Characteristics and osteoinductive activity of bone morphogenetic protein (BMP) encapsulated with poly (DL-lactide-co-glycolide)

Abstract

To develop a controlled release system for bone morphogenetic protein (BMP), encapsulation of BMP with poly (DL-lactide-co-glycolide) (PLGA)/poly (ethyleneglycol) (PEG) mixture was accomplished by an emulsion interfacial precipitation method. The surface morphology, average particle size and hydrolytic degradation rate of two types (PLGA and PLGA/PEG) of capsules were examined. The encapsulation yield and release rate of BMP in vitro were measured using fluorescein isothiocyanate-labeled BMP. The amount of BMP released from the PLGA and PLGA/PEG capsules increased between day 3 and day 5. The PLGA capsules released much BMP in this period compared to the PLGA/PEG capsules. These capsules containing BMP were implanted in subcutaneous areas of rats to examine the osteoinductive activity in vivo. They were digested completely, however, only the PLGA capsules containing BMP could induce new bone formation, including bone marrow, three weeks after implantation. From these results, it was considered that the PLGA capsules containing BMP are a prominent system to induce bone in clinics.