Showing papers by "Vadim G. Kessler published in 2017"

Maghemite Nanoparticles Acts as Nanozymes, Improving Growth and Abiotic Stress Tolerance in Brassica napus

Abstract: Yttrium doping-stabilized γ-Fe2O3 nanoparticles were studied for its potential to serve as a plant fertilizer and, through enzymatic activity, support drought stress management. Levels of both hydr ...

Cytoprotective Encapsulation of Individual Jurkat T Cells within Durable TiO2 Shells for T-Cell Therapy

Abstract: Lymphocytes, such as T cells and natural killer (NK) cells, have therapeutic promises in adoptive cell transfer (ACT) therapy, where the cells are activated and expanded in vitro, and then infused into a patient. However, the in vitro preservation of labile lymphocytes during transfer, manipulation, and storage has been one of the bottlenecks in the development and commercialization of therapeutic lymphocytes. Herein, we suggest a "cell-in-shell" (a.k.a. artificial spore) strategy to enhance the cell viability in the practical settings, while maintaining biological activities for therapeutic efficacy. A durable titanium oxide (TiO2) shell is formed on individual Jurkat T cells, and the CD3 and other antigens on cell surfaces remain accessible to the antibodies. Interleukin-2 (IL-2) secretion is also not hampered by the shell formation. This work suggests a chemical toolbox for effectively preserving lymphocytes in vitro and developing the lymphocyte-based cancer immunotherapy.

Dispersion of TiO2 nanoparticles improves burn wound healing and tissue regeneration through specific interaction with blood serum proteins

Abstract: Burn wounds are one of the most important causes of mortality and especially morbidity around the world. Burn wound healing and skin tissue regeneration remain thus one of the most important challenges facing the mankind. In the present study we have addressed this challenge, applying a solution-stabilized dispersion TiO2 nanoparticles, hypothesizing that their ability to adsorb proteins will render them a strong capacity in inducing body fluid coagulation and create a protective hybrid material coating. The in vitro study of interaction between human blood and titania resulted at enhanced TiO2 concentrations in formation of rather dense gel composite materials and even at lower content revealed specific adsorption pattern initiating the cascade response, promising to facilitate the regrowth of the skin. The subsequent in vivo study of the healing of burn wounds in rats demonstrated formation of a strongly adherent crust of a nanocomposite, preventing infection and inflammation with quicker reduction of wound area compared to untreated control. The most important result in applying the TiO2 dispersion was the apparently improved regeneration of damaged tissues with appreciable decrease in scar formation and skin color anomalies.

Nanoscale insights into doping behavior, particle size and surface effects in trivalent metal doped SnO 2

Abstract: Despite considerable research, the location of an aliovalent dopant into SnO2 nanoparticles is far to be clarified. The aim of the present study on trivalent lanthanide doped SnO2 is to differentiate between substitutional versus interstitial and surface versus bulk doping, delineate the bulk and surface defects induced by doping and establish an intrinsic dopant distribution. We evidence for the first time a complex distribution of intrinsic nature composed of substitutional isolated, substitutional associates with defects as well as surface centers. Such multi-modal distribution is revealed for Eu and Sm, while Pr, Tb and Dy appear to be distributed mostly on the SnO2 surface. Like the previously reported case of Eu, Sm displays a long-lived luminescence decaying in the hundreds of ms scale which is likely related to a selective interaction between the traps and the substitutional isolated center. Analyzing the time-gated luminescence, we conclude that the local lattice environment of the lattice Sn is not affected by the particle size, being remarkably similar in the ~2 and 20 nm particles. The photocatalytic measurements employed as a probe tool confirm the conclusions from the luminescence measurements concerning the nature of defects and the temperature induced migration of lanthanide dopants.

Development of Combining of Human Bronchial Mucosa Models with XposeALI® for Exposure of Air Pollution Nanoparticles.

