Combination of single walled carbon nanotubes/graphene oxide with paclitaxel: a reactive oxygen species mediated synergism for treatment of lung cancer

Heterogeneity in tumors has led to the development of combination therapies that enable enhanced cell death. Previously explored combination therapies mostly involved the use of bioactive molecules. In this work, we explored a non-conventional strategy of using carbon nanostructures (CNs) single walled carbon nanotube (SWNT) and graphene oxide (GO)] for potentiating the efficacy of a bioactive molecule paclitaxel (Tx)] for the treatment of lung cancer. The results demonstrated enhanced cell death following combination treatment of SWNT/GO and Tx indicating a synergistic effect. In addition, synergism was abrogated in the presence of an anti-oxidant, N-acetyl cysteine (NAC), and was therefore shown to be reactive oxygen species (ROS) dependent. It was further demonstrated using bromodeoxyuridine (BrdU) incorporation assay that treatment with CNs was associated with enhanced mitogen associated protein kinase (MAPK) activation that was ROS mediated. Hence, these results for the first time demonstrated the potential of SWNT/GO as co-therapeutic agents with Tx for the treatment of lung cancer.

Dielectric and electrical conductivity properties of multi-stage spark plasma sintered HA-CaTiO3 composites and comparison with conventionally sintered materials

One of the different issues limiting the wider application of monolithic hydroxyapatite (HA) as an ideal bone replacement material is the lack of reasonably good electrical transport properties. The comprehensive electrical property characterization to evaluate the efficacy of processing parameters in achieving the desired combination of electroactive properties is considered as an important aspect in the development of HA-based bioactive material. In this perspective, the present work reports the temperature (RT-200 degrees C) and frequency (100 Hz-1 MHz) dependent dielectric properties and AC conductivity for a range of HA-CaTiO3 (HA-CT) composites, densified using both conventional pressureless sintering in air as well as spark plasma sintering in vacuum. Importantly, the AC conductivity of spark plasma sintered ceramics similar to upto 10(-5) (Omega cm)(-1)] are found to be considerably higher than the corresponding pressureless sintered ceramics similar to upto 10(-8) (Omega cm)(-1)]. Overall, the results indicate the processing route dependent functional properties of HA-CaTiO3 composites as well as related advantages of spark plasma sintering route. (C) 2013 Elsevier Ltd. All rights reserved.

Facial selectivities in the nucleophilic additions of 2,3-unsaturated 3-arylsulfinyl pyranosides

2,3-Unsaturated 3-arylsulfinyl pyranosides undergo nucleophilic additions at C-2, with facial selectivities depending on the nucleophile and the substituent on sulfinyl sulfur. The reactions of such sugar vinyl sulfoxides lead to the addition of nucleophile preferring an axial orientation at C-2, with concomitant formation of an allylic bond at C-3 to C-4. This trend in the addition pattern is observed for primary amine, carbon and sulfur nucleophiles, whereas secondary amines prefer an equatorial addition at C-2. The effect of p-tolylthio-versus (p-isopropylphenyl)thio vinyl sulfoxide is that the equatorial nucleophilic addition is preferred even more with the latter vinyl sulfoxide. (C) 2013 Published by Elsevier Ltd.

Versatility of azide in serendipitous assembly of Copper(II) Magnetic Polyclusters

Engineering at the molecular level is one of the most exciting new developments for the generation of functional materials. However, the concept of designing polynuclear extended structures from bottom up is still not mature. Although progress has been made with secondary building units (SBUs) in metal organic frameworks (MOFs), the control seems to be just an illusion when it comes to bridging ligands such as the azide ion. When we say that the azido ligand is versatile in its bridging capabilities, what we mean is that it would be difficult to predict or control its bridging properties. However, this kind of serendipity is not always bad news. For example, scientists have shown that the azido ligand can mediate magnetic exchanges between paramagnetic metals in a predictable fashion (usually depending upon the bonding geometries). Therefore, it is a well-respected ligand in polynuclear assemblies. Serendipitous assemblies offer new magnetic structures that we may not otherwise even think about synthesizing. The azido ligand forms a variety of complexes with copper(II) using different blocking amines or pyridine based ligands. Its structural nature changes upon changing the substitution on amine, as well as the amount of blocking ligand. In principle, if we take any of these complexes and provide more coordination sites to the bridging azido ligands by removing a fraction of the blocking ligands, we can get new complexes with intricate structural networks and therefore different magnetic properties with the same components as used for the parent complex. In this Account, we mainly discuss the development of a number of new topological and magnetic exchange systems synthesized using this concept. Not all of these new complexes can be grouped according to their basic building structures or even by the ratio of the metal to blocking ligand. Therefore, we divided the discussion by the nuclearity of the basic building structures. Some of the complexes with the same nuclearities have very similar or even almost identical basic structures. However, the way these building units are joined together (by the azido bridges) to form the overall extended structures differ almost in every case. The complexes having the Cu-6 core are particularly interesting from a structural point of view. Although they have almost identical basic structures, some of them are extended in three dimensions, but two of them are extended in two dimensions by two different bridging networks. In the complexes having linear Cu-4 basic units, we find that using similar ligands does not always give the same bridging networks even within the basic building structures. These complexes have also enriched the field of molecular magnetism. One of the complexes with a Cu-3 building unit has provided us with the opportunity to study the competing behavior of two different kinds of magnetic exchange mechanism (ferromagnetic and antiferromagnetic) acting simultaneously between two metal ions. Through density functional theory calculations, we showed how they work independently and their additive nature to produce the overall effect. The exciting methodology for the generation of copper(II) polyclusters presented in this Account will provide the opportunity to explore analogous serendipitous assembly of diverse structures with interesting magnetic behavior using other transition metal ions having more than one unpaired electrons.

