Microspheres have been prepared from the resorbable linear polyester of β-hydroxybutyric acid (polyhydroxybutyrate, PHB) by the solvent evaporation technique and investigated in vitro and in vivo. Biocompatibility of the microspheres has been proved in tests in the culture of mouse fibroblast cell line NIH 3Т3 and in experiments on intramuscular implantation of the microspheres to Wistar rats for 3 months. Tissue response to the implantation of polymeric microspheres has been found to consist in a mild inflammatory reaction, pronounced macrophage infiltration that increases over time, involving mono-and poly-nuclear foreign body giant cells that resorb the polymeric matrix. No fibrous capsules

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An experimental dosage form of rubomycin is developed: the drug is incorporated in absorbable polymeric (polyhydroxybutyrate) matrix in the form of microparticles. Antitumor efficiency of this rubomycin dosage form was studied in laboratory mice with transplanted Ehrlich ascitic carcinoma. Rubomycin deposited in polymeric microparticles exhibited pronounced antitumor activity, inhibited the proliferative activity of Ehrlich ascitic carcinoma, and improved survival of mice with tumors. This dosage form of the drug can be used for local injections.

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The kinetics of polyhydroxyalkanoate (PHA) degradation in natural environment in two water reservoirs having various ecological characteristics was studied. It was shown that biodegradation of polymer essentially depends on the environment temperature and inorganic composition of water. The processes of polymer degradation under aerobic and anaerobic conditions were compared. The polymer degradation was slower under anaerobic conditions.