The Experiment Research Of Improving The Bioactivity Of Citrated Calcium Sulfate

The requirement of bone defect substitute has been more and more greater at present along with the development of orthopaedics. Homogenous and heterogenous bone is insufficient and also has the shortcoming of transmission contagious disease such as AIDS and their antigenicity can't be eliminated thoroughly. Hydroxyapatite and alcium phosphate and so on hardly degradate. Calcium sulfate is favored by the the orthopaedist for its satisfied degradation speed and biocompatibility. There has been surgical grade α-calcium sulfate overseas such as Osteoset? produced by American Wright company. We first prepared surgical-grade α-calcium sulfate with citric acid in our country which has good biocompatibility and can be absorbed along with its degradation. However the material has some disadvantage such as faster degradation speed than the new bone growth speed, poor intensity and supporting strength and cell adherence and bone inducibility. We intend to study the method that can prolong the degradation period of citrated calcium sulfate and increase its intensity and bone inducibility on behalf of its clinical application in the future.PurposeTo find out the method that can prolong the degradation period of citrated calcium sulfate and increase its intensity and bone inducibility.Materials and methods(1) The relationgship between the pressure and degradation speed during preparation: Exerting various pressure during the preparation of calcium sulphate dihydrate to elect the best pressure that can prolong the degradation period of citrated calcium sulfate and increase its intensity and bone inducibility. (2) Combining with various materials: Coating calcium sulfate with various materials and combining with PLGA to pick out the material that can prolong thedegradation time. (3) Physico-chemical property and biocompatibility: Iidentifing the composition of calcium sulfate coated by chitosan and detecting its value of PH and biocompatibility. (4) Implanting and restoring the contained bone defect of condyles of femur of rabbit: Observing the effect of restoration of contained bone defect with the use of compressed coated calcium sulphate dihydrate and the correlation of degradation speed of calcium sulphate dihydrate and bone growth speed. (5) Restoring the segmental bone defect of rabbit with the coated calcium sulphate dihydrate combining with rhBMP-2: Observing the osteoinduction role of the coated calcium sulphate dihydrate combing with rhBMP-2 on marrow stromal cells and heterotopic ossification and the result of the restoration of segmental radial bone defect of rabbit.Results(1) The pressure during preparation: The pressure during preparation can increase the strength of calcium sulphate dehydrate and prolong its degradation period. The calcium sulphate dehydrate obtains the maximum strength and degradation time under the pressure of 6 MPa. (2) Combing various materials: Coating calcium sulphate dehydrate with chitosan can prolong its degradation period which has no defference comparing with Osteoset?. It is documented that coated calcium sulphate dehydrate can be used as the bone substitute material to prolong the bone degradation period of calcium sulphate dehydrate. (3) Physico-chemical property and biocompatibility: The chitosan coats the calcium sulphate dehydrate thoroughly and the material has good biocompatibility and has no affection of the value of PH of the surrounding tissue. (4)Restoring the containing bone defect of condyles of femur of rabbit: The compressed and coated calcium sulphate dehydrate has the same degradation speed as the bong growth speed and it restores the contained bone defect through guiding osteanagenesis. (5) Restoring the segmental bone defect of rabbit with the coated calcium sulfate combining with rhBMP-2: The rhBMP-2 doesn't loss its physiological activity after combing with calcium sulphate dehydrate and still has osteoinduction whichis synergistic with the osteoconduction of calcium sulphate dehydrate to make it suitable for the restoration of segmental bone defect.Conclusion1 , The strength of calcium sulphate dehydrate rises along with the increase of pressure during its preparation, so does the degradation period of calcium sulphate dehydrate. The calcium sulphate dehydrate coated by chitosan can get the longer degradation period which is coincidence with the bone growth period.2, The chitosan coats the calcium sulphate dehydrate thoroughly and the material has good biocompatibility and has no affection of the value of PH of the surrounding tissue which makes it suitable not only for the contained bone defect but also for the segmental bone defect.3 , It is proved that the rhBMP-2 doesn't loss its physiological activity after combining with calcium sulphate dehydrate and still has osteoinduction which is synergistic with the osteoconduction of calcium sulphate dehydrate so as to get the best result of the restoration of segmental bone defect.