Background: The replacement of hard tissues demands biocompatible and sometimes\r\nbioactive materials with properties similar to those of bone. Nano-composites made of\r\nbiocompatible polymers and bioactive inorganic nano particles such as HDPE/HA have\r\nattracted attention as permanent bone substitutes due to their excellent mechanical\r\nproperties and biocompatibility.\r\nMethod: The HDPE/HA nano-composite is prepared using melt blending at different HA\r\nloading ratios. For evaluation of the degradation by radiation, gamma rays of 35 kGy,\r\nand 70 kGy were used to irradiate the samples at room temperature in vacuum. The\r\neffects of accelerated ageing after gamma irradiation on morphological, mechanical and\r\nthermal properties of HDPE/HA nano-composites were measured.\r\nResults: In Vitro test results showed that the HDPE and all HDPE/HA nano-composites\r\ndo not exhibit any cytotoxicity to WISH cell line. The results also indicated that the\r\ntensile properties of HDPE/HA nano-composite increased with increasing the HA\r\ncontent except fracture strain decreased. The dynamic mechanical analysis (DMA)\r\nresults showed that the storage and loss moduli increased with increasing the HA ratio\r\nand the testing frequency. Finally, it is remarked that all properties of HDPE/HA is\r\ndependent on the irradiation dose and accelerated aging.\r\nConclusion: Based on the experimental results, it is found that the addition of 10%,\r\n20% and 30% HA increases the HDPE stiffness by 23%, 44 and 59% respectively. At\r\nthe same time, the G� increased from 2.25E11 MPa for neat HDPE to 4.7E11 MPa when\r\n30% HA was added to the polymer matrix. Also, significant improvements in these\r\nproperties have been observed due to irradiation. Finally, the overall properties of HDPE\r\nand its nano-composite properties significantly decreased due to aging and should be\r\ntaken into consideration in the design of bone substitutes. It is attributed that the\r\ndeveloped HDPE/HA nano-composites could be a good alternative material for bone\r\ntissue regeneration due to their acceptable properties.
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