PREPARATION OF BIODEGRADABLE POLYMER MICROSPHERES ENCAPSULATING PROTEIN WITH MICRON SIZES

Biodegradable polymer poly-D,L-lactide-polyethylene glycol (PLA-PEG) w as synthesized with stannous octoate (SnOc(2)) as catalyst by a cation ic ring-opening polymerization. The molecular weight of PLA-PEG is the highest at a content of 0.1% SnOc(2). The PLA-PEG microspheres carryi ng protein were prepared by a solvent evaporation composite emulsion t echnique with a narrow size range (1-2 mu m). The sizes of PLA-PEG mic rospheres increased with the increase of the molecular weight of PLA-P EG. The PEG in PLA-PEG (10%) significantly improved the size control o f the microspheres of the PLA family as a drug carrier matrix. Polyvin yl alcohol (PVA) aqueous solution was used as dispersion medium for mi crosphere preparation. The concentration of the PVA solution can affec t the size of the PLA-PEG microspheres. The differential scanning calo rimetry data showed that the PLA-PEG microspheres can efficiently enca psulate the protein and that the crystalline of the microspheres carry ing protein was lower than that of the nonprotein-loading microspheres . The amount of protein carried in the PLA-PEG microspheres was relate d to the nature of the protein itself. (C) 1997 John Wiley & Sons, Inc .