Efficient Dendrimer-DNA Complexation and Gene Delivery Vector Properties of Nitrogen-Core Poly(propyl ether imine) Dendrimer in Mammalian Cells

Dendrimers as vectors for gene delivery were established, primarily by utilizing few prominent dendrimer types so far. We report herein studies of DNA complexation efficacies and gene delivery vector properties of a nitrogen-core poly(propyl ether imine) (PETIM) dendrimer, constituted with 22 tertiary amine internal branches and 24 primary amines at the periphery. The interaction of the dendrimer with pEGFPDNA was evaluated through UV-vis, circular dichroism (CD) spectral studies, ethidium bromide fluorescence emission quenching, thermal melting, and gel retardation assays, from which most changes to DNA structure during complexation was found to occur at a weight ratio of dendrimer:DNA similar to 2:1. The zeta potential measurements further confirmed this stoichiometry at electroneutrality. The structure of a DNA oligomer upon dendrimer complexation was simulated through molecular modeling and the simulation showed that the dendrimer enfolded DNA oligomer along both major and minor grooves, without causing DNA deformation, in 1:1 and 2:1 dendrimer-to-DNA complexes. Atomic force microscopy (AFM) studies on dendrimer-pEGFP DNA complex showed an increase in the average z-height as a result of dendrimers decorating the DNA, without causing a distortion of the DNA structure. Cytotoxicity studies involving five different mammalian cell lines, using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-tetrazolium bromide] (MTT) assay, reveal the dendrimer toxicity profile (IC50) values of similar to 400-1000 mu g mL(-1), depending on the cell line tested. Quantitative estimation, using luciferase assay, showed that the gene transfection was at least 100 times higher when compared to poly(ethylene imine) branched polymer, having similar number of cationic sites as the dendrimer. The present study establishes the physicochemical behavior of new nitrogen-core PETIM dendrimer-DNA complexes, their lower toxicities, and efficient gene delivery vector properties.

Isolation and characterization of biofumigant from leaves of Lantana camara for control of stored grain insect pests

Due to environmental concerns, health hazards to man and the evolution of resistance in insect pests, there have been constant efforts to discover newer insecticides both from natural sources and by chemical synthesis. Natural sources for novel molecules hold promise in view of their eco-friendly nature, selectivity and mammalian safety. We have isolated one natural bioactive molecule from the leaves of Lantana camara named Coumaran, based on various physical-chemical and spectroscopic techniques (IR, H-1 NMR, C-13 NMR and MS). Coumaran is highly toxic and very low concentration is needed for control of stored product insects. This molecule has potent grain protectant potential and caused significant reduction in F1 progeny of all the three species in the treated grain and the progeny was completely suppressed at 30 mu g/l. The differences in germination between the control and treated grains were not significant. The lack of any adverse effect of Coumaran on the seed germination is highly desirable for a grain protectant, becoming a potential source of biofumigant for economical and environmentally friendly pest control strategies against stored grain pests during storage of grains or pulses. (C) 2013 Elsevier B.V. All rights reserved.

