Structure assembly regularities in vapour-deposited gold-fullerene mixture films.

Self-assembly is an attractive phenomenon that, with proper handling, can enable the production of sophisticated hybrid nanostructures with sub-nm-scale precision. The importance of this phenomenon is particularly notable in the fabrication of metal-organic nanomaterials as promising substances for spintronic devices. The exploitation of self-assembly in nanofabrication requires a comprehension of atomic processes creating hybrid nanostructures. Here, we focus on the self-assembly processes in the vapour-deposited Au x C60 mixture films, revealing the exciting quantum plasmon effects. Through a systematic characterization of the Au x C60 films carried out using structure-sensitive techniques, we have established correlations between the film nanostructure and the Au concentration, x. The analysis of these correlations designates the Au intercalation into the C60 lattice and the Au clustering as the basic processes of the nanostructure self-assembly in the mixture films, the efficiency of which strongly depends on x. The evaluation of this dependence for the Au x C60 composite nanostructures formed in a certain composition interval allows us to control the size of the Au clusters and the intercluster spacing by adjusting the Au concentration only. This study represents the self-assembled Au x C60 mixtures as quantum materials with electronic functions tuneable by the Au concentration in the depositing mixture.

High resolution imaging of 2D distribution of lithium in thin samples measured with multipixel detectors in sandwich geometry.

A method that enables visualization of lateral distribution of Li in thin films is described. The method is based on the simultaneous detection of the reaction products of the 6Li(n,α)t nuclear reaction with thermal neutrons measured with two multipixel detectors in a sandwich geometry with a sample. Here, the principle and basic methodological parameters of the method, including tests with thin polymers with known Li microstructure, are discussed.

Polymer hydrogels usable for nervous tissue repair.

The implantation of non-resorbable biocompatible polymer hydrogels into defects in the central nervous system can reduce glial scar formation, bridge the lesion and lead to tissue regeneration within the hydrogel. We implanted hydrogels based on crosslinked poly hydroxyethyl-methacrylate (pHEMA) and poly N-(2-hydroxypropyl)-methacrylamide (pHPMA) into the rat cortex and evaluated the cellular invasion into the hydrogels by means of immunohistochemical methods and tetramethylammonium diffusion measurements. Astrocytes and NF160-positive axons grew similarly into both types of hydrogels. We found no cell types other than astrocytes in the pHEMA hydrogels. In the pHPMA hydrogels, we found a massive ingrowth of connective tissue elements. These changes were accompanied by corresponding changes in the extracellular space volume fraction and tortuosity of the hydrogels.

Silicone rubber-hydrogel composites as polymeric biomaterials. II. Hydrophilicity and permeability to water-soluble low-molecular-weight compounds.

The surface and transport properties of water-swollen silicone rubber-hydrogel composites were investigated. Surface wettability of these materials, composed of a polysiloxane matrix and the hydrogel phase consisting of very fine particles of lightly cross-linked poly(2-hydroxyethylmethacrylate), increased markedly with increasing content of the hydrogel phase. For composite materials containing a lightly cross-linked 2-hydroxyethylmethacrylate (HEMA)-methacrylic acid (MAA) copolymer and polymethacrylic acid (PMAA) as the hydrogel phase, permeability to water-soluble organic compounds and drugs were measured. The permeability varied within a broad range depending on the composition and content of the hydrogel phase. High permeation rates could be obtained while still retaining relatively fair mechanical properties. Relationships between the composition of silicone rubber-hydrogel composites, their structure and the permeation coefficients of the individual permeates are discussed.

Influence of intraperitoneal injection of three types of hydrogel beads on expression of carbohydrate-binding sites in spleen macrophages.

