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Characterization of hydrogenated silicon thin films and diode structures with integrated silicon and germanium nanoparticles
Stuchlík, Jiří ; Fajgar, R. ; Remeš, Zdeněk ; Kupčík, Jaroslav ; Stuchlíková, Hana
P-I-N diode structures based on the thin films of amorphous hydrogenated silicon (a-Si:H) deposited by Plasma Enhanced Chemical Vapor Deposition (PECVD) technique were prepared with embedded Si and Ge nanoparticles. The Reactive Laser Ablation (RLA) of germanium target was used to cover the intrinsic a-Si:H layer by Ge NPs under a low pressure of the silane. The RLA was performed using focused excimer ArF laser beam under SiH4 background atmosphere. Reaction between ablated Ge NPs and SiH4 led to formation of Ge NPs covered by thin GeSi:H layer. The deposited NPs were covered and stabilized by a-Si:H layer by PECVD. Those two deposition processes were alternated repeatedly. Volt-ampere characteristics of final diode structures were measured in dark and under illumination as well as their electroluminescence spectra.
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SIZE AS AN IMPORTANT FACTOR IN NANO-TiO2 TOXICITY IN MACROPHAGE-LIKE CELLS
Líbalová, Helena ; Sikorová, Jitka ; Brzicová, Táňa ; Milcová, Alena ; Vrbová, Kristýna ; Pikal, P. ; Topinka, Jan ; Rössner ml., Pavel
A set of NPs consists of 5 variants of anatase and 5 variants of rutile nanoparticles differing in their diameter (from 3 to 165 nm). TiO2 samples were characterized in the powder form and dispersed in water and cell culture media. Three cytotoxicity assays were used: MTS, WST-1, and LDH. For all nanomaterials, three independent repetitions were carried out. \n\nOverall, cytotoxicity of all NPs was low even at the highest concentration of 256 mu g/ml. The viability of cells did not decrease below 60% for WST-1 and MTS assays and 80% for the LDH assay. Besides concentration, crystalline size was identified as the most important cytotoxic factor. Clear nonlinear relationship between crystalline size and cytotoxicity was detected, higher toxicity induced NPs within the size range 20-60 nm. Increased cytotoxicity in given diameter size range would give an answer to inconsistent findings at size and cytotoxicity relationship.
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Use of the nanofiber scaffold for transfer of stem cells onto the injured ocular surface in mouse experimental model
Kössl, Jan ; Zajícová, Alena ; Heřmánková, Barbora ; Javorková, Eliška ; Boháčová, Pavla ; Holáň, Vladimír
Corneal damage is one of the most common causes of impaired vision or even blindness. When the injury is more extensive and the limbal region is involved, the natural regeneration of the cornea is not sufficient. Such damage can lead to the limbal stem cell deficiency (LSCD). The only option for LSCD treatment is transplantation of the limbal tissue or a transfer of limbal stem cells (LSCs) cultured from the healthy eye. The allogenic transplantation of the limbus or cultivated LSCs with a systemic administration of immunosuppressive drugs is needed in the case of bilateral LSCD. Nevertheless, the cell therapy is very promising approach for LSCD treatment. Transplantation of mesenchymal stem cells (MSCs) seeded on an appropriate scaffold turned out to be a suitable therapy of the LSCD. In our experimental model of LSCD we use nanofiber scaffold for MSC and LSC cultivation and for transplantation of these cells onto the chemically injured mouse eye. MSCs have immunosuppressive and immunomodulatory properties. We showed that MSCs have the ability to inhibit production of molecules associated with the inflammation and support epithelial regeneration in the damaged cornea. These inhibitory properties were confirmed in both in vitro and in vivo mouse model. Results thus showed beneficial effects of stem cell transplantation for murine corneal healing and for suppression of a local immune reaction which can impede the healing process. Such similarity of in vivo and in vitro results allows us further experiments to clarify mechanisms of MSC regenerative and healing properties after the transplantation onto the injured cornea.
