Search

Sustained interest in the use of renewable resources for the production of medical materials has stimulated research on bacterial cellulose (BC) and nanocomposites based on it. New Ag-containing nanocomposites were obtained by modifying various forms of BC with Ag nanoparticles prepared by metal–vapor synthesis (MVS). Bacterial cellulose was obtained in the form of films (BCF) and spherical BC beads (SBCB) by the Gluconacetobacter hansenii GH-1/2008 strain under static and dynamic conditions. The Ag nanoparticles synthesized in 2-propanol were incorporated into the polymer matrix using metal-containing organosol. MVS is based on the interaction of extremely reactive atomic metals formed by evaporation in vacuum at a pressure of 10−2 Pa with organic substances during their co-condensation on the cooled walls of a reaction vessel. The composition, structure, and electronic state of the metal in the materials were characterized by transmission and scanning electron microscopy (TEM, SEM), powder X-ray diffraction (XRD), small-angle X-ray scattering (SAXS) and X-ray photoelectron spectroscopy (XPS). Since antimicrobial activity is largely determined by the surface composition, much attention was paid to studying its properties by XPS, a surface-sensitive method, at a sampling depth about 10 nm. C 1s and O 1s spectra were analyzed self-consistently. XPS C 1s spectra of the original and Ag-containing celluloses showed an increase in the intensity of the C-C/C-H groups in the latter, which are associated with carbon shell surrounding metal in Ag nanoparticles (Ag NPs). The size effect observed in Ag 3d spectra evidenced on a large proportion of silver nanoparticles with a size of less than 3 nm in the near-surface region. Ag NPs in the BC films and spherical beads were mainly in the zerovalent state. BC-based nanocomposites with Ag nanoparticles exhibited antimicrobial activity against Bacillus subtilis, Staphylococcus aureus, Escherichia coli bacteria and Candida albicans and Aspergillus niger fungi. It was found that AgNPs/SBCB nanocomposites are more active than Ag NPs/BCF samples, especially against Candida albicans and Aspergillus niger fungi. These results increase the possibility of their medical application. [ABSTRACT FROM AUTHOR]

New hybrid materials based on Ag nanoparticles stabilized by a polyaminopropylalkoxysiloxane hyperbranched polymer matrix were prepared. The Ag nanoparticles were synthesized in 2-propanol by metal vapor synthesis (MVS) and incorporated into the polymer matrix using metal-containing organosol. MVS is based on the interaction of extremely reactive atomic metals formed by evaporation in high vacuum (10−4–10−5 Torr) with organic substances during their co-condensation on the cooled walls of a reaction vessel. Polyaminopropylsiloxanes with hyperbranched molecular architectures were obtained in the process of heterofunctional polycondensation of the corresponding AB2-type monosodiumoxoorganodialkoxysilanes derived from the commercially available aminopropyltrialkoxysilanes. The nanocomposites were characterized using transmission (TEM) and scanning (SEM) electron microscopy, X-ray photoelectron spectroscopy (XPS), powder X-ray diffraction (PXRD) and Fourier-transform infrared spectroscopy (FTIR). TEM images show that Ag nanoparticles stabilized in the polymer matrix have an average size of 5.3 nm. In the Ag-containing composite, the metal nanoparticles have a "core-shell" structure, in which the "core" and "shell" represent the M0 and Mδ+ states, respectively. Nanocomposites based on silver nanoparticles stabilized with amine-containing polyorganosiloxane polymers showed antimicrobial activity against Bacillus subtilis and Escherichia coli. [ABSTRACT FROM AUTHOR]

Methods for creating various 3D morphologies of composites based on chitosan and copper nanoparticles stabilized by it in carbonic acid solutions formed under high pressure of saturating CO2 were developed. This work includes a comprehensive analysis of the regularities of copper nanoparticles stabilization and reduction with chitosan, studied by IR and UV-vis spectroscopies, XPS, TEM and rheology. Chitosan can partially reduce Cu2+ ions in aqueous solutions to small-sized, spherical copper nanoparticles with a low degree of polydispersity; the process is accompanied by the formation of an elastic polymer hydrogel. The resulting composites demonstrate antimicrobial activity against both fungi and bacteria. Exposing the hydrogels to the mixture of He or H2 gases and CO2 fluid under high pressure makes it possible to increase the porosity of hydrogels significantly, as well as decrease their pore size. Composite capsules show sufficient resistance to various conditions and reusable catalytic activity in the reduction of nitrobenzene to aniline reaction. The relative simplicity of the proposed method and at the same time its profound advantages (such as environmental friendliness, extra purity) indicate an interesting role of this study for various applications of materials based on chitosan and metals. [ABSTRACT FROM AUTHOR]

New functional medical materials with antibacterial activity based on biocompatible bacterial cellulose (BC) and Ag nanoparticles (Ag NPs) were obtained. Bacterial cellulose films were prepared by stationary liquid-phase cultivation of the Gluconacetobacter hansenii strain GH-1/2008 in Hestrin–Schramm medium with glucose as a carbon source. To functionalize the surface and immobilize Ag NPs deposited by magnetron sputtering, BC films were treated with low-pressure oxygen–nitrogen plasma. The composition and structure of the nanomaterials were studied using transmission (TEM) and scanning (SEM) electron microscopy and X-ray photoelectron spectroscopy (XPS). Using electron microscopy, it was shown that on the surface of the fibrils that make up the network of bacterial cellulose, Ag particles are stabilized in the form of aggregates 5–35 nm in size. The XPS C 1s spectra show that after the deposition of Ag NPs, the relative intensities of the C-OH and O-C-O bonds are significantly reduced. This may indicate the destruction of BC oxypyran rings and the oxidation of alcohol groups. In the Ag 3d5/2 spectrum, two states at 368.4 and 369.7 eV with relative intensities of 0.86 and 0.14 are distinguished, which are assigned to Ag0 state and Ag acetate, respectively. Nanocomposites based on plasma-treated BC and Ag nanoparticles deposited by magnetron sputtering (BCP-Ag) exhibited antimicrobial activity against Aspergillus niger, S. aureus and Bacillus subtilis. [ABSTRACT FROM AUTHOR]