Antibacterial, mechanical and surface properties of Ag-DLC films prepared by dual PLD for medical applications.

Silver doped diamond-like carbon layers were deposited by dual pulsed laser deposition using two KrF excimer lasers. The concentration of Ag, determined by XPS and WDS, moved from zero to ~10at%. We found that the sp2/sp3 ratio, film roughness and the number of droplets (SEM and AFM) increased with increasing silver concentration. The sp3 content measurement (XPS) was influenced by ion cluster surface sputtering and varied from 71.0% (undoped DLC) to 36.2% (for 9.3at% Ag). Transmission was measured on the scale from 200nm to 1100nm, and decreased with increasing silver content. An increase of Ag content has an effect on the decrease of the storage modulus (E') and the indentation hardness (HIT). The highest values HIT=51.9GPa and E'=270.6GPa were measured on a sample with 0at% Ag. The lowest values HIT=26.0GPa and E'=180.2GPa were measured on a sample of 9.3at% Ag. Film adhesion was studied using the scratch test and was up to 20.8N for the highest Ag concentration. The contact angle (CA) measurements for water showed that the CA of Ag-DLC films was higher (78°-98°) that of DLC film (77°). The surface free energy of DLC and of Ag-DLC was about 40mJ·m-2. Antibacterial properties were studied using gram positive and gram negative bacteria. The antibacterial effects increased with the Ag concentration and were ~99.9% after 24h for the layers with the highest silver content (9.3at%). Our results demonstrate that the Ag-doped DLC films are potentially useful biomaterials having both good mechanical properties and antimicrobial characteristics. PRIME NOVELTY STATEMENT: Unique manufacturing technique dual pulsed laser deposition was applied on hydrogen-free diamond-like carbon doped by Ag including topological, physical and antibacterial characterization.

Effect of some aldoses on growth of Saccharomyces cerevisiae inhibited with molybdenum.

The inhibitory effect of molybdenum ions on growth of yeasts at pH 5.5 was found to be decreased by aldoses in the following order: D-talose greater than L-mannose greater than L-ribose greater than D-lyxose greater than L-galactose greater than L-arabinose greater than L-glucose greater than L-xylose. Increased concentrations of molybdenum brought about morphological changes of yeast cells. Cells grown under these conditions were smaller, had thicker walls and formed clusters.

Antimicrobial effects of some mono- and bishydrazones.

Antibacterial, antifungal and antiprotozoal effects of nine mono- and bishydrazones of glycolaldehyde, glyoxal, methoxyacetaldehyde and glutaraldehyde were studied using eight model organisms. It was found that bishydrazones are much more efficient antimicrobial agents than monohydrazones in the case of all model microorganisms.

Antibiotic properties of lignin components.

Inhibitory effects of compounds with guaiacyl and syringyl structure, representing the structure of native lignin, were studied on model cultures of bacteria, yeasts, yeast-like microorganisms and moulds. Isoeugenol exhibited the most pronounced inhibitory effect on growth of the studied microorganisms.

Antimicrobial effect of 4-nitrophenylhydrazones, isonicotinoylhydrazones and N-4-nitrophenylglycosylamines of D- and L-aldoses.

The antibacterial effect of 19 4-nitrophenylhydrazones, isonicotinoylhydrazones, and N-4-nitrophenylhydrazones, of 9 mono- and 2 disaccharides was tested with Micrococcus luteus, Bacillus licheniformis and Escherichia coli.

Production of alpha-amylase by microscopic fungi.

The amylolytic activity and especially the production of alpha-amylase (EC 3.2.1.1) and alpha-glucosidase (EC 3.2.1.20) was screened in imperfect fungi, mucoral fungi and some ascomycetes. The character of the polysaccharide system, which is responsible for the utilization of alpha (1 to 4) glucan, was specified with a concomitant screening of growth on soluble starch. The amylolytic activity was found in 29 strains out of the 49 tested.

Production of beta-glucosidase, exo-beta-1,4-glucanase and endo-beta-1,4-glucanase by selected microscopic fungi.

Production of beta-glucosidase, exo-beta-1,4-glucanase and endo-beta-1,4-glucanase was screened in 58 species of imperfect fungi, mucoral fungi and some ascomycetes. beta-Glucosidase activity was found in all of the tested microorganisms, exo-beta-1,4-glucanase activity in 23, and endo-beta-1,4=glucanase activity in 38 microorganisms. Growth on cellobiose was found in all tested microorganisms, growth on carboxymethylcellulose in in 38 tested strains.

Antiprotozoal effects of some hydrazones.

Antiprotozoal effects of hydrazones derived from compounds with 1 to 4 carbon atoms were studied on the model organism Trichomonas vaginalis isolated from a female patient with acute urogenital trichomoniasis.

Enzyme apparatus of the genus Fusarium.

The ability to degrade oligo- and polysaccharides by enzymes of the glycosidase and glucan-glucan hydrolyse type, and esterase, phosphatase, proteinase, peroxidase, catalase, laccase and tyrosinase activities were tested in 35 strains of 11 sections of the genus Fusarium.

Biochemical similarities among strains of Aureobasidium pullulans (de Bary) Arnaud.

