Synthesis of pH-responsive starch nanoparticles grafted poly (l-glutamic acid) for insulin controlled release

In this article, a novel oral protein drug delivery made of starch nanoparticles (SNPs) as backbone and poly (l-glutamic acid) (PGA) as graft chains was successfully synthesized by click reaction. The grafting efficiency and structure of the resultant copolymer SNP-g-PGA were verified by 1H NMR and FT-IR spectra. The copolymer could assemble into amphiphilic aggregates. Hydrodynamic radii (Rh) of the aggregate decreased obviously as increasing pH value due to its excellent pH-dependent property. To take advantage of this pH-responsive property, in vitro insulin release experiment was carried out. The loaded-insulin released from the copolymers more slowly in artificial gastric juice (pH = 1.2) than that in artificial intestinal liquid (pH = 6.8) due to the excellent stability in acidic condition. These results suggested that the natural starch based material with pH sensitivity could be a promising delivery for insulin controlled release.