The Histological Observation Of The Process Of HA/PDLLA Bone Formation And Degradation In Vivo

PartⅠ. The histological observation of the process of HA/PDLLA bone formation in vivoObjective:For establishment of experimental foundation for osteogenesis induction in vivo of HA(Hydroxyapatite)/PDLLA(DL-poly lactic acids) composite, the HA/PDLLA composite and autologous iliac were implant-ed in vivo for test. The in vivo induction process of osteogenesis and pra-ctical cicatrisation effect of HA/PDLLA composite material were investi-gated by histological methods, which biological function for the design of artificial bone substitute materials and bone tissue engineering scaffolds to provide experimental evidence.Materials and Methods:Selected 1 to 2 years of 40 local black goats, weight (15±5) kg, which were divided into 2 groups, one group was HA/-PDLLA composite (20 goats), the other was autologous iliac (20 goats). After the black goats were anesthetized, at L3/4 intervertebral space were implanted HA/PDLLA composite and autologous iliac by the rear approa-ch. Respectively, 1,3,6,12 months after surgery the local black goats were sacrificed 10 (each group was 5). Biopsy specimens were taken for histological observation.Results:1 month after surgery, the composite did not integrate into the bone tissues, its surrounding incomplete thin fibrous membrane, extrame-mbrane saw a lot of destruction of bone with osteoblast cells, and so on. 3th month, composite material had been integrated into bone tissues, ext-ramembrane began to appear new bone formation, with small amount of new bone trabeculae and microvascular. After that, fibrous tissue began ingrowthed composite material, extramembrane formatted irregular trab-ecular bone formation and neovascularization slowly. Until 12th month, composite material was well-integrated into bone tissue, trabecular bone was more regular and blood vessels had been existed, at this point the majority of composite material had been degraded, saw the scattered dist-ribution of it. The process of experiment compared with the autologous iliac group, the composite and autogenous iliac group to guide the process of bone formation was more similar.Conclusions:The HA/PDLLA composite not only had good biocompati-bility, proper biodegradation property, certain bioactivity, but also had good bone induction and bone formation, which was an ideal bone substitute material.PartⅡ. The degradation of HA/PDLLA in vivoObjective:By measuring the weight and the pH value's changes of the HA/PDLLA composite in vitro, which were to determine the relationship between the pH value and the degradation of composite's changes within the certain environment. And to improve the biomechanical properties of composite materials had some significance.Materials and Methods:A known weight of the (30%HA) HA/PDLLA composite material (experimental group) and pure PDLLA material (con-trol group) were put into the pH=7.4 PBS solution, the weight and the pH value were measured at 37℃every week. Weight loss percentage= [(in-itial weight—current weight)/initial weight]×100%.Results:The HA/PDLLA composite compared with the control group in the same period, the HA/PDLLA composite material's degradation rate and degradation of weight changes to be more relaxed, the pH value's decrease changes were smaller than the control group.Conclusions:HA/PDLLA composite may exist not only from the cataly-st, its degradation rate may also have a positive correlation effect with the changes of pH value in their environment.