Development of pH-responsive organic-inorganic hybrid nanocomposites as an effective oral delivery system of protein drugs

This research aimed to develop a pH-responsive organic-inorganic hybrid nanocomposite as an effective oral delivery system for protein drugs. Three different nanocomposites were prepared by using bovine serum albumin (BSA) as a model protein. A nanocomplex of BSA with 3-aminopropyl functionalized magnesium phyllosilicate (AC-BSA) was obtained via the spontaneous co-assembly and then sequentially coated with glycol-chitosan (GAC-BSA) and the pH sensitive polymer, Eudragit (R) L100-55 (EGAC-BSA). These organic-inorganic hybrid nanocomposites exhibited high entrapment efficiency (86-99%) and their structural characteristics were confirmed by using energy dispersive X-ray spectroscopy, Fourier transform infrared spectroscopy, and circular dichroism analysis, indicating that the secondary structure of BSA was well retained in the nanocomposites. At pH 1.2, AC-BSA achieved rapid drug release of about 80% within 2 h, while GAC-BSA and EGAC-BSA exhibited slow drug release of 30% and 15%, respectively, indicating that the surface-coated nanocomposites were more stable in the gastric condition. Furthermore, the conformational stability of BSA entrapped in EGAC-BSA was well retained in the presence of proteolytic enzymes, suggesting that EGAC-BSA should be effective in protecting the protein against gastrointestinal harsh environment. Compared to free BSA, all of tested nanocomposites demonstrated 2.1-3.8-fold higher cellular uptake in Caco-2 cells. Furthermore, energy-dependent endocytosis and paracellular pathway contributed to the cellular transport of nanoparticles. After oral administration in rats, EGAC-BSA significantly enhanced the intestinal permeation of BSA compared to free BSA. In conclusion, EGAC-BSA appears to be promising as an effective oral delivery system for proteins with enhanced intestinal absorption.