles (CNPs), and nanochains (CNHs). Their preparation is simple, one-pot, and performed in a mild reaction condition with a "green" synthetic approach. Most importantly, these three kinds of ceria-based nanostructures can be synthesized in a shape and size controllable manner by tuning the reaction time, temperature, and molar ratio. The formation mechanism shows that growth of these ceria nanostructures is mediated by Ce3+/Ce4+ switchable redox system, reducible disulfide bonds, and unique spatial structures in albumin proteins. More importantly, these albumin-based ceria nanostructures exhibit high superoxide dismutase (SOD) mimetic activity and good biocompatibility, providing a promising prospect in biomedical application.

Cerium-doped bioactive 45S5 glasses: spectroscopic, redox, bioactivity and biocatalytic properties

The ability of Ce-containing bioactive glasses, based on 45S5 Bioglass®, to inhibit oxidative stress in terms of reduction in hydrogen peroxide and superoxide (O2 −), by mimicking the catalase and superoxide dismutase activity is reported in this work. The characterization is performed on the powders of pristine glasses and after the soaking in H2O2 solutions and simulated body fluid. The glass samples are analysed by XPS, XRD, UV–Vis and FT-IR. The best catalyst activities are obtained for the glass with the highest content of cerium (H_5.3 = 5.3 mol% of CeO2 in the nominal glass composition), and the best Ce3+/Ce4+ ratio in terms of catalase mimetic activity is found to be a function of H2O2 concentration. Moreover, the detailed study of the surface during the mimic enzymatic activity tests shows the formation of a Ca-P-rich layer on the glass surface, where the presence of Ce ions favours the formation of CePO4. The phosphate in turn inhibits the formation of hydroxyapatite, decreasing the bioactivity of the glass with the highest of CeO2 in the glass composition. This work shows the effect of Ce3+/Ce4+ ratio towards the catalase mimetic activity and for the first time the superoxide dismutase mimetic activity of Ce-containing 45S5-derived glasses.

Synthesis, crystal structures, characterization and antitumor activities of two copper(II) complexes of a sulfonamide ligand

An N-sulfonamide (HL = N-(5-(4-methoxyph-enyl)-[1, 3, 4]–thiadiazole–2-yl)-naphtalenesulfonamide) and two of its Cu(II) complexes, [Cu(L)2(py)2] (C1) and [Cu(L)(phen)2](L)1.25(MeOH) (C2), were synthesized. The X-ray crystal structures of the complexes have been determined. In complex C1, the copper atom is four-coordinated, forming a CuN4 chromophore, while in complex C2, the copper atom is five-coordinated, forming a CuN5 chromophore. The ligand acts as monodentate, coordinating the metal through a single thiadiazole N atom. The molecules from the reaction medium (pyridine and phenanthroline) are also involved in coordination to the copper atoms. The complexes have a square planar (C1) and slightly distorted square pyramidal (C2) geometries. The compounds were characterized by physicochemical and spectroscopic methods. Nuclease activity studies of the complexes confirm their capacity to cleave DNA. Both complexes also have SOD-like activity, but weaker than the native Cu2Zn2SOD activity. Cytotoxicity studies were carried out on melanoma cell line B16F10 and on normal retinal epithelial cell line (D407) and confirmed that C2 inhibits the growth of B16F10 cells, in a dose-dependent manner. Also, C2 displays a cytoselective profile, since it is not toxic to the D407 cell line. The results of the cell cytotoxicity studies are in concordance with the DNA cleavage and SOD mimetic activity studies and indicate that complex C2 has a high biological activity.