The influence of the chemical structure of polymer implants on selected characteristics of macrophages was studied to improve our understanding of the mechanisms of non-self recognition of synthetic materials. Three types of polymers differing in net charge were prepared to compare in vivo responses. Beads from preparation of poly(2-hydroxyethyl methacrylate), a copolymer of 2-hydroxyethyl methacrylate with sodium methacrylate, and a copolymer of 2-hydroxyethyl methacrylate and dimethylaminoethyl methacrylate were injected intraperitoneally into rats and harvested 48 h later. The effects of these polymers on the presence of inflammatory cells in the peritoneal exudate, on the adhesion of macrophages to individual batches of the different types of beads and on distinct molecular aspects of macrophages in the red pulp of spleen were evaluated. Beads from both types of copolymer caused an elevation in the number of macrophages in the exudate, in contrast to the situation in rats treated with poly(2-hydroxyethyl methacrylate) beads and physiological saline solution as control. The molecular design of the implant had no significant influence on the extent of macrophage adhesion to beads or on the expression of selected carbohydrate-binding sites. Since important cellular functions such as cell adhesion and glycoprotein routing depend on the sugar part of glycoconjugates, labelled neoglycoproteins were employed to analyse this aspect of macrophages in the tested animals. The beads of the copolymer of 2-hydroxyethyl methacrylate with dimethylaminoethyl methacrylate clearly led to an elevation of the expression of specific binding sites for beta-galactoside-terminating structures which are presented by asialofetuin, for mannose, fucose, sialic acid and N-acetylgalactosamine, which had been used as the ligand parts of biotinylated neoglycoproteins, in spleen macrophages whereas the levels of sites which recognize mannose-6-phosphate were unaffected. Expression of sites with specificity to N-acetylglucosamine was lessened. The effect of beads from the copolymer of 2-hydroxyethyl methacrylate with sodium methacrylate on the measured glycobiological features in the splenic macrophages was only negligible. These results suggest the possibility of systemic effects of implanted polymers on the distinct recognitive functions of macrophages.

Mapping of endogenous lectins in macrophages colonizing an implanted polymer surface--effect of polymer structure.

The design of synthetic polymers may affect structural features of inflammatory cells, for example the expression of endogenous sugar receptor molecules like lectins in macrophages and foreign body giant multinucleate cells. This characteristic was studied histochemically by use of biotinylated (neo)glycoproteins. The results demonstrate the influence of polymer structure on the phenotypic expression of molecules recognizing carbohydrates in these cells. Very strong activity was observed for carrier-immobilized beta-galactose in cells colonizing hydrophobic polystyrene implants. Sialic acid moieties were not recognized by cells located on the surface of all types of polymeric implant. This study encourages investigation of the influence of polymer design on the differentiation of macrophages.

Effect of chemical structure of hydrogels on the adhesion and phenotypic characteristics of human monocytes such as expression of galectins and other carbohydrate-binding sites.

The reactivity of diverse immune aspects to the presence of synthetic polymers represents one of the most important aspects of implantable device biocompatibility. In this report, we show the effect of the chemical structure of a synthetic polymer support on monocyte adhesion and selected phenotypic characteristics in vitro as a model for the initial steps of non-self-recognition of an implant. The extent of monocyte adhesion was significantly influenced by the support chemistry. The highest level of monocyte adhesion was observed on a surface copolymer of 2-hydroxyethyl methacrylate with dimethyl aminoethyl methacrylate relative to results of experiments in which poly(2-hydroxyethyl methacrylate) or the copolymer of 2-hydroxyethyl methacrylate with the sodium salt of methacrylic acid was used. Cell adhesion to the polymers tested and to glass was accompanied by enhanced expression of the carbohydrate-binding sites tested for asialoglycoprotein beta-galactosides such as galectins, beta-N-acetylgalactosamine, alpha-mannoside, specific lectin for heparin as well as the lymphokine-macrophage migration inhibitory factor in the monocytes tested. These results suggest the importance of monocyte adhesion to the biomaterial surface for their development into macrophages and further non-self-recognition of the implanted device.

Cultivation and grafting of human keratinocytes on a poly(hydroxyethyl methacrylate) support to the wound bed: a clinical study.

Cultured epithelial sheets on a textile support are used for the treatment of seriously burned patients. In this study we demonstrate a new procedure for the grafting of keratinocytes directly on a polymer cultivation support. This procedure is much easier in comparison with classical techniques, and encouraging results of clinical trials demonstrate the improved healing of the wound bed after the use of this procedure. There is no difference in the cytokeratine pattern (LP-34, cytokeratin-10) of the reconstructed epidermis and normal human skin.

Development of hydrogel implants for urinary incontinence treatment.

