Trypsin inhibition, calcium and zinc ion binding of starch– g-poly(acrylic acid) copolymers and starch/poly(acrylic acid) mixtures for peroral peptide drug delivery

Newly synthesised starch– g-poly(acrylic acid) copolymers and starch/poly(acrylic acid) mixtures were evaluated for their in vitro inhibition potency towards the proteolytic enzyme trypsin. Their Ca 2+ and Zn 2+ binding capacity was measured. Carbopol ® 934P was used as reference polymer. Starch– g-poly(acrylic acid) copolymers were prepared by chemical grafting and 60Co irradiation, the starch/poly(acrylic acid) mixtures by freeze–drying. The influence of preparation method, the ratio starch:acrylic acid, the neutralisation degree and for the freeze–dried polymers the influence of heat treatment after freeze–drying was investigated. All freeze–dried polymers showed a higher inhibition factor (IF) than the chemically grafted and 60Co irradiated starches, which all showed significantly lower IF than Carbopol ® 934P. The heat treated freeze–dried polymer Amioca ®/poly(acrylic acid) (1:1) showed a significantly higher IF than the reference polymer (Mann–Whitney test, p