Anna A. Shumilova

An in vivo study of osteoplastic properties of resorbable poly-3-hydroxybutyrate in models of segmental osteotomy and chronic osteomyelitis.

Abstract A series of 3D implants and filling materials prepared from powdered biodegradable polymers, polyhydroxyalkanoates (PHAs), have been designed for the purposes of reparative osteogenesis. The 3D implants are made of resorbable polymer of hydroxybutyric acid (poly-3-hydroxybutyrate, P3HB) and a composite of this polymer with hydroxyapatite (HA) (P3HB/HA). The properties of the implants were studied in vivo in a model of segmental osteotomy and compared with commercial material Bio-Oss®. All implants containing P3HB as the main component facilitate reconstructive osteogenesis. P3HB and P3HB/HA show pronounced osteoplastic properties; their in vivo degradation is slow and corresponds to the growth of a new bone tissue, facilitating normal reparative osteogenesis. Also, powdered P3HB and P3HB/tienam can be used as filling materials for osteoplasty of bone cavities infected by Staphylococcus aureus. Biodegradable 3D implants and P3HB-based filling materials show pronounced osteoplastic properties and degrade in vivo at a slow rate, enabling normal reparative osteogenesis.

Constructing herbicide metribuzin sustained-release formulations based on the natural polymer poly-3-hydroxybutyrate as a degradable matrix.

ABSTRACT Polymer poly(3-hydroxybutyrate) [P(3HB)] has been used as a matrix in slow-release formulations of the herbicide metribuzin (MET). Physical P(3HB)/MET mixtures in the form of solutions, powders, and emulsions were used to construct different metribuzin formulations (films, granules, pellets, and microparticles). SEM, X-Ray, and DSC proved the stability of these formulations incubated in sterile water in vitro for long periods of time (up to 49 days). Metribuzin release from the polymer matrix has been also studied. By varying the shape of formulations (microparticles, granules, films, and pellets), we were able to control the release time of metribuzin, increasing or decreasing it.

Efficacy of tebuconazole embedded in biodegradable poly-3-hydroxybutyrate to inhibit the development of Fusarium moniliforme in soil microecosystems.

BACKGROUND An important line of research is the development of a new generation of formulations with targeted and controlled release of the pesticide, using matrices made from biodegradable materials. In this study, slow-release formulations of the fungicide tebuconazole (TEB) have been prepared by embedding it into the matrix of poly-3-hydroxybutyrate (P3HB) in the form of films, microgranules and pellets. RESULTS The average rates of P3HB degradation were determined by the geometry of the formulation, reaching, for 63 days, 0.095-0.116, 0.081-0.083 and 0.030-0.055 mg day-1 for films, microgranules and pellets respectively. The fungicidal activity of P3HB/TEB against the plant pathogen Fusarium moniliforme was compared with that of the commercial formulation Raxil Ultra. A pronounced fungicidal effect of the experimental P3HB/TEB formulations was observed in 2-4 weeks after application, and it was retained for 8 weeks, without affecting significantly the development of soil aboriginal microflora. CONCLUSION TEB release can be regulated by the process employed to fabricate the formulation and the fungicide loading, and the TEB accumulates in the soil gradually, as the polymer is degraded. The experimental forms of TEB embedded in the slowly degraded P3HB can be used as a basis for developing slow-release fungicide formulations.

Porous 3D implants of degradable poly-3-hydroxybutyrate used to enhance regeneration of rat cranial defect.

The study describes preparation and testing of porous 3D implants of natural degradable polymer of 3-hydroxybutyric acid P(3HB) for regeneration of bone tissue defects. The ability of the P(3HB) implants to favor attachment and facilitate proliferation and directed differentiation of mesenchymal stem cells (MSCs) was studied in the culture of MSCs isolated from bone marrow and adipose tissue. Tissue-engineered hybrid systems (grafts) constructed using P(3HB) and P(3HB) in combination with osteoblasts were used in experiments on laboratory animals (n = 48) with bone defect model. The defect model (5 mm in diameter) was created in the rat parietal bone, and filling of the defect by the new bone tissue was monitored in the groups of animals with P(3HB) implants, with commercial material, and without implants (negative control). Computed tomography (CT) and histologic examination showed that after 120 days, in the group with the osteoblast-seeded P(3HB) implants, the defect was completely closed; in the group with the cell-free P(3HB) implants, the remaining defect was no more than 10% of the initial one (0.5 mm); in both the negative and positive controls, the size of the defect was about 1.0-1.2 mm. These results suggest that P(3HB) has good potential as osteoplastic material for reconstructive osteogenesis.

