The Preparation And Biodegradable Evaluation Of The Degreased And Deproteined Bovine Bone Particles/ Poly (L-lactic Acid) Internal Fixation Composites

Objective: The research on the fracture internal fixation composites is one of the most attractive aspects of biomedical engineering. For a long time, the metal fixation is the traditional fracture internal fixation for its very strong mechanics strength, but it can not be degraded and absorbed in the human body. So the second operation will be needed to take out the metal fixation, and patients will suffer the pain and economy loss. Therefore, it has become an aim for most scientists to make some fracture internal fixation materials that can be degraded and absorbed in the human body. PLA has no toxicity and harm to the human body; it has good biocompatibility and mechanical property. PLA can degrade slowly when it is transplanted into the body, and becomes to CO₂ and H₂O after degradation. The degreased and deproteined bovine bone is a heterogeneous bone of little immunogenicity, it contains basic components of bone. This research makes the degreased and deproteined bovine bone/PLLA compound stick, investigates its mechanical properties and biodegradation, evaluates its prospect as the fracture internal fixation.Method: This research makes the calf os integumentale into the degreased and deproteined bovine bone particles, analyzes these elementary composition and functional group. Then with the degreased and deproteined bovine bone particles for strengthen materials, polymers of PLLA for base materials, makes the composite materials by aqua dispersion method, makes the compound stick by hot pressure moulding. This research does the biodegradable test in vitro by putting the sticks into the phosphate-buffered saline at 37℃, takes the samples after 2,4,6, 8,10,12 weeks, then measures the PH of the phosphate-buffered saline, the water absorption rate and the weight loss rate, the viscosity-average molecular weight of PLLA, the bending strength and the micro-construction of the surface and the cross section by scanning electron microscope.Result: The basic components of the degreased and deproteined bovine bone are hydroxyapatite and few proteins. It's an incompletely deproteined bone. The degreased and deproteined bovine bone particles/PLLA compound stick can maintain a low water absorption rate in the early stage. During the whole degradation of 12 weeks, the PH of the phosphate-buffered saline hasn't decreased obviously, the viscosity-average molecular weight of PLLA has decreased slowly, and the bending strength can keep in a higher level.Conclusion: The degreased and deproteined bovine bone particles /PLLA compound stick has a good mechanic properties and biodegradation. It can satisfy the requirements of internal fixation for cancellous bone.