Publications by authors named "Klára Safářová"

13 Publications

  • Page 1 of 1

Magnetically assisted surface-enhanced raman scattering selective determination of dopamine in an artificial cerebrospinal fluid and a mouse striatum using Fe(3)O(4)/Ag nanocomposite.

Anal Chem 2014 Mar 7;86(6):2939-46. Epub 2014 Mar 7.

Regional Center of Advanced Technologies and Materials, Department of Physical Chemistry, Faculty of Science, Palacky University Olomouc , 17. listopadu 1192/12, 771 46 Olomouc, Czech Republic.

The dopaminergic neural system is a crucial part of the brain responsible for many of its functions including mood, arousal, and other roles. Dopamine is the key neurotransmitter of this system, and a determination of its level presents a demanding task needed for a deeper understanding of the processes, even pathological, involving this brain part. In this work, we present a method for a fast analysis of dopamine levels in samples of cerebrospinal fluid and mouse striatum. The method is based on a nanocomposite composed of magnetite and silver nanoparticles, whose surface is modified with iron nitriloacetic acid (Fe-NTA)-a dopamine-selective compound. The magnetic properties of this nanocomposite enable simple separation of targeted molecules from a complex matrix while the silver acts as a platform for surface-enhanced Raman scattering (SERS). Silver and magnetite nanoparticles are joined by carboxymethyl chitosan, useful in biological environments and enhancing the sensitivity due to the presence of carboxyl groups. This system reveals a good stability and reproducibility. Moreover, rapid and simple quantitative experiments show an improvement in the detection of dopamine levels in biological assays at low femtomolar concentrations. The comparative data performed with clinical samples of mouse striatum show that the developed magnetic SERS is a strong alternative to conventional high-performance liquid chromatography-mass spectrometry (HPLC-MS) with even several superior aspects including faster and cheaper analysis and no necessity of sample preconcentration or derivatization.
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http://dx.doi.org/10.1021/ac500394gDOI Listing
March 2014

The effect of photodynamic treatment on the morphological and mechanical properties of the HeLa cell line.

Gen Physiol Biophys 2013 Sep 2;32(3):337-46. Epub 2013 Jul 2.

Department of Medical Biophysics, Faculty of Medicine and Dentistry, Institute of Molecular and Translational Medicine, Palacky University, Hnevotinska 3, 775 15 Olomouc, Czech Republic.

High resolution imaging of biological structures and changes induced by various agents such as drugs and toxins is commonly performed by fluorescence and electron microscopy (EM). Although high-resolution imaging is possible with EM, the requirements for fixation and staining of samples for image contrast severely limits the study of living organisms. Atomic force microscopy (AFM), on the other hand, is capable of simultaneous nanometer spatial resolution and piconewton force detection, allowing detailed study of cell surface morphology and monitoring cytomechanical information. We present a method that images and studies mechanically characterized cells using AFM. We used a HeLa cell line (cervix carcinoma cell), which is sensitive to photodynamic treatment (PDT); growth media as a scanning surrounding; atomic force microscopy NT-MDT Aura for cytomechanical measurement; and scanning electron microscope Hitachi Su 6600 for control images of the cells. The modulus of elasticity for intact and photodynamically damaged cells can indicate mechanical changes to the main properties of cells. Cell elasticity changes can provide information on the degree or value of cell damage, for example after PDT. Measurements were carried out on approximately sixty cells, including three independent experiments on a control group and on sixty cells in a photodamaged group. Cells before PDT show higher elasticity: the median of Young´s modulus on the nucleus was 35.283 kPa and outside of the nucleus 107.442 kPa. After PDT, the median of Young's modulus on the nucleus was 61.144 kPa and outside of the nucleus was 193.605 kPa.
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http://dx.doi.org/10.4149/gpb_2013042DOI Listing
September 2013

Fe3O4 nanocrystals tune the magnetic regime of the Fe/Ni molecular magnet: a new class of magnetic superstructures.

Inorg Chem 2013 Jul 24;52(14):8144-50. Epub 2013 Jun 24.

Regional Centre of Advanced Technologies and Materials, Department of Physical Chemistry, Faculty of Science, Palacky University, 17. listopadu 1192/12, 771 46 Olomouc, Czech Republic.