Hydrogel implants for urinary incontinence treatment based on HEMA supplemented with 10% methacrylic acid have been developed. The swelling properties of implants were tested in vitro and in vivo after implantation to laboratory mice. Biocompatibility has been determined by incubation of implants in tissue culture, by histological examination of adjacent tissues after subcutaneous application of implants to laboratory mouse in a long-term experiment, and by flow cytometry examination of blood cells. The swelling of hydrogel implants was completed in 6-24 h. There was no effect on in vitro growth of cells incubated with implants. In mice, implants were well tolerated without any sign of inflammatory reaction. The material allows an elastic compression of urethra compensating a damaged sphincter after trans-urethral sub-mucosal implantation of hydrogel cylinders.

Anionic polymers for implantation.

The biocompatibility of hydrogels containing carboxylate anions was studied by a panel of tests in vitro and in vivo. In comparison with other types of similar hydrogels, those with COO- anions induced a lower extent of foreign body reaction, and their systemic effect on the immune system also seems lower. The biomimetic effect of carboxylate anions on biocompatibility of synthetic materials could be explained by a similar biomimetic effect of N-acetylneuraminic acid inhibiting the non-self recognition of bacterial cells by non-specific immunity. The encouraging long-term results of clinical trials of intraocular lenses prepared from copolymer of 2-hydroxyethyl methacrylate and sodium methacrylate support this hypothesis.

Reactive oxygen species (ROS) generated by xanthine oxidase in the corneal epithelium and their potential participation in the damage of the corneal epithelium after prolonged use of contact lenses in rabbits.

Prolonged use of contact lenses (for 14 days) evoked an imbalance between the activity of xanthine oxidase (an enzyme belonging to reactive oxygen species-generating oxidases) and catalase (an enzyme belonging to reactive oxygen species-scavenging oxidases) in the corneal epithelium of rabbits. The activity of catalase decreased, while xanthine oxidase activity was very high. Of other enzymes studied in the corneal epithelium, the activities of xanthine oxidoreductase, glucoso-6-phosphate dehydrogenase and succinate dehydrogenase were decreased. In contrast, the activities of lactate dehydrogenase and lysosomal hydrolases (acid beta-galactosidase, dipeptidyl peptidase II) were increased and appeared in animals sacrificed immediately after contact lens removal. In rabbits sacrificed later (after 1 h), an additional increase of lactate dehydrogenase and lysosomal hydrolase activities developed in the superficial layers of the corneal epithelium. Catalase supplementation during use of contact lenses prevented both the significant decrease of catalase activity in the corneal epithelium and the development of additional epithelial damage. In contrast, topical treatment with 3-aminotriazole (an inhibitor of catalase) resulted in the nearly complete loss of catalase activity in the corneal epithelium and the appearance of more serious epithelial damage. We conclude that ROS generated by xanthine oxidase induce additional damage of the corneal epithelium related to the use of contact lenses.

Cultivation of keratinocytes on poly HEMA and their migration after inversion.

This study demonstrates how the pretreatment of poly HEMA disks with bovine serum influences the adhesion of human keratinocytes in vitro. The ability of these cells to migrate from poly HEMA disks to a polystyrene petri dish surface colonized with irradiated 3T3 cells is also evaluated. The stimulatory effect of 24-h preincubation of the poly HEMA disks with bovine serum on the keratinocyte adhesion and growth was dependent on the concentration of the serum used. The keratinocytes migrated from the poly HEMA disks to polystyrene colonized with irradiated 3T3 cells. The numerous cells which migrated from the poly HEMA were positive for cytokeratin 10 (suprabasal layers) after 3 weeks and for cytokeratin 1 (cornified layer) after 1 month. These results seem to be encouraging for further experiments with respect to clinical application.

Synthetic hydrogel capacity to induce formation of foreign-body giant multinucleate cells differs in vivo and in vitro.

