Gulaim A. Seisenbaeva

Drought-Tolerance of Wheat Improved by Rhizosphere Bacteria from Harsh Environments: Enhanced Biomass Production and Reduced Emissions of Stress Volatiles

Water is the key resource limiting world agricultural production. Although an impressive number of research reports have been published on plant drought tolerance enhancement via genetic modifications during the last few years, progress has been slower than expected. We suggest a feasible alternative strategy by application of rhizospheric bacteria coevolved with plant roots in harsh environments over millions of years, and harboring adaptive traits improving plant fitness under biotic and abiotic stresses. We show the effect of bacterial priming on wheat drought stress tolerance enhancement, resulting in up to 78% greater plant biomass and five-fold higher survivorship under severe drought. We monitored emissions of seven stress-related volatiles from bacterially-primed drought-stressed wheat seedlings, and demonstrated that three of these volatiles are likely promising candidates for a rapid non-invasive technique to assess crop drought stress and its mitigation in early phases of stress development. We conclude that gauging stress by elicited volatiles provides an effectual platform for rapid screening of potent bacterial strains and that priming with isolates of rhizospheric bacteria from harsh environments is a promising, novel way to improve plant water use efficiency. These new advancements importantly contribute towards solving food security issues in changing climates.

Chemically triggered biodelivery using metal-organic sol-gel synthesis.

The application of inorganic materials for drug delivery and bioencapsulation has recently attracted the attention of researchers. Silica-based mesoporous monoliths and sol– gel-derived amorphous silica particles have been actively studied for their slow release of adsorbed pharmaceutical agents, while soft silica gels have been demonstrated to act as highly biocompatible matrices for bacterial encapsulation. Silica matrices have even been tested for biodelivery applications, specifically for medical treatments that exploit the delayed liberation of microorganisms able to attack target diseases. In particular, the liberation of viruses from silica gels has been studied for the development of viral gene therapy. The disadvantages of silica gels for such applications are connected with the combination of high porosity and slow biodegradability, which means that the encapsulated viruses may cause an immune rejection before they are released in efficient amounts. Many metal oxides, in particular titanium dioxide, are known to be highly biocompatible, at least when photochemical oxidation processes are prevented. In addition, aluminum oxide gels, produced from inorganic salt precursors and washed to remove excess electrolyte, were demonstrated to be biocompatible hosts for microorganisms. Titania nanotubes have even been investigated as a possible source in the context of slow drug release. Development of titaniabased sol–gel materials for bioencapsulation and controlled drug release has so far been hindered by the high reactivity of the metal–organic sol–gel precursors, titanium alkoxides, which require anhydrous media for the preparation of colloid solutions. We report herein the preparation of biocompatible aqueous titania sols and gels and their application in the encapsulation of microorganisms and pharmaceuticals with the possibility of controlled and chemically and biologically triggered release. Stabilization of metal alkoxide sols is usually achieved by modifying the precursors with chelating organic ligands. This chelation increases the reactivity of the alkoxides in hydrolysis/polycondensation, resulting in facile formation of self-assembled micellar aggregates. These structures, micelles templated by self-assembly of ligands (MTSALs), are covered by residual heteroligands. Commonly applied ligands such as b-diketonates and carboxylates are hydrophobic, which helps in the stabilization of the colloids in organic solvents. We have applied a hydrophilic ligand, triethanolamine, which is highly basic and easily charged (protonated) by the addition of strong acids. The proposed stabilization mechanism for micelles is displayed in Figure 1. In our experiments, solutions of titanium alkoxides

Precursor and solvent effects in the nonhydrolytic synthesis of complex oxide nanoparticles for bioimaging applications by the ether elimination (Bradley) reaction.

