Introduction: Diabetes mellitus is one of the challenging health problems worldwide. Multiple daily subcutaneous injection of insulin causes poor compliance in patients. Development of efficient oral formulations to improve the quality of life of such patients has been an important goal in pharmaceutical industry. However, due to serious issues such as low bioavailability and instability, it has not been achieved yet.
Areas covered: Due to functional properties of the vesicles and the fact that hepatic-directed vesicles of insulin could reach the clinical phases, we focused on three main vesicular delivery systems for oral delivery of insulin: liposomes, niosomes, and polymersomes. Recent papers were thoroughly discussed to provide a broad overview of such oral delivery systems.
Expert opinion: Although conventional liposomes are unstable in the presence of bile salts, their further modifications such as surface coating could increase their stability in the GI tract. Bilosomes showed good flexibility and stability in GI fluids. Also, niosomes were stable, but they could not induce significant hypoglycemia in animal studies. Although polymersomes were effective, they are expensive and there are some issues about their safety and industrial scale-up. Also, we believe that other modifications such as addition of a targeting agent or surface coating of the vesicles could significantly increase the bioavailability of insulin-loaded vesicles.
Keywords: Diabetes; insulin; liposome; niosome; oral delivery; polymersome; vesicles.