[Study of electrokinetic potential of drug micro-carriers prepared from resorbable polymers bioplastotan].

The study investigates electrokinetic potential of microparticles prepared from biodegradable poly-3-hydroxybutyrate depending upon the method of preparation employed and taking into account the size of particles maintained in liquid media. The ζ-potential of microparticles. prepared from emulsion by solvent evaporation method was -20 mV; the ζ-potential of microparticles prepared by spray drying was reduced to -95 mV. The value of ζ-potential was influenced by drug loading into microparticles; the drug-loaded microparticles maintained in balanced phosphate buffer for 30 days had higher physical stability than those without drug loading.

[Modification of the surface of bioresorbed polymer matrices by laser treatment].

The effect of laser irradiation on the properties of the surface of film matrices obtained from the bioresorbed polymer polyhydroxybuturate has been studied. To determine the spectral region of the polymer optimal for the effective action of radiation on electron molecular bonds, theoretical investigations have been performed, which have shown that, for modifying the surface of matrices obtained from polyhydroxybuturate, it is expedient to use a vacuum laser at a wavelength of 160 nm. Using the laser regime of irradiation of matrices at a radiation power from 3.0 to 30 Wt, a series of films with modified surface, from roughnesses to perforations, have been obtained. The microstructure and properties of the film surface depending on the mode of irradiation have been examined, and conditions have been found under which the contact marginal angles of moistening of films with water can be decreased to 50 degrees (compared with 76-80 degrees in starting products). Thus, the conditions of laser treatment of polyhydroxybuturate matrices have been theoretically substantiated and experimentally realized that provide a beneficial effect on the properties of the surface without destroying the structure of the material.

[Biodegradable polyhydroxyalkanoates as carriers for antitumor agents].

The possible use of biodegradable polyethers of microbial origin (polyhydroxyalkanoates) as matrices for deposition of daunorubicin (rubomycin), an antitumor anthracycline, was studied. The tablet dosage form of various rubomycin load (from 1 to 60% w/w) was prepared by cold compaction under pressure. The in vitro kinetics of the rubomycin release from the polymer matrix was investigated. It was shown that the rubomycin release to the medium resulted from the drug solution and diffusion within various periods, from tens hours to several weeks and months depending on the load. When the rubomycin load was under 20% w/w the drug release was prolonged and directly proportional to the observation time. When the rubomycin concentration was under 5%, the drug release kinetics corresponded to the type of the zero order reaction with prolonged release without sharp efflux at the initial stage of the observation. The findings showed that the polyhydroxyalkanoates were applicable as matrices for deposition of rubomycin and preparation of drugs with prolonged action.

[Rubomycin microincapsulation with biodegradable polymer matrix].

A procedure for preparation of microspheres from biodegradable linear polyether of microbiological origin (polyhydroxybutirate, PHB) with using the technology of solvent evaporation was developed considering a specific example of two- and three-component emulsions. The procedure provided permanent preparation of the microspheres of high quality. The influence of the procedure (emulsion type, dispersion process and medium temperature) on the yield of the microspheres, their structure and size was shown. The temperature had a significant impact on incorporation of the antitumor anthracycline antibiotic daunorubicin (rubomycin) to the polymer matrix. The microspheres with various levels of the drug load (29 and 90% of the initial content in the emulsion) were prepared and the kinetics of the in vitro rubomycin release was studied. The dynamics of the highly toxic rubomycin release from the microspheres was on the whole even with the curve profile reaching the plateau in 20-22 hours of the observation period. The rate of the rubomycin release to the medium depended on the value of the antibiotic incorporation and was maximum within the first two hours (3.3 and 13.0 mcg/ml.h) that corresponded to the release of 0.97 and 3.89 of the incorporated antibiotic. The average rate of rubomycin release during 300 hours was 0.81 x 10(-4) and 2.3 x 10(-4) mcg/ml x h. The release constituted respectively 3.9 and 13.11% of the antibiotic incorporated to the microspheres.

[Physicochemical properties of two-component polyhydroxyalkanoates based on 3-hydroxybutyrate and 3-hydroxyvalerate]. / Fisiko-khimicheskie svoistva dvukhkomponentnykh--3-gidroksibutirata i 3-gidroksivalerata poligidroksialkanoatov.

A series of two-component polyhydroxyalkanoates consisting of hydroxybutyrate and hydroxyvalerate monomer at different ratios were synthesized using the bacterium Ralstonia eutropha B5786. The properties of polyhydroxyalkanoates were compared with those of the homopolymer of hydroxybutyric acid by X-ray structure analysis, IR spectroscopy, differential scanning calorimetry, and viscosimetry. With an increase in the molar fraction of hydroxyvalerate, an equalization of the ratio of the crystalline and amorphous phases in the copolymer was observed. The degree of crystallinity of the polymer decreased from 70-80 to 45-50%; in the range of an increase in the hydroxyvalerate molar fraction from several to 25-30 mol%, the dependence was linear. The temperature characteristics, the melting temperature (T(m)), and the degradation temperature (T(d)) were lower in polyhydroxyalkanoates than in polyhydroxybutyrate, for which T(m) and T(d) were 168-170 and 260-265 degrees C, respectively. In the copolymer, as the molar fraction of hydroxyvalerate grew, both parameters decreased. In the range of variation of monomer ratio studied, they decreased to 150-160 and 200-220 degrees C, respectively. No distinct correlation between the composition of the polymer and its molecular mass was found.

[Biological properties of polyoxyalkanoates in chronic experiments in vivo]. / Issledovanie biologicheskikh svoistv polioksialkanoatov v khronicheskom éksperimente in vivo.

Chronic experiments on mature Wistar rats studied the biological properties of suture threads from two types of polyoxyalkanoates (POA), such as polyoxybutyrate (POB) and the copolymer of POB and polyoxyvalerate (POV) (POB/POV) as compared to the conventional surgical material (silk and catgut). The physiological and biochemical parameters that reflect the status of the animals, including their behaviour, height and development, the weight of the body and viscera, the morphology of peripheral blood, the biochemical parameters of blood, the activity of some enzymes, as well as histological findings of the viscera, and lymphoid tissue responses were assessed. POA was found to produce no negative effect on the physiological, biochemical, and functional characteristics of the animals irrespective of the duration of contact with the internal medium of the body and of the chemical composition of a material.

[Tissue reactions to biodegradable suture materials from polyoxyalkanoates]. / Reaktsiia tkanei na biodegradiruemye shovnye niti iz polioksialkanoatov.

The paper presents data on the materials, methods, and results of a study of tissue responses in the postoperative period to implanted suture threads made of the polymer fatty acid derivatives (polyoxyalkanoates). These suture threads have been shown to have the required strength and meet a number of other requirements for currently available materials.