ABSTRACT
The advances in molecular biology and recombinant DNA technology over the past 30 years has made it possible for the biopharmaceutical industry to develop protein and peptide drugs, such as human insulin (In), human growth hormone (hGH), human granulocyte colony-stimulating factor (G-CSF), and human erythropoietin (EPO).1,2 The peptide and protein drugs have been available for clinical use in the market for many years.3 However, one drawback of these drugs is that patients have to take them either subcutaneously (s.c.), intramuscularly (i.m.), or intravenously (i.v.) by injection. These invasive techniques are associated with pain, unwanted site effects, and low patient compliance. Therefore, noninvasive routes, such as oral, nasal, rectal, ocular, and pulmonary routes, have long been sought after by the pharmaceutical industry, but with little success.4
