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

Abstract

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°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.

Key Words:

• W/o/w multiple emulsion
• insulin
• oral route
• proteolytic degradation
• stability