A new composite material that is a layered film based on cellulose obtained by static cultivation of Komagataeibacter rhaeticus and hydroxyapatite nanocrystals was studied. Samples with a mass ratio of cellulose and hydroxyapatite of 1 : 25, 1 : 4, and 1 : 1 were obtained in two ways—joint disintegration of aqueous suspensions of nanocrystals of hydroxyapatite with macrofragmented bacterial cellulose nanogel film and synthesis of hydroxyapatite nanocrystals in a suspension of disintegrated bacterial cellulose. It is shown that, regardless of the method, an increase in the proportion of cellulose leads to an increase in the density of the composite material, the degree of texturing, the Young’s modulus, and tensile strength, as well as a decrease in porosity and pore volume. Analysis of cytotoxicity carried out on fibroblasts isolated from the subcutaneous connective tissue cells of C3H/An mice demonstrated the absence of cytotoxicity of the films studied.

A comparative study of dried nanogel films of the Gluconacetobacter xylinus cellulose (GXC) in native and disintegrated forms treated with AgNO3 solution has been carried out by means of SEM and XRD. The supermolecular structure of samples studied was shown to be 3D network of nanostrips formed with oriented macrofibrils in which amorphous and crystalline regions alternate. XRD patterns of the GXC dry films, pre-treated with AgNO3 aqueous solution, demonstrate both residual AgNO3 and reduced Ag-0, the latter positioned in longwise direction of morphologic structure elements. The XRD and SEM studies of dried GXC films disintegrated in 1 % AgNO3 aqueous solution showed the presence of reduced Ag-0 in the form of nanoparticles 10 - 50 nm in diameter located in the free volume of the GXC 3D network nearby structural elements.

Scanning electron microscopy, ultra-small-angle neutron scattering (USANS), small-angle neutron and X-ray scattering (SANS and SAXS), as well as low-temperature nitrogen adsorption, were used in the studies of micro- and mesostructure of polymer matrix prepared from air-dry preliminarily disintegrated cellulose nano-gel film (synthesized by Gluconacetobacter xylinus) and the composites based on this bacterial cellulose. The composites included ZrO2 nanoparticles, Tb3+ in the form of low molecular weight salt and of metal-polymer complex with poly(vinylpyrrolydone)-poly(methacryloyl-o-aminobenzoic acid) copolymer. The combined analysis of the data obtained allowed revealing three levels of fractal organization in mesostructure of G. xylinus cellulose and its composites. It was shown that both the composition and an aggregation state of dopants have a significant impact on the structural characteristics of the organic-inorganic composites. The composites containing Tb3+ ions demonstrate efficient luminescence; its intensity is an order of magnitude higher in the case of the composites with the metal-polymer complex. It was found that there is the optimal content of ZrO2 nanoparticles in composites resulting in increased Tb3+ luminescence.

The concentration dependencies of dielectric permittivity and dielectric loss factor have been studied for the water suspensions of nanogel films of bacterial cellulose Gluconacetobacter xylinus (BC) disintegrated with the blade rotation rates of 15,000 and 20,000rpm. The dipole moments of BC colloids have been evaluated using Buckingham's statistical theory of dielectric polarization modified for binary polar systems. The number of monomer units of cellobiose in the BC colloid being equal to 113, the volume and the characteristic rotation time of the colloid particles were calculated. The difference between the values of dielectric parameters for BC samples disintegrated at 15,000 and 20,000rpm were within experimental error. The constant stoichiometry of BC colloids and the identity of orientation ordering of microfibrills in colloids to that of the BC nanogel films have been shown by dielectric and X-ray studies.

We demonstrated flexible light-emitting transparent bacterial cellulose (BC) paper modified with semiconducting polymer operated by pulse voltage. We prepared thin (∼ 35 μm) transparent BC films modified with luminescent conjugated polymer MEH:PPV with Ag electrodes. It was shown that the photoluminescence (PL) spectrum of BC/MEH:PPV films contains emission contributions from both BC and MEH:PPV components and that the PL intensity of BC and MEH:PPV maxima versus excitation power is sublinear. This indicates that exciton–exciton annihilation occurs in the light-emitting polymer at high excitation power. We found that the dependences of the spike-like electroluminescence (EL) intensity of BC/MEH:PPV films excited by the pulse voltage at different frequencies versus applied pulse bias and pulse frequency are superlinear. We assume that the turn-on and turn-off spikes originate from the recombination of charges accumulated in the bulk of the semiconducting polymer (bulk de-trapping) during the voltage pulse. The results demonstrate that such composites are prospective for application as flexible, transparent and environmentally friendly light-emitting cellulose-based papers for displays and lighting as well as biosensors.

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.