Modulation of surface structure and catalytic properties of cerium oxide nanoparticles by thermal and microwave synthesis techniques

Cerium oxide nanoparticles (CNPs) have been intensively explored for biomedical applications in recent few years due to the versatile enzyme mimetic activities of the nanoparticles. However, the control of CNPs quality through the optimization of synthesis conditions remains largely unexplored as most of the previous studies only focus on utilizing the catalytic activities of the nanoparticles. In the present study, CNPs with size about 5nm were synthesized by thermal decomposition method using traditional convective heating and recently developed microwave irradiation as heating source. The quality of CNPs synthesized by the two heating manner was evaluated. The CNPs synthesized by convective heating were slightly smaller than that synthesized by microwave irradiation heating. The cores of the CNPs synthesized by the two heating manner have similar crystal structure. While the surface subtle structures of the CNPs synthesized by two heating manner were different. The CNPs synthesized by microwave irradiation have more surface reactive hot spot than that synthesized by convective heating as the nanoparticles responded more actively to the redox environment variation. This difference resulted in the higher superoxide dismutase (SOD) mimetic activity of CNPs synthesized by microwave irradiation heating than that of the convective heating. Preliminary experiments indicated that the CNPs synthesized by microwave irradiation heating could better protect cells from oxidative stress due to the higher SOD mimetic activity of the nanoparticles.

Synthesis, Characterization and Antimicrobial Activities of Copper Derivatives of NHC-II Complexes.

Caffeine, 1, 3, 7-trimethylxanthine is one of the xanthine derivatives that are for the most part utilized as a part of solutions as diuretics. The Cu (II) complexes have been synthesized from the N-heterocyclic carbene ligands. The Cu (II) NHC complexes were characterized using analytical and spectral techniques. Antibacterial and antifungal activities of the Cu (II) NHC complexes were determined using the reported techniques. The SOD activity was assayed using nitrobluetetrazolium as O2 scavenger. The X-band ESR spectra of the copper complexes in DMSO solution at 300 and 77 K were recorded and their salient features are reported. The in vitro biological screening effects of the investigated compounds were tested against the bacterial species, Staphylococcus aureus, Escherichia coli, Klebsiella pneumoniae, Proteus vulgaris and Pseudomonas aeruginosa and fungal species, Aspergillus niger, Rhizopus stolonifer, Aspergillus flavus, Rhizoctonia bataicola and Candida albicans by serial dilution method. The Cu (II) complexes exhibit square planar geometry. A comparative study of inhibition values of the individual metals and their complexes indicate that the complexes exhibit higher antimicrobial activity than the individual metals. Superoxide dismutase and reducing power activities of the copper complexes have also been studied. Depending on the molecular structure, the Cu (II) NHC complex possess promising SOD mimetic activities. Further we are trying to explore more biological properties of Cu (II) NHC complexes in vitro and in vivo.

Synthesis, spectral, magnetic properties, electrochemical evaluation and SOD mimetic activity of four mixed-ligand Cu(II) complexes

Four new methylsalicylato copper(II) complexes with formula [Cu(4-Mesal)2(2-Meim)2] (1), [Cu(4-Mesal)2(im)2] (2), [Cu(3-Mesal)2(bzim)2]·2H2O (3), [Cu(5-Mesal)2(im)2]n (4) (where 3-Mesal−=3-methylsalicylato, 4-Mesal−=4-methylsalicylato, 5-Mesal−=5-methylsalicylato anion, im=imidazole, 2-Meim=2-methylimidazole and bzim=benzimidazole) are reported. The solid state complexes were characterized by IR, UV–Vis, EPR, X-ray and magnetic measurements. Despite common coordination environment {CuO2N2O′2} different supramolecular structures were found for the compounds: 1 is a 1-D supramolecular chain, 2 and 3 form 2-D supramolecular networks and 4 is a 1D coordination polymer. The superoxide dismutase-like (SOD-like) activity of complexes 1–4 was studied in solution by NBT assay, compared with the activity of the parent ligand, copper acetate and native SOD enzyme and correlated to the redox stability determined by cyclic voltammetry. The exceptionally low SOD-like activity of 3, its lower redox reversibility and higher electron-withdrawing ability could be related to the lowest axial distortion of its coordination environment.