Abstract: Background Exposure to agents via inhalation is of great concerns both in workplace environment and in the daily contact with particles in the ambient air. Reliable human airway exposure systems will most likely replace animal experiment in future toxicity assessment studies of inhaled agents. Methods In this study, we successfully established a combination of an exposure system (XposeALI) with 3D models mimicking both healthy and chronic bronchitis-like mucosa by co-culturing human primary bronchial epithelial cells (PBEC) and fibroblast at air-liquid interface (ALI). Light-, confocal microscopy, scanning- and transmission electron microscopy, transepithelial electrical resistance (TEER) measurement and RT-PCR were performed to identify how the PBEC differentiated under ALI culture condition. Both models were exposed to palladium (Pd) nanoparticles which sized 6–10 nm, analogous to those released from modern car catalysts, at three different concentrations utilizing the XposeALI module of the PreciseInhale® exposure system. Results Exposing the 3D models to Pd nanoparticles induced increased secretion of IL-8, yet the chronic bronchitis-like model released significantly more IL-8 than the normal model. The levels of IL-8 in basal medium (BM) and apical lavage medium (AM) were in the same ranges, but the secretion of MMP-9 was significantly higher in the AM compared to the BM. Conclusion This combination of relevant human bronchial mucosa models and sophisticated exposure system can mimic in vivo conditions and serve as a useful alternative animal testing tool when studying adverse effects in humans exposed to aerosols, air pollutants or particles in an occupational setting.

Toward Molecular Recognition of REEs: Comparative Analysis of Hybrid Nanoadsorbents with the Different Complexonate Ligands EDTA, DTPA, and TTHA.

Abstract: Highly efficient tailored SiO2-based nanoadsorbents were synthesized for the selective extraction of rare-earth elements (REEs). Three different complexonates (EDTA, DTPA, and TTHA) were investigated in terms of uptake capacity and selectivity, showing capacities of up to 300 mg of RE3+/g and distinct preferential trends depending on the complexonate. EDTA-functionalized nanoadsorbents showed higher uptake for Dy3+, DTPA-functionalized ones for Nd3+, and TTHA-functionalized ones for La3+. The selectivity was even more pronounced in desorption at pH 3, with separation factors of up to 76 in ternary mixtures. A broad comparative study of single-crystal structures of the complexes between REE and the nongrafted complexonates at different pHs led to a molecular understanding of their individual modes of action. EDTA-derived nanoadsorbents combine concerted action and chelation, whereas the latter is the preferential coordination mechanism for DTPA- and TTHA-derived nanoadsorbents. These different mechanisms r...

Sol-Gel Derived Adsorbents with Enzymatic and Complexonate Functions for Complex Water Remediation

Abstract: Sol-gel technology is a versatile tool for preparation of complex silica-based materials with targeting functions for use as adsorbents in water purification. Most efficient removal of organic pollutants is achieved by using enzymatic reagents grafted on nano-carriers. However, enzymes are easily deactivated in the presence of heavy metal cations. In this work, we avoided inactivation of immobilized urease by Cu (II) and Cd (II) ions using magnetic nanoparticles provided with additional complexonate (diethylene triamine pentaacetic acid or DTPA) functions. Obtained nanomaterials were characterized by Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), and scanning electron microscopy (SEM). According to TGA, the obtained Fe₃O₄/SiO₂-NH₂-DTPA nanoadsorbents contained up to 0.401 mmol/g of DTPA groups. In the concentration range Ceq = 0-50 mmol/L, maximum adsorption capacities towards Cu (II) and Cd (II) ions were 1.1 mmol/g and 1.7 mmol/g, respectively. Langmuir adsorption model fits experimental data in concentration range Ceq = 0-10 mmol/L. The adsorption mechanisms have been evaluated for both of cations. Crosslinking of 5 wt % of immobilized urease with glutaraldehyde prevented the loss of the enzyme in repeated use of the adsorbent and improved the stability of the enzymatic function leading to unchanged activity in at least 18 cycles. Crosslinking of 10 wt % urease on the surface of the particles allowed a decrease in urea concentration in 20 mmol/L model solutions to 2 mmol/L in up to 10 consequent decomposition cycles. Due to the presence of DTPA groups, Cu2+ ions in concentration 1 µmol/L did not significantly affect the urease activity. Obtained magnetic Fe₃O₄/SiO₂-NH₂-DTPA-Urease nanocomposite sorbents revealed a high potential for urease decomposition, even in presence of heavy metal ions.

