The Study Of Biodegradable,Bioabsorbable Poly(DL-Lactide)and Its Complex Material:The Synthesis Of Material,Degradation Property In Vitro And Tissue Biocompatibility

Over a long period, healing bone defects is a perplexing issue for orthopaedic. Because new bone using tissue engineering technique has the advantage of autologous grafts, orthopedics have paid more and more attention to this technique. Tissue engineering technique places three-dimension matrices and undifferentiated osteogenic cells in an optimum condition. The cell absorb the nutrient and attach to the matrice on which new bone is formed under the modulation of regulatory factors. Poly-DL-lactide(PDLLA) is a kind of cheep, bioabsorbable polymer, which has good initial strength. When degrading, its micro-environment turns acid and its initial strength becomes weaker, which restrict its application. In order to improve the property of PDLLA, HA or B-TCP was added to PDLLA in different scales. The aims of this study were to study the synthesis and fabrication, the degradation property in vitro and tissue response of PDLLA and its complex material, to evaluate the prospect to orthopaedic use, and to develop a new kind of absorbable osteosynthesis material. Part 1. With ZnO as the catalyst, the lactide(LA) was polymerized by DL-lactic acid. Calcium hydroxide and phosphate was polymerized HA, then was calcined at 8000C for 3 hours and whetted. CaHPO4 2H20 and CaCO3 were mixed, whetted and stored at 9800C for 2 hours, then cooled. 1 g pdlla were?immersed in 8 ml CHCL3, then 4 g sodium chloride were added. The mixture were separated in ultrasonic apparatus, extended into membrane, -7- air-dried at 250C for 24 hours, then vacuum-dried until use. 0.95 g pdlla were immersed in 8 ml CHCL3, then 4 g sodium chloride and 0.05 g HA were added. The mixture were separated in ultrasonic apparatus, extended into membrane, air-dried at 250C for 24 hours, then vacuum-dried until use. The complex material were immersed in 250ml water at 250C for 48 hours( the water was changed every 6h to leach out the salt, then the 慡%PDLLAIHA was gotten. The other kinds of complex material were prepared like this. Part 2. Every kind of former were immersed in the distilled water, or implanted into the muscle of mice, and removed at~ 2,4,6,8,10,12 weeks. 4 Different methods such as weight, viscosity measurement and mechanical strength were employed to study the degradation property in vitro, and microscopy to the tissue response. The results showed the pH indicator didn抰 change obvious. The viscosity-average molecular weight turned down at first 2 weeks. There was a degrading peak for every kind of material. PDLLA appeared in 4-6 weeks; appeared PDLLAI P -TCP appeared in 6-8 weeks, and 5% PDLLAI P -TCP is the most evident; PDLLAIHA appeared in 10-12 weeks. Weight didn抰 change obvious, but PDLLA is the most evident. Weight of every kind of material changed more at some period: PDLLA was in 6-8 weeks; PDLLAI P -TCP was in 8-10 weeks; PDLLAIHA was in 10-12 weeks. PDLLAI P -TCP had a better biomechanical property than PDLLA and PDLLA/HA. All samples were well tolerated by the tissue, but PDLLAI P -TCP had a stronger response early. The result indicated following conclusions: The PDLLAI P -TCP has good biomechanical property and biocompatibility, and degenerate with time. It is an appropriate material for tissue engineering and 20% PDLLAI P -TCP is the best one.