Zdeňka Kolská

Properties of gold nanostructures sputtered on glass

We studied the electrical and optical properties, density, and crystalline structure of Au nanostructures prepared by direct current sputtering on glass. We measured temperature dependence of sheet resistance and current-voltage characteristics and also performed scanning electron microscopy [SEM] analysis of gold nanolayers. It was shown that within the wide range of temperatures, gold nanolayers (<10 nm) exhibit both metal and semiconducting-like type of conductivity. UV/Vis analysis proved the semiconducting characteristic of intrinsic Au clusters. SEM analysis showed the initiatory stadium of gold layer formation to be running over isolated islands. Gold density calculated from the weight and effective thickness of the layers is an increasing function of the layer thickness up to approximately 100 nm. In thin layers deposited on solid surface, a lattice expansion is observed, which is manifested in the increase of the lattice parameter and the decrease of metal density. With increasing layer thickness, the lattice parameter and the density approach the bulk values.

Antibacterial wound dressing: plasma treatment effect on chitosan impregnation and in situ synthesis of silver chloride on cellulose surface

The treatment of wounds often deals with bacterial infections which complicate healing. Our aim was to prepare cellulose wound dressings with antibacterial properties. A cellulose dressing was exposed to argon plasma discharge, impregnated with chitosan and then silver chloride particles were precipitated in situ on the dressings surface. The effect of plasma treatment on both the chitosan impregnation and silver chloride precipitation was studied, together with the antibacterial properties of the prepared dressings. The materials were characterized by optical microscopy, scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), goniometry, absorption atomic spectroscopy (AAS) and zeta potential measurement. The antibacterial potency of the dressings was assessed using environmental bacterial strains of Escherichia coli and Staphylococcus epidermidis. Plasma treatment had a positive effect on both chitosan impregnation and the silver chloride precipitation. The antibacterial tests performed on these wound dressings exhibited growth prevention of the two representative strains of Gram-positive and Gram-negative bacteria. These results are of medical interest.

Poly- l - lactic acid modified by etching and grafting with gold nanoparticles

This work is focused on characterization of plasma treated and consequently etched and grafted biocompatible polymer poly(l-lactide acid) (PLLA). The interaction of biodegradable polymers with cold plasma is of a great importance in a tissue engineering and surface science. Cold plasma exposure, grafting with gold nanoparticles and etching processes were successfully applied to biopolymer substrate. A method for biopolymer nanostructuring as combination of cold plasma treatment and Au nanoparticle grafting for biocompatibility improvement is introduced. Surface roughness, morphology and surface chemistry was determined. The plasma modification leads to significant increase in surface roughness of PLLA and appearance of sharp spikes and ridges on the PLLA surface. Modification by grafting and etching leads to significant changes in PLLA surface morphology and chemistry. The surface ablation of PLLA has been proved to be significant. In etching of plasma-modified PLLA, methanol proves to be stronger etching agent than water. The grafting of PLLA with gold nanoparticles improved mouse embryonic fibroblasts (NIH 3T3) adhesion and proliferation significantly.

Grafting of bovine serum albumin proteins on plasma-modified polymers for potential application in tissue engineering

In this work, an influence of bovine serum albumin proteins grafting on the surface properties of plasma-treated polyethylene and poly-l-lactic acid was studied. The interaction of the vascular smooth muscle cells with the modified polymer surface was determined. The surface properties were characterized by X-ray photoelectron spectroscopy, atomic force microscopy, nano-LC-ESI-Q-TOF mass spectrometry, electrokinetic analysis, and goniometry. One of the motivations for this work is the idea that by the interaction of the cell with substrate surface, the proteins will form an interlayer between the cell and the substrate. It was proven that when interacting with the plasma-treated high-density polyethylene and poly-l-lactic acid, the bovine serum albumin protein is grafted on the polymer surface. Since the proteins are bonded to the substrate surface, they can stimulate cell adhesion and proliferation.

Cytocompatibility of plasma and thermally treated biopolymers

This paper is focused on the surface characterization of plasma and consequently thermally treated biocompatible polymers. PLLA (poly(L-lactide acid) and PMP (poly-4-methyl-1-pentene) are studied. The influence of Ar plasma treatment on the surface polarity of substrate measured immediately after treatment and during the polymer surface aging is studied. Surface roughness, morphology, wettability, and surface chemistry were determined. Plasma treatment leads to significant changes in PLLA surface morphology and chemistry, with the PMP being slightly affected. The higher resistance to plasma fluence results in smaller ablation of PMP than that of PLLA. The plasma treatment improves cell adhesion and proliferation on the PMP. Plasma treatment of PLLA influences mostly the homogeneity of adhered and proliferated VSMC.