A new class of organometallic-inorganic magnetic material was engineered by a sonochemically assisted self-assembly process between magnetite nanoparticles (biogenic Fe3O4, hard constituent) functionalized with isonicotinic acid and a metamagnetic organometallic complex ([Ni(en)2]3[Fe(CN)6]2·3H2O, soft constituent). In such bottom-up methodology, hard and soft counterparts form well-organized microdimensional clusters that showed morphological fingerprints and magnetic behavior clearly distinct from those of the initial building units. In the engineered soft-hard material, the magnetite nanocrystals induced ferromagnetic ordering at room temperature of closer contact layers of [Ni(en)2]3[Fe(CN)6]2·3H2O, thus demonstrating the ability to sensibly modify the [Ni(en)2]3[Fe(CN)6]2·3H2O paramagnetic regime. The magnetic ordering of [Ni(en)2]3[Fe(CN)6]2·3H2O was triggered by the intrinsic local field of the hard magnetic nanocrystals, which resembled, to some extent, the effects promoted by large, external magnetic fields.
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http://dx.doi.org/10.1021/ic4008729DOI Listing
July 2013

Air stable magnetic bimetallic Fe-Ag nanoparticles for advanced antimicrobial treatment and phosphorus removal.

Environ Sci Technol 2013 May 6;47(10):5285-93. Epub 2013 May 6.

Regional Centre of Advanced Technologies and Materials, Departments of Physical Chemistry and Experimental Physics, Faculty of Science, Palacký University, 17. listopadu 1192/12, 771 46 Olomouc, Czech Republic.

We report on new magnetic bimetallic Fe-Ag nanoparticles (NPs) which exhibit significant antibacterial and antifungal activities against a variety of microorganisms including disease causing pathogens, as well as prolonged action and high efficiency of phosphorus removal. The preparation of these multifunctional hybrids, based on direct reduction of silver ions by commercially available zerovalent iron nanoparticles (nZVI) is fast, simple, feasible in a large scale with a controllable silver NP content and size. The microscopic observations (transmission electron microscopy, scanning electron microscopy/electron diffraction spectroscopy) and phase analyses (X-ray diffraction, Mössbauer spectroscopy) reveal the formation of Fe₃O₄/γ-FeOOH double shell on a "redox" active nZVI surface. This shell is probably responsible for high stability of magnetic bimetallic Fe-Ag NPs during storage in air. Silver NPs, ranging between 10 and 30 nm depending on the initial concentration of AgNO₃, are firmly bound to Fe NPs, which prevents their release even during a long-term sonication. Taking into account the possibility of easy magnetic separation of the novel bimetallic Fe-Ag NPs, they represent a highly promising material for advanced antimicrobial and reductive water treatment technologies.
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http://dx.doi.org/10.1021/es304693gDOI Listing
May 2013

Adsorption of small organic molecules on graphene.

J Am Chem Soc 2013 Apr 16;135(16):6372-7. Epub 2013 Apr 16.

Regional Centre of Advanced Technologies and Materials, Department of Physical Chemistry, Faculty of Science, Palacký University Olomouc, 771 46 Olomouc, Czech Republic.

We present a combined experimental and theoretical quantification of the adsorption enthalpies of seven organic molecules (acetone, acetonitrile, dichloromethane, ethanol, ethyl acetate, hexane, and toluene) on graphene. Adsorption enthalpies were measured by inverse gas chromatography and ranged from -5.9 kcal/mol for dichloromethane to -13.5 kcal/mol for toluene. The strength of interaction between graphene and the organic molecules was estimated by density functional theory (PBE, B97D, M06-2X, and optB88-vdW), wave function theory (MP2, SCS(MI)-MP2, MP2.5, MP2.X, and CCSD(T)), and empirical calculations (OPLS-AA) using two graphene models: coronene and infinite graphene. Symmetry-adapted perturbation theory calculations indicated that the interactions were governed by London dispersive forces (amounting to ∼60% of attractive interactions), even for the polar molecules. The results also showed that the adsorption enthalpies were largely controlled by the interaction energy. Adsorption enthalpies obtained from ab initio molecular dynamics employing non-local optB88-vdW functional were in excellent agreement with the experimental data, indicating that the functional can cover physical phenomena behind adsorption of organic molecules on graphene sufficiently well.
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http://dx.doi.org/10.1021/ja403162rDOI Listing
April 2013

Comparing biocompatibility of gingival fibroblasts and bacterial strains on a different modified titanium discs.

J Biomed Mater Res A 2013 Oct 25;101(10):2915-24. Epub 2013 Mar 25.

Department of Medical Chemistry and Biochemistry, Faculty of Medicine and Dentistry, Palacký University Olomouc, Olomouc, Czech Republic.