Mixed-Ligand Titanium “Oxo Clusters”: Structural Insights into the Formation and Binding of Organic Molecules and Transformation into Oxide Nanostructures on Hydrolysis and Thermolysis

Abstract: We present the structure of a new tetranuclear titanium oxo complex containing the antibacterial agent triclosan. This provides a good model for the interaction between triclosan and titania, which may be used for drug-delivery applications. The antibacterial activity of the hydrolyzed complex against Staphylococcus aureus is investigated. Thereafter, we use the obtained titanium oxo complex to demonstrate its susceptibility towards hydrolysis, contrary to the widespread belief that titanium oxo complexes are water-stable, and demonstrate that it transforms into titania (anatase) on contact with water. Both hydrolysis and thermolysis of the complex yield titania particles, of very uniform size and shape, that connect into 3D nanostructures; this is of interest for practical applications.

Tailoring bifunctional hybrid organic–inorganic nanoadsorbents by the choice of functional layer composition probed by adsorption of Cu2+ ions

Abstract: Spherical silica particles with bifunctional (≡Si(CH2)3NH2/≡SiCH3, ≡Si(CH2)3NH2/≡Si(CH2)2(CF2)5CF3) surface layers were produced by a one-step approach using a modified Stober method in three-component alkoxysilane systems, resulting in greatly increased contents of functional components. The content of functional groups and thermal stability of the surface layers were analyzed by diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy, and 13C and 29Si solid-state NMR spectroscopy revealing their composition and organization. The fine chemical structure of the surface in the produced hybrid adsorbent particles and the ligand distribution were further investigated by electron paramagnetic resonance (EPR) and electron spectroscopy of diffuse reflectance (ESDR) spectroscopy using Cu2+ ion coordination as a probe. The composition and structure of the emerging surface complexes were determined and used to provide an insight into the molecular structure of the surfaces. It was demonstrated that the introduction of short hydrophobic (methyl) groups improves the kinetic characteristics of the samples during the sorption of copper(II) ions and promotes fixation of aminopropyl groups on the surface of silica microspheres. The introduction of long hydrophobic (perfluoroctyl) groups changes the nature of the surface, where they are arranged in alternately hydrophobic/hydrophilic patches. This makes the aminopropyl groups huddled and less active in the sorption of metal cations. The size and aggregation/morphology of obtained particles was optimized controlling the synthesis conditions, such as concentrations of reactants, basicity of the medium, and the process temperature.

Mesoporous Tantalum Oxide Photocatalyst: Structure and Activity Evaluation

Abstract: Mesoporous nanostructured pure tantalum pentoxide and Eu-doped Ta2O5 were produced by facile and reproducible one-pot procedure not involving structure directing agents. The as-produced material is poorly crystalline and catalytically inactive. Photoluminescence behavior of the doped oxide indicates that it is formed by quick nucleation of pure Ta2O5, leaving the Eu-dopant only on the surface of the formed material. Further thermal treatment leads to crystallization and structural transformation as revealed by in situ X-Ray Diffraction (XRD) and Rietveld refinement used to identify and quantify the emerging phases as well as Diffuse Reflectance UV-vis Spectroscopy (DR-UV-Vis) and Raman Spectroscopy studies. The thermally induced transformation results in generation of surface oxygen vacancies that provide the material with pronounced photocatalytic activity in selective oxidation of aromatic amine compounds. The processes of generation and curing of the vacancies have been followed and quantified by temperature programmed oxidation and reduction and photoluminescence studies, offering in depth insight into the reaction mechanism.