Titanium promoted reduction of imines with Grignards, silanes, and zinc: identification of a new mechanism with silanes

Aldimines react with reducing agents, such as Grignards, phenylsilane or zinc in the presence of titanium(IV) isopropoxide to form amines and reductively coupled imines (diamines). Using deuterium labeled reagents, the mechanism of reduction to form amines is described. Reducing agents, such as the Grignard and zinc result in the formation of low valent titanium (LVT), which in turn reduces the imine. On the other hand, phenylsilane reacts by a distinctly different mechanism and where a hydrogen atom from silicon is directly transferred to the titanium coordinated imine. (c) 2014 Elsevier Ltd. All rights reserved.

Mechanistic studies on the diazo transfer reaction

The mechanism of the diazo transfer reaction which converts amines to azides has been studied with labeled amino acids and labeled imidazole-l-sulfonyl azides. Retention of amine nitrogen in the amine, and transfer of the two terminal nitrogen atoms of the imidazole-l-sulfonyl azide to the product, were unambiguously established. (C) 2014 Elsevier Ltd. All rights reserved.

Hydrogen-Bond-Driven Controlled Molecular Marriage in Covalent Cages

A supramolecular approach that uses hydrogen-bonding interaction as a driving force to accomplish exceptional self-sorting in the formation of imine-based covalent organic cages is discussed. Utilizing the dynamic covalent chemistry approach from three geometrically similar dialdehydes (A, B, and D) and the flexible triamine tris(2-aminoethyl)amine (X), three new 3+2] self-assembled nanoscopic organic cages have been synthesized and fully characterized by various techniques. When a complex mixture of the dialdehydes and triamine X was subjected to reaction, it was found that only dialdehyde B (which has OH groups for H-bonding) reacted to form the corresponding cage B3X2 selectively. Surprisingly, the same reaction in the absence of aldehyde B yielded a mixture of products. Theoretical and experimental investigations are in complete agreement that the presence of the hydroxyl moiety adjacent to the aldehyde functionality in B is responsible for the selective formation of cage B3X2 from a complex reaction mixture. This spectacular selection was further analyzed by transforming a nonpreferred (non-hydroxy) cage into a preferred (hydroxy) cage B3X2 by treating the former with aldehyde B. The role of the H-bond in partner selection in a mixture of two dialdehydes and two amines has also been established. Moreover, an example of unconventional imine bond metathesis in organic cage-to-cage transformation is reported.

Evaluation of hexane and ethyl acetate extracts of the sponge Jaspis diastra collected from Mauritius Waters on HeLa cells

Objectives Based on previous screening results, the cytotoxic effect of the hexane (JDH) and ethyl acetate extracts (JDE) of the marine sponge Jaspis diastra were evaluated on HeLa cells and the present study aimed at determining their possible mechanism of cell death. Methods Nuclear staining, membrane potential change, flow cytometry analysis of cell cycle distribution and annexin V staining were undertaken to investigate the effects of JDE and JDH. Electrospray ionization mass spectrometry (ESI-MS) and nuclear magnetic resonance were used to characterize an isolated bioactive molecule. Key findings JDE displayed an IC50 25 times more significant than the JDH. Flow cytometry analysis revealed JDE induced apoptosis in HeLa cells accompanied by the collapse of mitochondrial membrane potential. Fractionation of JDE resulted in the isolation of the known cytotoxic cyclodepsipeptide, Jaspamide. Conclusions Taking our results together suggest that JDE can be valuable for the development of anticancer drugs, especially for cervical cancer. Further investigations are currently in progress with the aim to determine and isolate other bioactive compounds from this extract.

Characterisation and bioactivity of oosporein produced by endophytic fungus Cochliobolus kusanoi isolated from Nerium oleander L.

Bioactive compounds comprising secondary metabolites produced by endophytic fungi have wide applications in pharmacology and agriculture. Isolation, characterisation and evaluation of biological activities of secondary metabolites were carried out from Cochliobolus kusanoi an endophytic fungus of Nerium oleander L. The fungus was identified based on 18S rDNA sequence analysis. There are no reports available on the compounds of C. kusanoi hence, antimicrobial metabolite produced by this fungus was extracted and purified by fractionation using hexane, diethyl ether, dichloromethane, ethyl acetate and methanol. Out of all the solvent fractions, the methanol fraction exhibited better antimicrobial activity which was further purified and characterised as oosporein. Oosporein from C. kusanoi exhibited broad spectrum in vitro antimicrobial, antioxidant and cytotoxic activities. The characterisation and antioxidant activity of oosporein from C. kusanoi are reported for the first time.

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.