Shape design of cerium oxide nanoparticles for enhancement of enzyme mimetic activity in therapeutic applications

Cerium oxide nanoparticles (CONPs), widely used in catalytic applications owing to their robust redox reaction, are now being considered in therapeutic applications based on their enzyme mimetic properties such as catalase and super oxide dismutase (SOD) mimetic activities. In therapeutic applications, the emerging demand for CONPs with low cytotoxicity, high cost efficiency, and high enzyme mimetic capability necessitates the exploration of alternative synthesis and effective material design. This study presents a room temperature aqueous synthesis for low-cost production of shape-selective CONPs without potentially harmful organic substances, and additionally, investigates cell viability and catalase and SOD mimetic activities. This synthesis, at room temperature, produced CONPs with particular planes: {111}/{100} nanopolyhedra, {100} nano/submicron cubes, and {111}/{100} nanorods that grew in [110] longitudinal direction. Enzymatic activity assays indicated that nanopolyhedra with a high concentration of Ce4+ ions promoted catalase mimetic activity, while nanocubes and nanorods with high Ce3+ ion concentrations enhanced SOD mimetic activity. This is the first study indicating that shape and facet configuration design of CONPs, coupled with the retention of dominant, specific Ce valence states, potentiates enzyme mimetic activities. These findings may be utilized for CONP design aimed at enhancing enzyme mimetic activities in therapeutic applications.

Synthesis, structure, and antioxidant activity of methoxy- and hydroxyl-substituted 2'-aminochalcones.

Three 2'-aminochalcone derivatives (E)-1-(2-aminophenyl)-3-(4-hydroxyphenyl)prop-2-en-1-one, (E)-1-(2-aminophenyl)-3-(3,4-dihydroxyphenyl)prop-2-en-1-one, and (E)-1-(2-amino-4,5-dimethoxyphenyl)-3-(4-methoxyphenyl)prop-2-en-1-one, have been synthesized, characterized, and tested in vitro in order to assess their antioxidant activity. All compounds were characterized on the basis of 1H NMR, 13C NMR, ESI-mass spectrometry, FT-IR, UV/Vis, and elemental analysis. The X-ray crystal structures of (E)-1-(2-aminophenyl)-3-(4-hydroxyphenyl)prop-2-en-1-one and (E)-1-(2-amino-4,5-dimethoxyphenyl)-3-(4-methoxyphenyl)prop-2-en-1-one were successfully determined showing a planar molecule geometry. Studies on the biological properties including test of free radical scavenging ability (DPPH test) and superoxide dismutase mimetic activity were performed. The results indicate that the aminochalcone carrying two hydroxyl functionalities in adjacent meta and para position exhibits a stronger antioxidant activity than the other derivatives.Graphical abstractElectronic supplementary materialThe online version of this article (doi:10.1007/s00706-016-1812-9) contains supplementary material, which is available to authorized users.

Synthesis, characterization and pharmacological studies of copper complexes of flavone derivatives as potential anti-tuberculosis agents

Novel series of different hydroxyflavone derivatives and their copper complexes were synthesized. They were characterized using analytical and spectral techniques. The superoxide dismutase (SOD) mimetic activity of the synthesized complexes demonstrated that copper complex of L10 has promising SOD-mimetic activity than other ligands & complexes. The in vitro antimicrobial activities of the synthesized compounds were tested against the bacterial species and fungal species. The DNA binding properties of copper complexes were studied using cyclic voltametry and electronic absorption techniques. Anti-tuberculosis activity was also performed. The effective complexes was subjected to antimycobacterial activity using MABA method and summarized. The antimycobacterial activity of copper complexes have been evaluated and discussed.

Evaluating the influence of the diamine unit (ethylenediamine, piperazine and homopiperazine) on the molecular structure, physical chemical properties and superoxide dismutase activity of copper complexes

The synthesis, characterization and superoxide dismutase (SOD) mimetic activity of three copper(II) complexes are presented. The complexes were synthesized with similar ligands that differ from each other in their diamine units (ethylenediamine, piperazine and homopiperazine). Two propanamide units were attached to these diamines, resulting in tetradentate ligands that induce N2O2 coordination to the copper(II) ions. The X-ray analyses of the complexes showed that the complex containing the ethylenediamine unit presents a square planar geometry, whereas the structures of the complexes containing piperazine and homopiperazine were square pyramidal due to the presence of water in the apical position. Studies in solution indicated that the complexes showed a pseudo-octahedral geometry in water. This geometry was maintained in a DMSO solution for the complexes containing ethylenediamine and homopiperazine. However, the complex containing piperazine presented a five coordinate copper center in a DMSO solution. All three complexes presented high SOD-like activity with IC50 values in the nanomolar range (100–200nmoldm−3).