Seventy-seven properties of Aureobasidium pullulans including utilization of various carbon sources, decomposition of the lignin-cellulose complex and the respective enzymes were checked in the present communication. According to these properties the group of 43 strains was separated in three parts, out of which two groups were found to belong to varieties A. pullulans var. pullulans and A. pullulans var. melanigenum. The third group formed a marginal part. The two varieties differed in numerous biochemical markers, particularly in the absence of monophenol monooxygenase in the variety A. pullulans var. pullulans.

Cellulase activity of higher fungi.

The method of liquefaction of gel from cross-linked cellulose was used for monitoring the cellulolytic activity of 114 cultures of higher fungi, 47 of which belonged to Pleurotus ostreatus. All cultures of P. ostreatus had a low activity. The highest cellulase activity, manifested by Piptoporus betulinus, was comparable with that of Tricloderma viride QM6a.

Production of alpha-amylase by yeasts and yeast-like organisms.

Of a total of 177 strains of yeasts and yeast-like organisms only 8 were capable of producing alpha-amylase; most strains were able to utilize 1,4-alpha-glucans by means of enzymes acting on the non-reducing ends of the outer glucan chains.

Antimicrobial effect of sugar osazones and anhydro sugars.

The antimicrobial effect of 14 sugar osazones and anhydro sugars was studied with model strains of Micrococcus luteus, Bacillus licheniformis, Escherichia coli and strains Staphylococcus aureus and Pseudomonas aeruginosa isolated from clinical material. The relationship between the structure of these compounds, their solubility in water and 1-octanol and antimicrobial effect was investigated.

Antimicrobial properties of aromatic compounds of plant origin.

The antimicrobial action of 11 compounds involving guaiacyl- and syringyl-like structures (low-molecular-weight part of lignin), gallic acid and its derivatives, cinnamic acid and its derivatives, veratric acid, anisic acid and crotonic acid (a total of 25 compounds) against bacteria, yeast-like organisms and protozoa was examined. Aromatic compounds modified in the C-side chain and aldehydes were effective preferentially against Trichomonas vaginalis, whereas against bacteria and yeast-like organisms eugenol was the most effective inhibitor.

Mannan-hydrolyzing enzymes of yeasts and yeast-like organism.

The ability to degrade mannan in the yeast Saccharomyces cerevisiae, i.e. the ability to produce an enzyme of the alpha-mannosidase type was tested in 57 representatives of various genera and species of yeasts and yeast-like organisms. Their growth was simultaneously monitored on soluble mannan and on 4-nitrophenyl-alpha-D-mannopyradnoside. The majority of strains produced alpha-mannosidase (EC 3.2.1.24).

Electron spectroscopy of corrugated solid surfaces.

This paper reviews work done of the influence of non-ideal surface topography on electron spectral intensities of surface-sensitive electron spectroscopic methods: primarily X-ray induced photoelectron spectroscopy (XPS) and concise Auger electron spectroscopy (AES), electron energy loss spectroscopy in the reflection mode (REELS), and elastic peak electron spectroscopy (EPES). Several attempts to solve the problem are mentioned, where (i) the effect of surface roughness is corrected using a single parameter, (ii) computer simulations based on a model of surface roughness composed of regular geometrical units are used for electron spectral intensity calculations, and finally, (iii) a semi-empirical method based on careful surface mapping of analyzed sample by atomic force microscopy (AFM) is discussed in greater detail. The first approach was found to be rather simple to properly include any complex surface topography. The second technique can help us to understand surface topography related phenomena. The latter method, suitable for arbitrary rough solid surfaces covered by conformal overlayer(s), can be incorporated in current quantitative procedures valid for ideally flat surfaces.

Remarks on some reference materials for applications in elastic peak electron spectroscopy.

The quantification of results of electron spectroscopies, AES and XPS, requires knowledge of the inelastic mean free path (IMFP) of signal electrons in solids. This parameter determines the surface sensitivity of both techniques. There are two methods of determining the IMFPs that provide these parameters in agreement with the definition: (i) calculations based on the experimental optical data, and (ii) calculations based on measurements of the electron elastic backscattering intensity. The latter method requires the use of some reference material for which the IMFP is known. In 1999, an extensive analysis of the published IMFPs has been performed; the results indicated that there is a very good agreement between the calculated and measured IMFPs for four elemental solids: Ni, Cu, Ag and Au. The averaged IMFPs for these elements are known under the name of the recommended IMFPs. However, no preference among these four elements has been established. In the present work, an attempt is made to select an element for which the recommended IMFPs result in the best agreement between the calculated and measured intensities of elastic electron backscattering. For this purpose, the elastic backscattering intensity has been measured at eight electron energies varying from 200 to 1500 eV. At each energy, the intensity was measured over a wide range of emission angles from 35 degrees to 74 degrees . The experiments were accompanied with Monte Carlo calculations of the elastic backscattering probability for the same energies and experimental configurations. It has been found, from comparison, that the best agreement is observed for Au, and this element is thus recommended as the reference material. It has been shown that the shape of the emission angle dependence of the elastic backscattering intensity is noticeably influenced by the surface energy losses.