Microparticles of poly(DL-lactic-co-glycolic acid)/poly(ethylene glycol) blends for controlled drug delivery

We fabricated microparticles of poly(or-lactic-co-glycolic acid) (PLGA) 50:50 and poly(ethylene glycol) (PEG) blends with entrapped model drug compounds to investigate the effect of blend ratio on release kinetics. Two model drugs (FITC-IgG and FITC-dextran) were entrapped using a double-emulsion-solvent-extraction technique with high efficiency. In vitro release studies showed that the initial burst effect was dependent on the PLGA/PEG blend ratio. Moreover, the release rate increased in direct relation to PEG content for up to 28 days. A linear release profile was obtained for microparticles loaded with FITC-IgG for initial PEG weight fractions up to 5 wt%, and a constant rate of 0.021, 0.068, 0.132, and 0.214 mu g FITC-IgG/day was measured per mg polymer for formulations of 0, 1, 2, 5 wt% initial PEG content, respectively. A biphasic release profile was obtained for FITC-dextran loaded microparticles with rates dependent on the PEG content. These results demonstrate the feasibility of modulating the release profile of entrapped compounds in biodegradable microparticles by adjusting the PLGA/PEG blend ratio. (C) 1997 Elsevier Science B.V.