Preparation of recombinant human bone morphogenetic protein-2 loaded dextran-based microspheres and their characteristics

Aim: To prepare new pharmaceutical forms with sustained delivery properties of recombinant human bone morphogenetic protein-2 (rhBMP(2)) for tissue engineering and guided tissue regeneration (GTR) use. Methods: rhBMP(2)-loaded dextran-based hydrogel microspheres (rhBMP(2)-MPS), which aimed to keep rhBMP(2) bioactivity and to achieve long-term sustained release of rhBMP(2) were prepared by double-phase emulsified condensation polymerization. The physical, chemical performances and biological characteristics of those microspheres were studied both in vitro and in vivo. Results: The microspheres' average diameter was 30.33 +/- 4.32 mu m with 75.4% ranging from 20 mu m to 40 mu m and the drug loading and encapsulation efficiency were 7.82% and 82.25%, respectively. The rhBMP(2-) releasing profiles in vitro showed that rhBMP(2) release could be maintained more than 10 d. The rhBMP(2)-MPs, with good swelling and biodegradation behavior, could be kept for 6 months at below 4 degrees C without significant characteristic change or bioactivity loss. Cytology studies showed that rhBMP(2)-MPs could promote the proliferation of periodontal ligament cells (PDLCs) approximately 10 d, while the bioactivity of concentrated rhBMP(2) solution could keep no more than 3 d. Scanning electron microscope showed that rhBMP(2)-MPs could be enchased into the porous structure of calcium phosphate ceremic (CPC) and the eugonic growth of PDLCs in CPC/rhBMP(2)-MP scaffolds. Animal experiments indicated that using CPC/rhBMP(2)-MPs scaffolds could gain more periodontal tissue regeneration than using rhBMP(2) compound firsthand with CPC (CPC/rhBMP(2)). Conclusion: By encapsulating rhBMP(2) into dextran-based microspheres, a small quantity of rhBMP(2) could achieve equivalent effects to the concentrated rhBMP(2) solution and at the same time, could prolong rhBMP(2) retention both in vitro and in vivo.