Preparation and biological characteristics of recombinant human bone morphogenetic protein-2-loaded dextran-co-gelatin hydrogel microspheres, in vitro and in vivo studies

Hydrogels are based on hydrophilic polymers which are cross-linked to prevent dissolution in water. Because hydrogels can contain large amounts of water, they are interesting devices for the delivery of protein drugs. In this contribution, biodegradable dextran-co-gelatin hydrogel microspheres (DG-MPs) are described which are based on physical interactions and are particularly suitable for the controlled delivery of pharmaceutically active proteins. The unique feature of this preparation system is that the hydrogel microsphere formation takes place in an all-aqueous solution, by which the use of organic solvents is avoided. We investigated the preparation and biological activities of recombinant human bone morphogenetic protein-2 (rhBMP(2))-loaded dextran-cogelatin hydrogel microspheres (rhBMP(2) -DG-MPs), which aimed to keep rhBMP(2) ' s biological activity and to achieve a long-term sustained release of rhBMP(2). The microspheres' average diameter was about 20 - 40 mu m and rhBMP(2) release in vitro could be maintained for > 10 days. Cytology studies showed that using rhBMP(2)-DGMPs could promote the proliferation and osteoblastic differentiation of periodontal ligament cells better than using rhBMP(2) aqueous solution. By a freeze-drying method, rhBMP(2) - DG- MPs could be adhered in chitosan membranes for guided tissue regeneration use, namely functionalized membranes. To evaluate bone regeneration induced by rhBMP(2) - DG- MPs, an animal experiment with canine class III furcation defects was adopted and the results indicated that using rhBMP(2) - DG- MPs incorporating scaffolds and functionalized membranes could gain more periodontal tissue regeneration than using scaffolds and general membranes soaked with concentrated rhBMP(2) aqueous solution. Therefore, those studies demonstrate the potential of DG- MPs in the sustained delivery of low dosages of rhBMP(2) to periodontal defects. Copyright (C) 2005 S. Karger AG, Basel.