t-Na-2(VO)P2O7: A 3.8 V Pyrophosphate Insertion Material for Sodium-Ion Batteries

Pyrophosphate oxyanionic framework compounds offer a great platform to investigate new battery materials. In our continuing effort to explore pyrophosphate cathodes for sodium-ion batteries, we report, for the first time, the synthesis and use of tetragonal Na-2(VO)P2O7 as a potential sodium-ion insertion material. This material can be easily prepared by using a conventional solid-state route at a relatively low temperature of 400 degrees C. Stabilizing as a tetragonal structure with an open framework, the material offers pathways for Na+ diffusion. The as-synthesized material, with no further cathode optimization, yields a reversible capacity (Q) approaching 80 mAh g(-1) (Q(Theoretical) = 93.4 mAh g(-1)) involving a one electron V5+/V4+ redox potential located at 3.8 V (vs. Na/Na+). Furthermore, the material exhibits decent rate kinetics and reversibility. Combining green synthesis and moderate electrochemical properties, t-Na-2(VO)P2O7 is reported as a new addition to the growing family of pyrophosphate cathodes for sodium-ion batteries.

Matrix-Assisted Refolding, Purification and Activity Assessment Using a `Form Invariant' Assay for Matrix Metalloproteinase 2 (MMP2)

Matrix metalloproteinases expression is used as biomarker for various cancers and associated malignancies. Since these proteinases can cleave many intracellular proteins, overexpression tends to be toxic; hence, a challenge to purify them. To overcome these limitations, we designed a protocol where full length pro-MMP2 enzyme was overexpressed in E. coli as inclusion bodies and purified using 6xHis affinity chromatography under denaturing conditions. In one step, the enzyme was purified and refolded directly on the affinity matrix under redox conditions to obtain a bioactive protein. The pro-MMP2 protein was characterized by mass spectrometry, CD spectroscopy, zymography and activity analysis using a simple in-house developed `form invariant' assay, which reports the total MMP2 activity independent of its various forms. The methodology yielded higher yields of bioactive protein compared to other strategies reported till date, and we anticipate that using the protocol, other toxic proteins can also be overexpressed and purified from E. coli and subsequently refolded into active form using a one step renaturation protocol.

An antioxidant nanozyme that uncovers the cytoprotective potential of vanadia nanowires

Nanomaterials with enzyme-like properties has attracted significant interest, although limited information is available on their biological activities in cells. Here we show that V2O5 nanowires (Vn) functionally mimic the antioxidant enzyme glutathione peroxidase by using cellular glutathione. Although bulk V2O5 is known to be toxic to the cells, the property is altered when converted into a nanomaterial form. The Vn nanozymes readily internalize into mammalian cells of multiple origin (kidney, neuronal, prostate, cervical) and exhibit robust enzyme-like activity by scavenging the reactive oxygen species when challenged against intrinsic and extrinsic oxidative stress. The Vn nanozymes fully restore the redox balance without perturbing the cellular antioxidant defense, thus providing an important cytoprotection for biomolecules against harmful oxidative damage. Based on our findings, we envision that biocompatible Vn nanowires can provide future therapeutic potential to prevent ageing, cardiac disorders and several neurological conditions, including Parkinson's and Alzheimer's disease.

Structural, magnetic and electrochemical investigation of novel binary Na2-x(Fe1-yMny)P2O7 (0 <= y <= 1) pyrophosphate compounds for rechargeable sodium-ion batteries

Pyrophosphate cathodes have been recently reported as a competent family of insertion compounds for sodium-ion batteries. In the current study, we have investigated the binary Na2 - x(Fe1 - yMny)P2O7 (0 <= y <= 1) pyrophosphate family, synthesized by the classical solid-state method. They form a continuous solid solution maintaining triclinic P-1 (#2) symmetry. The local structural coordination differs mainly by different degrees of Na site occupancy and preferential occupation of the Fe2 site by Mn. The structural and magnetic properties of these mixed-metal pyrophosphate phases have been studied. In each case, complete Fe3+/Fe2+ redox activity has been obtained centered at 3 V vs. Na. The Fe3+/Fe2+ redox process involves multiple steps between 2.5 and 3 V owing to Na-cation ordering during electrochemical cycling, which merge to form a broad single Fe3+/Fe2+ redox peak upon progressive Mn-doping. (C) 2014 Elsevier B.V. All rights reserved.