The modification of implant surface situated in the area of peri-implant sulcus has important role in bacterial and cell adhesion. Six different chemically and physically modified titanium discs were prepared: glazed (Tis-MALP), unglazed (Tis-O), unglazed and alkali-etched (Tis-OA), unglazed and coated with ZrN (Tis-OZ), unglazed, sand blasted, and acid etched (Tis-OPAE), and unglazed, sand blasted, acid, and alkali etched (Tis-OPAAE). Analysis of surface topography was determined using scanning electron microscopy and atomic force microscopy (AFM). Biocompatibility of gingival fibroblasts was characterized by the production of tumor necrosis factor alpha, collagen I, matrix metalloproteinase 2 (MMP-2) after 24 and 72 h and expression of α3 β1 integrin and vinculin using enzyme-linked immunosorbent assay (ELISA) or modified ELISA after 6 and 24 h. Microorganism adhesion (five bacterial strains) and biofilm formation was also evaluated. The adhesion of bacteria and gingival fibroblasts was significantly higher on titanium disc Tis-OPAAE and biofilm formation on the same surface for Streptococcus mutans, Streptococcus gordonii, and Streptococcus intermedius. The gingival fibroblasts on Tis-OPAAE disc had also significantly lower production of MMP-2. The collagen production was significantly lower on all surfaces with roughness higher than 0.2 μm. This study confirmed that the titanium disc with the surface roughness 3.39 μm (Tis-OPAAE) supported the adhesion of bacterial strains as well as gingival fibroblasts.
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http://dx.doi.org/10.1002/jbm.a.34598DOI Listing
October 2013

Quantification of the interaction forces between metals and graphene by quantum chemical calculations and dynamic force measurements under ambient conditions.

ACS Nano 2013 Feb 30;7(2):1646-51. Epub 2013 Jan 30.

Regional Centre of Advanced Technologies and Materials, Department of Physical Chemistry, Faculty of Science, Palacký University, 77146 Olomouc, Czech Republic.

The two-dimensional material graphene has numerous potential applications in nano(opto)electronics, which inevitably involve metal graphene interfaces.Theoretical approaches have been employed to examine metal graphene interfaces, but experimental evidence is currently lacking. Here, we combine atomic force microscopy (AFM) based dynamic force measurements and density functional theory calculations to quantify the interaction between metal-coated AFM tips and graphene under ambient conditions. The results show that copper has the strongest affinity to graphene among the studied metals (Cu, Ag, Au, Pt, Si), which has important implications for the construction of a new generation of electronic devices. Observed differences in the nature of the metal-graphene bonding are well reproduced by the calculations, which included nonlocal Hartree-Fock exchange and van der Waals effects.
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http://dx.doi.org/10.1021/nn305608aDOI Listing
February 2013

Surface design of core-shell superparamagnetic iron oxide nanoparticles drives record relaxivity values in functional MRI contrast agents.

Chem Commun (Camb) 2012 Dec 12;48(93):11398-400. Epub 2012 Oct 12.

Regional Centre of Advanced Technologies and Materials, Palacky University, Olomouc, Czech Republic.

Core-shell hydrophilic superparamagnetic iron oxide (SPIO) nanoparticles, surface functionalized with either terephthalic acid or 2-amino terephthalic acid, showed large negative MRI contrast ability, validating the advantage of using low molecular weight and π-conjugated canopies for engineering functional nanostructures with superior performances.
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http://dx.doi.org/10.1039/c2cc35515aDOI Listing
December 2012

Synthesis and characterization of γ-Fe2O3/carbon hybrids and their application in removal of hexavalent chromium ions from aqueous solutions.

Langmuir 2012 Feb 10;28(8):3918-30. Epub 2012 Feb 10.

Department of Materials Science and Engineering, University of Ioannina, GR-45110 Ioannina, Greece.

Magnetic Fe(2)O(3)/carbon hybrids were prepared in a two-step process. First, acetic acid vapor interacted with iron cations dispersed on the surface of a nanocasted ordered mesoporous carbon (CMK-3). In the second step, the primarily created iron acetate species underwent pyrolysis and transformed to magnetic iron oxide nanoparticles. X-ray diffraction, Fourier-transform infrared, and Raman spectroscopies were used for the chemical and structural characterization of the hybrids, while surface area measurements, thermal analysis, and transmission electron microscopy were employed to determine their physical, surface, and textural properties. These results revealed the preservation of the host carbon structure, which was homogenously and controllably loaded (up to 27 wt %) with nanosized (ca. 20 nm) iron oxides inside the mesoporous system. Mössbauer spectroscopy and magnetic measurements at low temperatures confirmed the formation of γ-Fe(2)O(3) nanoparticles exhibiting superparamagnetic behavior. The kinetic studies showed a rapid removal of Cr(VI) ions from the aqueous solutions in the presence of these magnetic mesoporous hybrids and a considerably increased adsorption capacity per unit mass of sorbent in comparison to that of pristine CMK-3 carbon. The results also indicate highly pH-dependent sorption efficiency of the hybrids, whereas their kinetics was described by a pseudo-second-order kinetic model. Taking into account the simplicity of the synthetic procedure and possibility of magnetic separation of hybrids with immobilized pollutant, the developed mesoporous nanomaterials have quite real potential for applications in water treatment technologies.
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http://dx.doi.org/10.1021/la204006dDOI Listing
February 2012

Multimodal action and selective toxicity of zerovalent iron nanoparticles against cyanobacteria.

