Formation and pharmacological activity of silicon—chitosan-containing glycerohydrogels obtained by biomimetic mineralization

The biomimetic sol—gel synthesis of silicon—chitosan-containing glycerohydrogels was carried out using silicon tetraglycerolate as a precursor. It was found that chitosan accelerates gel formation in weakly acidic media. In more acidic media, the kinetics of the process changes according to the curve with a maximum, which can be attributed to different mechanisms of silanol condensation before and after the isoelectric point. The investigated silicon—chitosan-containing glycerohydrogels exhibit antibacterial, anti-inflammatory, and wound healing activity. The synthesized hybrid glycerohydrogels are promising materials for biomedical applications.     

Structurization and Optical Activity in Cellulose Triacetate Modified with Trifluoroacetic Acid Vapor

Structurization in cellulose triacetate modified with trifluoroacetic acid vapor and its effect on the optical activity are studied.     

Sorption of iodine-containing vapor onto chitosan

The kinetics of sorption of vapor over aqueous and aqueous-alcoholic solutions of potassium iodide and potassium iodine–iodide and over crystalline iodine onto chitosan powder or film was studied. The vapor diffusion coefficients in the initial and final sorption steps were calculated from the data obtained. For all the chitosan–sorbate vapor systems studied, the mass transfer relationships are not described by Fick’s law and are characterized by anomalous sorption kinetics. The properties of chitosan powder after the uptake of the sorbate vapor were evaluated by electronic and IR spectroscopy, X-ray diffraction, and differential thermal and thermal gravimetric analysis. Sorption of iodine-containing vapor onto the polymer is accompanied by complexation of the components. The iodine–chitosan complexes are stable in storage and resistant to heat treatment. The results obtained served as a basis for developing a procedure for preparing kinetically and thermally stable powdered iodinated chitosan derivatives.     

Obtaining and Properties of L-Aspartic Acid Solutions of Chitosan

Russian Journal of Applied Chemistry - Conditions for obtaining L-aspartic acid solutions of chitosan were considered: dissolution of the polymer with the formation of chitosan aspartate occurs in...     

Structure Formation and Optical Activity of Cellulose Acetate Modified by the Vapors of Mesophasogenic Solvents

The effect of the vapors of mesophasogenic solvents, i.e., forming a lyotropic liquid-crystal phase with a polymer, on the structure formation and optical activity of acetate cellulose is studied. It is established that the action of vapors of such a type is accompanied by changes in the supramolecular structure of cellulose ester and spatial organization of macromolecules. Modification of a polymer by vapors of the mixtures of mesophasogenic solvents and water does not decrease (but in some cases enhances) the observed effects. As for individual solvents, the action of their mixtures with water obeys the dose–effect law, with a greater influence of small doses of absorbed vapors on the polymer structure and optical activity. The implementation of such conditions makes it possible to purposefully create different structures based on the same polymeric matrix and, thus, produce materials with improved properties and new functional potentialities.     

Optical activity of films based on chitosan of various molecular masses and modifications

The effect of chemical (polysalt → polybase reaction) and physicochemical (heat and vapor processing) modifications of the films of chitosan of various molecular masses and prehistories on the optical activity of the polysaccharide is studied. For both of the chitosan chemical modifications, the following dependence that is nontrivial for high-molecular compounds is established: [α] = f(log\({\bar M_\eta }\)); as the degree of polymerization decreases, the modulus of [α] of the films increases. The X-ray diffraction study shows that the differences in the optical activity of the samples with different \({\bar M_\eta }\) are caused by a restriction in the mobility of the macromolecular sections upon formation of the films of high-molecular chitosan and incompleteness of the relaxation processes of the film systems to the state with energetically favorable conformations. The comparison of humidity and optical and biological activities of the initial and dehydrated chitosan films is performed. The chitosan films in the salt modification feature moderate bactericidal activity, which decreases with an increase in \({\bar M_\eta }\) of the polymer. The thermal processing of the salt modification reduces the antibacterial action; a conversion to the base form is accompanied by the loss of bactericidal activity.     

Effect of molecular mass on the optical activity of chitosan

The optical activity of chitosan has been examined by the optical rotary dispersion method in a wide molecular mass range, beginning from low-molecular analogs of the monomer unit and oligomers. In the spectral range from 300 to 710 nm, all samples demonstrate smooth curves of the optical rotary dispersion. For the polymers and oligomers, these curves lie in the region of negative values of specific optical rotation [α], while for monosaccharides, these curves are in the positive region. High-molecular-mass samples are characterized by maximal ?[α] values that are practically independent of molecular mass. For partially depolymerized samples with M < 2 × 10⁵ and for oligomers, the smaller the molecular mass of the sample, the greater the decrease in the modulus of ?[α]. The passage to D-glucosamine chlorohydrate and to N-acetyl-D-glucosamine is characterized by inversion of the sign of rotation and achievement of high +[α] values.     

Orientational processes in the yarns of high-molecular-mass cellulose acetate in vapors of nitromethane and its mixture with water

The phenomenon of spontaneous changes in the linear dimensions (elongation-contraction) is described for commercial and laboratory samples of acetate yarns processed by wet spinning from high- molecular -mass cellulose diacetate in vapors of a mesophas ogenic solvent (which is able to form a lyotropic LC phase with the polymer), nitromethane, and its mixtures with water. The thermodeformational, elastic- plastic, physicomechanical, and surface characteristics of the yarns at different stages of their spontaneous deformation are analyzed. When samples are treated with probe vapors, orientational processes in the polymer matrix are activated, and this observation makes it possible to prepare yarns with improved physicomechanical characteristics and with low linear density. A new phenomenon (to our knowledge) of cyclic three- stage deformation of acetate monofilaments in nitromethane vapors is discovered. This evidence is interpreted from the standpoint of phase (amorphous glassy-liquid crystalline state) and conformational transitions as well as by the mechanism of interaction between polymers and solvent vapors and related development of the LC phase.     

Physicochemical Modification of Cellulose Acetate for Manufacturing Films,Membranes, and Biofilters

Modification of cellulose acetate with vapor of a mixture of water and a solvent in which cellulose derivatives form a lyotropic liquid-crystal phase, aimed at preparation of films, membranes, and biofilters, is studied. The resulting materials are capable of removing excess blood cholesterol with no concomitant decrease in the blood protein and electrolyte levels.