Laser processing of polymer constructs from poly(3-hydroxybutyrate).

CO2 laser radiation was used to process poly(3-hydroxybutyrate) constructs – films and 3D pressed plates. Laser processing increased the biocompatibility of unperforated films treated with moderate uniform radiation, as estimated by the number and degree of adhesion of NIH 3T3 mouse fibroblast cells. The biocompatibility of perforated films modified in the pulsed mode did not change significantly. At the same time, pulsed laser processing of the 3D plates produced perforated scaffolds with improved mechanical properties and high biocompatibility with bone marrow-derived multipotent, mesenchymal stem cells, which show great promise for bone regeneration.

Preparation and Characterization of Bacterial Cellulose Composites with Silver Nanoparticles

Bacterial cellulose (BC) is widely used in medicine as a dressing material due to its good biological properties – high biocompatibility, low adhesion and the ability to absorb wound exudate. The BC does not have antimicrobial activity itself, which limits the use of products in infected wounds, and also treatment of wounds in hospitals. A method for producing a two-component composite material based on bacterial cellulose (BC) synthesized in culture of Komagataeibacter xylinus B-12068 with silver nanoparticles [BC/AgNps], by hydrothermal synthesis of AgNO3 in the layer of BC at different temperatures and concentrations of AgNO3, is proposed. The antibacterial activity of BC/AgNps samples against Escherichia coli, Pseudomonas aeruginosa, Klebsiella pneumonia, and Staphylococcus aureus has been confirmed in vitro with the disc diffusion method. It is shown, that the antibacterial activity of samples is mostly expressed in cultures of P. aeruginosa and S. aureus.

Biocomposites Based on Degradable Materials as Biotechnological Dermal Equivalents

Hybrid tissue-engineered biosystems based on biodegradable polymers of microbiological origin – bacterial cellulose (BC) and a copolymer of 3-hydroxybutyric and 4-hydroxybutyric acid P(3HB/4HB) – were constructed using various methods: 1) the dried BC pellicles were soaked with a 2% P(3HB/4HB) solution in chloroform, kept for 24 h, and dried in a dust-free cabinet until the solvent had completely evaporated; 2) nonwoven membranes were placed into the K. xylinus B-12068 culture, and bacterial cellulose synthesized in it grew under static conditions; 3) powdered cellulose (particle size of 120 μm) was added to a 3% P(3HB/4HB) solution in chloroform and mixed ultrasonically to homogeneity; then, the films were produced by the solvent evaporation technique, at polymer to cellulose ratios of 2:1 and 1:1. Investigation of surface properties of the samples showed an increase in surface hydrophilicity of the composites produced by mixing a solution of P(3HB/4HB) with BC at ratios of 2:1 and 1:1 (the contact angle was 43.9±17.55° and 36.1±0.66°) relative to the starting materials. The physical/mechanical properties of the composites based on P(3HB/4HB) and BC were superior to the properties of the neat materials, and they were largely determined by the methods of production of the composite and the properties of the materials used. Based on the study of surface and physical/mechanical properties of the hybrids, films prepared by casting the polymer solution with BC powder (2:1 and 1:1) followed by solvent evaporation were chosen for studying cell adhesion. These scaffolds were loaded with drugs promoting wound healing (actovegin, solcoseryl) and tested in the culture of fibroblasts derived from the adipose tissue MSCs. The MTT assay showed that the most effective hybrid systems were polymer:bacterial cellulose powder (1:1) samples loaded with actovegin or solcoseryl at a concentration of 5%. Those systems produced a stimulating effect on fibroblasts, and, thus, they can be regarded as promising wound dressings to repair skin defects.

Differentiation of Mscs into Osteoblasts on a Porous 3D -carrier of Poly-3-Hydroxybutyrate

The study describes preparation and testing of porous 3D implants of natural degradable polymer of 3-hydroxybutyric acid (P(3HB)) for regeneration of bone tissue defects. The ability of the 3D carriers to favor attachment and facilitate proliferation and directed differentiation into osteoblasts of mesenchymal stem cells (MSCs) was studied in the culture of MSCs isolated from bone marrow and adipose tissue. MSC differentiation into osteoblasts was confirmed by measurements of the activity of alkaline phosphatase, gene expression of the marker of bone protein BGP (glutamic protein participating in mineralization) and measurements of intracellular precipitates of calcium and phosphorus salts.