Ivan Jirka

On the role of Nb-related sites of an oxidized β-TiNb alloy surface in its interaction with osteoblast-like MG-63 cells.

β-Stabilized titanium (Ti) alloys containing non-toxic elements, particularly niobium (Nb), are promising materials for the construction of bone implants. Their biocompatibility can be further increased by oxidation of their surface. Therefore, in this study, the adhesion, growth and viability of human osteoblast-like MG 63 cells in cultures on oxidized surfaces of a β-TiNb alloy were investigated and compared with the cell behavior on thermally oxidized Ti, i.e. a metal commonly used for constructing bone implants. Four experimental groups of samples were prepared: Ti or TiNb samples annealed to 600 °C for 60 min in a stream of dry air, and Ti and TiNb samples treated in Piranha solution prior to annealing. We found that on all TiNb-based samples, the cell population densities on days 1, 3 and 7 after seeding were higher than on the corresponding Ti-based samples. As revealed by XPS and Raman spectroscopy, and also by isoelectric point measurements, these results can be attributed to the presence of T-Nb2O5 oxide phase in the surface of the alloy sample, which decreased its negative zeta (ζ)-potential in comparison with zeta (ζ)-potential of the Ti sample at physiological pH. This effect was tentatively explained by the presence of positively charged defects acting as Lewis sites of the surface Nb2O5 phase. Piranha treatment slightly decreases the biocompatibility of the samples, which for the alloy samples may be explained by a decrease in the number of defective sites with this treatment. Thus, the presence of Nb and thermal oxidation of β-stabilized Ti alloys play a significant role in the increased biocompatibility of TiNb alloys.

Interaction of Human Osteoblast-Like Saos-2 and MG-63 Cells with Thermally Oxidized Surfaces of a Titanium-Niobium Alloy

An investigation was made of the adhesion, growth and differentiation of osteoblast-like MG-63 and Saos-2 cells on titanium (Ti) and niobium (Nb) supports and on TiNb alloy with surfaces oxidized at 165°C under hydrothermal conditions and at 600°C in a stream of air. The oxidation mode and the chemical composition of the samples tuned the morphology, topography and distribution of the charge on their surfaces, which enabled us to evaluate the importance of these material characteristics in the interaction of the cells with the sample surface. Numbers of adhered MG-63 and Saos-2 cells correlated with the number of positively-charged (related with the Nb2O5 phase) and negatively-charged sites (related with the TiO2 phase) on the alloy surface. Proliferation of these cells is correlated with the presence of positively-charged (i.e. basic) sites of the Nb2O5 alloy phase, while cell differentiation is correlated with negatively-charged (acidic) sites of the TiO2 alloy phase. The number of charged sites and adhered cells was substantially higher on the alloy sample oxidized at 600°C than on the hydrothermally treated sample at 165°C. The expression values of osteoblast differentiation markers (collagen type I and osteocalcin) were higher for cells grown on the Ti samples than for those grown on the TiNb samples. This was more particularly apparent in the samples treated at 165°C. No considerable immune activation of murine macrophage-like RAW 264.7 cells on the tested samples was found. The secretion of TNF-α by these cells into the cell culture media was much lower than for either cells grown in the presence of bacterial lipopolysaccharide, or untreated control samples. Thus, oxidized Ti and TiNb are both promising materials for bone implantation; TiNb for applications where bone cell proliferation is desirable, and Ti for induction of osteogenic cell differentiation.

H- and Cu- Forms of MFI Boralites with Enhanced Number of Skeletal Boron Atoms. Synthesis and Properties

Abstract Preparation, physico-chemical properties and catalytic activity in the selective reduction of NO are described for CuH-[B]ZSM-5 metallosilicates with relatively high number of B atoms inside the skeleton and, consequently, unusually small unit cell. Na content is so small that Na+compensation of skeleton charge can be neglected. It is shown that Cu ions are introduced into the boralites directly during the synthesis if tetrapropylammonium TPA+template is replaced by ethylamine which forms complexes with Cu2+. These complexes are located inside the boralite channels together with protonated ethylamine, and on the outer surface of zeolite grains. EAH+is easily decomposed already at 200°C while EA ligands on Cu2+are removed at 350-400°C. The decomposition in oxygen (at 450°C) and the rehydration are accompanied with the migration of Cu2+ions from the outer surface to the interior where they remain in the form of isolated and small oxidic species. Simultaneously, some of the tetrahedral B atoms change the coordination to the trigonal one. The Cu samples prepared by direct synthesis are compared with (EA)-boralites impregnated with Cu2+and with CuH-boralites prepared by ionic exchange. Synthesized Cu boralites were found to be good catalysts for selective reduction of NO by ammonia to N2.

Facile synthesis of CuO nanosheets via the controlled delamination of layered copper hydroxide acetate

CuO nanosheets were prepared by the controlled delamination of layered copper hydroxide acetate followed by the in situ solvothermal transformation of hydroxide to oxide. The reaction was performed in 1-butanol in order to prevent recrystallization or nanoparticle aggregation. Analyses by small angle X-ray scattering, transmission electron microscopy, and atomic force microscopy revealed that the CuO nanosheets are approximately 1 nm thin, corresponding to three to four stacked CuO6 octahedral layers. The average lateral size is approximately 5 nm. The nanosheets form stable dispersions in 1-butanol that are suitable for the fabrication of transparent and homogeneous CuO thin films by spin-coating or inkjet printing techniques. The present synthesis is a rare example of the top down strategy leading to the nanometric two-dimensional nanosheets of non-layered oxide materials.