2-(Phenylazo)pyridineplatinum(II) Catecholates Showing Photocytotoxicity, Nuclear Uptake, and Glutathione-Triggered Ligand Release

Platinum(II) complexes Pt(pap)(an-cat)] (1) and Pt(pap)(py-cat)] (2) with 2-(phenylazo)pyridine (pap), 4-2-(anthracen-9-ylmethylene)amino]ethyl]benzene-1,2-diol (H(2)an-cat), and 4-2-(pyren-1-ylmethylene)amino]ethyl]benzene-1,2-diol (H2py-cat) were prepared, and their photoinduced cytotoxicity was studied. The complexes were found to release catecholate ligand in the presence of excess glutathione (GSH), resulting in cellular toxicity in the cancer cells. The catecholate complex Pt(pap)(cat)] (3) was prepared and used as a control. Complex 3, which is structurally characterized by X-ray crystallography, has platinum(II) in a distorted square-planar geometry. The complexes are redox-active, showing responses near 0.6 and 1.0 V versus SCE in N,N-dimethylformamide/0.1 M tetrabutylammonium perchlorate corresponding to a two-step catechol oxidation process and at -0.3 and -1.3 V for reduction of the pap ligand. Complex 1 showed remarkable light-induced cytotoxicity in HaCaT (human skin keratinocytes) and MCF-7 (human breast cancer) cells, giving IC50 value of similar to 5 mu M in visible light of 400-700 nm and >40 mu M in the dark. The 2',7'-dichlorofluorescein diacetate (DCFDA) assay showed the generation of reactive oxygen species (ROS), which seems to trigger apoptosis, as is evident from the annexin V-fluorescein isothiocyanate (FITC)/propidium iodide (PI) assay. The fluorescence microscopic images showed significant nuclear localization of the complexes and free ligands. A mechanistic study revealed possible reduction of the coordinated azo bond of pap by cellular GSH, releasing the catecholate ligand and resulting in remarkable photochemotherapeutic action of the complexes.

Oxygen-participated electrochemistry of new lithium-rich layered oxides Li3MRuO5 M = Mn, Fe)

We describe the synthesis, crystal structure and lithium deinsertion-insertion electrochemistry of two new lithium-rich layered oxides, Li3MRuO5 (M = Mn, Fe), related to rock salt based Li2MnO3 and LiCoO2. The Li3MnRuO5 oxide adopts a structure related to Li2MnO3 (C2/m) where Li and (Li0.2Mn0.4Ru0.4) layers alternate along the c-axis, while the Li3FeRuO5 oxide adopts a near-perfect LiCoO2 (R (3) over barm) structure where Li and (Li0.2Fe0.4Ru0.4) layers are stacked alternately. Magnetic measurements indicate for Li3MnRuO5 the presence of Mn3+ and low spin configuration for Ru4+ where the itinerant electrons occupy a pi*-band. The onset of a net maximum in the chi vs. T plot at 9.5 K and the negative value of the Weiss constant (theta) of -31.4 K indicate the presence of antiferromagnetic superexchange interactions according to different pathways. Lithium electrochemistry shows a similar behaviour for both oxides and related to the typical behaviour of Li-rich layered oxides where participation of oxide ions in the electrochemical processes is usually found. A long first charge process with capacities of 240 mA h g(-1) (2.3 Li per f.u.) and 144 mA h g(-1) (1.38 Li per f.u.) is observed for Li3MnRuO5 and Li3FeRuO5, respectively. An initial sloping region (OCV to ca. 4.1 V) is followed by a long plateau (ca. 4.3 V). Further discharge-charge cycling points to partial reversibility (ca. 160 mA h g(-1) and 45 mA h g(-1) for Mn and Fe, respectively). Nevertheless, just after a few cycles, cell failure is observed. X-ray photoelectron spectroscopy (XPS) characterisation of both pristine and electrochemically oxidized Li3MRuO5 reveals that in the Li3MnRuO5 oxide, Mn3+ and Ru4+ are partially oxidized to Mn4+ and Ru5+ in the sloping region at low voltage, while in the long plateau, O2- is also oxidized. Oxygen release likely occurs which may be the cause for failure of cells upon cycling. Interestingly, some other Li-rich layered oxides have been reported to cycle acceptably even with the participation of the O2- ligand in the reversible redox processes. In the Li3FeRuO5 oxide, the oxidation process appears to affect only Ru (4+ to 5+ in the sloping region) and O2- (plateau) while Fe seems to retain its 3+ state.