Annealing of gold nanostructures sputtered on polytetrafluoroethylene

Gold nanolayers sputtered on polytetrafluoroethylene (PTFE) surface and their changes induced by post-deposition annealing at 100°C to 300°C are studied. Changes in surface morphology and roughness are examined by atomic force microscopy, electrical sheet resistance by two point technique, zeta potential by electrokinetic analysis and chemical composition by X-ray photoelectron spectroscopy (XPS) in dependence on the gold layer thickness. Transition from discontinuous to continuous gold coverage takes place at the layer thicknesses 10 to 15 nm and this threshold remains practically unchanged after the annealing at the temperatures below 200°C. The annealing at 300°C, however, leads to significant rearrangement of the gold layer and the transition threshold increases to 70 nm. Significant carbon contamination and the presence of oxidized structures on gold-coated samples are observed in XPS spectra. Gold coating leads to a decrease in the sample surface roughness. Annealing at 300°C of pristine PTFE and gold-coated PTFE results in significant increase of the sample surface roughness.

Properties of silver nanostructure-coated PTFE and its biocompatibility

Silver nanolayers were sputtered on polytetrafluoroethylene (PTFE) and subsequently transformed into discrete nanoislands by thermal annealing. The Ag/PTFE composites prepared under different conditions were characterized by several complementary methods (goniometry, UV-visible spectroscopy, X-ray photoelectron spectroscopy, and atomic force microscopy), and new data on the mechanism of Ag layer growth and Ag atom clustering under annealing were obtained. Biocompatibility of selected Ag/PTFE composites was studied in vitro using vascular smooth muscle cell (VSMC) cultures. Despite of the well-known inhibitory properties of silver nanostructures towards broad spectrum of bacterial strains and cells, it was found that very thin silver coating stimulates both adhesion and proliferation of VSMCs.

A novel method for biopolymer surface nanostructuring by platinum deposition and subsequent thermal annealing

A novel procedure for biopolymer surface nanostructuring with defined surface roughness and pattern dimension is presented. The surface properties of sputtered platinum layers on the biocompatible polymer poly(l-lactic acid) (PLLA) are presented. The influence of thermal treatment on surface morphology and electrical resistance and Pt distribution in ca. 100 nm of altered surface is described. The thickness, roughness and morphology of Pt structures were determined by atomic force microscopy. Surface sheet resistance was studied by a two-point technique. It was the sequence of Pt layer sputtering followed by thermal treatment that dramatically changed the structure of the PLLA’s surface. Depending on the Pt thickness, the ripple-like and worm-like patterns appeared on the surface for thinner and thicker Pt layers, respectively. Electrokinetic analysis confirmed the Pt coverage of PLLA and the slightly different behaviour of non-annealed and annealed surfaces. The amount and distribution of platinum on the PLLA is significantly altered by thermal annealing.

Direct immobilization of biotin on the micro-patterned PEN foil treated by excimer laser

Polymers with functionalized surfaces have attracted a lot of attention in the last few years. Due to the progress in the techniques of polymer micro-patterning, miniaturized bioanalytical assays and biocompatible devices can be developed. In the presented work, we performed surface modification of polyethylene naphthalate (PEN) foil by an excimer laser beam through a photolithographic contact mask. The aim was to fabricate micro-patterned areas with surface functional groups available for localized covalent immobilization of biotin. It was found out that depending on the properties of the laser scans, a polymer surface exhibits different degrees of modification and as a consequence, different degrees of surface biotinylation can be achieved. Several affinity tests with optical detection of fluorescently labeled streptavidin were successfully performed on biotinylated micro-patterns of a PEN foil. The polymer surface properties were also evaluated by electrokinetic analysis, Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM). The results have shown that PEN foils can be considered suitable substrates for construction of micro-patterned bioanalytical affinity assays.

Enhancement of polymer cytocompatibility by nanostructuring of polymer surface

Polymers with their advantageous physical, chemical, mechanical, and electrical properties and easy manufacturing are widely used in biology, tissue engineering, and medicine, for example, as prosthetic materials. In some cases the polymer usage may be impeded by low biocompatibility of common synthetic polymers. The biocompatibility can be improved by modification of polymer surface, for example, by plasma discharge, irradiation with ionizing radiation, and sometime subsequent grafting with suitable organic (e.g., amino-acids) or inorganic (e.g., gold nanoparticles) agents. In this way new chemically active structures are created on the polymer surface, and in some cases new surface relief is created. Recent advances in nanotechnology and in characterization of nanostructured objects open the way to development of new polymer-based materials with better bioproperties and higher application potential in biomedicine. Some of recent results obtained in the field are summarized and discussed in this paper.