Investigation of the solvent and alkoxide precursor effect on the nonhydrolytic sol-gel synthesis of oxide nanoparticles by means of an ether elimination (Bradley) reaction indicates that the best crystallinity of the resulting oxide particles is achieved on application of aprotic ketone solvents, such as acetophenone, and of smallest possible alkoxide groups. The size of the produced primary particles is always about 5 nm caused by intrinsic mechanisms of their formation. The produced particles, possessing the composition of natural highly insoluble minerals, are biocompatible. Optical characteristics of the perovskite complex oxide nanoparticles can easily be controlled through doping with rare earth cations; for example, by Eu(3+). They can be targeted through surface modification by anchoring the directing biomolecules through a phosphate or phosphonate moiety. Testing of the distribution of Eu-doped BaTiO(3) particles, modified with ethylphosphonic acid, demonstrates their facile uptake by the plants with active fluid transport, resulting finally in their enhanced concentration within the cell membranes.

Biomimetic Synthesis of Hierarchically Porous Nanostructured Metal Oxide Microparticles—Potential Scaffolds for Drug Delivery and Catalysis

Hierarchically porous hybrid microparticles, strikingly reminiscent in their structure of the silica skeletons of single-cell algae, diatoms, but composed of titanium dioxide, and the chemically bound amphiphilic amino acids or small proteins can be prepared by a simple one-step biomimetic procedure, using hydrolysis of titanium alkoxides modified by these ligands. The growth of the hierarchical structure results from the conditions mimicking the growth of skeletons in real diatoms--the self-assembly of hydrolysis-generated titanium dioxide nanoparticles, templated by the microemulsion, originating from mixing the hydrocarbon solvent and water on action of amino acids as surfactants. The obtained microsize nanoparticle aggregates possess remarkable chemical and thermal stability and are promising substrates for applications in drug delivery and catalysis. They can be provided with pronounced surface chirality through application of chiral modifying ligands. They display also high selectivity in sorption of phosphorylated biomolecules or medicines as demonstrated by (1)H and (31)P NMR studies and by in vitro modeling using (32)P-marked ATP as a substrate. The release of the adsorbed model compounds in an inert medium is a very slow process directed by desorption kinetics. It is enhanced, however, noticeably in contact with biological fluids modeling those of the tissues suffering inflammation, which makes the produced material highly attractive for application in medical implants. The developed synthetic approach has been applied successfully also for the preparation of analogous hybrid microparticles based on zirconium dioxide or aluminum sesquioxide.

Solution-engineered palladium nanoparticles: model for health effect studies of automotive particulate pollution.

Palladium (Pd) nanoparticles are recognized as components of airborne automotive pollution produced by abrasion of catalyst materials in the car exhaust system. Here we produced dispersions of hydrophilic spherical Pd nanoparticles (Pd-NP) of uniform shape and size (10.4 ± 2.7 nm) in one step by Bradleys reaction (solvothermal decomposition in an alcohol or ketone solvent) as a model particle for experimental studies of the Pd particles in air pollution. The same approach provided mixtures of Pd-NP and nanoparticles of non-redox-active metal oxides, such as Al(2)O(3). Particle aggregation in applied media was studied by DLS and nanoparticle tracking analysis. The putative health effects of the produced Pd nanoparticles and nanocomposite mixtures were evaluated in vitro, using human primary bronchial epithelial cells (PBEC) and a human alveolar carcinoma cell line (A549). Viability of these cells was tracked by vital dye exclusion, and apoptosis was also assessed. In addition, we monitored the release of IL-8 and PGE(2) in response to noncytotoxic doses of the nanoparticles. Our studies demonstrate cellular uptake of Pd nanoparticles only in PBEC, as determined by TEM, with pronounced and dose-dependent effects on cellular secretion of soluble biomarkers in both cell types and a decreased responsiveness of human epithelial cells to the pro-inflammatory cytokine TNF-α. When cells were incubated with higher doses of the Pd nanoparticles, apoptosis induction and caspase activation were apparent in PBEC but not in A549 cells. These studies demonstrate the feasibility of using engineered Pd nanoparticles to assess the health effects of airborne automotive pollution.