The granulomatous reaction accompanied with MGC formation represents the most striking feature of the non-favourable biological tolerance of implanted devices. We compared MGC formation in the course of the granulomatous reaction in vitro and in vivo employing three types of hydrogels whose biocompatibility had been well studied earlier. The efficiency of the in vitro assay for the granulomatous reaction, including MGC formation, was verified employing the nematode Nippostrongylus brasiliensis, a well-known inductor of MGC formation in vitro. The in vitro results demonstrated a very low level of MGC formation in reaction against all three types of hydrogels without polymer-specific differences in comparison with the nematode experiment characterized by a high extent of MGC formation. On the other hand, the extent of MGC formation was implant type-specific in vivo: pHEMA-co-DMAEMA > pHEMA > pHEMA-co-NaMA. These results indicate that in the in vitro assay it was not possible to discriminate among the types of polymers used in the experiment in comparison with the animal experiment. They also indicate potential differences between granuloma formation induced by parasites and by foreign bodies.

Detection of cell type and marker specificity of nuclear binding sites for anionic carbohydrate ligands.

The emerging functionality of glycosaminoglycan chains engenders interest in localizing specific binding sites using cytochemical tools. We investigated nuclear binding of labeled heparin, heparan sulfate, a sulfated fucan, chondroitin sulfate, and hyaluronic acid in epidermal keratinocytes, bone marrow stromal cells, 3T3 fibroblasts and glioma cells using chemically prepared biotinylated probes. Binding of the markers was cell-type specific and influenced by extraction of histones, but was not markedly affected by degree of proliferation, differentiation or malignancy. Cell uptake of labeled heparin and other selected probes and their transport into the nucleus also was monitored. Differences between keratinocytes and bone marrow stromal cells were found. Preincubation of permeabilized bone marrow stromal cells with label-free heparin reduced the binding of carrier-immobilized hydrocortisone to its nuclear receptors. Thus, these tools enabled binding sites for glycosaminoglycans to be monitored in routine assays.

Effects of crude extracts of various plants on infectious bovine rhinotracheitis virus-plaque production.

Extracts of 28 plants were tested without demonstable antiviral activity in an agar-overlay plaque-reduction antiviral assay system, using infectious bovine rhinotracheitis virus and bovine endocardial cell cultures. Ethanolic extract of Narcissus tazetta L bulb elicited antiviral activity by inhibition of viral plaque formation. Antiviral activity was demonstrated against infectious bovine rhinotracheitis and equine rhinopneumonitis viruses. Narcissus tazetta L bulb did not directly inactivate the virus extracellularly. The extract exhibited only limited toxicity to rapidly multiplying bovine endocardial cells at plaque-inhibitory levels and was not cytoxic to preformed confluent cell monolayers. Narcissus extract did not induce the formation of drug-resistant viral strains.

[Experimental implantation of hydrogel into bone]. / Experimentální implantace hydrogelu do kosti.

In spite of the rapid development of various natural and artifical implants of bone tissue, bones or whole joints, no material was found as yet which would maximally resemble the structure of the bone tissue and would also be maximally compatible. The present study deals with the application possibilities of unsoluble hydrophilic gels (hydrogels) as substitutes of bone tissue in experiment. The study concerns above all their biocompatibility with regard to the porous qualities of the implant and to its chemical structure, and evaluates their behaviour in the spongious and compact bone. It was used polyhydroxyethylmethacrylate (polyHEMA) which is crossling with small amount of glycoldimethacrylate when by changing of ratio monomer: water is possible obtain from homogeneous to macroporous structure of polymers. The macroporous structure was increased and the surface of the macroporous structure of polymers. The macroporous structure was increased and the surface of the macroporous, sinterted HEMA modified and implanted. The so-called double porosity was thus obtained. The implants were prepared in the form of cylinders (3.5 mm in diameter) in 8 different modifications and surgically implanted into the subtrochanteric and supracondylic part of the rabbit femurs. 42 animals were operated on. The obtained preparations were then evaluated macroscopically, and histologically processed in half-thin cuts (3-4 micrones). 124 samples were thus obtained. Some samples were radiographically contrasting. The rabbits were killed at intervals from 1-6 months, i.e. 32-193 days. It was found that the hydrogels modifications used in the experiment are biocompatible, their compatibility increasing in dependence on the increasing porosity. The non-porous and microporous hydrogels are not compatible and are damarked. The sintered macroporous gel is surrounded by a thin fibrine membrane signifying a high degree of compatibility with the bone tissue. By adding metacrylate acid to the hydrogel, the adhesivity of the macrophages increases markedly. There also appears the destruction of the polymer, marked, above all, in the spongious bone. The gel is actively degraded in the marrow, although the direct phagocytosis can be proved. At degradation of the implant in the compact bone the activity of the macrophages is belated; at application of the gel without methacrylate acid it does not occur even after 193 days and the implant is pervaded only by the bone beams. When adding methacrylate acid to the polymer degradation occurs, in which process there play also an active role the blood vessels pervading the site of the gel implantation.(ABSTRACT TRUNCATED AT 400 WORDS)

[Surgical treatment of recurrent urethral strictures in males after unsuccessful operations]. / Nové moznosti chirurgické lécby muzu po neúspesných operacích recidivujících striktur mocové trubice.

