| A novel biomedical composite of nano-hydroxyapatite/polyamide (n-HA/PA) hasbeen developed in recent years. This composite has many similar properties to thoseof human bone, that is, n-HA has similar composition and crystal structure to themineral of natural bone and PA has similar molecular constitution to collagen protein.The polar amide bond and carboxyl group of PA can conduct the growth and formingosteoid and mineralization of tissue cell, and promote healing of bone defects.Moreover, this composite has good mechanical performances and can serve asload-bearing bone substitutes. For example, its density productions have beenextensively used in vertebralis and vertebral plates repair. All results showed thatnano-hydroxyapatite/polyamide composite has excellent biocompatibility, bioactivityand mechanical properties and is a novel biomimetic composite which can be used ashard-tissue substitutes and regeneratives.In this study, the porous form of n-HAfPA composite was foamed bythermal-pressing and injection molding techniques and its performances were alsoinvestigated.The porous n-HA/PA66 composite prepared by thermal-pressing method has highcompressive strength of 13～46MPa and excellent porous structure. The averagediameter of pores in the matrix is in range of 280μm to 500μm and porosity of 36％to 57％. The porous architecture can be adjusted by the combination of processingparameters such as the weight of starting mixture used per mold and the ratio ofcomposite to foamer as well as n-HA content in n-HA/PA66 composite. No apparentchanges in composition and structure of n-HA/PA66 composite were found by XRD and IR determination before and after formation of porous species.The porous n-HA/PA66 composite prepared by injection molding method has anuniformly distribution of ball-like pores with average diameter in the range from300μm to 500μm and high porosity of 87％. The compressive strength of this porousmaterial is in range of 1～33MPa. A comparative study was performed on the pore'sstructure and mechanical behaviors of the porous composites obtained by theabove-mentioned two methods. The results indicate that injection molding method issuitable for the preparation of porous n-HA/PA66 composites with high porosity.Moreover, injection molding technique allows rapid production of implants andscaffolds of many shapes and sizes.Porous n-HA/PA6 composite was also developed by injection molding technique.The performances of the porous material and the optimal amount of foamer wereinvestigated. The results show that the optimal amount of foamer is 0.5 wt％and thisporous material has excellent porous structure, that is, interconnected and uniformlydistributed pores with the diameter of pores ranging from about 100μm to 700μm.Total porosity of this porous composite can be controlled by adjusting the processingparameters. Additionally, the porous composite has good compressive strength(1.1～15.6MPa) and compressive modulus (0.4～1.4GPa), which are similar to thoseof human cancellous bone.The evaluation of biological safety of the porous n-HA/PA66 composite includingcell cytoxicity test, sensitivity test, pyrogen test, haemolysis test was carried outaccording to GB/T16886 and GB/T16175. The results show that the porousn-HA/PA66 composite is of no cytotoxicity, no allergen and pyrogen reactions aswell as no hemolytic effect.
|
PDF Full Text Request