Anticancer Effects of Brominated Indole Alkaloid Eudistomin H from Marine Ascidian Eudistoma viride Against Cervical Cancer Cells (HeLa)

Marine invertebrates called ascidians are prolific producers of bioactive substances. The ascidian Eudistoma viride, distributed along the Southeast coast of India, was investigated for its in vitro cytotoxic activity against human cervical carcinoma (HeLa) cells by the MTT assay. The crude methanolic extract of E. viride, with an IC50 of 53 mu g/ml, was dose-dependently cytotoxic. It was more potent at 100 mu g/ml than cyclohexamide (1 mu g/ml), reducing cell viability to 9.2%. Among nine fractions separated by chromatography, ECF-8 exhibited prominent cytoxic activity at 10 mu g/ml. The HPLC fraction EHF-21 of ECF-8 was remarkably dose- and time-dependently cytotoxic, with 39.8% viable cells at 1 mu g/ml compared to 51% in cyclohexamide-treated cells at the same concentration; the IC50 was 0.49,mu g/ml. Hoechst staining of HeLa cells treated with EHF-2I at 0.5 mu g/ml revealed apoptotic events such an cell shrinkage, membrane blebbing, chromatin condensation and formation of apoptotic bodies. Cell size and granularity study showed changes in light scatter, indicating the characteristic feature of cells dying by apoptosis. The cell-cycle analysis of HeLa cells treated with fraction EHF-21 at 1 mu g/ml showed the marked arrest of cells in G(0)/G(1), S and G(2)/M phases and an increase in the sub G(0)/G(1) population indicated an increase in the apoptotic cell population. The statistical analysis of the sub-G(1) region showed a dose-dependent induction of apoptosis. DNA fragmentation was also observed in HeLa cells treated with EHF-21. The active EHF-2I fraction, a brominated indole alkaloid Eudistomin H, led to apoptotic death of HeLa cells.

Measuring Glutathione Redox Potential of HIV-1-infected Macrophages

Redox signaling plays a crucial role in the pathogenesis of human immunodeficiency virus type-1 (HIV-1). The majority of HIV redox research relies on measuring redox stress using invasive technologies, which are unreliable and do not provide information about the contributions of subcellular compartments. A major technological leap emerges from the development of genetically encoded redox-sensitive green fluorescent proteins (roGFPs), which provide sensitive and compartment-specific insights into redox homeostasis. Here, we exploited a roGFP-based specific bioprobe of glutathione redox potential (E-GSH; Grx1-roGFP2) and measured subcellular changes in E-GSH during various phases of HIV-1 infection using U1 monocytic cells (latently infected U937 cells with HIV-1). We show that although U937 and U1 cells demonstrate significantly reduced cytosolic and mitochondrial E-GSH (approximately -310 mV), active viral replication induces substantial oxidative stress (E-GSH more than -240 mV). Furthermore, exposure to a physiologically relevant oxidant, hydrogen peroxide (H2O2), induces significant deviations in subcellular E-GSH between U937 and U1, which distinctly modulates susceptibility to apoptosis. Using Grx1-roGFP2, we demonstrate that a marginal increase of about similar to 25 mV in E-GSH is sufficient to switch HIV-1 from latency to reactivation, raising the possibility of purging HIV-1 by redox modulators without triggering detrimental changes in cellular physiology. Importantly, we show that bioactive lipids synthesized by clinical drug-resistant isolates of Mycobacterium tuberculosis reactivate HIV-1 through modulation of intracellular E-GSH. Finally, the expression analysis of U1 and patient peripheral blood mononuclear cells demonstrated a major recalibration of cellular redox homeostatic pathways during persistence and active replication of HIV.

Poly(alkylene itaconate)s - an interesting class of polyesters with periodically located exo-chain double bonds susceptible to Michael addition

Itaconic acid is a bio-sourced dicarboxylic acid that carries a double bond; although several reports have dealt with the radical-initiated chain polymerization of dialkyl itaconates, only a few studies have utilized it as a di-acid monomer to prepare polyesters. In this study, we demonstrate that dibutyl itaconate can be melt-condensed with aliphatic diols to generate unsaturated polyesters; importantly, we show that the double bonds remain unaffected during the melt polymerization. A particularly useful attribute of these polyesters is that the exo-chain double bonds are conjugated to the ester carbonyl and, therefore, can serve as excellent Michael acceptors. A variety of organic thiols, such as alkane thiols, MPEG thiol, thioglycerol, derivatized cysteine etc., were shown to quantitatively Michael-add to the exo-chain double bonds and generate interesting functionalized polyesters. Similarly, organic amines, such as N-methyl-benzylamine, diallyl amine and proline, also add across the double bond; thus, these poly(alkylene itaconate)s could serve as potentially bio-benign polyesters that could be quantitatively transformed into a variety of interesting and potentially useful functionalized polymers.