The Study On The Sustained-release Bistratal Bone Morphogenetic Protein

Objective:To study and construct the BMP-2rich biodegradable sustained release film with strong biological activity, and detect the biological tissue compatibility as well as the roles in promoting bone regeneration, bone nonunion of fracture and bone defect healing.Research methods:1. The nanoscale diameter rhBMP-2/chitosan particle microspheres were prepared by the method of emulsion, and observed by field emission scanning electron microscopy for detection of drug loading rate, biological degradation and sustained release pharmacokinetics.2. Choose the chitosan microspheres as the slow release carrier of rhBMP-2, constructed the rhBMP-2/chitosan microspheres/gelatin sponge-collagen composite film using absorbable gelatin sponge and collagen membrane, observed and analyzed the slow release mechanism of the composite film loading rhBMP-2/chitosan microspheres in vitro, and detected the biological compatible of the composite film materials.3.48adult rabbits were selected to build the1/3middle medille femora10mm long bone fracture and defect model by surgery operation.48rabbits were divided into3groups randomly. The experimental group:hBMP-2/chitosan microspheres/gelatin sponge collagen composite scaffold group, the rhBMP-2loaded chitosan microspheres/gelatin sponge collagen composite were fixed in the bone fracture and defect and reconstruction by titanium plate. Control group:gelatin sponge collagen composite; blank control group:in this group, the rabbit fracture defect area were fixed only by titanium plate, the fracture and bone defect healing naturely without any material. The accidental death experimental rabbits were suppled in time from various causes by experimental failure,4rabbits were used for experiment for each time point, after2weeks,4weeks,8weeks,12weeks, the femur in rabbits with experimental site were selected respectively for gross specimens observation, imaging examination, histochemistry and imrnunohistochemistry analysis, electron microscopy scanning. All data were analysed by SPSS11.0statistical software, set the detection level as a=0.05and significant difference as p<0.05. Results:our experimental results showed that the area of bone defect repair degree and active metabolism of bone defect healing rate in the experimental group was significantly better than that in the control group.4and8weeks after surgery, X-ray observations show that bone fracture end were irregular slightly, soft tissue could be saw in the edge, the bone defect site rare high density while the end of fracture defect edge irregular, high density and new bone formation could be obvioused in the experimental group which containing rhBMP-2/chitosan microspheres/gelatin sponge collagen composite membrane in the control group and blank control group (simple operation fixed without any biological material). After12weeks, in the control group and blank control group there were little new bone formated while a large number of new bone formated in the experimental group.Conclusion:(1) As a member of bone morphogenetic protein family, BMP-2is a high active growth factor, could induce new bone formation and osteoblast differentiation, promote early bone formation, accelerate bone healing.(2) The composite film loaded hBMP-2/chitosan microspheres/gelatin sponge collagen has good biological compatibility and bone regeneration, this study suggests that the composite as a scaffold material can promote early bone formation, continued to stimulate the local tissue during the long time of new bone occurred, accelerate bone regeneration and calcification, accelerate bone defect healing, shorten the treatment period.