IR laser photodeposition of a-Fe/Si films developing nanograins of ferrisilicate, iron disilicide and rare hexagonal iron upon annealing.

IR laser-induced gas-phase photolysis of Fe(CO)(5)-SiH(4) mixtures occurs as SiH(4)-photosensitized decomposition of Fe(CO)(5) is accelerated by products of this decomposition and it results in deposition of amorphous Si/Fe nanocomposite films. Analyses of the deposited and subsequently annealed solid films were made by FTIR, Raman and X-ray photoelectron spectroscopy, X-ray diffraction and electron microscopy. The deposited films are amorphous, contain crystalline nanostructures of iron silicide FeSi(2) and undergo atmospheric oxidation in topmost layers to iron oxide and hydrogenated silicon oxide. Upon annealing they develop nanocrystalline structures of ferrisilicate, Fe(1.6)SiO(4), carbon-encaged iron disilicide, FeSi(2), and very rare hexagonal (high-pressure) Fe surviving at ambient conditions. The mechanism of formation of these nanostructures is discussed in terms of gas-phase and solid-phase reactions.

Surface modification of cyclic olefin copolymers for osteochondral defect repair can increase pro-destructive potential of human chondrocytes in vitro.

Materials on the basis of cycloolefin copolymers (COC) are suitable for subchondral defect repairs. The objective of this study was to evaluate the influence of surface modification of COC and COC/LLDPE blends on the viability and gene expression of chondrocytes. Human chondrocytes were incubated on the surface of the studied materials. Half of the materials were plasmatically modified with a subsequent type II collagen application. The gene expression of matrix metalloproteinases (MMP-1,-3,-13), pro-inflammatory cytokines (IL-1, TNF-alpha) and apoptotic molecules (BAX, Bcl-2) was evaluated using quantitative Taq-Man PCR after 48 h incubation. Chondrocyte viability was evaluated by the MTT test after 2, 4 and 8 days of incubation. The synthesis of MMPs was measured by ELISA assay in cell culture medium after 48 h of incubation. Chondrocytes incubated on plasmatically modified in contrast to unmodified materials demonstrated significantly increased gene expression of IL-1 (p<0.05), MMP-1 and MMP-3 (p<0.05 for both comparisons) as well as MMP-13 (p<0.001). Increased gene expression was confirmed by significantly increased production of active forms of particular MMPs into the cell culture medium. Unlike surface unmodified polymers, the modified materials showed time-dependent reduction of chondrocyte viability. The gene expression of TNF-alpha and apoptotic molecules by chondrocytes was not significantly changed by different materials. Cycloolefin copolymers and their blends may represent suitable materials for tissue engineering, however, their surface modification followed by collagen type II application may, at least under in vitro conditions, reduce the viability of chondrocytes and induce their pro-destructive behavior. The potential benefit or disadvantage of surface modifications of materials for osteochondral defect repairs needs to be further elucidated.

[New materials suitable for implantation--preparation for implants]. / Nové materiály vhodné pro implantáty--príprava implantátu.

PURPOSE OF THE STUDY: Connective tissue components, particularly collagen and proteoglycan, stimulate cell proliferation and thus promote tissue regeneration. This fact was utilized to test some new implant materials, which were covered by these components, for the speed and quality of their encapsulation. MATERIAL: The materials tested included polyethylene (PE) with either a hydrophobic (HPHO) or a hydrophilic (HPHI) surface and the C-C composite. Before implantation in experimental animals, the materials were coated with a thin layer of collagen-proteoglycan copolymer. METHODS: Collagen was obtained from calf hide (ISC 40 fraction) and proteoglycan was isolated from calf cartilage with 2M GuHCl. The concentrations of elements in implant materials were assessed by the method of ESCA photoelectron spectroscopy (electron spectroscopy for chemical analysis) and, using a comparison of the values of electron binding energies at inner levels with the published ones, the chemical states of elements were identified. RESULTS: Carbon, oxygen and silicon were identified on the surface of the PE HPHI sample; carbon, oxygen, calcium, manganese and sulfur were found on the PE HPHO sample and nitrogen, oxygen and fluorine were present on the C-C composite. DISCUSSION: In our group of patients there was a small rate of rheumatoid arthritis, while in most literature these patients are predominant. In accordance with the outcomes of other authors, ASS is fraught with recurrence. ASS does not strike to fibrous capsule, like an open surgery synovectomy, and from these islands synovialis could regenerate. CONCLUSIONS: The presence of manganese and calcium on the surfaces of the materials investigated indicates the existence of a collagen-proteoglycan copolymer, which contains NH2 and COO groups derived from collagen and SO4 groups from proteoglycan. It is necessary to verify this theoretical assumption based on measurement data in a biological experiment.

Atomic surface characterisation and modification of the layered compounds Bi2Se3, Bi1.9Sb0.1Se3 and Bi1.6Sb0.4Se3.

In this work, we show atomic STM images of the layered compound Bi2Se3. We study the effect in the surface of the substitution of 5% and 20% of the Bi atoms for Sb in Bi1.9Sb0.1Se3 and Bi1.6Sb0.4Se3. The images of the three samples show similar trigonal structures corresponding probably to the van der Waals Se atoms. The distance measured between surface atoms in Bi2Se3 is 4.04 A, in Bi1.9Sb0.1Se3 is 4.16 A and in Bi1.6Sb0.4Se3 is 4.26 A. In Bi1.6Sb0.4Se3 some atomic sites appear brighter than others. The effect is accentuated at higher tunnelling currents and is not observed in the other compounds. Nanoscopic range depressions on the sample might be related to the skeletal crystal structure since the images show atomic corrugations that align slightly in one direction. We explain the results as the effects of the interactions between tip and sample, and discuss two interpretations: on the one hand, localised depression of the individual atomic sites, and on the other the possible elevation of the atoms of the surface due to a phase transition of the compounds induced by STM.

Formation of nano-pyramids of layered materials with AFM

We have been able to raise squares of around 2 A in height of the layered materials Bi1.6Sb0.4Se3, Bi1.9Sb0.1Se3 and Bi2Se3 by means of contact atomic force microscopy in air. By raising squares on/beneath previously produced squares, Mayan-like pyramids have been constructed, each step of the pyramid being around 2 A in height. We neither remove matter from the surface nor produce a localized oxidation of the sample; we elevate a portion of it. When the surface is oxidized, the AFM cantilever pulls the oxide off producing holes. The raising of the squares is also possible in a nitrogen atmosphere.