J. Vacik

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.

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.

Macrophage recognition of polymers: effect of carboxylate groups

The effect of anionic carboxylate groups in copolymers of 2-hydroxyethyl methacrylate with sodium methacrylate on the adsorption of albumin, adhesion, spreading and fusion of macrophages has been demonstrated. The results show an inhibitory effect of increasing concentration of carboxylate groups of polymers on all studied parameters.

Neutron depth profiling by large angle coincidence spectrometry

Abstract A measuring device for large angle coincidence neutron depth profiling was installed behind a 5.6 m long neutron guide. Two large area PIN diodes placed at a distance of 2 mm from the sample serve for the detection of particles emitted at different angles. Coincidence event registration and sorting was accomplished using a PC AT computer. A simple but effective technique for two-dimensional data evaluation is proposed. The feasibility of the method was tested on various standards. The detection limits and the depth resolution are determined and possible refinements of the technique are discussed.

Transport processes during the incubation time of ion track etching in polymers

Abstract The processes which take place in polymers before visible etch track formation sets in after exposure to alkaline solutions, i.e. during the so-called “incubation time”, are thought to consist of the penetration of the liquid into the polymer and the polymer’s subsequent glassy-to-rubbery phase transformation. We have studied systematically the first of these steps – the penetration process – by measuring the depth distributions of tracer ions dissolved in the penetrant solutions in different polymers as a function of pH value, temperature, and penetration time. Determination of the free volume of pristine and ion-irradiated polymers by positron annihilation spectroscopy served as an additional important source of information. Our findings show that the solutions’ penetration is often a highly complex process which eventually dominates the overall incubation time.

NEW WAYS OF POLYMERIC ION TRACK CHARACTERIZATION

Abstract New ways have been applied for characterization of ion tracks in polymers in the last few years, which are essentially related to depth profile determinations of ions, molecules, or positrons penetrating into these tracks. In combination with tomography, the first three-dimensional results have been obtained. Extensive diffusion simulations accompanying the measurements have enabled us to obtain a better understanding of the transport processes going on in ion tracks. This paper gives an overview about the range of new possibilities accessible by these techniques, and summarizes the presently obtained understanding of ion tracks in polymers.

Changes of PEEK surface chemistry by ion irradiation

Abstract The changes of chemical structure, induced by irradiation with 2 MeV O + ions on the surface of poly(aryl-ether-ether-ketone) (PEEK), were investigated by using IR and UV–VIS spectroscopies. The surface topography of the irradiated PEEK was determined by X-ray diffraction (XRD). The ion irradiation results in a degradation of aromatic rings and in the production of regions enriched with conjugated double bonds. Implanted oxygen is bound to the ion beam-modified polymer structures. The ion irradiation has no effect on the content of the PEEK crystalline phase.

New technique for nondestructive examination of latent track etching

New technique for examination of latent track etching based on the transmission of charged particles is suggested and some of preliminary experimental results are presented proving the feasibility of the method.

On the penetration of etchant into tracks in polycarbonate

The time dependence of the uptake of NaOH/LiOH etchant in pristine polycarbonate (PC) and in PC irradiated with 3 GeV Pb ions has been examined. Different stages of etchant penetration can be distinguished. The overall surface-near etchant uptake along tracks is always higher than the the one of the nonirradiated pristine material. Furthermore, the directional dependence of the etchant penetration during the incubation time is studied. Though the shapes of the etchant distributions along the tracks are practically the same in all directions, they differ in their absolute magnitudes. This can be explained by the different cross-sectional track areas exposed at the surface, which enable different etchant penetration efficiencies. Therefore, tracks which run more or less parallel to the surface normal show less etchant uptake than those being strongly tilted.

Degradation of polyimide and polyethyleneterephtalate irradiated with 150 and 200 keV Ar+ ions, studied by RBS and ERD techniques

Abstract Polyimide (Upilex, PI) and polyethyleneterephtalate (Mylar, PET) were irradiated with 200 and 150 keV Ar + ions respectively to different fluences and the depth profiles of hydrogen and oxygen atoms in polymer surface layer were determined using standard Rutherford backscattering (RBS) and elastic recoil detection (ERD) techniques. Significant hydrogen and oxygen depletion is observed at the ion fluences above 1×10 14 cm −2 . Above 5×10 15 cm −2 a saturated state is achieved when another fluence increase does not result in significant changes of the H and O profile shape. At higher fluences the H and O depth profiles are rather flat with no local minima. This finding indicates only minor role of nuclear stopping in production of volatile degradation products.