Electrochemical Behavior of Nanocrystalline Ru0.8Me0.2O2 − x ( Me = Fe , Co , Ni ) Oxide Electrodes in Double-Layer Region

Nanocrystalline oxides with average chemical composition corresponding to Ru 0.8 Me o.2 O 2-x (Me = Fe, Co, Ni) were prepared by the sol-gel approach. All prepared materials were of single-phase character with rutile-type structure. The effect of nanocrystal size and nature of doping cation on electrochemical supercapacitor behavior was studied by means of cyclic voltammetry and electrochemical impedance. The specific capacitance of the Ru-based oxides increases by doping with lower-valence cation from ca. 22 μF cm -2 of actual electrode surface area observed for pure RUO 2 to 230 μF cm -2 in the case of Ni doped material. The improved capacitance behavior of the doped materials is ascribed to improvement of transport properties of the oxide structure enabling easier diffusion of compensating protons.

Protective sliding carbon-based nanolayers prepared by argon or nitrogen ion-beam assisted deposition on Ti6Al4V alloy

The microstructure and the surface properties of samples coated by carbon-based nanolayer were investigated in an effort to increase the surface hardness and reduce the coefficient of friction of the Ti6Al4V alloy. Protective carbon-based nanolayers were fabricated by argon or nitrogen ion-beam assisted deposition at ion energy of 700 eV on Ti6Al4V substrates. The Raman spectra indicated that nanolayers had a diamond-like carbon character with sp2 rich bonds. The TiC and TiN compounds formed in the surface area were detected by X-ray diffraction. Nanoscratch tests showed increased adhesion of a carbon-based nanolayer deposited with ion assistance in comparison with a carbon nanolayer deposited without ion assistance. The results showed that argon ion assistance leads to greater nanohardness than a sample coated by a carbon-based nanolayer with nitrogen ion assistance. A more than twofold increase in nanohardness and a more than fivefold decrease in the coefficient of friction were obtained for samples coated by a carbon-based nanolayer with ion assistance, in comparison with the reference sample.

Interaction of human osteoblast-like Saos-2 cells with stainless steel coated by silicalite-1 films

This paper investigates the interaction of human osteoblast-like Saos-2 cells with stainless steel covered by a film of densely inter-grown silicalite-1 crystals with defined outer and inner surfaces. The chemical composition of this film, labeled as SF(RT), was tuned by heat treatment at 300°C and 500°C (labeled as SF(300) and SF(500), respectively) and characterized by X-ray photoelectron spectroscopy (XPS), water drop contact angle (WCA) measurements and scanning electron microscopy (SEM). The number, the spreading area and the activity of alkaline phosphatase of human osteoblast-like Saos-2 cells in cultures on the silicalite-1 film were affected by the chemical composition of its outer surface and by its micro-porous structure. The number and the spreading area of the adhered osteoblast-like cells on day 1 was highest on the surface of SF(RT) relative to their adhesion and spreading on a glass cover slip due to the SF(RT) topology. However, SF(300) markedly supported cell growth during days 3 and 7 after seeding.

REMOVAL OF DIQUATERNARY AMMONIUM CATIONS FROM AS-SYNTHESIZED SSZ-16 ZEOLITE

Zeolites are stable microporous aluminosilicates with numerous applications in chemical technology such as separation of species and catalytic transformations. Our study is focused on a weakly explored zeolite SSZ-16 with pore constrictions defined by 8-membered oxygen rings. Key results are the preparation of Et6-diquat-5 dication used as a structure directing agent (SDA) and finding the optimum synthesis conditions with respect to zeolite phase purity. Stability of SDA was examined in conditions similar to those of autoclave synthesis (concentration, pH, temperature). Moreover, the content and location of SDA species in zeolite phase and conditions of SDA decomposition were investigated.

Mathematical modelling of multicomponent transport in composite all-ceramic membranes containing a zeolitic phase

Abstract The membrane model describes (i) mass transport in macroporous support comprising diffusion in transition region between Knudsen and bulk diffusion superimposed on convective flow and (ii) mass transport in zeolitic phase accompanied by a parallel transport in defects of zeolitic layer. The mass transport in the support is described by Dusty Gas Model (DGM) and that in the zeolitic phase by Generalized Maxwell Stefan (GMS) approach. Parallel transport in defects of zeolitic layer is also described by DGM. Modelling is exemplified on dynamics of a semi-open Wicke-Kallenbach (W-K) cell operated with a flat silicalite-1-α-Al2O3 membrane using a CH4/N2 mixture. It appeared that measurement of dynamic responses of the semi-open W-K cell represents a rapid and precise method to characterize composite membrane quality.

14-P-38-Topochemical changes in large MFI-type crystals upon thermal treatment in oxidizing and non-oxidizing atmosphere

Publisher Summary This chapter discusses topochemical changes in large MFl-type crystals upon thermal treatment in oxidizing and nonoxidizing atmosphere. Tetrapropylammonium hydroxide (TPAOH) removal from large as syntesized silicalite-1 crystals with internal morphology of 90°-intergrowths has been investigated in regimes with gas flow in parallel to and through the crystal layer both in the absence and presence of oxygen. The void space accessibility of crystals is estimated from the sorption isotherms of nitrogen (N2), which is exhibited as a rule two step. The topochemical changes in crystals after a partial template removal are evaluated using light microscopy, electron spectroscopy for chemical analysis (ESCA) measurements, and elemental analysis of organic residues.