A polysorbate-based non-ionic surfactant can modulate loading and release of beta-lactoglobulin entrapped in multiphase poly(DL-lactide-co-glycolide)microspheres

Purpose. The goal of the present paper was to investigate the role of a sur factant, Tween 20, in the modulation of the entrapment and release of beta- lactoglobulin (BLG) from poly (DL-lactide-co-glycolide) microspheres. Methods. Poly(DL-lactide-co-glycolide) microspheres containing BLG were pre pared by a water-in-oil-in-water emulsion solvent procedure. Tween 20 was u sed as a surfactant in the internal aqueous phase of the primary emulsion. BLG entrapment efficiency and burst release were determined. Displacement o f BLG from microsphere surface was followed by confocal microscopy observat ions and zeta potential measurements, whereas morphological changes were ob served by freeze-fracture electron microscopy. Results. Tween 20 was shown to increase 2.8 fold the encapsulation efficien cy of BLG without any modification of the stability of the first emulsion a nd the viscosity of the internal aqueous phase. In fact, Tween 20 was shown to be responsible for removing the BLG molecules that were adsorbed on the particle surface or very close to the surface as shown by confocal microsc opy and zeta potential measurements. Tween 20 reduced the number of aqueous channels between the internal aqueous droplets as well as those communicat ions with the external medium. Thus, the more dense structure of BLG micros pheres could explain the decrease of the burst release. Conclusions, These results constitute a step forward in the improvement of existing technology in controlling protein encapsulation and delivery from microspheres prepared by the multiple emulsion solvent evaporation method.