E. I. Kulish

Enzymatic degradation of chitosan films by collagenase

Special features of enzymatic degradation of chitosan samples prepared as films from solutions in acetic acid under the action of collagenase as a nonspecific enzyme are considered. Variations in acid concentration in the casting solution had a substantial effect on the chitosan structure in the film formed and, as a consequence, on the degree of degradation of film samples. The addition of poly(vinyl alcohol) upon the formation of a chitosan film led to an increase in the extent of enzymatic degradation of the film.

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.

Thermal modification of chitosan films as a way to control their transport properties

The possibility of using heat treatment (∼120°C) for controlling the drug release from chitosan films prepared from acetic acid solutions and containing antibiotics cefazolin and cefotaxime was examined.

Enzymatic degradation of chitosan films under the action of nonspecific enzymes

The features of the enzymatic degradation process mediated by the nonspecific enzymes collagenase and Lyrase are discussed for chitosan films prepared from acetic acid solutions. It was shown that variations in the acid concentration in the initial solution have a substantial effect on both the structure of chitosan in the film formed and the degree of degradation of film samples.

Macromolecular effects upon enzymatic degradation of chitosan in solution

Macromolecular effects were revealed in the course of enzymatic degradation of chitosan in an acetic acid solution under the action of hyaluronidase, a nonspecific enzyme. It was shown that the concentration of chitosan in the initial solution determines its supramolecular organization and, hence, the degree of enzymatic degradation.

Enzymatic degradation of modified chitosan films

The features of enzymatic degradation of modified chitosan films prepared from acetic acid solutions using Collagenase KK enzyme preparation was studied.

Transport properties of chitosan films

Effect of the history of chitosan films on their transport characteristics in relation to elimination of drugs from the body is studied.

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.