Study On The Properties Of Polyhydroxybutyrate/Hydroxyapatite Absorbable Material For Internal Fixation Of Fracture

Objective To study the biocompatibility, biodegradability and mechanical properties of Polyhydroxybutyrate/Hydroxyapatite (PHB/HA) composite as the material of bioabsorbable internal fixation devices, and study the relation of mechanical properties with the content of HA, times of degradation in vitro.Methods Based on the study of physicochemical properties of PHB, the PHB/HA composites were prepared by physical blending, and the standard samples for mechanical and transplant experiment were made in different ratios of PHB and HA. The L929 cells were cultured in the lixivium of PHB/HA, then the morphology of L929 cells was observed under microscope and the cytotoxicity of lixivium to L929 cells was measured by MTT test; the samples of PHB/HA were implanted in rabbits subcutaneous tissue and shinbone, and the biocompatibility of composites was assessed by histological and roentgenographic analysis in the different periods. The samples of mechanics experiment were immersed in PBS, then the pH value of immersion solution, the appearance, the weight-loss ration and microstructure of material were also investigated in the different periods. The strength and modulus of PHB/HA were tested by tensile, compressive and flexural experiment.Results In cytotoxic test, the L929 cells were found growing steadily and the morphology was similar to that of the negative control group. Obvious different cell activity was not observed between the study and control groups by MTT. In vivo transplant experiment, good biocompatibility was obtained by histological and roentgenographic analysis. The degradation experiment in vitro showed that the pH value of immersion solution decreased, the weight-loss ration of samples increased, as degradation on the surface of samples was observed as time going. The modulus of PHB/HA composites increased and the strength decreased with HA content increasing. The composites containing 10% HA was better than others in tensile, compressive and flexural properties. The mechanical properties of PHB/HA composites decreased with time after degradation in vitro.Conclusion The PHB/HA absorbable material had good biocompatibility, appropriate mechanical properties and low cost. It could be a promising implant material in orthopaedic surgery. The controlment of degradation, mechanical properties and manufacture processing of degradable polymer must be improved further.