An alluaudite Na-2+Fe-2x(2-x)(SO4)(3)(x=0.2) derivative phase as insertion host for lithium battery

A new desodiated derivative compound, Na0.89Fe1.8(SO4)(3), was prepared by the chemical oxidation of alluaudite Na2.4Fe1.8(SO4)(3) Phase using NOBF4 as oxidant. The structure and valency of Fe were characterized by X-ray diffraction (XRD) and Fe-57 Mossbauer spectroscopy. Intercalation behavior of lithium ions in the structure of Na0.89Fe1.8(SO4)(3) was gauged by electrochemical analyses and ex-situ X-ray diffraction. A high capacity of 110 mAh g(-1) at 0.1 C was obtained with a good rate kinetics within a range of 0.1-10 C(1 C = 118 mAh g-1) involving a high Fe3+/Fe2+ redox potential of 3.75 V (vs. Li/Li+). These results confirmed that the Na2.4-delta Fe1.8(SO4)(3) framework was stable even after oxidation and forms a new competitive cathode for the reversible intercalation of lithium ions. (C) 2014 Elsevier B.V. All rights reserved.

Photocytotoxic oxovanadium(IV) complexes of ferrocenyl-terpyridine and acetylacetonate derivatives

Oxovanadium(IV) complexes VO(Fc-tpy)(acac)](ClO4) (1), VO(Fc-tpy)(nap-acac)](ClO4) (2), VO(Fc-tpy)(py-acac)](ClO4) (3) and VO(Ph-tpy)(py-acac)](ClO4) (4) of 4'-ferroceny1-2,2':6',2 `'-terpyridine (Fc-tpy) and 4'-phenyl-2,2':6',2 `'-terpyridine (Ph-tpy) having monoanionic acetylacetonate (acac), naphthylacetylacetonate (nap-acac) or pyrenylacetylacetonate (py-acac) ligand were prepared, characterized and their photocytotoxicity in visible light studied. The ferrocenyl complexes 1-3 showed an intense charge transfer band near 585 nm in DMF and displayed Fc(+)/Fc and V(IV)/V(III) redox couples near 0.66 V and -0.95 V vs. SCE in DMF-0.1 M TBAP. The complexes as avid binders to calf thymus DNA showed significant photocleavage of plasmid DNA in green light (568 nm) forming center dot OH radicals. The complexes that are photocytotoxic in HeLa and MCF-7 cancer cells in visible light (400-700 nm) with low dark toxicity remain nontoxic in normal fibroblast 3T3 cells. ICP-MS and fluorescence microscopic studies show significant cellular uptake of the complexes. Photo-irradiation of the complexes causes apoptotic cell death by ROS as evidenced from the DCFDA assay. (C) 2015 Elsevier Masson SAS. All rights reserved.

Mitochondria-Targeting Photocytotoxic Ferrocenyl Conjugates of N-Alkylpyridinium Salts

Ferrocenyl (Fc) conjugates (1-3) of alkylpyridinium cations (E)-N-alkyl-4-2-(ferrocenyl)vinyl]pyridinium bromide (alkyl = n-butyl in 1, N,N,N-triethylbutan-1-aminium bromide in 2, and n-butyltriphenylphosphonium bromide in 3) were prepared and characterized, and their photocytotoxicities and cellular uptakes in HeLa cancer and 3T3 normal cells were studied. The species with a 4-methoxyphenyl moiety (4) instead of Fc was used as a control. The triphenylphosphonium-appended 3 was designed for specific delivery into the mitochondria of the cells. Compounds 1-3 showed metal-to-ligand charge-transfer bands at approximate to 550 nm in phosphate buffered saline (PBS). The Fc(+)/Fc and pyridinium core redox couples were observed at 0.75 and -1.2 V versus a saturated calomel electrode (SCE) in CH2Cl2/0.1 M (nBu(4)N)ClO4. Conjugate 3 showed a significantly higher photocytotoxicity in HeLa cancer cells IC50 = (1.3 +/- 0.2) M] than in normal 3T3 cells IC50 = (27.5 +/- 1.5) M] in visible light (400-700 nm). The positive role of the Fc moiety in 3 was evident from the inactive nature of 4. A JC-1 dye (5,5,6,6-tetrachloro-1,1,3,3-tetraethylbenzimidazolylcarbocyanine iodide) assay showed that 3 targets the mitochondria and induces apoptosis by the mitochondrial intrinsic pathway caused by reactive oxygen species (ROS). Annexin/propidium iodide studies showed that 3 induces apoptotic cell death in visible light by ROS generation, as evidenced from dichlorofluorescein diacetate assay. Compounds 1-3 exhibit DNA photocleavage activity through the formation of hydroxyl radicals.

