Optimization of the encapsulation and release of beta-lactoglobulin entrapped poly(DL-lactide-co-glycolide) microspheres

The goal of the present paper was to optimize the encapsulation of beta-lac toglobulin (BLG) within poly(lactide-co-glycolide) (PLGA) microparticles pr epared by the multiple emulsion solvent evaporation method. The role of the pH of the external phase and the introduction of the surfactant Tween 20, in the modulation of the entrapment and release of BLG from microparticles, was studied. Reducing the solubility of BLG by decreasing the pH of the ex ternal phase to a value close to the pi of BLG resulted in a better encapsu lation with, however, a larger burst release effect. By contrast, Tween 20 was shown to increase the encapsulation efficiency of BLG and reduce consid erably the burst release effect. In fact, Tween 20 was shown to be responsi ble for removing the BLG molecules that were adsorbed on the particle surfa ce. In addition, Tween 20 reduced the number of aqueous channels between th e internal aqueous droplets as well as those communicating with the externa l medium. Thus, the more dense structure of BLG microspheres could explain the decrease in the burst release. These results constitute a step ahead in the improvement of an existing technology in controlling protein encapsula tion and delivery from microspheres prepared by the multiple emulsion solve nt evaporation method. (C) 1999 Elsevier Science B.V. All rights reserved.