الفهرس 
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Abstract
Diabetes mellitus is a serious increasing global health burden and one of the most common endocrinal diseases in the world. It is defined as a chronic metabolic disorder resulting from defective insulin secretion, action or both. Exogenous supply of insulin is consistently and essentially needed to maintain normal glycaemia in diabetic patients.
However, conventionally for over 80 years, subcutaneous (SC) insulin injection has been the main style of insulin delivery used clinically in order to supply its physiological secretion. although this parenteral route of administration is satisfactory in terms of efficacy, SC insulin administration has associated several side effects such as hyperinsulinemia, localized deposition of insulin, local hypertrophy, pain, psychological discomfort, high probability of infections and poor patient compliance.
To circumvent this tedious regimen of therapy, considerable research efforts have been devoted to exploit different mucosal surface. among different routes, the oral route is considered to be the most convenient and physiological because insulin would be directly channeled from the intestine to the liver (major site of action).
However, oral insulin delivery is not an easy task and is hurdled by different barriers. The gastrointestinal (GI) enzymatic barrier is a major challenge since gut proteases act to break large ”active” proteins into smaller ”inactive” amino acids. In addition to these GI barriers, the large molecular weight and hydrophilic nature of insulin mean that it cannot diffuse across GI epitelial leading to low bioavilability.