Preparation, structure and BMP-2 controlled release of heparin-conjugated hyaluronan microgels

► Heparin-conjugated hyaluronan microgels are prepared for BMP-2 controlled release. ► Rougher surface and looser interior are formed by increasing heparin content. ► The water equilibrium swelling ratio of microgels increases with heparin content. ► The BMP-2 loading efficiency of microgels increases with heparin content. ► A slower BMP-2 release profile is obtained by increasing heparin content.