Antioxidant and starch hydrolase inhibitory properties of extracts of the antidiabetic herb Pterocarpus marsupium

Pterocarpus marsupiumis a popular spice incorporated into culinary preparations around the world, which is also used for its antidiabetic treatment in traditional medicine. The objective of the study was to evaluate the antioxidant and starch hydrolase inhibitory properties ofPterocarpus marsupiumleaves. The total antioxidant capacity, total phenolics content, starch hydrolase inhibitory activities and superoxide dismutase mimetic (SODm) activity of various leaf extracts ofPterocarpus marsupiumwere studied. Extracts of dichloromethane (DCM), ethanol (EtOH), ethyl acetate (EtOAc), hexane (HEX), methanol (MeOH) and water were compared. The total phenolics contents of the extracts decreased in the order of water > EtOH > EtOAc > MeOH > DCM > HEX. The antioxidant and SODm activity values of the extracts decreased in the same order as the total phenolics contents, while the DPPH EC50values increased in the reverse order. Pterosupin and pterostilbene had the highest content out of all the phenolic compounds quantified across all solvent extracts. The highest starch hydrolase inhibitory activities were observed in the water extract.Pterocarpus marsupiumwas observed to be a good source of antioxidant compounds and therapeutic properties.

Synthesis, Structural Diversity and Mimic Superoxide Dismutase of Mn(II) Complexes Derived from N, O-donor Schiff bases.

Two new potentially tetradentate Schiff base ligands N'-(pyridin-2-ylmethylene)nicotinohydrazide (L1), and N'-(pyridin-2-ylmethylene)isonicotinohydrazide (L(2)) were synthesized. Reactions of hydrazone ligands L(1) and L(2) with Mn(NO(3))(2) afford two mononuclear Mn(II) complexes, [Mn(L(1))(NO(3))(H(2)O)(2)]•(NO(3)) (1) and [Mn(L(2))(2)(NO(3))(H(2)O)]•(NO(3)) (2). For complexes 1 and 2, L(1) and L(2) act as pincer-like tridentate or bidentate ligands, respectively. The Mn(II) ions in the two compounds are both in heptacoordinated environment, while the two molecules display diverse solid-state supramolecular structures because of the different orientation of Npyridine and hydrogen bonding patterns of nitrate anions. Complex 1 features 2D supramolecular sheet, while complex 2 is double-chain supramolecular structure. Both of the two complexes exhibit moderate superoxide dismutase (SOD) mimetic activity.

Controlling the surface chemistry of cerium oxide nanoparticles for biological applications.

The catalytic activity of cerium oxide nanoparticles (CNPs) depends on the surface Ce3+/Ce4+ oxidation state. CNPs with a higher Ce3+ to Ce4+ ratio, oxygen vacancies and higher superoxide dismutase (SOD) mimetic activity are more effective against diseases associated with oxidative stress or inflammation. CNPs with a lower Ce3+/Ce4+ ratio show higher catalase mimetic activity and possess anticancer/antibacterial activity. However, different synthesis methods of CNPs and capping agents/surface coatings result in various Ce3+/Ce4+ oxidation states, thus limiting the use of particular CNPs for specific biological applications. In this study, we have shown that by selecting an appropriate doping method we can control the surface Ce3+/Ce4+ oxidation state to tune the catalytic activity and biological response. Importantly, superior SOD mimetic activity and efficient reactive oxygen species scavenging capability of one-step synthesized CNPs are linked to a uniform distribution of dopants in the CNP lattice and changes in the surface Ce3+/Ce4+ oxidation state.