Abstract
BackgroundThe replacement of hard tissues demands biocompatible and sometimes bioactive materials with properties similar to those of bone. Nano-composites made of biocompatible polymers and bioactive inorganic nano particles such as HDPE/HA have attracted attention as permanent bone substitutes due to their excellent mechanical properties and biocompatibility.MethodThe HDPE/HA nano-composite is prepared using melt blending at different HA loading ratios. For evaluation of the degradation by radiation, gamma rays of 35 kGy, and 70 kGy were used to irradiate the samples at room temperature in vacuum. The effects of accelerated ageing after gamma irradiation on morphological, mechanical and thermal properties of HDPE/HA nano-composites were measured.ResultsIn Vitro test results showed that the HDPE and all HDPE/HA nano-composites do not exhibit any cytotoxicity to WISH cell line. The results also indicated that the tensile properties of HDPE/HA nano-composite increased with increasing the HA content except fracture strain decreased. The dynamic mechanical analysis (DMA) results showed that the storage and loss moduli increased with increasing the HA ratio and the testing frequency. Finally, it is remarked that all properties of HDPE/HA is dependent on the irradiation dose and accelerated aging.ConclusionBased on the experimental results, it is found that the addition of 10%, 20% and 30% HA increases the HDPE stiffness by 23%, 44 and 59% respectively. At the same time, the G’ increased from 2.25E11 MPa for neat HDPE to 4.7E11 MPa when 30% HA was added to the polymer matrix. Also, significant improvements in these properties have been observed due to irradiation. Finally, the overall properties of HDPE and its nano-composite properties significantly decreased due to aging and should be taken into consideration in the design of bone substitutes. It is attributed that the developed HDPE/HA nano-composites could be a good alternative material for bone tissue regeneration due to their acceptable properties.
Highlights
Bone is one of the most commonly replaced tissues in the human body
In Vitro test results showed that the High density polyethylene (HDPE) and all HDPE/HA nano-composites do not exhibit any cytotoxicity to Wistar Institute Susan Hayflick (WISH) cell line
The results indicated that the tensile properties of HDPE/HA nano-composite increased with increasing the HA content except fracture strain decreased
Summary
Bone is one of the most commonly replaced tissues in the human body. Native bone tissues mainly consist of nonstoichiometric hydroxyapatite (HA; Ca10(PO4)6(OH)2) and collagen fiber matrix that provide physical and biological properties and mechanical support and protection from the vertebrate skeleton [1]. Many studies have been carried out for developing different materials for bone tissue engineering such as metals, ceramics and polymers [1,2,3,4,5]. The stress shielding is induced because the metallic bone substitute stiffness is far greater than the surrounding bone tissue. Nano-composites made of biocompatible polymers and bioactive inorganic nano particles have attracted attention as bone regeneration materials and even permanent bone substitutes due to their excellent mechanical properties and biocompatibility [8,9]. The replacement of hard tissues demands biocompatible and sometimes bioactive materials with properties similar to those of bone. Nano-composites made of biocompatible polymers and bioactive inorganic nano particles such as HDPE/HA have attracted attention as permanent bone substitutes due to their excellent mechanical properties and biocompatibility
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