Environ Sci Technol 2012 Feb 31;46(4):2316-23. Epub 2012 Jan 31.

Institute of Botany, Academy of Sciences of the Czech Republic, Lidická 25/27, 657 20 Brno, Czech Republic.

Cyanobacteria pose a serious threat to water resources around the world. This is compounded by the fact that they are extremely resilient, having evolved numerous protective mechanisms to ensure their dominant position in their ecosystem. We show that treatment with nanoparticles of zerovalent iron (nZVI) is an effective and environmentally benign method for destroying and preventing the formation of cyanobacterial water blooms. The nanoparticles have multiple modes of action, including the removal of bioavailable phosphorus, the destruction of cyanobacterial cells, and the immobilization of microcystins, preventing their release into the water column. Ecotoxicological experiments showed that nZVI is a highly selective agent, having an EC(50) of 50 mg/L against cyanobacteria; this is 20-100 times lower than its EC(50) for algae, daphnids, water plants, and fishes. The primary product of nZVI treatment is nontoxic and highly aggregated Fe(OH)(3), which promotes flocculation and gradual settling of the decomposed cyanobacterial biomass.
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http://dx.doi.org/10.1021/es2031483DOI Listing
February 2012

Non-chemical approach toward 2D self-assemblies of Ag nanoparticles via cold plasma treatment of substrates.

Nanotechnology 2011 Jul 20;22(27):275601. Epub 2011 May 20.

Regional Centre of Advanced Technologies and Materials, Department of Physical Chemistry, Faculty of Science, University of Palacky, Slechtitelu 11, 78371 Olomouc, Czech Republic.

The nano-modification of selected substrates by means of atmospheric cold plasma treatment was exploited for the two-dimensional (2D) self-assembling of silver nanoparticles (Ag NPs). Such a useful combination of the cold plasma treatment of substrate surface and an immediate easy deposition of Ag NPs creating the 2D self-assemblies on the substrates is published for the first time, to the best of our knowledge. Except for the cold plasma treatment, mainly the following parameters influenced the resulting NP assemblies: the choice of solvent mixture, concentration of Ag NP dispersions, and the deposition technique. The 2D self-assemblies of Ag NPs, providing the same work function as a Ag electrode, were formed on the cold plasma-treated substrates when a drop-casting technique was employed. The possibility of an easy preparation of the Ag NP 2D self-assemblies on substrates without using any chemical agents and/or evaporating chamber could be exploited, e.g. in photovoltaic and light-emitting diode devices.
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http://dx.doi.org/10.1088/0957-4484/22/27/275601DOI Listing
July 2011

On airborne nano/micro-sized wear particles released from low-metallic automotive brakes.

Environ Pollut 2011 Apr 17;159(4):998-1006. Epub 2011 Jan 17.

Technical University Ostrava, Nanotechnology Center, Ostrava-Poruba, Czech Republic.

The paper addresses the wear particles released from commercially available "low-metallic" automotive brake pads subjected to brake dynamometer tests. Particle size distribution was measured in situ and the generated particles were collected. The collected fractions and the original bulk material were analyzed using several chemical and microscopic techniques. The experiments demonstrated that airborne wear particles with sizes between 10 nm and 20 μm were released into the air. The numbers of nanoparticles (< 100 nm) were by three orders of magnitude larger when compared to the microparticles. A significant release of nanoparticles was measured when the average temperature of the rotor reached 300°C, the combustion initiation temperature of organics present in brakes. In contrast to particle size distribution data, the microscopic analysis revealed the presence of nanoparticles, mostly in the form of agglomerates, in all captured fractions. The majority of elements present in the bulk material were also detected in the ultra-fine fraction of the wear particles.
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http://dx.doi.org/10.1016/j.envpol.2010.11.036DOI Listing
April 2011

Graphene fluoride: a stable stoichiometric graphene derivative and its chemical conversion to graphene.

Small 2010 Dec;6(24):2885-91

Regional Center of Advanced Technologies and Materials, Department of Physical Chemistry, Faculty of Science, Palacky University, tr. 17. listopadu 12, Olomouc 77146, Czech Republic.

Stoichoimetric graphene fluoride monolayers are obtained in a single step by the liquid-phase exfoliation of graphite fluoride with sulfolane. Comparative quantum-mechanical calculations reveal that graphene fluoride is the most thermodynamically stable of five studied hypothetical graphene derivatives; graphane, graphene fluoride, bromide, chloride, and iodide. The graphene fluoride is transformed into graphene via graphene iodide, a spontaneously decomposing intermediate. The calculated bandgaps of graphene halides vary from zero for graphene bromide to 3.1 eV for graphene fluoride. It is possible to design the electronic properties of such two-dimensional crystals.
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http://dx.doi.org/10.1002/smll.201001401DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3020323PMC
December 2010