Oligopeptides as an Oral Delivery System: I. Aggregation Characteristics and Drug Encapsulation
Abstract
A series of glutamic acid(E)-phenylalanine(F) oligopeptides were studied as potential oral drug delivery systems for protein and polysaccharide drugs. The aggregation behavior of the tri- and tetrapeptides (pEE(a)F, pEE(y)F, pEE(a)F(y)F) were characterized by light scattering and light microscopy. The tripeptides did not form aggregates up to 0.1 M at pH 2. On the other hand, the tetrapeptide pEE(a)F(y)F formed self-aggregates at relatively low concentrations (11.8 mM). This tetrapeptide also associated preferentially with several drug molecules, such as insulin and bovine serum albumin, below the concentration at which the aggregation occurred. The same concentration of unassociated pEE(a)F(y)F was necessary to achieve aggregation whether the pEE(a)F(y)F was associated with drugs or not. The pEE(a)F(y)F also formed unique spheres in the presence of protein drugs.