Influence of heteroligands on the composition, structure and properties of homo- and heterometallic zirconium alkoxides. Decisive role of thermodynamic factors in their self-assembly

Interaction of the commercial “Zr(OnPr)4” with an excess of iPrOH provides in high yields a new solid crystalline but highly soluble precursor Zr2(μ-OnPr)2(OiPr)6(iPrOH)2 (2). Interaction of 1 eq. of 2 with 1 eq. of Co(acac)2 results in quantitative transformation into a mixture of Co2Zr2(OnPr)4(OiPr)6(acac)2 (3), with a structure representing a fragment of hexagonal packing of metal atoms and alkoxide ligands (typical for derivatives of primary alcohols), and Zr2(OiPr)6(acac)2 (4). Reaction of 1 eq. of homoleptic zirconium isopropoxide, Zr2(OiPr)8(iPrOH)2 (1), with 1 eq. of Co(acac)2 provides a new complex CoZr2(OiPr)8(acac)2 (5) having a linear chain structure (characteristic of sec-alcohol derivatives) in quantitative yield. Microhydrolysis of a mixture of 1.5 eq. of 2 and 1 eq. of Co(acac)2 gave in moderate yield CoZr3O(OnPr)3(OiPr)5(acac)4 (6), with a tetrahedral CoZr3O core characteristic of zirconium sec-oxoalkoxides. Modification of a solution of barium and zirconium isopropoxides in toluene (Ba∶Zr = 1∶1) with 1.5 eq. of Hacac results almost quantitatively in a mixture of insoluble Ba(acac)2 and soluble and volatile heterometallic alkoxide Ba2Zr4(OiPr)18(acac)2 (7). Addition of 2 eq. of Hthd to a mixture of barium and zirconium n-propoxides in toluene (Ba∶Zr = 1∶1) gives highly soluble and volatile complex Ba2Zr2(thd)4(OnPr)8(nPrOH)2 (8). Reaction of the in situ obtained Ba(thd)2 with 0.5 eq. of 2 provided almost quantitatively another highly soluble and volatile precursor Ba2Zr2(thd)4(OnPr)2(OiPr)6 (9). Addition of 2 eq. of Hthd to a mixture of strontium and zirconium isopropoxides in toluene (Sr∶Zr = 1∶1) gives highly soluble complex Sr2Zr2(thd)4(OiPr)8 (10) volatilized on heating via complete decomposition into Sr(thd)2, Zr(thd)2(OiPr)2 and non-volatile products. Bimetallic hydroxo-isopropoxides of strontium and barium, Sr2Zr2(OH)2(OiPr)10(iPrOH)4 (11) and Ba2Zr2(OH)2(OiPr)10(iPrOH)6 (12), have been obtained in good yields via microhydrolysis of solutions of isopropoxides in toluene/isopropanol media. All compounds have been characterized by a variety of spectroscopic techniques, and compounds 1–9 and 11–12 also by X-ray single crystal studies. The principles in construction of zirconium alkoxides – products of thermodynamically controlled molecular self-assembly – and their stability and reactivity are discussed in connection with the sterical role played by the chosen ligands.

The Effect of a Magnetic Field on a RAPET (Reaction under Autogenic Pressure at Elevated Temperature) of MoO(OMe)4: Fabrication of MoO2 Nanoparticles Coated with Carbon or Separated MoO2 and Carbon Particles

In this article, we present results of the RAPET dissociation of MoO(OMe)4 at 700 degrees C in a closed Swagelok cell. The reaction produces molybdenum dioxide nanoparticles (20 nm) coated with carbon (20 nm). We have also carried out the same reaction under an applied magnetic field of 10 T. This reaction yielded different products. It produces a mixture of comparatively larger (50 nm) molybdenum dioxide nanoparticles and separated uncoated carbon particles (20-30 nm).

