PREPARATION OF BIODEGRADABLE POROUS POLY(BUTYLENE SUCCINATE) MICROSPHERES

The aim of this study was to determine the optimal conditions for the fabrication of porous microspheres based on poly(butylene succinate), PBS. The biodegradable non-porous PBS microspheres were prepared by the oil-in-water (o/w) emulsion solvent evaporation method using poly(vinyl alcohol), PVA, as the surfactant. Fabrication conditions, such as stirring rate, organic/aqueous ratio, PBS concentration and surfactant (PVA) concentration, which have an important influence on both the particle size and the morphology of the microspheres, were varied. Scanning electron microscopy, SEM, observations confirmed the size, size distribution and surface morphology of the microspheres. The optimal conditions for the preparation of the non-porous microspheres were found to be: concentration the PBS solution, 10 mass%; PVA concentration, I mass%; the organic/aqueous ratio CHCl3/H2O = 1/20 and stirring rate 800 rpm. Porous PBS microspheres were fabricated under the optimal conditions using various amounts of hexane and poly(ethylene oxide), PEO, as porogens. The influence of the amount of porogen on the pore size and the particle size was investigated using SEM and the apparent density. The microspheres exhibited various porosities and the pore sizes. The average particle size of the microspheres with PEO as the porogen was from 100 to 122 pm and that of the microspheres with hexane as the porogen was from 87 to 97 pm. The apparent density of the porous microspheres with PEO as the porogen, from 0.16 to 0.23 g/cm(3), was much smaller than the non-porous microspheres, 0.40 g/cm(3). In the in vitro degradation experiments, the porous microspheres were incubated in phosphate buffer solution (pH 7) at 37 degrees C. After incubating for one month, the microspheres showed significant extent of the hydrolytic degradation of the porous PBS microspheres.