A new oral microsphere drug delivery system

Oligopeptides as an Oral Delivery System: I. Aggregation Characteristics and Drug Encapsulation

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.

Oligopeptides as an Oral Delivery System II. Effect of Amino Acid Sequences on Aggregation Behavior

The effect of amino acid sequences on the aggregation and the subsequent sphere formation behavior of tetrapeptides, pEE(a)X(y) involving glutamic acid (E), phenylalanine (F), tyrosine (Y), alanine (A), and leucine (L) were investigated by light scattering and light microscopy. At 0.1 M pEE(a)Y(y)Y and pEE(a)F(y)F showed similar pH and concentration-dependent aggregation behaviors. These tetrapeptides also showed similar aggregation profiles in the presence of macromolecular drugs. Only pEE(a)F(y)F produced discrete spheres in the presence of protein drugs. Neither pEE(a)A(y)A nor pEE(a)L(y)L gave aggregates even at 0.1 M at pH 2. Consequently, the amino acids terminal positions are important in the aggregation characteristics of the tetrapeptides.

The antitumor immune responses induced by nanoemulsion-encapsulated MAGE1-HSP70/SEA complex protein vaccine following peroral administration route

Previous studies have shown that there are profuse lymphatic tissues under the intestinal mucous membrane. Moreover, vaccine administered orally can elicit both mucous membrane and system immune response simultaneously, accordingly induce tumor-specific cytotoxic T lymphocyte. As a result, the oral route is constituted the preferred immune route for vaccine delivery theoretically. However, numerous vaccines especially protein/peptide vaccines remain poorly available when administered by this route. Nanoemulsion has been shown as a useful vehicle can be developed to enhance the antitumor immune response against antigens encapsulated in it and it is good for the different administration routes. Of particular interest is whether the protein vaccine following peroral route using nanoemulsion as delivery carrier can induce the same, so much as stronger antitumor immune response to following conventional ways such as subcutaneous (sc.) or not. Hence, in the present study, we encapsulated the MAGE1-HSP70 and SEA complex protein in nanoemulsion as nanovaccine NE (MHS) using magnetic ultrasound method. We then immuned C57BL/6 mice with NE (MHS), MHS alone or NE (-) via po. or sc. route and detected the cellular immunocompetence by using ELISpot assay and LDH release assay. The therapeutic and tumor challenge assay were examined then. The results showed that compared with vaccination with MHS or NE (-), the cellular immune responses against MAGE-1 could be elicited fiercely by vaccination with NE (MHS) nanoemulsion. Furthermore, encapsulating MHS in nanoemulsion could delay tumor growth and defer tumor occurrence of mice challenged with B16-MAGE-1 tumor cells. Especially, the peroral administration of NE (MHS) could induce approximately similar antitumor immune responses to the sc. administration, but the MHS unencapsulated with nanoemulsion via po. could induce significantly weaker antitumor immune responses than that via sc., suggesting nanoemulsion as a promising carrier can exert potent antitumor immunity against antigen encapsulated in it and make the tumor protein vaccine immunizing via po. route feasible and effective. It may have a broad application in tumor protein vaccine.