Preparation And Evaluation Of PLLA/PLGA/HA Composite Material

objectiveTo explore the advanced composite material whose matrix ingredient is polylactic acid,which is systematically and deeply investigated by its phase component,mechanical property,degradation property,microstructure, biological behavior,in order to find out whether it can be applicated to Clinical work or not,if in accordance with the need of biological engineering materials.methodThe new monomer is made up of the L-lactide and L-glycolide with the mol ratio(5:1),which is adopted ring opening polymerization process to preparate multipolymer PLGA in vacuum and in 140℃.The composite materialis consisted raw material of PLLA,PLGA and HA kernel, adopted compression moulding forming method with column sample. Test different mass ratio HA type with flexure strength,flexure modulus, shear(ing) strength and anti-torsional strength separately.To understand the influence of degradation with PLLA,PLGA and composite material,and autocatalysis 24 weeks in simulated-body fluid. The degradated-liquids tests are carried out in different periods with PH, rate of weight loss,water absorption,the changeable of mechanical property, the changeable or distribution of molecular weight,and concentration of calciumion.Further the surface and section appearance in SEM were detected in different time in order to explore the machine processed of degradation.The Osteoplast MG-63 with contents of 10~5/ml and composite material are co-cultivation,the forms of cells are detected by inverted microscope and the adhesive are detected by electron microscope.The cells are stained by Von Kossa,alkaline phosphatase,and the determination of alkaline also measured.The composite materials are put into the musculature of the rabbits,which are taken out and stained in the stuff-tissue inter face at 1w,2w,4w,8w,16w and 32w.Biological safty tests of the composite materials,such as acute toxicity,subacute toxicity, pyrogen,hemolysis,and antibacterial,which were performed according to the biomedical safty assessment standards.Twenty-seven rabbits are divided into three groups which are nine ones,it turns out the osteogenesis fusion and degradation of composite materials procedures by histological observation at 4w,12w,24w and 36w.The iliac bone group,the composite material group,bone cement group were taken anterioposterior and lateral film at 4w,12w,24w and 36w.The three rabbits of composite material group were implement by MRI at 4w,12w,24w and 36w.The section and material-bone surface appearance in SEM and energy spectrum were detected at 12w,24w and 36w.The intervertebral bone fusion were observed by all the rabbits. ResultWith the increasing of the HA,the flexure strength is raising,while the flexure modulus is reducing.When the HA is 15%,the flexure strength of the composite materials are reaching 220MPa and 5.35GPa respectively.With degradation of the PLLA,PLGA and composite material in PBS,the rate of weight loss and water absorption are increasing,and the pH is decreasing.The changeable of the composite material and mechanical property are slower than the former two.After twelve week's degradation The mechanical property of the PLLA can offer Define spongy bone fixation,and the composite material still can supplied cortex bone fixation.The changeable of molecular weight are reducing fast at the beginning,and slowly in the end.The degradation kinetics of the composite material were indicative of an autocatalysis process simple bulk hydrolysis,and presented the modal of "biomodal degradation".The Osteoplast MG-63 growth adherence in the composite materials with,polygon Shape,star pattern,outstretch pseudopod in electron microscope. Seven days after cultivation,there was nebulous calcific focus in the corpus neuroni.Four weeks later,big black nodus was occurred by Von Kossa staining.The corpus neuroni were blue with kernels by alkaline phosphatase staining,there were polygon Shape,fusiformis,oval pattern.The alkaline phosphatase was 14.7U/L in the twelve days after cultivation. The composite material,iliac bone and bone cement were put into three group rabbits.Thirty-six weeks later,the scattered-lump bone were turned to union with the new bone formation.At the same time,the big mass of composite material were degradation thoroughly,like "vacuolated-shape" There was no signs of subsidence,prolapsus,loosen, dislocation and no loss of the intervertebral height.The fusion is satisfying in the 36 weeks X-ray after operation.The area of middle-signal image in T2 are from 30mm~2 in the four weeks postoperatively to 6mm~2 in the Thirty-six weeks postoperatively.The fusion of which is good in the composite material group,is fair in the iliac bone group,and is poor in the bone cement group by SEM in thirty-six weeks postoperatively.No toxicity of the composite material,such as acute toxicity,subacute toxicity,pyrogen,hemolysis,antibacterial were detected by the toxicology studies.ConclusionThe composite material of which is made up of PLLA,PLGA and HA is a safety,effective internal fixation,because it has a good mechanical property,degradation property and no toxicity.Furthermore,it can promote osteogenesis in vivo.