Physiological resorption of bone tissue after tooth extraction leads to a decrease in the volume of bone tissue available for implantation and makes it difficult to install dental implants. Preservation of the well after tooth extraction is the solution to this problem, with the choice of bone plastic material playing an important role. The development of an "ideal" bone plastic material with osteoinductive properties that promotes reparative bone regeneration remains an urgent task. The aim of the study was to evaluate the regeneration of bone tissue of the alveolar ridge during implantation of a new osteoinductive bone plastic material containing simvastatin into the wells of extracted teeth in sheep using microcomputer tomography. Materials and Methods. The study was conducted on 24 adult sheep with a total of 48 teeth removed. 12 wells were filled with material based on poly(3-hydroxybutyrate) (PHB) with simvastatin; 12 wells were filled with PHB-based material without simvastatin, 24 wells were used as a control. Micro-CT was used for comparative analysis of bone tissue formation between the test groups after 3 and 6 months. Results. The results of the study confirm the positive effect of simvastatin released from the PHB-based osteoplastic material on the volume of the formed bone tissue and the total bone volume in the defect area (BV/TV) and bone mineral density (BMD) 3 and 6 months after surgery. Conclusion. The study demonstrated that simvastatin, released from the PHB-based osteoplastic material, has an osteoinductive effect, promoting bone tissue regeneration in the wells left after tooth removal. Higher BV/TV and BMD values in the wells indicate better efficacy of the material in terms of regeneration support.

The study involved the fabrication of films with different roughness and scaffolds made of poly-3-hydroxybutyrate using various methods. Chaotic and oriented scaffolds with varying fiber thickness were obtained through the electrospinning method, depending on the polymer concentration and electrospinning parameters. Films with different surface roughness were obtained using spin coating and self-assembly methods. It was demonstrated that the varying microstructure of the surface does not affect the growth of mesenchymal stem cells over the course of 1 week; however, it does influence the morphology of the adhered cells.

Various variants of poly(3-hydroxybutyrate) (PHB) were synthesized by varying three factors (sucrose concentration, phosphate concentration, and aeration level) while growing the producer Azotobacter vinelandii 12 using full-factorial design. Bacteria grown at elevated sucrose concentration, low phosphate concentration, and high aeration level (C+/P−/O+) showed the maximum PHB yield (0.49 g/L). Molecular weights (MW) of PHB samples obtained under diverse conditions differed by more than 30 times (from 49 to 1698 kDa). Low molecular weight PHBs were observed at low sucrose levels and high aeration (C–/O+). All other PHB samples had MW over 1200 kDa. The crystallinity of all PHB samples was determined by differential scanning calorimetry and was within the range of 62–68%. These results show that, with optimization, it will be possible to synthesize PHBs with different physicochemical properties for a wide range of biomedical problems, including tissue engineering.

We studied the effect of porous composite scaffolds based on poly(3-hydroxybutyrate) (PHB) loaded with simvastatin on the growth and differentiation of mesenchymal stem cells. The scaffolds have a suitable microstructure (porosity and pore size) and physicochemical properties to support the growth of mesenchymal stem cells. Scaffold loading with simvastatin suppressed cell growth and increased alkaline phosphatase activity, which can attest to their osteoinductive properties.

The ability of Azotobacter agile 12 to produce the polymers alginate (ALG) and poly(3-hydroxybutyrate) (PHB) and their physicochemical properties is studied in the work. It was shown that the strain A. agile 12 produces ALG and PHB simultaneously, thought predominantly ALG, under the conditions of high aeration levels. Infrared spectroscopy of bacterial ALG showed a prevalence of mannuronic over guluronic residues (M/G = 70/30) in the polymer chain and the presence of acetyl groups on the mannuronic monomers. No acetyl groups were found in seaweed ALG. Infrared spectroscopy showed that PHB is characterized by an absorption band in the region 1760 cm –1 . The chemical nature of PHB as a homopolymer consisting of resides of 3-hydroxybutyric acid was confirmed by 1 H-NMR analysis. The thermal behavior of bacterial ALG by thermogravimetric analysis is characterized by three stages (dehydration, first decomposition, and second decomposition). In contrast to ALG, PHB had only one stage of decomposition with a prior very low mass loss (1.25%) at the dehydration stage. The water absorption test showed that bacterial ALG has a higher capacity for water absorption in comparison with seaweed ALG, whereas PHB is a hydrophobic polymer. Thus, PHB and ALG synthesized simultaneously by A. agile 12 differ in their physicochemical properties: PHB is a hydrophobic, thermoplastic, mechanically strong polyester, while alginate is hydrophilic, hydrogel-forming, temperature unstable, elastic and mechanically destructible polysaccharide.

