Vera Kasparkova

On the development and characterisation of crosslinked sodium alginate/gelatine hydrogels.

Sodium alginate (SA) and gelatine (G) based hydrogels with various SA/G ratios, crosslinked with calcium ions (Ca(2+)) and glutaraldehyde (GTA), respectively, were developed. Scanning electron microscopy, Fourier transform infrared spectroscopy (FTIR), and dynamic mechanical analysis (DMA) were applied to determine their physicochemical characterization. The swelling studies, conducted in phosphate-buffered saline with a pH ranging from 1 to 11 at 37 °C, were utilized for an evaluation of their absorption ability. FTIR spectra of the Ca(2+) crosslinked SA/G hydrogels revealed a small shift in symmetric stretching carboxyl groups, indicating an ionic binding between the Ca(2+) ions and the SA. Increasing the G content in hydrogels crosslinked with GTA significantly changed the shapes of the amide I and II bands in the FTIR spectra, thus confirming the G-GTA crosslink formation. After crosslinking, a DMA study proved the enhanced viscoelastic properties and improved thermal stability of the prepared samples. The obtained data indicated that Ca(2+) crosslinked hydrogels with a SA/G 50/50 ratio provide a good balance of swelling and viscoelastic properties, making them applicable as a potential nontoxic wound dressing material capable of adequately assuring a moist environment, elasticity and mechanical strength for comfortable wound healing.

Colloidal polyaniline dispersions: Antibacterial activity, cytotoxicity and neutrophil oxidative burst

Polyaniline colloids rank among promising application forms of this conducting polymer. Cytotoxicity, antibacterial activity, and neutrophil oxidative burst tests were performed on cells treated with colloidal polyaniline dispersions. The antibacterial effect of colloidal polyaniline against gram-positive and gram-negative bacteria was most pronounced for Bacillus cereus and Escherichia coli, with a minimum inhibitory concentration of 3,500 μg mL(-1). The data recorded on human keratinocyte (HaCaT) and a mouse embryonic fibroblast (NIH/3T3) cell lines using an MTT assay and flow cytometry indicated a concentration-dependent cytotoxicity of colloid, with the absence of cytotoxic effect at around 150 μg mL(-1). The neutrophil oxidative burst test then showed that colloidal polyaniline, in concentrations <150 μg mL(-1), was not able to stimulate the production of reactive oxygen species in neutrophils and whole human blood. However, it worked efficiently as a scavenger of those already formed.

Antibacterial properties of polyaniline-silver films

In situ polymerised thin polyaniline (PANI) films produced on polystyrene dishes were tested for their antibacterial activity with respect to Escherichia coli and Staphylococcus aureus, representing both gram-positive and gram-negative bacteria. PANI films were subsequently used for the reduction of silver ions to metallic Ag. PANI salt and base in original forms and after the deposition of Ag were studied. PANI salt showed a significant antibacterial effect against both bacteria strains while the efficacy of neat PANI base was only marginal. After the Ag deposition, the PANI base exhibited different levels of antibacterial effect depending on the type of the bacterial strain; the growth of gram-positive Staphylococcus aureus was inhibited depending on the Ag concentration on the film, while Escherichia coli remained uninfluenced. Efficacy of the PANI salt with deposited Ag against both bacteria strains was comparable with that of PANI alone and was not affected by the Ag concentration. The results show that Ag deposition can be a suitable method for the preparation of PANI base films with improved antibacterial properties.

Rheological and thermal performance of newly developed binder systems for ceramic injection molding

In a novel binder system, carnauba wax was considered to replace the synthetic backbone polymers (polyolefins) enhancing the environmental sustainability of Ceramic Injection Molding (CIM) technology. The paper presents comparison of the rheological performance and thermal behavior of the aluminum oxide CIM feedstocks based on a binder containing carnauba wax with those consisting of a commercial binder. Further, acrawax (N, N’-Ethylene Bis-stearamide) has been considered as another possible substitute of polyolefins. For both proposed substitutes there is a significant reduction in viscosity, and in case of carnauba wax based feedstock also in processing temperature, which is essential for injection molding of reactive powders. Thermal characterization comprised analyses of single neat binders, their mixtures and mixtures with aluminum oxide. The presence of powder lowered melting temperatures of all tested binders except of polyolefin. Further depression in melting point of poly(ethylene glycol) is obse...