V. V. Chernova

Enzymatic hydrolysis of chitosan in acetate buffer solution

To examine the influence exerted on the degree of hydrogenation and hydrogenolysis by the content of olefin (diolefin) and polycyclic aromatic hydrocarbons at different fractional compositions of distillate mixtures, joint hydropurification of vacuum gasoil with benzine and light and heavy coking gasoils was performed. The study was carried out in a laboratory installation under a hydrogen pressure of 5.0 MPa, temperature of 375°C, volumetric flow rate of raw materials of 1 h−1, and H2/raw material ratio of 1000/1. The effect of the composition of raw materials and process conditions on the chemical composition and quality parameters of the resulting products was demonstrated. It was shown that a pronounced competition between olefin and polycyclic aromatic hydrocarbons in hydrogenation reactions is observed for mixtures of heavy vacuum gasoil and light coking gasoil, in contrast to mixtures of straight-run diesel fraction and light coking gasoil.

On the possibility of preparing stable silver iodide nanosols in the presence of chitosan used as a polymer stabilizer

The effect of preparation conditions for positively and negatively charged silver iodide sols on the particle size and number concentration has been determined. It has been found that the preparation of a mixture of precursors with a concentration of 0.01 mol/L at a KI to AgNO3 volume ratio of 10: 7 or 7: 10 leads to the formation of a large number of small particles (on the order of 50–60 nm) corresponding to the range of true colloidal systems with a maximum interfacial area. The presence of a polymer stabilizer–chitosan–leads to a significant improvement of the stability of the sol particles, which makes it possible to use the resulting polymer-colloidal dispersions containing nanoparticles of silver iodide sols to design hybrid materials for biomedical applications.

A rheological study of molecular and supramolecular organization of chitosan succinamide in a mixed water–etanol solvent

An approach based on quality reduction of the solvent, namely, the use of mixed water–ethanol solvents of variable volume ratio was used for control over the aggregation and formation of a physical net of bonds in chitosan succinamide solutions. A study of the molecular and supramolecular organization of chitosan succinamide in solution showed that this polymer, which does not aggregate in a dilute (to the crossover point) aqueous solution, aggregates in a mixed water–ethanol solvent even at high dilution. Polymer structurization in solution is accompanied by the formation of an additional net of physical bonds, whose nodes are aggregates of chitosan succinamide macromolecules formed in the mixed solvent. It leads to earlier formation of viscoelastic properties, which is ultimately reflected by the regularities of some physicochemical properties of materials formed from solution.

Kinetics of the enzymatic hydrolysis of chitosan films

The kinetics of the enzymatic hydrolysis of chitosan film samples under the action of the enzyme hyaluronidase was studied. It was found that, although a monolithic film sample was subjected to hydrolysis, the enzymolysis of chitosan in this case obeyed the same laws as the enzymatic hydrolysis of chitosan in solution at small substrate concentrations.

The role of low-molecular-mass electrolyte drug substances in the modification of the chitosan matrix

The effect of antibiotics of the aminoglycoside and cephalosporin series on the properties of chitosan films formed from acetic acid solutions is studied. It is shown that the introduction of the indicated substances substantially affects the conformational state of chitosan acetate and its supramolecular structure. The modification of chitosan by drug substances, accompanied by loss in solubility of chitosan films in water, leads to a decrease in the rate of desorption of antibiotics from the polymer matrix.

Rheological properties of solutions of chitosan and its complexes with colloid particles of a silver iodide sol

Rheological properties of chitosan solutions have been studied. The region of nonstructured semidilute solutions free of fluctuation networks has been revealed. The addition of oppositely charged micelles of a lyophobic sol to a semidilute polymer solution results in structurization of the solution owing to the appearance of an additional network formed by the polyelectrolyte complex between the polymer and the colloid particles. As a result, the interval between the crossover concentration and the concentration of the fluctuation-network formation decreases, whereas the viscosity of the semidilute solution grows.

Possible causes of “inconstancy” in the intrinsic viscosity of chitosan

It is found that there is substantial difference in the intrinsic viscosities of solutions of chitosan before and after its reprecipitation from acetic acid solutions. It is shown that this fact is not related to destructive processes, but is caused by the tendency toward a change in the supramolecular structure of chitosan during its dissolution in a thermodynamically good solvent.

Supramolecular Conformational Effect in Complexations of Pectin and Chitosan Polysaccharides with Some Cephalosporin and Aminoglycoside Antibiotics

The reactions of the polysaccharides pectin (Pc) and chitosan (CTS) with antibiotics of cephalosporin and aminoglycoside series were studied. The complexation between the drugs and polymers was found to occur via hydrogen bonding. Dilution of the chitosan polycation increased the probability of occurrence of the negative ions of the cephalosporin antibiotic near the chain and lowered the probability of occurrence of the positive ions of aminoglycoside antibiotics, which affected the amount of adducts. When the pectin polyanion was diluted, the opposite situation was observed.

Enzymatic Decomposition of Chitosan-Based Film Materials Modified by Antibiotics of the Cephalosporin Series

The enzymatic decomposition of film materials based on chitosan with inclusions of cephalosporin antibiotics on a substrate impregnated with Ringer–Locke’s solution was studied. The introduction of antibiotics led to a decrease in the rate of the enzymatic decomposition of chitosan, as in the case of chitosan lysis in the presence of aminoglycoside antibiotics. A possible reason for the decrease in the rate of the enzymatic decomposition of chitosan is suppression of polyelectrolyte swelling in the presence of low-molecular electrolytes including medicinal agents. The introduction of drugs in the chitosan-based film is a potential method for selectively decreasing the rate of enzymatic hydrolysis of chitosan for increasing the service life of the film material on a wound surface.

On the possibility of regulating the rate of enzymatic destruction of chitosan in an acetic acid solution

The enzymatic destruction of chitosan in an acetic acid solution in the presence of sodium chloride and sulfate was considered. It was shown that the addition of these low-molecular electrolytes is accompanied by a tightening of the macromolecular coil, as indicated by a decrease in the α constant in the Mark–Kuhn–Houwink equation and the intrinsic viscosity of chitosan. As a consequence, the chitosan units become less accessible for interaction with the enzyme, and the kinetic parameters of the process (Michaelis constant KM and the maximum rate of enzymatic destruction Vmax) change accordingly. This suggests that the resistance of this polymer to the enzyme action can be enhanced by introducing low-molecular electrolyte salts in the solution or film coating to suppress the polyelectrolyte swelling of chitosan.