New type of hydrogel for controlled drug delivery.

The new type of hydrogel system (which is known under the trademark HYPAN), is described in some detail here, emphasizing its grades and those properties potentially useful in controlled drug delivery systems. HYPAN hydrogels are distinguished by a physical network of crystalline clusters which fully replace the covalent network typical of other hydrogels. As a result, HYPAN hydrogels can be processed by a number of methods unusual for hydrogels, such as extrusion, injection molding and the like. The crystalline network also provides HYPAN with improved mechanical properties at higher water contents, which in turn allows for higher permeabilities of aqueous solutes. The combination of improved mechanical properties and permeabilities with improved processability and good biocompatibility is believed to open some new possibilities in targeted and controlled drug delivery. This paper is written as an overview of the compositions, structures and essential properties of HYPAN materials. It will soon be followed by more detailed studies in selected areas.