Preparation and Hydrolytic Degradation of Hydroxyapatite-Filled PLGA Composite Microspheres

Abstract

Various hydroxyapatite-filled and unfilled microspheres based on lactide and glycolide copolymers were prepared. The synthesized poly(lactic-co-glycolic acid) (PLGA) samples were characterized by GPC and 1H NMR spectroscopy, the morphology was characterized by SEM. It was shown that under the tin (II) 2-ethylhexanoate catalysis the glycolide is highly active in copolymerization as compared with lactide. According to the data on weight loss and the weight average molecular weight shift of PLGA over time (pH = 6.5; t = 25 °C), an increase in the rate of microsphere destruction was noted when macromolecules were enriched with glycolic acid residues, as well as when filled with hydroxyapatite. It was shown that the rate of PLGA degradation was determined by the water-accessible surface of a sample. The rate increase in PLGA hydrolytic degradation both with an increase in glycolic acid residues mole fraction in the chain and upon filling with hydroxyapatite was the result of the microspheres’ surface hydrophilization, an increase in capillary pressure upon filling of the pores as well as of the defects with water, and an increase in the number of structural defects. Approaches to the creation of composite microspheres based on PLGA degrading at a controlled rate were proposed.