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Biomedical subjects

T G Volova

Publications and source records attributed to T G Volova.

At least 19 recordsLinked to original sources
PubMed2006

Physiological-biochemical properties and the ability to synthesize polyhydroxyalkanoates of the glucose-utilizing strain of the hydrogen bacterium Ralstonia eutropha B8562.

Physiological-biochemical, genetic, and cultural properties of the glucose-utilizing mutant strain Ralstonia eutropha B8562 have been compared with those of its parent strain R. eutropha B5786. It has been shown that growth characteristics of the strain cultured on glucose as the sole carbon and energy source are comparable with those of the parent strain. Strain B8562 is characterized by high polyhydroxyalkanoate (PHA) yields on different carbon sources (CO(2), fructose, and glucose). PHA accumulation in the strain batch cultured on glucose under nitrogen deficiency reaches 90 %. The major monomer in the PHA is beta-hydroxybutyric acid (more than 99 mol %); the identified minor components are beta-hydroxyvaleric acid (0.25-0.72 mol %) and beta-hydroxyhexanoic acid (0.08-1.5 mol %). The strain is a promising PHA producer on available sugar-containing media with glucose.

Biotechnology↗
PubMed2006

A hybrid PHB-hydroxyapatite composite for biomedical application: production, in vitro and in vivo investigation.

Samples of a hybrid composite of polyhydroxybutyrate (PHB), a biodegradable polyester, and hydroxyapatite (HA), with different PHB/HA ratios, have been prepared using mechanical-physical method. Electron microscopy, X-ray structure analysis and differential thermal analysis have been used to investigate the structure and physicochemical properties of the composite, depending on the PHB/HA ratio. The properties of the surface of the HA-loaded composite are significantly different from those of the pure polymer. As the HA percentage in the composite increases, free interface energy, the cohesive force, i.e., the strength of the adhesive bond between the composite surface and the water phase, and surface wettability increase. The HA percentage of the composite does not influence its melting temperature, but affects the temperature for the onset of decomposition: as the HA content increases from 0 to 10% (w/w), Td decreases from 260 degrees C to 225 degrees C. The degree of crystallinity of PHB/HA increases from 77% to 89% with an increase in the HA fraction from 10% to 50%. Functional properties of the composites have been investigated in vitro and in vivo. The best parameters of growth and differentiation of murine marrow osteoblasts are registered on PHB/HA samples containing 10% and 20% HA. In ectopic bone formation assay it has been proven that the hybrid PHB/HA composites can function as scaffolds and that bone tissue develops on their surface and in pores.

Animals↗
PubMed2005

Degradation of P(3HB) and P(3HB-co-3HV) in biological media.

The biodegradability of oriented fibers made of polyhydroxybutyrate (P(3HB)) and its co-polymer with beta-hydroxyvalerate (P(3HB-co-3HV)) was investigated in buffer solutions and in biological media in vitro and in vivo. The fibers of both polymer types demonstrated resistance to hydrolytic degradation in buffer solutions at 38 degrees C and pH from 4.5 to 7.0 (for up to 180 days). It has been found that the biodegradation of the fibers in vitro in blood and serum and in vivo is accompanied by weight losses and minor changes in the microstructure with no significant losses in the tensile strength over a long time (up to 180 days). The biodegradation rate of the less crystalline co-polymer P(3HB-co-3HV) fibers was 1.4-2.0-times higher than that of the homopolymer P(3HB). It has also been shown that the degradation of the fibers in vivo is influenced both by tissue fluid enzymes and cells (macrophages and foreign-body giant cells). The fibers were eroded on the surface only with no gross defects and no dramatic effects on their mechanical performance.

Animals↗
PubMed2005

[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.

Antibiotics, Antineoplastic↗
PubMed2004

Tissue response to the implantation of biodegradable polyhydroxyalkanoate sutures.

Polyhydroxyalkanoate (PHA) sutures were implanted to test animals intramuscularly, and tissue reaction was investigated and compared with the reaction to silk and catgut. Tested monofilament sutures made of PHAs of two types--polyhydroxybutyrate (PHB) and a copolymer of hydroxybutyrate and hydroxyvalerate (PHV)--featured the strength necessary for the healing of muscle-fascial wounds. The reaction of tissues to polymeric implants was similar to their reaction to silk and was less pronounced than the reaction to catgut; it was expressed in a transient post-traumatic inflammation (up to four weeks) and the formation of a fibrous capsule less than 200 microm thick, which became as thin as 40-60 microm after 16 weeks, in the course of reverse development. Macrophages and foreign-body giant cells with a high activity of acid phosphatase were actively involved in this process. PHB and PHB/PHV sutures implanted intramuscularly for an extended period (up to one year) did not cause any acute vascular reaction at the site of implantation or any adverse events, such as suppurative inflammation, necrosis, calcification of the fibrous capsule or malignant tumor formation. No statistically significant differences were revealed in the tissue response to polymer sutures of the two types. Capsules around silk and catgut sutures did not become significantly thinner.

