Optimization of a thermally reversible W/O/W multiple emulsion for shear-induced drug release.

Abstract Purpose . The present work aimed at improvement of the formulation of a previously developed thermo-reversible W/O/W multiple emulsion by increasing the emulsion stability and reaching a higher fraction of an encapsulated drug released under shear. The emulsion was based on high molecular weight graft-copolymers of poly(acrylic acid) and Pluronic F127 as stabilizing agents. Methods . Once a stable W/O/W thermo-reversible multiple emulsion was obtained via a fine-tuning of the formulation, rheological, granulometric and conductometric tests were performed to assess the thermo-reversible behavior and the fragmentation-release characteristics of the new W/O/W multiple emulsion. Results . The emulsion exhibited a 10 3 fold increase in viscosity over a range of temperatures from 20 to 40 °C. At moderate shearing, a complete release of the marker encapsulated in the internal aqueous phase was observed (99.6%) at 35 °C, whereas only 30% was released at 20 °C. Under similar conditions at 35 °C, slightly more than 50% was released for the initial formula. Conclusion . Additionally, the ease of fabrication of the thermo-reversible W/O/W multiple emulsion combined with the complete release under shear at body temperature and the superior emulsion stability suggest numerous applications in the controlled release of drugs.