Insulin in w/o/w multiple emulsions: Preparation, characterization and determination of stability towards proteases in vitro

In this work two w/o/w multiple emulsions composed of soybean oil or medium-chain triglycerides and containing insulin were studied. These emulsions were prepared by means of two-step emulsification procedure. The w/o/w emulsions obtained were stable for at least 6 months of storage at 4-6 degrees C. The yield of encapsulation of insulin was >95%. The main release mechanism is a swelling-breakdown phenomenon. In vitro, the two w/o/w multiple emulsions were able to protect insulin against enzymatic degradation. These results indicate that multiple emulsions have potential as a carrier of insulin for oral administration.