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GENOTOXICITY OF NANOMATERIALS IN BEAS-2B CELLS ANALYZED BY THE IN VITRO MICRONUCLEUS ASSAY
Rössnerová, Andrea ; Červená, Tereza ; Brzicová, Táňa ; Vrbová, Kristýna ; Sikorová, Jitka ; Topinka, Jan ; Rössner ml., Pavel
The tremendous increase of the use of nanomaterials (NMs) has been witnessed during the last decade in many areas of human life including the chemical industry, cosmetics, biomedicine or food technology. The variety of NMs, their unique properties, almost ubiquitous presence and the size range of 1-100 nm raised the interest of toxicologists. The evaluation of the frequency of micronuclei (MN) as a result of the genotoxic events is a broadly utilized and well-established approach in in vitro studies for testing the risk of chemical exposure. Nevertheless, properties of the NMs give rise to the questions concerning the optimal methodological variants of the MN assay. \n\nIn our study, five types of well-characterized NMs (TiO2: NM-101 and NM-103, SiO2: NM-200, Ag: NM-300K and NM-302) of specific size, shape, or e.g. dimensions of aggregates were involved in the genotoxicity testing using four variants of protocols differing in the time of NM exposure, application of cytochalasin-B combined with simultaneous and delayed co-treatment with nanoparticles (NPs). Bronchial epithelial cells (BEAS-2B) were used in this study to fulfil these tasks. Presence of NPs was controlled by transmission electron microscopy (TEM). \n\nObtained results showed the different genotoxic potential of the various TiO2 and Ag NMs (NM-101< NM-103 and NM-300K> NM-302, respectively). Comparison of all testing strategies revealed, that the level of DNA damage can differ based on the time of exposure and the methodological approach. In general, using cytochalasin-B led most frequently to the increase of the genotoxic potential of the tested NMs.
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WHOLE-GENOME EXPRESSION ANALYSIS IN THP-1 MACROPHAGE-LIKE CELLS EXPOSED TO DIVERSE NANOMATERIALS
Brzicová, Táňa ; Líbalová, Helena ; Vrbová, Kristýna ; Sikorová, Jitka ; Philimonenko, Vlada ; Kléma, J. ; Topinka, Jan ; Rössner ml., Pavel
From the perspective of the immune system, nanomaterials (NMs) represent invading agents. Macrophages are immune cells residing in all organs and tissues as the first line of defense. Interactions of macrophages with NMs can determine the fate of NMs as well as their potential toxic effects. In the present study, we compared toxicity of four different types of NMs [NM-100 (TiO2, 110 nm), NM-110 (ZnO, 20 nm), NM-200 (SiO2, 150 nm) and NM-300K (Ag, 20 nm)], towards THP-1 macrophage-like cells. Cells were incubated with non-cytotoxic concentrations (1-25 mu g/ml) of NMs for 24 hours and microarray technology was used to analyze changes in whole-genome expression. Gene expression profiling revealed a substantially different molecular response following exposure to diverse NMs. While NM-100 did not exert any significant effect on gene expression profile, all other NMs triggered a pro-inflammatory response characterized by an activation of the NF-kappa B transcription factor and induced expression of numerous chemokines and cytokines. NM-110 and NM-300K further modulated processes such as DNA damage response, oxidative and replication stress as well as cell cycle progression and proteasome function. We suppose that genotoxicity of ZnO and Ag NMs leading to DNA damage and alternatively to apoptosis in THP-1 macrophages is probably caused by the extensive intracellular dissolution of these NPs, as confirmed by TEM imaging.
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Nanofiber scaffolds for local delivery of stem cells and immunosuppressive drugs for therapeutic purposes
Zajícová, Alena ; Kössl, Jan ; Heřmánková, Barbora ; Boháčová, Pavla ; Holáň, Vladimír
Cell-based therapy of local tissue injuries or damages requires application of stem cells and inhibition of harmful inflammatory reaction which could impede the healing process. To increase the effectiveness of this therapy, a local administration of drugs can avoid their side effects associated with a systemic treatment. A local therapy requires suitable carriers, which can transfer the cells and drugs to the site of injury. As a promising carriers turned out nanofiber scaffolds prepared by electrospinning technology from various types of polymers. The main advantage of this technology is a possibility to define properties of nanofiber scaffolds, optimal for the growth and transfer of stem cells, and which could incorporate various types of immunosuppressive drugs. Here we describe the formation and use of nanofiber scaffolds prepared by needleless electrospinning technology from poly (L-lactic acid) (PLA) which are loaded with immunosuppressive drug Cyclosporine A (CsA). We show that CsA-loaded nanofibers effectively and selectively inhibit proliferation of activated T cells and suppress the production of T cell cytokines in vitro. Simultaneously, these nanofiber scaffolds enable growth of mesenchymal stem cells (MSCs) and thus can serve as stem cell carriers. Moreover, using an experimental mouse model of skin transplantation, we showed that covering skin allografts with MSC-seeded and CsA-loaded nanofibers significantly inhibited the local production of pro-inflammatory cytokines IL-2, IL-17 and IFN-gamma, and supported healing. Thus, nanofiber scaffolds seeded with stem cells and loaded with CsA can serve as carriers of cells and drugs for a local cell therapy and for simultaneous effective immunosuppression.