Composite films based on bacterial cellulose (BC) modified with conductive polymer PEDOT/PSS are synthesized. Structural, optical and electrical properties of such composite films are investigated. It was found that the obtained BC:PEDOT/PSS films characterized by strong absorption in the red and near-infrared spectral region and by weak intensity of photoluminescence at 300 K. The temperature dependence of the resistivity of the BC:PEDOT/PSS films follows a power law in the temperature interval 300-80 K and the resistivity values vary weakly with time. The charge carrier transport in the BC:PEDOT/PSS composite films governed mainly by the charge transport in the conducting polymer. The obtained BC:PEDOT/PSS films are promising for application as biocompatible electrodes, temperature sensors and other biochips, which are compatible with technology of printable organic electronics. (C) 2014 Elsevier B.V. All rights reserved.

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.

New composite hydrogels based on cellulose and poly(acrylamide) have been synthesized via radical polymerization of acrylamide in cellulose swollen in a reaction solution. In this study, both a plant form of cellulose and a bacterial form—that cultivated by Acetobacter xylinum bacteria—were used. The behavior of synthesized hydrogels during swelling in water, as well as the behavior of the samples swollen at equilibrium during deformation under uniaxial compression under various test conditions, have been studied. A comparative analysis of the main mechanical characteristics of hydrogels and the appropriate data for various types of articular cartilage, one of which—rabbit knee meniscus—has been tested in this study, has been performed. An average-strength hydrogel is very close to articular cartilage in all mechanical characteristics. The degrees of loading at the highest compression deformations observed during the function of joint cartilage (30–50%) is in the range 4–12 MPa for this hydrogel, and the average values of the compression modulus in the deformation ranges of 10–15 and 25–30% are 8.8 and 23.7 MPa, respectively. The behavior of hydrogels and rabbit meniscus under cyclic compression with the amplitude of 50% has been studied. Hydrogels and meniscus under this test conditions demonstrate clear viscoelastic behavior, evidenced by noticeable hysteresis for the first cycle and a decrease in the value of the maximum load with an increase in the number of cycles. Structural features of hydrogels, which can affect the behavior of the hydrogels under study, have been considered. On the whole, the results demonstrate the possibility of modeling the mechanical behavior of cartilage with the use of hydrogels of this type.

Методом радикальной полимеризации акриламида в набухшей в реакционном растворе целлюлозе синтезированы новые композиционные гидрогели на основе целлюлозы и полиакриламида. В работе использована как растительная форма целлюлозы, так и бактериальная – особый вид, выращенный бактериями Acetobacter Xylinum. Изучено поведение синтезированных гидрогелей при набухании в воде, а также поведение равновесно-набухших образцов при деформировании в условиях одноосного сжатия в различных режимах испытания. Проведен анализ основных механических характеристик гидрогелей в сравнении с данными для различных видов суставных хрящей, один из которых (мениск коленного сустава кролика) протестирован в настоящей работе. Показано, что средний по жесткости гидрогель по всем механическим характеристикам очень близок к суставным хрящам. Для него уровень нагрузок при наиболее высоких значениях величин деформаций сжатия, наблюдаемых при функционировании хрящей в суставах (30–50%), находится в диапазоне 4–12 МПа, а средние показатели модуля сжатия на участках деформаций 10–15 и 25–30% равны 8.8 и 23.7 МПа соответственно. Исследовано поведение гидрогелей и мениска кролика в режиме циклического сжатия с амплитудой 50%. Гидрогели и мениск в таком режиме испытания демонстрируют выраженное вязко-упругое поведение, что фиксируется по сильному гистерезису для первого цикла и падению величины максимальной нагрузки с ростом числа циклов. Рассмотрены структурные особенности гидрогелей, которые могут повлиять на наблюдаемое поведение. В целом результаты показывают возможность моделирования механического поведения хрящей с помощью гидрогелей данного вида.

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.

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 Ca 2.6 Mg 0.4 (PO 4 ) 2 (whitlockite) and hydroxyapatite Ca 5 (PO 4 ) 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.

Bacterial cellulose–polyacrylamide (BC–PAAm) composite hydrogels are prepared by synthesis of PAAm networks inside the BC matrices. The behavior of these gels and of the ionic ones obtained via partial hydrolysis of BC–PAAm gels is studied under swelling and compressive deformation conditions. The dependences of the hydrogels’ properties on the BC matrix preparation conditions, gel synthesis conditions and the BC content in the hydrogel compositions are studied. Two types of BC gel pellicle are used in the hydrogel synthesis, namely matrix pellicles subjected to pre-pressing (samples of series A) and those not subjected to any mechanical actions before synthesis (series B samples) containing about 99% water. The effect of anisotropic swelling of type A hydrogels is detected. The type B specimens swell isotropically. Both types of hydrogel exhibit substantial anisotropy of their mechanical properties, apparent in different shapes of compression stress–strain curves of samples cut out from the gel plates in various directions. Composite hydrogels show superb mechanical properties, including compression strength up to 10 MPa and the ability to withstand long-term cyclic stresses (up to 2000–6000 cycles) without substantial reduction of mechanical properties.

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.

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.

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.

Formation of a composite from Se 0 nanoparticles stabilized with polyvinylpyrrolidone and Acetobacter xylinum cellulose gel films was studied. The optimal sorption parameters at which the amorphous form of the selenium complex is preserved in the composite were suggested.