Preparation of Hydroxyapatite/Polylactide Bicomposites by Absorption Process in Liquid Phase

Vol.20 Suppl.Joural of Wuhan University of Technology - Mater. Sei. Ed.Dec.2005Preparation of Hydroxyapatite/ Polylactide Bicomposites byAbsorption Process in Liquid PhaseLI Jianhua FANG Yuan DAI Honglian LI Shipu HAN Yinchao( Biomedical Materials and Engineering Research Centre, Wuhan University of Science and Technology , Wuhan 430070, China)Abstract: The hydroxapatitel plblatde bicopsites nre prepared by absorption process in liquidphase。The method aroided many disaduntages，such as intefusion of chemical impurity substances ，nonunijfor-mity dispersal of HA in PLA，louv molecular ueight of PLA. HA particles uere unifomly dispersed in PLA matrir,and shoved vell adhesion uith PLA matrix . The bioconuposiles haue the higher mechanical properties and suitabledecomnposable capability.Key words: hydroxyapatite ; polyluctide composite ; absorption process1 Introduction2 ExperimentalThe PLA/HA biocomposites have good biocompati-2.1 Materialsbility and fine mechanical property, and they do not needLactic acid: analytically pure, the chemical reagentsecond operation and would not release metal ion whichfactory in Guangzhou; Stannous octoate: analyticallycan bring a series of untoward effects. The hydroxyapa-pure, the medical chemistry reagent company in China;tite/polylactide biocomposites are greatly used in many as-Ethanol: analytically pure, the chemical reagent factorypects such as internal fixing material of fracture, tissuein Shanghai; Phosphatic acid: analytically pure, the bodiengineering support material, flling material and antico-chemical incorporated company in Tianjin; Calciumagulant material. .hydroxide: analytically pure，the chemical reagent factoryThe PLA/HA biocomposites were mainly prepared. byin Shanghai .the fllowing three methods: (1) melting blend method22 :2.2 MethodsPut the HA powder after surface treatment into the PLA,2.2.1 Composition of PLAthen melted and blended the two materials when the tem-Put lactide and stannous octoate in Ampere botleperature was higher than PLA vitrification point. (2) so-according to the batch design, after vacuming and seal-lution dispersion method: Put suspending liquid of HAing tube the bottle is polymerized for 48 hours by puttingparticles treated by ultrasonic oscillation into trichlo-the bottle in oil bath when its temperature is , then trans-romethane solution including melted PLA, and mixing andparent solid PLA is obtained by cooling.supersonic wave made HA particles to disperse uniformnly2.2.2 Preparation of HAin PLA solution, then deleted solvent. (3) in situ copo-The method of HA powder made by liquid depositionlymerization: Entrained given HA particles in polymeriza-is to make use of the neutral reaction between Ca( OH)2tion before ring-opening polymerization of lactide, then in .and H3 PO, to generate HA, and the chemical formula is:the state of certain temperature and high vacum, the ini-6H,PO4 + 10Ca(OH)2一Cap(P04)。(OH)2 + 18H20tiator made lactide to polymerize and the PLA/HA bio-Drop slowly 1 000 mL 10.3 M H PO4 solution into 1conposites were obtainedsThough the three methods000 mL 10.5 M Ca(OH)2 suspending liquid, and thehad respective advantages，there were many disadvantagestemperature is set at 60 C，then stir mechanically andwhich limit the use of PLA/HA，such as interfusion ofcontinuously. When the PH value is 9.0，react for 7chemical impurity substances, nonuniformity dispersal ofhours, dry. it at certain temperature, dry in vacuum theHA in PLA，low molecular weight of PLA and not masslA powder deposition for 24 hours at 60 C, then cal-production. To overcome these defects， this paper willcine, grind, sieve, put them into vacuum desiccators asstudy the preparation of PLA/HA biocomposites by ab-spare materials .sorption process in liquid phase.2.2.3 Preparation and analysis of biocompositesProcess the PLA rod solid matter to be strip solidmatter with the width of 0.7 mm and the thickness of 0.1mm.