Supramolecular hydrogels based on inclusion complexation between poly(ethylene oxide)-b-poly (epsilon-caprolactone) diblock copolymer and alpha-cyclodextrin and their controlled release property.

Supramolecular hydrogels formed through inclusion complexation between high molecular weight poly(ethylene oxide) (PEO) and alpha-cyclodextrin (alpha-CD) showed the most sustained release kinetics in vitro with molecular weight of PEO of 35,000 within 5 days. To improve the sustained release and overcome using high molecular weight PEO, novel supramolecular hydrogels have been prepared by using biodegradable amphiphilic poly(ethylene oxide)-b-poly(epsilon-caprolactone) (PEO-PCL) diblock copolymer instead of PEO. Rheologic studies indicate that the prepared hydrogel is thixotropic and reversible. The in vitro release kinetics of hydrogels has been studied by using fluorescein isothiocyanate labeled dextran (dextran-FITC) as model drug. Compared with that of alpha-CD/PEO supramolecular hydrogels, the sustained release of alpha-CD/PEO-PCL supramolecular hydrogel was increased significantly even if with much lower molecular weight of PEO block. This result indicates incorporating hydrophobic PCL block could reduce the molecular weight of PEO required for long-term drug release system. The sustained release is also dependent on the alpha-CD content in supramolecular hydrogels. Thus, the properties of supramolecular hydrogel can be fine-tuned with different polymer and at different alpha-CD content, opening a wide range of applications.