Unusual seeding mechanism for enhanced performance in solid-phase magnetic extraction of Rare Earth Elements.

Abstract: Due to the increasing demand of Rare Earth Elements (REE or RE), new and more efficient techniques for their extraction are necessary, suitable for both mining and recycling processes. Current techniques such as solvent extraction or solid adsorbents entail drawbacks such as using big volumes of harmful solvents or limited capacity. Hybrid nanoadsorbents based on SiO2 and highly stable γ-Fe2O3-SiO2 nanoparticles, proved recently to be very attractive for adsorption of REE, yet not being the absolute key to solve the problem. In the present work, we introduce a highly appealing new approach in which the nanoparticles, rather than behaving as adsorbent materials, perform as inducers of crystallization for the REE in the form of hydroxides, allowing their facile and practically total removal from solution. This induced crystallization is achieved by tuning the pH, offering an uptake efficiency more than 20 times higher than previously reported (up to 900 mg RE3+/g vs. 40 mg RE3+/g). The obtained phases were characterized by SEM-EDS, TEM, STEM and EFTEM and 13C and 29Si solid state NMR. Magnetic studies showed that the materials possessed enough magnetic properties to be easily removed by a magnet, opening ways for an efficient and industrially applicable separation technique.

Cu(II) frameworks from a “mixed-ligand” approach

Abstract: Employment of di-2-pyridyl ketone and poly-carboxylates in CuII chemistry afforded four complex hydrogen-bonded frameworks, one one-dimensional (1D), one 2D and three 3D coordination polymers. Di-2-pyridyl ketone underwent several metal-assisted transformations to yield three CuII structural units which, in combination with the poly-carboxylate anions of the trimesic, isophthalic, 5-hydroxy-isophthalic and pyromellitic acids, provided access to extended frameworks by dative or hydrogen bonds. All nine complex frameworks were realized in terms of their topological analysis. The 3D and the 2D polymers consisted of [Cu2] dimers and were found to be dominated by ferromagnetic interactions. The origin of the ferromagnetic coupling was attributed to the counter complementarity of the simultaneous alkoxo/syn,syn-carboxylate bridges within the dimers.

Group III quinaldates: synthesis, structure and photoluminescence

Abstract: The reactions of Al(III), Ga(III) and In(III) nitrates with 2-quinaldic acid (qaH) afforded [Al2(OH)2(qa)4]·2H2O (1), [Ga(qa)2(H2O)2]NO3 (2) and [In(qa)2(NO3)(H2O)] (3), respectively, in high yields. The crystal structures of 1, 2 and 3 have been determined by single-crystal X-ray crystallography. The structure of 1 features a di-hydroxo bridged [Al2(μ-OH)2]4+ dimer in which each Al(III) is further ligated by two bidentate chelate qa− ligands. Complexes 2 and 3 are mononuclear with the M(III) ions in octahedral environments surrounded by two bidentate chelate qa− and two H2O in 2 or one H2O and a terminal NO3− in 3. Characteristic IR as well as thermal analysis and solid-state fluorescence are discussed.

Separation of rare earth elements from other elements

Abstract: A process for separating rare earth elements (REE) from Ca, Mg and other non-REE elements comprises raising the pH of an acidic aqueous solution of REE to pH 8 to pH 11; adding nano- or micro (NoM) particles having a silica or titanium oxide surface; agitating the suspension for 6 h to 48 h to provide for adherent crystallization of REE hydroxide on the particles; separating the particles from the solution; releasing REE by treatment with aqueous acid to form an aqueous solution of REE salt; separating them from the aqueous solution of REE salt formed. The acidic aqueous solution comprising REE is preferably provided by leaching of an REE mineral with aqueous acid; adding a base to bring the pH to from pH 4.0 to pH 6.5; separating precipitated non-REE hydroxide from the solution.