中国煤化工and supersonie oscil-(Received: Feb.24 ,2004; Accepted: May 23 ,2005)latiolCNMHG， suspend in alcohol.II Jianhua( 李建华): Engineer; E mail: yu3838 @ public . wh. ho. cnImmesuspnding liquid of* Supported by the Key Research Project of the Ministry of Educa-HA and to stir, then to take out stip matter. HA parti-tion( No.00085)cles are atached to PLA strip matter because of absorption264Jounal of Wuhan University of Technology - Mater. Sci. Ed.Dec.2005fect, then are dried by vacuum drying chamber at 80and distribution of HA particles by applying JSM-T300C. Through putting dried PLA/HA into mixing roll totype scanning electron microscope made in Japan.mix and compoundt，we can get block PLA/HA compos-The fllwing is SEM cross sections with 5%，10%ite materials, then the bars which the diameter of 3.5 mmand 15% HA particle percents. 'The average particle di-is obtained by die pressing at 135 C. The biocompositesameter is 200 nm with a standard deviation of 10 nn.with different HA mass percents are obtained by adjusting3.2 The Testing of Mechanical PropertiesHA alcohol solution with different concentrations. We willWe use PLA/HA composite bar material which theget biocomposites with 5%，10%，15% and 20% HAdiameter is 3.5 mm to make splice with 30 mm length,mass percent by the fllowing experiments.then test its tensile strength, flexural strength and flexuralmodulus by using MTS -858 Mini bionix biomechanics test3 Results and Discussionmachine.Table 1 shows that the tensile strengh， flexural3.1 SEM Observationstrength and flexural modulus of pure PLA and PLA bio-We observe fracture shape of PIL A/HA biocompositescomposites with 5%，10% and 15% HA percents.29kU X5.888 Sum 0279 JS-O18L.0020X5.088800279 -60u 29w0 x5,860 0276 91e0(旧) 5% HA/95%PLA composite(b) 10% HA/90%PLA composite心) 15% HA/85%PLA compositeFig.1 Scarning electron microphotograph for composite of PLA/HATable 1 Resuts of mechanical strength testingThough when the percentage of HA is 5%，there is still aof PLA/HA compositesbetter effect.HTensileBending3.3 The pH change of the Composite BiomaterialscontentstrenghmodulusTake the PLA/HA composite biomaterials during19/Mpa/Cpawhich the mass percent of HA particles is 10% and six43.6136.82.3pieces of the pure PLA materials. Put each in vessel133.52.51039.8146.2which is held by the solution of the pH value is 0.7, then1535.7157.3.6they are preserved at and their pH values are measured bythe PH meter weekly .20165.62.7The pH value of the pure PLA solution slowly de-The mechanical testing shows that the tensile-strength of pure PLA is higher than that of PLA/HA biocreases in three weeks, then decreases clearly. The pHcomposites, and this is because the bond between the HAvalue remains nearly 3.9 in nine weeks. The pH value ofparticle and the PLA matrix is so weak that it is damagedthe PLA/HA solution is 4.7 in the fourth week, then iteasilys. When the percentage of HA particle is lowerfalls very fast, but the fall extent is lower than the purethan 10%，the loss of tensile-strength is not obvious;PLA, and finally it stays near4.4 (Fig.2) .when the content is above 10%，the tensile-strength falls3.4 The external decomposable capability of thebiocompositesfaster. 'The physical bond between the reinforced materialPut PLA/HA biocomposites including 10% HA andHA and the matrix induces cohesion is very weak. Beforecomposition we can use coupling regent to treat HA parti-pure PLA sample in PBS solution that the PH value iscles, which makes hydroxy in HA and functional group in7.4, see its degradation at 37 degrees centigrade, changecoupling reagent to react and form chemical bond, tienthe solution every seven days, take the three differentcomposite，the drain side of coupling reagent and molecu-samples based on the different experimental stages, deletelar chain of PLA wineing together in which coupling re-the surface moisture by filter paper, dry it for three daysagent acts as a bridge'。