A. A. Tkachenko

Structure of cellulose Acetobacter xylinum

The data are presented on optimization of cellulose synthesis by Acetobacter xylinum (strain VKM V-880) and the structural characteristics of A. xylinum cellulose gel film synthesized during static cultivation. The structural changes caused by the removal of water from gel films are established and the structural organization of macromolecular chains in cellulose A. xylinum is studied.

Formation of organic-inorganic composite materials based on cellulose Acetobacter xylinum and calcium phosphates for medical applications

The formation of composites based on the cellulose Acetobacter xylinum and calcium phosphates has been investigated using X-ray diffraction, electron diffraction, electron microscopy, energy-dispersive analysis, and differential scanning calorimetry. It has been demonstrated that the planar morphology of calcium phosphate nanoparticles capable of interacting with nanofibrils of the cellulose matrix is an important factor providing interfacial contacts in the formation of organic-inorganic composite materials. It has been established that magnesium-containing calcium phosphates represent two-phase systems consisting of calcium magnesium phosphate Ca2.6Mg0.4(PO4)2 (whitlockite) and hydroxyapatite Ca5(PO4)3(OH). The biocompatibility of the composite materials based on two-phase calcium phosphate systems and the temperature range of their stability (∼20–250°C) determined by the thermal stability of the organic component have been investigated.

Network Model of Acetobacter Xylinum Cellulose Intercalated by Drug Nanoparticles

It was shown that Acetobacter xylinum cellulose gel-films can sorb silver and selenium nanoparticles stabilized by N-poly(vinyl-2-pirrolidone). The structure of original cellulose matrix, isolated nanoparticles and cellulose with sorbed nanoparticles was characterized by electron diffraction, electron microscopy, small- and wide-angle x-ray scattering methods, and atomic force microscopy. It was found that in static culture Acetobacter xylinum bacterium (strain VKM B-880) may synthesize high-molecular cellulose with narrow molecular weight distribution and a considerable number of carbon sources. The structures of cellulose microfibrilles and ribbons correspond mainly to polymorphous Iβ modification. We concluded from structural studies that textured cellulose films were formed. The sorption conditions of poly(vinylpyrrolidone)-Se° and poly(vinylpyrrolidone)-Ag° nanoparticles were optimized to obtain a cellulose template that can be used in medical practice.

Investigation of nanocomposites based on hydrated calcium phosphates and cellulose Acetobacter xylinum

Composites based on two biocompatible compounds, namely, inorganic hydrated calcium phosphates and organic microfibrillar ribbons of cellulose Acetobacter xylinum, are prepared by aggregation in an aqueous suspension. The influence of the structural organization of the hydroxyapatite and temperature-time conditions on the formation of the composite materials of different compositions is investigated. It is revealed that the composite materials are textured and retain the crystal structure of cellulose and the structure of initial hydrated calcium phosphates. The analysis of the crystal structures allows us to propose a model of the interaction between the mineral and organic components of the composite material. In the framework of the model, the interaction is provided through the formation of hydrogen bonds with the participation of hydroxyl groups and oxygen atoms of the phosphor group of the hydroxyapatite and primary OH groups located at the (−110) and (110) faces of cellulose nanocrystals.

Interaction of Se0 nanoparticles stabilized by poly(vinylpyrrolidone) with gel films of cellulose Acetobacter xylinum

The sorption and desorption of poly(vinylpyrrolidone)-Se0 (PVP-Se0) nanoparticles on gel films of cellulose Acetobacter xylinum (CAX) are investigated. It is revealed that the hydrodynamic radius Rh of PVP-Se0 nanoparticles decreases from 57 nm in the initial solution (without CAX gel films) to 25 nm after the sorption of nanostructures on gel films and then increases to approximately 100 nm after the desorption of nanoparticles with water from dry samples of the CAX gel film-PVP-Se0 nanocomposite. It is found that selenium atoms do not penetrate into crystallites of the cellulose nanofibrils and replace water molecules sorbed by the primary hydroxyl groups of their walls. Poly(vinylpyrrolidone)-Se0 nanoclusters differ in the number and size upon their sorption inside the cellulose gel film and on the film surface.

Composites based on Gluconacetobacter xylinus bacterial cellulose and calcium phosphates and their dielectric properties

Dielectric properties a Gluconacetobacter xylinus bacterial cellulose and its composites with calcium phosphates were studied and used to analyze structural changes in a matrix polymer upon its mechanical treatment and introduction of a mineral fi ller. It was found that, when composites are formed, the ratio between amorphous and crystalline regions is disturbed in the cellulose matrix.

Nanotextures of composites based on the interaction between hydroxyapatite and cellulose Gluconacetobacter xylinus

Organic-inorganic composite materials with different nanotextures have been prepared using three methods based on two nanosized and biocompatible compounds—cellulose Gluconacetobacter xylinus (CGX) and hydroxyapatite Ca5(PO4)3OH (HA). The structure of the initial components and their composites has been studied using the methods of X-ray diffraction, electron microscopy, and computer simulation. During the combined aggregation of aqueous HA and CGX suspensions, the phenomenon of their adsorption, in the process of which the axis c of HA crystals is oriented parallel to the plane (−110) of CGX microfibrillas, was observed. By varying the quantitative ratio of the components and the methods of introducing HA into composites, it is possible to obtain a wide spectrum of materials for medical practice.

Formation of a composite based on selenium nanoparticles stabilized with poly-N,N,N,N-trimethylmethacryloyloxyethylammonium methyl sulfate and on Acetobacter xylinum cellulose gel films

Formation of a composite based on selenium nanoparticles stabilized with poly-N,N,N,N-trimethylmethacryloyloxyethylammonium methyl sulfate and on Acetobacter xylinum cellulose gel films was studied. Optimal sorption parameters at which the amorphous form of selenium is preserved in the composite film were suggested.

Phase transitions of native celluloses from evolutionarily different sources into polymorph IV

A procedure was suggested for preparing cellulose polymorph IV by dissolution of native celluloses from evolutionarily different sources in trifluoroacetic acid to molecularly dispersed state, followed by regeneration and treatment under hydrothermal conditions.