Gray to transmissive electrochromic switching based on electropolymerized PEDOT-ionic liquid functionalized graphene films

A supporting electrolyte based on lithium perchlorate has been functionalized with graphene (ionic liquid functionalized graphene (IFGR)) by facile electrochemical exfoliation of graphite rods in aq. LiClO4 solution. Poly(3,4-ethylenedioxythiophene) (PEDOT)-IFGR films were prepared by electropolymerization of EDOT monomer with IFGR as supporting electrolyte in ethanol at static potential of 1.5 V. The Raman, SEM, and XPS analysis of PEDOT-IFGR film confirmed the presence of functionalized graphene in the film. The PEDOT-IFGR films showed good electrochemical properties, better ionic and electrical conductivity, significant band gap, and excellent spectroelectrochemical and electrochromic properties. The electrical conductivity of PEDOT-IFGR film was measured as about 3968 S cm(-1). PEDOT-IFGR films at reduced state showed strong and broad absorption in the whole visible region and remarkable absorption at near-IR region. PEDOT-IFGR film showed electrochromic response between transmissive blue and darkish gray at redox potential. The color contrast (%T) between fully reduced and oxidized states of PEDOT-IFGR film is 25 % at lambda (max) of 485 nm. The optical switching stability of PEDOT-IFGR film has retained 80 % of its electroactivity even after 500 cycles.

Iron(III) Complexes of a Pyridoxal Schiff Base for Enhanced Cellular Uptake with Selectivity and Remarkable Photocytotoxicity

Iron(III) complexes of pyridoxal (vitamin B6, VB6) or salicylaldehyde Schiff bases and modified dipicolylamines, namely, Fe(B)(L)](NO3) (15), where B is phenyl-N,N-bis((pyridin-2-yl)methyl)methanamine (phbpa in 1), (anthracen-9-yl)-N,N-bis((pyridin-2-yl)methyl)methanamine (anbpa in 2, 4) and (pyren-1-yl)-N,N-bis((pyridin-2-yl)methyl)methanamine (pybpa in 3, 5) (H2L1 is 3-hydroxy-5-(hydroxymethyl)-4-(((2-hydroxyphenyl)imino)methyl)-2-methylp yridine (13) and H2L2 is 2-(2-hydroxyphenyl-imino)methyl]phenol), were prepared and their uptake in cancer cells and photocytotoxicity were studied. Complexes 4 and 5, having a non-pyridoxal Schiff base, were prepared to probe the role of the pyridoxal group in tumor targeting and cellular uptake. The PF6 salt (1a) of complex 1 is structurally characterized. The complexes have a distorted six-coordinate FeN4O2 core where the metal is in the +3 oxidation state with five unpaired electrons. The complexes display a ligand to metal charge transfer band near 520 and 420 nm from phenolate to the iron(III) center. The photophysical properties of the complexes are explained from the time dependent density functional theory calculations. The redox active complexes show a quasi-reversible Fe(III)/Fe(II) response near -0.3 V vs saturated calomel electrode. Complexes 2 and 3 exhibit remarkable photocytotoxicity in various cancer cells with IC50 values ranging from 0.4 to 5 mu M with 10-fold lower dark toxicity. The cell death proceeded by the apoptotic pathway due to generation of reactive oxygen species upon light exposure. The nonvitamin complexes 4 and 5 display 3-fold lower photocytotoxicity compared to their VB6 analogues, possibly due to preferential and faster uptake of the vitamin complexes in the cancer cells. Complexes 2 and 3 show significant uptake in the endoplasmic reticulum, while complexes 4 and 5 are distributed throughout the cells without any specific localization pattern.

DNA intercalative 4-butylaminopyrimido4',5':4,5]thieno(2,3-b)quinoline induces cell cycle arrest and apoptosis in leukemia cells

