Biological Evaluation Of The Process Of HA/PDLLA Degradation And Bone Formation In Vivo

Skeleton is a load-bearing apparatus, it exists to to maintain load bearing and the capacity to regulate calcium homeostasis and hematopoiesis and to repair structural damage. Bone necrosis, defect and other pathological changes can be caused by tumor, infection, congenital defect and wound. So, it is important to find perfect biomaterials to repair the bone defect. Hydroxyapatite/poly lactide biomaterial has become one of the most important and potential bone graft substitutes because of its favorable biocompatibility and bioactivity. The composition of these two materials can enhance the toughness to meet the mechanical strength of the bone substitues;on the other hand, the acid degradation production of poly lactide can be amortized by hydroxyapatite, which provides better environment for cell proliferation, regeneration and vessel development to fit the biological requirements for bone tissue engineering materials.HA/PDLIA composite materials were prepared by liquid phase absorption and PDLIA were chosen as control materials. Mechanical property showed that bend intensity and bend mould were both enhanced after addition of HA granules. Simulating test in vitro validated that obvious weight loss occurred in single PDLIA at 4^th week, and composite material with 10% HA occurred at 7^th week, which avoided the excessive dynamic loss in earlier stage and helped the fracture healing.Histological observation of implantation test showed that HA/PDLIA composite material is of better biocompatibility, adequate biodegradable capability, definite biological activity and osteoconductibility. After implantation, asepsis inflammation was slighter and the rate of bone formation was higher in HA/PDLIA group than that in single PDLIA. The existence of HA granules enhanced the mechanical strength of composite materials.Based on fluorescence pictures marked by acheomycin and advanced image analysis system, the trend of bone formation in HA/PDLIA composite material and single PDLIA were deduced. The quantitative analysis of the process of biochemical transformation from composite materials to organic bone tissue provides evidence for HA/PDLIA degradation and new bone formation.SEM showed that after the absence of HA granules from the surface, fibroblast started ingrowing and fresh callus came into being. This indicated that HA/PDLIA composite material had certain bioactivity and bone connectivity. A favorable biocompatibility was seen from the material/bone interface. At 24th week, the material was seperated and enwraped by tissue, and the fracture healed up successfully.