ИСТИНА

Poly(3-hydroxybutyrate) (PHB) is a biocompatible and biodegradable polymer produced by a microbiological way that is promising for use in medicine and tissue engineering. The polymer microspheres can be used both as formulations for drugs controlled delivery and as substrate for cells cultivation. We produced PHB microspheres for both controlled release of antibacterial protein lysozyme and 3D cultivation of mesenchymal stem cells (MSCs). This combined functionality can be achieved by producing highly porous microspheres with modified polymer surface. To produce highly porous microspheres the double water-oil-water emulsification technique using ammonium carbonate as a blowing agent was used. In addition, the polymer surface with a greatly increased area was hydrophilized by treatment with NaOH and subsequent ionization. These procedures gave polymer surface the properties of absorbent and cation exchanger for positively charged proteins and, at the same time, made them a suitable substrate for cell attachment and growth. Lysozyme was immobilized in PHB porous microspheres by multi-stage incubation in protein solution. Then the release of lysozyme from PHB porous microspheres in phosphate buffered saline at 37º C under stirring was studied. The release of lysozyme was carried out according to the kinetics of the first order during 13 days. MSCs were isolated from bone marrow of newborn rats. To study the growth pattern of MSCs on porous microspheres they were analyzed by scanning electron microscopy during three weeks of cells cultivation. The produced porous microspheres were able to support growth of MSCs, cells grew on the surface of microspheres and between them that simulated 3D cell growth. Thus, the produced PHB microspheres can be used for bone tissue engineering to provide osteoblasts adhesion and proliferation in combination with prolonged antibacterial action.