Cellulose nanofiber–titania nanocomposites as potential drug delivery systems for dermal applications

In this work, new efficient drug delivery systems based on cellulose nanofiber-titania nanocomposites grafted with three different types of model drugs such as diclofenac sodium, penicillamine-D and phosphomycin were successfully synthesized and displayed distinctly different controlled long-term release profiles. Three different methods of medicine introduction were used to show that various interactions between TiO2 and drug molecules could be used to control the kinetics of long-term drug release. All synthesis reactions were carried out in aqueous media. The morphology, chemical structure and properties of the obtained materials were characterized by SEM, TEM and AFM microscopy, nanoparticle tracking analysis, X-ray diffraction, and TGA analysis. According to FT-IR and UV-Vis spectroscopy data, the titania binds to cellulose nanofibers via formation of ester bonds and to drug molecules via formation of surface complexes. The drug release kinetics was studied in vitro for diclofenac sodium and penicillamine-D spectrophotometrically and for phosphomycin using a radio-labeling analysis with 33P-marked ATP as a model phosphate-anchored biomolecule. The results demonstrated that the obtained nanocomposites could potentially be applied in transdermal drug delivery for anesthetics, analgesics and antibiotics.

Visualization of custom-tailored iron oxide nanoparticles chemistry, uptake, and toxicity

Nanoparticles of iron oxide generated by wearing of vehicles have been modelled with a tailored solution of size-uniform engineered magnetite particles produced by the Bradley reaction, a solvothermal metal-organic approach rendering hydrophilic particles. The latter does not bear any pronounced surface charge in analogy with that originating from anthropogenic sources in the environment. Physicochemical properties of the nanoparticles were thoroughly characterized by a wide range of methods, including XPD, TEM, SEM, DLS and spectroscopic techniques. The magnetite nanoparticles were found to be sensitive for transformation into maghemite under ambient conditions. This process was clearly revealed by Raman spectroscopy for high surface energy magnetite particles containing minor impurities of the hydromaghemite phase and was followed by quantitative measurements with EXAFS spectroscopy. In order to assess the toxicological effects of the produced nanoparticles in humans, with and without surface modification with ATP (a model of bio-corona formed in alveolar liquid), a pathway of potential uptake and clearance was modelled with a sequence of in vitro studies using A549 lung epithelial cells, lymphocyte 221-B cells, and 293T embryonal kidney cells, respectively. Raman microscopy unambiguously showed that magnetite nanoparticles are internalized within the A549 cells after 24 h co-incubation, and that the ATP ligand is retained on the nanoparticles throughout the uptake process. The toxicity of the nanoparticles was estimated using confocal fluorescence microscopy and indicated no principal difference for unmodified and modified particles, but revealed considerably different biochemical responses. The IL-8 cytokine response was found to be significantly lower for the magnetite nanoparticles compared to TiO(2), while an enhancement of ROS was observed, which was further increased for the ATP-modified nanoparticles, implicating involvement of the ATP signalling pathway in the epithelium.

Synthesis, X-ray single crystal and magnetic study of new heteroleptic late transition metal alkoxides with tetranuclear square planar metal core, Co4Cl2(OC2H4OEt)6, Co4(OMe)2(acac)6(MeOH)2 and Zn4(OMe)2(acac)6(C7H8)

Abstract Interaction of 4 equiv. CoCl2 with 6 equiv. of NaOC2H4OEt in toluene/HOC2H4OEt medium provided Co4Cl2(OC2H4OEt)6 (1) with practically quantitative yield. Reaction of Co(acac)2 with Ti(OMe)4 in 1:1 ratio in toluene gave Co4(OMe)2(acac)6(MeOH)2 (2) with moderate yields. The same reaction for Zn(acac)2 resulted in formation of Zn4(OMe)2(acac)6(C7H8) (3). The structures of 1–3 contain planar tetranuclear cores of M4(μ3-OR)2(μ2-OR)4 type ([Ti(OMe)4]4 type structure), where the metal atoms are pentacoordinated in 1, hexacoordinated in 2, and both penta- and hexacoordinated in 3. The magnetic measurements have revealed competing ferromagnetic and antiferromagnetic interactions between the 4 Co(II) atoms in 1, but only ferromagnetic in 2.