The supramolecular inclusion of -cyclodextrin (-CD) and PEG contained block copolymer Pluronic F127 was used to build a supramolecular hydrogel system.The composition and gelation behavior of the system were evaluated.There were two kinds of crosslinks in the hydrogels.One was the microcrystalline structure of packed PEG/-CD inclusion complexes

and the other was the aggregated hydrophobic blocks of Pluronic F127.An optimized gel system with low solid content (17.7 wt%) and short gelation time (6~8 min) was established for sustained release of insulin.The structure of -CD and PEG inclusion was characterized by wide-angle X-ray diffraction (XRD).The scanning electron microscopy (SEM) images of the freeze-dried powders of the gels showed a porous structure

because of the high water content of the hydrogels. In vitro insulin release was monitored by UV analysis

and the release was sustained in 65 h with a burst release of 30% in the first 5 h.In vitro cytotoxicity studies showed that the hydrogels (without insulin) had no evident growth inhibition to BEL-7402 cells when the concentration was lower than 109 mg/L.Animal experiment showed that the hydrogel was positive to prolong the in vivo insulin release.These results suggested that the supramolecular hydrogels hold great potential as a sustained delivery system of hydrophilic drugs and proteins

such as insulin.