ABSTRACT
Two-level delivery systems (DSs) for oral administration of therapeutic proteins and peptides were developed. The first level consists of outer walls of Lycopodium clavatum spores (sporopollenin exine capsules, SECs) with included target objects; the alginate microgranules serve as the second (outer) level. Alginate (a pH-dependent natural polymer) protects peptides from gastric acidity and enzyme exposure and provides slow release of target objects in an alkaline intestinal medium. Introducing ovomucoid (a peptidase inhibitor) into alginate coatings prevents enzymatic hydrolysis of peptide objects in the intestinal medium. The elemental composition of spores and SECs was controlled using energy-dispersion spectroscopy and combustion analysis; their morphology was visualized by SEM. The efficiencies of different methods of SEC loading were compared. It was demonstrated that the load value was controlled by molecular mass and the value of the isoelectric point of target objects. A comparison of peptide in vitro release profiles from DSs of various structures into simulated gastric and intestinal fluids was carried out. The mechanism of peptide release from two-level DSs was suggested. SECs were found in rat blood after intragastric administration of the two-level DSs. Time profiles of therapeutic peptide release were obtained in vivo.