Изготовлены пористые матриксы для тканевой инженерии на основе поли-3-оксибутирата (ПОБ) и его сополимера с полиэтиленгликолем (ПОБ-ПЭГ), который был получен по технологии биоПЭГилирования. Исследована морфология полученных матриксов и адсорбция на них модельного белка, бычьего сывороточного альбумина (БСА). Показано, что матриксы на основе биоПЭГили­рованного ПОБ сорбировали больше БСА, а доля необратимо сорбированного белка на них значительно меньше (33%), чем на матриксах из гомополимера ПОБ (47%). Влияние адсорбции белка на биосовместимость матриксов in vitro было проверено путем культивирования на них фибробластов линии COS-1. Показано, что матриксы на основе ПОБ-ПЭГ в большей степени поддерживали рост клеток на них по сравнению с матриксами на основе ПОБ. Таким образом, полученные полимерные матриксы на основе биоПЭГилированного ПОБ могут быть более перспективны для использования в инженерии мягких тканей.

Development of biocompatible 3D scaffolds is one of the most important challenges in tissue engineering. In this study, we developed polymer scaffolds of different design and microstructure to study cell growth in them. To obtain scaffolds of various microstructure, e.g., size of pores, we used double- and one-stage leaching methods using porogens with selected size of crystals. A composite of poly(3-hydroxybutyrate) (PHB) with poly(ethylene glycol) (PEG) (PHB/PEG) was used as polymer biomaterial for scaffolds. The morphology of scaffolds was analyzed by scanning electron microscopy; the Young modulus of scaffolds was measured by rheometry. The ability to support growth of mesenchymal stem cells (MSCs) in scaffolds was studied using the XTT assay; the phenotype of MSC was preliminarily confirmed by flow cytometry and the activity of alkaline phosphatase and expression level of CD45 marker was studied to test possible MSC osteogenic differentiation. The obtained scaffolds had different microstructure: the scaffolds with uniform pore size of about 125 µm (normal pores) and 45 µm (small pores) and scaffolds with broadly distributed pores size from about 50–100 µm. It was shown that PHB/PEG scaffolds with uniform pores of normal size did not support MSCs growth probably due to their marked spontaneous osteogenic differentiation in these scaffolds, whereas PHB/PEG scaffolds with diverse pore size promoted stem cells growth that was not accompanied by pronounced differentiation. In scaffolds with small pores (about 45 µm), the growth of MSC was the lowest and cell growth suppression was only partially related to stem cells differentiation. Thus, apparently, the broadly distributed pore size of PHB/PEG scaffolds promoted MSC growth in them, whereas uniform size of scaffold pores stimulated MSC osteogenic differentiation.

Porous scaffolds for tissue engineering have been prepared from poly(3-hydroxybutyrate) (PHB) and a copolymer of poly(3-hydroxybutyrate) and polyethylene glycol (PHB-PEG) produced by bioPEGylation. The morphology of the scaffolds and their capacity for adsorption of the model protein bovine serum albumin (BSA) have been studied. Scaffolds produced from bioPEGylated PHB adsorbed more BSA, whereas the share of protein irreversibly adsorbed on these scaffolds was significantly lower (33%) than in the case of PHB homopolymer-based scaffolds (47%). The effect of protein adsorption on scaffold biocompatibility in vitro was tested in an experiment that involved the cultivation of fibroblasts (line COS-1) on the scaffolds. PHB-PEG scaffolds had a higher capacity for supporting cell growth than PHB-based scaffolds. Thus, the bioPEGylated PHB-based polymer scaffolds developed in the present study have considerable potential for use in soft tissue engineering.

The hydrolytic degradation of polymer films of poly(3-hydroxybutyrate) of different molecular weights and its copolymers with 3-hydroxyvalerate (9 mol % 3-hydroxyvalerate in the poly(3-hydroxybutyrate) chain) of different molecular weights was studied in model conditions in vitro. The changes in the physicochemical properties of the polymers were investigated using different analytical techniques: viscometry, differential scanning calorimetry, gravimetrical method, and water contact angle measurement for polymers. The data showed that in a period of 6 months the weight of polymer films decreased insignificantly. The molecular weight of the samples was reduced significantly; the largest decline (up to 80% of the initial molecular weight of the polymer) was observed in the high-molecular-weight poly(3-hydroxybutyrate). The surface of all investigated polymers became more hydrophilic. In this work, we focus on a mathematical model that can be used for the analysis of the kinetics of hydrolytic degradation of poly(3-hydroxyaklannoate)s by noncatalytic and autocatalytic hydrolysis mechanisms. It was also shown that the degree of crystallinity of some polymers changes differently during degradation in vitro. Thus, the studied polymers can be used to develop biodegradable medical devices such that they can perform their functions for a long period of time.