Absorbable Implants↗
PubMed2004

A comparative investigation of biodegradable polyhydroxyalkanoate films as matrices for in vitro cell cultures.

The paper describes the production and investigation of flexible films made of high-purity polyhydroxyalkanoates (PHAs)--polyhydroxybutyrate [poly-(3HB)] and poly-3-hydroxybutyrate-co-poly-3-hydroxyvalerate [poly(3HB-co-3HV)], containing 4-30 mol % hydroxyvalerate. Poly(3HB-co-3HV) films have a more porous structure than poly-(3HB) films, which are more compact, but their surface properties, such as wettability and surface and interface energies, are the same. Sterilisation of the PHA films by conventional methods (heat treatment and gamma-irradiation) did not impair their strength. Cells cultured on PHA films exhibited high levels of cell adhesion. Cell morphology, protein synthesis and DNA synthesis were estimated by extent of 3H-thymidine incorporation into the animal cell cultures of various origins (fibroblasts, endothelium cells, and isolated hepatocytes) in direct contact with PHAs. The investigation showed that this material can be used to make matrices for in vitro proliferous cells. The investigated properties of poly-(3HB) and poly(3HB-co-3HV) films proved to be fundamentally similar.

Absorbable Implants↗
PubMed2003

Production of purified polyhydroxyalkanoates (PHAs) for applications in contact with blood.

Samples of olyhydroxyalkanoates (PHAs), polyhydroxybutyrate (PHB) and copolymers poly(hydroxybutyrate-co-hydroxyvalerate) (PHBV) with 4 and 18 mol% hydroxyvalerate, synthesized by the bacteria Ralstonia eutropha B5786, were investigated. PHA films in contact with blood did not activate the hemostasis system at the level of cell response, but they did activate the coagulation system and the complement reaction. To detect biologically-active components in the PHAs, a detailed analysis of the composition of the polymers was conducted. Gas chromatography-mass spectrometry revealed long-chain fatty acids (FAs) in the tested PHAs. Their total concentration in the polymer ranged from tenths of mol% to 2-3 mol%, depending on the purification method. C16:0 constituted the largest proportion, up to 70%. Of the long-chain hydroxy acids, only beta-OH-C14:0 was detected and it did not exceed 0.06 mol%. The analysis of the hemocompatibility properties of the PHAs purified by a specialized procedure, including the quantitative and morphological estimation of platelets adherent to the surface of polymer films, the plasma recalcification time and complement activation studies, indicated that PHB and PHBV can be used in contact with blood. It has been found out that the lipopolysaccharides of bacteria producing PHAs, which contain mostly long-chain hydroxy acids, can be the factor activating the hemostasis systems. Thus, the technology of PHA purification must satisfy rather stringent specific requirements.

Biocompatible Materials↗
PubMed2002

Autotrophic synthesis of polyhydroxyalkanoates by the bacteria Ralstonia eutropha in the presence of carbon monoxide.

It has been found that the carbon monoxide (CO)-resistant strain of the hydrogen bacteria Ralstonia eutropha B5786 is able to synthesise polyhydroxyalkanoates (PHAs) in the presence of CO under autotrophic conditions. This strain, grown on model gas mixtures containing 5-25% CO (v/v), accumulates up to 70-75% (of absolutely dry matter) PHA, without significant variation in the yield coefficient on hydrogen. No suppression of the activities of the key enzymes of PHA synthesis ( beta-ketothiolase, acetoacetyl-CoA-reductase, butyrate dehydrogenase and poly-3-hydroxybutyrate synthase) was recorded. The PHA synthesised is a co-polymer containing mostly beta-hydroxybutyrate (more than 99 mol%) with trace amounts of beta-hydroxyvalerate. The investigated properties of the polymer (molecular weight, crystallinity, temperature characteristics) do not differ from those of the polymer synthesised on electrolytic hydrogen.

Carbon Monoxide↗
PubMedDate not supplied

[Study of molecular structure of polyhydroxybutyrate-a termoplastic anddegradable biopolymer].

The molecular structure of polyhydroxybutyrate from hydrogen-oxidizing bacteria Alcaligenes eutrophus was studied by X-ray diffraction analysis. It was shown that the degree of crystallinity of various samples depends little on the conditions of their preparation and is equal to 0.62-0.76. The molecular structure of solid samples and solution of polyhydroxybutyrate in chloroform were studied by the NMR and EPR methods. The conclusion is made that the molecular structure of polyhydroxybutyrate does not depend on the features of the strain and conditions of carbon nutrition of microorganisms producing polyhydroxybutyrate. Defects induced by gamma-radiation in polyhydroxybutyrate were studied. Free radicals were isolated, and their structure was decoded.

Alcaligenes↗