Tatiana Vasilieva

A Beam-Plasma Source for Protein Modification Technology

A design of the plasmachemical reactor is described. The reaction zone of the reactor is the plasma generated by injecting the continuous or intermittent electron beam into dense gaseous or vapor media containing dispersed powders of the material to be treated. Tests of the reactor showed the beams of the moderate electron energy needed to create the uniform reaction bulk, with the plasma parameters (such as densities of chemically active plasma particles, the local and whole power input, and temperatures of the gas and powder particles) being predictable and controllable. The reactor was used to modify native proteins. The modification was found to change protein properties and their bioactivity radically.

Formation of low molecular weight oligomers from chitin and chitosan stimulated by plasma-assisted processes.

The controlled degradation of solid powders of chitin and chitosan stimulated by electron-beam plasma (EBP) was experimentally studied. Crab shell chitin and chitosan were used as original substances. The non-equilibrium low temperature EBP was generated by injecting an electron beam into a gaseous medium. Chitooligosaccharides with Mw=800-2000Da and polydispersion 1.5-2.5 were formed due to the EBP-treatment of chitin and chitosan. The β-1,4 glycosidic bounds in original polymers degrade under the action of active oxygen species produced in the EBP. Low molecular weight products of chitosan inhibited the growth of various yeast-like and filamentous fungi at minimum inhibitory concentration 500mcg/ml. By optimizing the treatment conditions and using special techniques of reaction volume formation the 95% yield of chitooligosaccharides was obtained after 2min whereas the conventional chemical hydrolysis usually takes several days. The EBP-stimulated hydrolysis is promising for effective polysaccharides degradation and can be competitive with traditional technologies.

Experimental study of nitrogen-doped graphene by spectroscopic and probe methods of surface analysis

Abstract. This work demonstrates an integrated approach for studying graphene films with various doping levels of nitrogen. The graphene films grown by a chemical vapor deposition technique were doped by treatment in ammonia radio-frequency plasma discharge. The graphene samples were investigated by x-ray photoelectron spectroscopy with a parallel registration of photoemission angular dependence. The depth-dependent changes in the valence band structure and the nitrogen peak position were recorded. The shift of valence band maximum relative to the initial value (0.13±0.04  eV) was observed using ultraviolet photoelectron spectroscopy. The dispersion and the shift of π-plasmon maximum were registered while the percentage of nitrogen atoms in two-dimensional graphene network increased.

Chitin and Cellulose Processing in Low-Temperature Electron Beam Plasma

Polysaccharide processing by means of low-temperature Electron Beam Plasma (EBP) is a promising alternative to the time-consuming and environmentally hazardous chemical hydrolysis in oligosaccharide production. The present paper considers mechanisms of the EBP-stimulated destruction of crab shell chitin, cellulose sulfate, and microcrystalline cellulose, as well as characterization of the produced oligosaccharides. The polysaccharide powders were treated in oxygen EBP for 1–20 min at 40 °C in a mixing reactor placed in the zone of the EBP generation. The chemical structure and molecular mass of the oligosaccharides were analyzed by size exclusion and the reversed phase chromatography, FTIR-spectroscopy, XRD-, and NMR-techniques. The EBP action on original polysaccharides reduces their crystallinity index and polymerization degree. Water-soluble products with lower molecular weight chitooligosaccharides (weight-average molecular mass, Mw = 1000–2000 Da and polydispersity index 2.2) and cellulose oligosaccharides with polymerization degrees 3–10 were obtained. The 1H-NMR analysis revealed 25–40% deacetylation of the EBP-treated chitin and FTIR-spectroscopy detected an increase of carbonyl- and carboxyl-groups in the oligosaccharides produced. Possible reactions of β-1,4-glycosidic bonds’ destruction due to active oxygen species and high-energy electrons are given.

Hydrolysis of chitin and chitosan in low temperature electron-beam plasma

Abstract Hydrolysis of natural chitin and chitosans was performed in the electron beam plasma (EBP) of oxygen, by means of specially designed electron beam plasmachemical reactor (EBPR). Low molecular water-soluble chitin oligosaccharides with weight-average molecular mass 800–2000 Da and polydispersion index 1.5–2.5 were produced due to action of active oxygen species formed in the EBP. By optimizing the treatment conditions the 95% yield of chitin oligosaccharides was obtained after 2 min whereas the conventional chemical hydrolysis usually takes several days. The studies of the antimicrobial activity of low molecular products formed due to EBP-stimulated degradation showed that they inhibit the multiplication of various mycelial and yeast-like fungi. The technique involved is likely to be promising for the production of bioactive low molecular chitin oligosaccharides and the EBP-stimulated hydrolysis appears to be competitive with technologies conventionally used in the industry.

The Supramolecular Complex Production in Dust-Plasma Structures Controlled by the Electron Beam Plasma

The reaction volume formation by means of the protein powder dispersion inside the RF discharge with the subsequent dust-plasma structure formation is studied experimentally. The plasma-assisted deposition of low-molecular-weight organic vapors on the levitating protein particles is studied as well. Supramolecular complex “protein-drug agent” was shown to be produced by the aforementioned technique, and the addressed drug delivery complexes can be designed. Dry plasma-assisted processes are considered as the promising alternative for the conventional pharmaceutical technologies.

Synthesis of bio-active titanium oxide coatings stimulated by electron-beam plasma

Abstract Advantages of the electron-beam plasma (EBP) for production of bioactive titanium oxide coatings were experimentally studied. The coatings were synthesized in EBP of oxygen on the surface of plane titanium substrates. A number of analytical techniques were used to characterize morphology, chemical composition, and structure of the synthesized titanium oxide. The analysis showed the titanium oxide (IV) in the rutile form to predominate in the coatings composition. The samples with plasmachemically synthesized TiO2-coatings were more hydrophilic than untreated titanium. The effect was stable during two weeks and then the degradation of the wettability began. The EBP-stimulated TiO2 synthesis improved the hydroxyapatite formation on the surface of plane titanium substrates. The EBP-stimulated TiO2 synthesis is promising technique to produce bioactive coatings on the surface of titanium medical dental and bone implants. The computer simulation of plasma-surface interaction was carried out to predict the plasma composition, to find the spatial distribution of the sample temperature, and to calculate the flows of the chemically active plasma particles bombarding the tube wall. The flows of atomic and singlet oxygen were found to be the most intensive and, therefore, these particles are likely to be responsible for the formation of the biocompatible TiO2-coaings.