BACKGROUND: Subvesical obstructions of any origin represent a frequent and serious disorder occurring predominantly in males. Often it brings incontinence and/or erectility dysfunction, infection of urinary tract. Relapses of the acute pyelonephritis can turn into chronic tubulointersticial one and terminate in the renal insufficiency. To treat strictures, dilation, intermittent catheterization and recently stent introduction were used. Most suitable appears a stent from composite polymers. The aim of our work was to test properties of stents developed in the Institute of Macromolecular Chemistry ASCR. METHODS AND RESULTS: Stents from composite polymers, which are non-toxic, not-irritable can swell in body fluids and have mechanical properties similar to that of silicone rubber. Properties of the material are functionally graded and the casting or repoussé from the material can subsequently change its shape. Ten patients (males, aged 25 to 78 years) with long urethral strictures in its bulbocavernous part (50%) were treated with this method. Strictures were caused by pelvical fractures (4 times), prostate hypertrophy surgery (4 times), prolonged catheterizations (2 times). All patients were followed for 16 to 26 month and had no severities. CONCLUSION: Our results indicate that stent from composite polymers and silicone may have long-acting effects without irritation or crust formation and beneficially effected healing of the spongio-fibrous process.

[The histopathologic picture of experimental poisoning with ethylmethacrylates]. / Histopatologický obraz experimentální intoxikace ethylmethakryláty.

Toxic effect of hydroxyethylmethacrylate, acetoxyethylmethacrylate and diethylenglycomethacrylate were studied in rats surviving as long as 1 to 20 days after intramuscular administration. Conspicuous lesion were found only in calf muscles at the site of application. Muscle fibre necroses with inflammatory reaction occurred repeatedly in animals surviving 1-2 days. Newly formed connective tissue replacing impaired muscle fibres was found in rats surviving 5 days. Intoxication related other lesion in rat organs were not identified.

[Modern dressings. Hydrogels]. / Moderní obvazy. Hydrogely.

Hydrogels are occlusive types of dressings. They are three-dimensional nets made up of hydrophil polymers. They can be produced from synthetic or semisynthetic materials or a combination of the two. Hydrogels retain different percentages of water but are themselves insoluble in water. This is why they maintain on the wound surface their structure and do not dissolve. They are suited for the dressing of wounds with low secretion such as grade I and II burns, grade I and II bedsores and above all epithelial defects, major skin abrasions and areas after collection of epithelial grafts. Their use is contraindicated in infected wounds, in wounds with a massive secretion and ulcers of arterial origin. Although the domain of their clinical use are clean granulating or already epithelizing wounds, they are very well suited also for rehydration of dry and black skin necroses. Their advantages include minimal pain in the wound as well as the fact that they can be left on the wound without redressing till complete healing. This is made possible also by the fact that they are translucent.

Position sensitive detection of neutrons in high radiation background field.

We present the development of a high-resolution position sensitive device for detection of slow neutrons in the environment of extremely high γ and e(-) radiation background. We make use of a planar silicon pixelated (pixel size: 55 × 55 µm(2)) spectroscopic Timepix detector adapted for neutron detection utilizing very thin (10)B converter placed onto detector surface. We demonstrate that electromagnetic radiation background can be discriminated from the neutron signal utilizing the fact that each particle type produces characteristic ionization tracks in the pixelated detector. Particular tracks can be distinguished by their 2D shape (in the detector plane) and spectroscopic response using single event analysis. A Cd sheet served as thermal neutron stopper as well as intensive source of gamma rays and energetic electrons. Highly efficient discrimination was successful even at very low neutron to electromagnetic background ratio about 10(-4).