Pulsatile peptide release from multi-layered hydrogel formulations consisting of poly(ethylene glycol)-grafted and ungrafted dextrans

Multi-layered hydrogel formulations consisting of poly(ethylene glycol)-gra fted dextran (PEG-g-Dex) and ungrafted Dex were investigated as a model of pulsatile drug. release. In these formulations, it is considered that the g rafted PEC domains act as a drug reservoir dispersed in the Dex matrix base d on aqueous polymer two-phase systems. The formulations exhibited surface- controlled degradation by dextranase, and insulin release was observed in a pulsatile manner because of the multi-layered structure; PEG-g-Dex hydroge l layers containing insulin and Insulin-free Dex hydrogel layers. Thus, it is suggested that the multi-layered hydrogel formulations using PEG-g-Dex a nd Dex are feasible for chronopharmacological drug delivery systems.