This is very helpful to improvein中国煤化Tr the weight losss per-the performance of biocomposites. The flexural strengthcentreen the initial weightandCNMH Glivided by the initialbegins to fall when the percentage of HA is 5%，and itnot only begins to increase but also surpasses the pureweight.PLA when it is higher than 10%. As the content of HAWith the degradation of the PLA, the released acidincreases ，the strengthen efect turms more clear. Flexuralproducts will create the aseptic inflammatory reaction aftermodulus have an increase after entering the HA particles.the pure PLA is implanted into the human body. The HAVol.20 Suppl.LI Jianhua et al : Preparation of Hydroxyapatite/Polylactide Bicomposites by....265degradation product is alkali, so it can neutralize partialweek. So this avoids the more weight loss which appearsacid products, change the partial pH value and reduce orearlier in time and it is helpful for the fracture patients todelete the aseptic inflammatory reaction. The study showscure bettert9.that the PLA degradation exists self-catalyzed phenomena,.5 The weight changes of material degradationits acid products can accelerate the degradation' whichThe weight loss of pure PLA is 1% in the fourthwill result in the mechanical loss in a short time, but theweek, then accelerates degradation. When it is in theHA particles act as physical barrier in composite biomate-second week, the loss reaches 8. 4%. The weight of therials, and the barrier action can slow the entry of the deg-biocomposites, which consists of 10% HA and 90%radation medium such as the water molecule and the r-PLA/HA, is 1% in the seventh week. The weight loss oflease velocity of the degradation products, then the degra-the periodic biocomposites is lower 1%-2% than that ofdation velocity is controlled in reasonable field. This isthe pure PLA from the fth week. The loss gap betweenalso seen from the exteral degradation weight percentagethe two materials reaches the maximum 3. 29% . 'The deg-loss of the biocomposites. The weight loss of the pureradation loss of the bhiocomposites is 5. 4% in .the twelfthPLA is very obvious in the fourth week, but the biocom-week (Fig.3).posites including 10% HA shows obvious in seventh8◆100%PLA■90%PLA/10%HA■90%PLAV10%HA0η234567891189101112t/weekFig.2 The pH value changes in solution of materialFig.3 The weight changes of materialThe PLA/HA prepared by absorption process in liq-uid phase avoids interfusion of the toxic chemical impurityReferencessubstances, it is easy to process compositely and suitablefor manufacture on a large scale. The HA content of the[1] T Kasuga, Y. Ota, M Nogami. Preparation and Mechanicalbiocomposites can be contolled by adjusting the HA con-Properties of Polylactic Acid Composites ContainingHydroxyapatite Fibers. Biomaterials ,2001 ,22,19-23centration in alcohol solution, and the percent is usually[2] C-C Chen, J_Y Chueh, How Tseng. Preparation and Charac-0-20%. Because for stip PLA to absorb HA is limited,terzation of Biodegradable PLA Polymeric Blends. Biomateri-it is dificult to get the HA percent which is above 20% ,als ,2003,24,1167-1173and this is the defect. We can see from Fig. I that though[3] N Ignjatovic, s Tormnie, M Dakie, Synthesis and Properties ofthe HA particle diameter is near, HA particles still areHydroxyapatite/poly-L-lactide Composite Biomaterials. Biouniformly dispersed in PLA matrix and HA shows well ad-materials, 9920:809-816hesion with PLA matrix .[4] Y Shikinami, Y Matsusue, T Nakamura. The Complete Pro-cess of Bioresorption and Bone Replacement Using Devices4 ConclusionsMade of Forged Composites of Raw Hydroxyapatite Particles/poly Ilactide. Biomatrials ,2005 ,2655-5551The hydroxyapatite/polylactide biocomposites are[5] QLiu, J R, K Groot. Surface Mdifcation of Nano apatileby Grafing Organic Polymer. Biomaterias , 1998, 19: 1067-prepared by absorption process in liquid phase. The1072method is easy and has low cost, and it avoids the inter-[6] H Tanaka, T Watanabe, M Chikazawa. TPD FTIR and Mo-fusion of chemical impurity subtances. The mechanicallecular Adsorption Studies of Calcium Hydroxyapatite Surfaceproperties and decomposable capability of the materialModified with Hexanoic and Decanoic Acids.J. of Colloidand Inefrce Science , 199214:31-373meet the clinical application. The material has better me-[7] M Viljanma, A Sodlergard, R Mattila. Hydrolytic and Envir-chanical properties and decomposable capability when theHA component is 10%，and it can offer the strong inter-中国煤化工Be Hin Mod Ahbility ,002,78:269-28nal fixing for fracture union and gradually decompose in[8DHCNMHG(D,L-Lacide/e- caprolac-the course of the fracture union. This indicates that thisBiomaterials , 2000, 21:material well matches the body bone and has good medical2147-2154effects .