Biocompatible and biodegradable polymer microparticles are contemporary medicines able to eliminate the side effects and unsatisfactory pharmacokinetics of already existing preparations. In this work we have developed a high-tech scalable method for the synthesis of paclitaxel-loaded poly(3-hydroxybutyrate) (PHB)-based microparticles. These particles were synthesized on a B-90 Buchi nano spray dryer by piezoelectric spray drying in an inert atmosphere. A regular spherical shape, narrow size distribution, and satisfactory results for the release of paclitaxel from the polymeric matric of microparticles in vitro make this polymeric medicinal form promising for its further application in pharmaceutics. Nanoparticles with a similar composition synthesized via the laboratory one-stage emulsification method were used for comparison. This study is the first stage in the creation of a sustained-action anticancer paclitaxel preparation.

A study of in vitro biodegradation of poly(3-hydroxybutyrate) (PHB) in model conditions was performed. The porcine pancreatic lipase solutions at different concentrations in the two buffer systems (phosphate-buffered saline (PBS) and simulating body fluid (SBF)) were chosen as model biodegradation media. At first, optimal concentration of pancreatic lipase (0.25 mg/ml in PBS) was determined: in these media the decomposition of PHB films realized faster according to the data of gravimetric analysis. Differential scanning calorimetry showed an increase in the crystallinity of the samples (from 49% to 59%) after enzymatic degradation. These data are confirmed by method of nanoindentation, where the increase of the Young's modulus during the degradation (from 1.37 GPa to 4.4 GPa) was shown. This is due to the crystallization of the amorphous polymer component, and its decomposition and dissolving. During biodegradation three types of polymer ultrastructure changes were observed on the surfaces of the films: appearance of new lamellae, disappearance of lamellae and disintegration of lamellae into shorter fragments.

The ability of representatives of various species of the bacterial genus Azotobacter (A. chroococcum 7B, A. chroococcum 12B, A. chroococcum 12BS, A. agile 12, A. indicum 8, A. vinelandii 17, and A. vinelandii 5B) to alginate synthesis has been studied. It has been shown that all tested bacterial strains have this ability to different extents. Capsular alginate comprises from 2.6 to 32% of the total amount of synthesized alginate in various bacterial species. Strains that are able to active synthesis of alginate have been selected; the effect of the medium composition on their biosynthesis has been studied. The optimal conditions for alginate synthesis by the A. chroococcum 12BS producer strain include the presence of mannitol (40 g/L), yeast extract (1%), and low concentration of phosphates (KH2PO4—0.008 g/L, K2HPO4—0.032 g/L) in the medium; alginate production under these conditions is 4.5 g/L. The effect of aeration on polymer biosynthesis has been revealed: an increase in aeration causes an increase in alginate synthesis, while its decrease promotes the synthesis of poly-3-hydroxybutirate. It has been shown by IR spectroscopy that alginates obtained under various conditions of cultivation contain different ratios of residues of mannuronic and guluronic acids (M/G from 70/30 to 80/20) in the polymer chain and also differ in the amount of acetyl groups (from 10 to 25%) in the polyme structure.

Poly(3-hydroxybutyrate)-poly(ethylene glycol) (PHB-PEG) copolymer is a novel member of poly-hydroxyalkanoates (PHAs) produced by biotechnological PEGylation with improved biocompatibility and biodegradability. We used the PHB-PEG to produce the porous 3D scaffolds for bone tissue engineering. The PHB-PEG scaffolds were made by gas porous formation technique using ammonium carbonate as a porogen. The 3D-scaffolds on the base of homopolymer poly(3-hydroxybutyrate) (PHB) and its blend with PEG 70:30 w/w (PHB+PEG) were used for comparison. In this study morphology (e.g., porosity), hydrophilicity, thermal properties and protein adsorption of PHB-PEG 3D scaffolds were examined. Bone marrow stromal cells (BMSCs) and 3T3 fibroblast cells were cultured on PHB-PEG 3D scaffolds. Cell viability, growth and adhesion on polymer 3D scaffolds were investigated by XTT test and scanning electron microscopy. The obtained data showed that the PHB-PEG copolymer scaffolds demonstrated lower hydrophobicity and better biocompatibility in comparison with the PHB homopolymer scaffolds and these indicators were not inferior to the PHB+PEG blend. It was also shown that PHB-PEG 3D scaffolds are suitable substrate for cell growth and could be applied for bone tissue engineering.