DNA intercalators are one of the interesting groups in cancer chemotherapy. The development of novel anticancer small molecule has gained remarkable interest over the last decade. In this study, we synthesized and investigated the ability of a tetracyclic-condensed quinoline compound, 4-butylaminopyrimido4',5':4,5]thieno(2,3-b)quinoline (BPTQ), to interact with double-stranded DNA and inhibit cancer cell proliferation. Circular dichroism, topological studies, molecular docking, absorbance, and fluorescence spectral titrations were employed to study the interaction of BPTQ with DNA. Cytotoxicity was studied by performing 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) and lactate dehydrogenase (LDH) assay. Further, cell cycle analysis by flow cytometry, annexin V staining, mitochondrial membrane potential assay, DNA fragmentation, and western blot analysis were used to elucidate the mechanism of action of BPTQ at the cellular level. Spectral, topological, and docking studies confirmed that BPTQ is a typical intercalator of DNA. BPTQ induces dose-dependent inhibitory effect on the proliferation of cancer cells by arresting cells at S and G2/M phase. Further, BPTQ activates the mitochondria-mediated apoptosis pathway, as explicated by a decrease in mitochondrial membrane potential, increase in the Bax:Bcl-2 ratio, and activation of caspases. These results confirmed that BPTQ is a DNA intercalative anticancer molecule, which could aid in the development of future cancer therapeutic agents.

Noble metal ion substituted CeO2 catalysts: Electronic interaction between noble metal ions and CeO2 lattice

In last 40 years, CeO2 has been found to play a major role in the area of auto exhaust catalysis due to its unique redox properties. Catalytic activity is enhanced when CeO2 is added to the noble metals supported Al2O3 catalysts. Reason for increase in catalytic activity is due to higher dispersion of noble metals in the form of ions in CeO2. This has led to the idea of substitution of noble metal ions in CeO2 lattice acting as adsorption sites instead of nanocrystalline noble metal particles on CeO2. In this article, a brief review of synthesis, structure and catalytic properties of noble metal ions dispersed on CeO2 resulting in noble metal ionic catalysts (NMIC) like Ce1-xMxO2-delta, Ce1-x-yTixMyO2-delta, Ce1-x-yZrxMyO2-delta, Ce1-x-ySnxMyO2-delta and Ce1-x-yFexMyO2-delta (M = Pt, Pd, Rh and Ru) are presented. Substitution of Ti, Zr, Sn and Fe in CeO2 increases oxygen storage capacities (OSC) due to structural distortion, whereas dispersion of noble metal ions in Ti, Zr, Sn and Fe substituted CeO2 supports increase both OSC and catalytic activities. Electronic interaction between noble metal ions and CeO2 in NMICs responsible for higher OSC and higher catalytic activities is discussed. (C) 2015 Published by Elsevier B.V.

Suspended core-shell Pt-PtOx nanostructure for ultrasensitive hydrogen gas sensor

High sensitivity gas sensors are typically realized using metal catalysts and nanostructured materials, utilizing non-conventional synthesis and processing techniques, incompatible with on-chip integration of sensor arrays. In this work, we report a new device architecture, suspended core-shell Pt-PtOx nanostructure that is fully CMOS-compatible. The device consists of a metal gate core, embedded within a partially suspended semiconductor shell with source and drain contacts in the anchored region. The reduced work function in suspended region, coupled with builtin electric field of metal-semiconductor junction, enables the modulation of drain current, due to room temperature Redox reactions on exposure to gas. The device architecture is validated using Pt-PtO2 suspended nanostructure for sensing H-2 down to 200 ppb under room temperature. By exploiting catalytic activity of PtO2, in conjunction with its p-type semiconducting behavior, we demonstrate about two orders of magnitude improvement in sensitivity and limit of detection, compared to the sensors reported in recent literature. Pt thin film, deposited on SiO2, is lithographically patterned and converted into suspended Pt-PtO2 sensor, in a single step isotropic SiO2 etching. An optimum design space for the sensor is elucidated with the initial Pt film thickness ranging between 10 nm and 30 nm, for low power (< 5 mu W), room temperature operation. (C) 2015 AIP Publishing LLC.

New dimeric carbazole-benzimidazole mixed ligands for the stabilization of human telomeric G-quadruplex DNA and as telomerase inhibitors. A remarkable influence of the spacer

for selectively targeting cancer cells. Herein, we report the design and evolution of a new kind of carbazole-based benzimidazole dimers for their efficient telomerase inhibition activity. Spectroscopic titrations reveal the ligands high affinity toward the G4 DNA with significantly higher selectivity over duplex-DNA. The electrophoretic mobility shift assay shows that the ligands efficiently promote the formation of 04 DNA even at a lower concentration of the stabilizing K+ ions. The TRAP-LIG assay demonstrates the ligand's potential telomerase inhibition activity and also establishes that the activity proceeds via G4 DNA stabilization. An efficient nuclear internalization of the ligands in several common cancer cells (HeLa, HT1080, and A549) also enabled differentiation between normal HFF cells in co-cultures of cancer and normal ones. The ligands induce significant apoptotic response and antiproliferative activity toward cancer cells selectively when compared to the normal cells.