Influence of degree of substitution of HES–HEMA on the release of incorporated drug models from corresponding hydrogels

Hydrogel microparticles were produced by a radical polymerization of hydroxyethyl methacrylate–hydroxyethyl starch (HES–HEMA) in an all aqueous two-phase system (ATPS). The microspheres show a monomodal size distribution and have the ability to entrap high amounts of water. The release of proteins or other testing substances from the HES–HEMA hydrogels can be controlled by the choice of the network density of the hydrogel by varying the degree of substitution (DS), the size of the entrapped substance, and by conditions enhancing the degradation of the hydrogel network.