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MICROSTRUCTURE AND COMPOSITION OF FINE PARTICLES RELEASED BY CAR BRAKING
Švábenská, Eva ; Roupcová, Pavla ; Pizúrová, Naděžda ; Schneeweiss, Oldřich
Vehicular traffic is connected with large volume of fine particles released during brake processes of cars. Our research is focused on the phase, structure and chemical analysis of the fine particles taken from some car brake parts by their services. The information on structure and phase composition was obtained by X-Ray Powder Diffraction, Mossbauer Spectroscopy, scanning electron microscopy with EDX and transmission electron microscopy. The results of the wear debris analysis are compared with original brake materials components. Most of recognized particles are based mainly on iron oxides. Wear brake particles are discussed in the relation to the potential risk to the environment and human health.
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INFLUENCE OF GRAPHITE UPON THE KINETICS OF HYDROGEN SORPTION IN Mg@Mg17Al12
Čermák, Jiří ; Král, Lubomír ; Roupcová, Pavla
Influence of graphite addition to the ball-milling charge composed of Mg splinters and Mg17Al12 particles upon the hydrogen sorption was investigated at sorption temperature 623 K. Measurements were carried out by Sieverts method. Graphite facilitates the ball-milling: It prevents re-agglomeration of crushed particles into large secondary particles. It also suppresses sticking the milled material to the balls and walls of the milling jar. It was found that an increase of carbon concentration up to a certain limit c(L) lying between 14 and 23 wt. % C, carbon increases both the absorption and the desorption rates and hydrogen storage capacity. Above c(L), carbon causes a considerable decrease in HS capacity, which spoils the application potential of Mg@Mg17Al12/C. Crystallite size of the material under study, obtained by XRD, is in the order of tens of nm.
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Effect of iron oxide nanoparticles with ascorbic acid on neural stem cells
Jiráková, Klára ; Moskvin, Maksym ; Horák, Daniel ; Jendelová, Pavla
Cells labelled with iron oxide nanoparticles (ION) can be tracked by magnetic resonance imaging (MRI) in several applications. However, various studies demonstrated toxicity and oxidative stress induction associated with nanoparticles exposure. We analysed biologic effects after the exposure of two types of iron oxide nanoparticles (with and without an antioxidative agent, an ascorbic acid) on human neural stem cells. The labelled cells in gel phantoms were detected in MRI and they showed decreased relaxation rates in comparison with control. ION slightly decreased cell proliferation in comparison with unlabelled cells, which was dependent on concentration and presence of ascorbic acid. None of the nanoparticle type showed negative effect on cell viability and both demonstrated minor effect on reactive oxygen species (ROS) formation. Unfortunately, ascorbic acid bound to nanoparticles did not show any effect on ROS attenuation. Cells exposed to both types of nanoparticles showed increased positivity for a phosphorylated form of H2AX a marker of double strand breaks. We showed that ION in low concentrations do not affect cell viability, but have negative effect on cells on DNA level. Their potential use for oxidative stress reduction is dependent on the concentration of ascorbic acid bound to the nanoparticles and this should be further increased.
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Photolitography on flexible substrates
Urbánek, M. ; Urbánek, P. ; Kuřitka, I. ; Kolařík, Vladimír
Nowadays preparation of structures on flexible substrates is highly demanded because of using this patterns in field of flexible electronics. This contribution deals with photolitographic procces for preparation of structures on flexible substrates. The method of photolitography enables to create designed patterns in various material (e.g. metals as conductive layers) on various substrates (silicon wafers, foils, etc.). First the designed pattern is exposed through the mask by UV light into polymer resist, then the pattern is transfered into metal layer by wet etching through the developed windows in resist. In this paper several patterns are prepared through the positive resist PMMA by photolitography into various metal layer (Cu, Al) on flexible substrates.
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