Study On Nano-Hydroxyapatite And Its Composite With Chitosan Carried Herba Epimedii

Hydroxyapatite(HA), showing chemical and crystallographic similarity to the apatite in human bone and teeth, can form a direct chemical bond with surrounding bone tissue and therefore has been used extensively in orthopedics and bone regeneration. Nano particles tend to show some unique specialities, nano hydroxyapatite (n-HA), therefore, has attracted much more attation in recent years.The synthesis method, compositions and the structure of n-HA often determine the bioactivity and the physico-chemical properties. Thus, in this study Ca(OH)₂ and H3PO4 were selected as the reagents and dionized water, ethonal, glycol and ethylacetate were choosed as mediums respectively to prepare n-HA with similarities of size, morphology and crystallinity to those of natural bone apatite, and the influence of mediums on the n-HA was also investigated by means of TEM, XRD and IR. The results show that solvent mediums have obviously effect on the morphology, crystallinity and the size of the synthesized n-HA crystals. The crystal size, crystallinity and the Ca/P ratio of the n-HA using inorganic solvent are all more than those of n-HA using organic solvents, indicating that the polarity of solvents may be responsible for the phenomena. The order of solvent polarity is as follows: H₂O>ethanol>glycol >ethylacetate. The more polar of the solvent, the more easily the carbonated hydroxyapatite crystals form.Chitosan (CS) is an N-deacetylated form of chitin and has various degrees of substitution for N-acetyl groups. It has been proven that CS can degrade in vivo into non-harmful and non-toxic products and thus has been used in many biomedical applications, including wound dressings and drug or gene delivery. In addition,a large amount of amino groups that present in the chains give CS high positive charges, through which CS can bind tightly with negatively charged cells via electrostatic interaction. When applied to bone defects in animal models, CS was found to improve osteogenesis and angiogenic activity. However, the poorer mechanical strength of CS makes it impossible to bear the load usually evoked on bone and thus tend to collapse.Accordingly, inorganic-organic composites for bone repair should be developed and are expected to enhance the mechanical properties of the polymer matrix with particle reinforcement and to reduce the disadvantages associated with every component as well as to improve the overall biological response of the implant. In the paper, n-HA/CS membrance carrying Herba epimedii was fabricated by the method of solution mixing and was also characterized using scanning electron microscopy (SEM), X ray diffraction (XRD), infrared spectroscopy (IR) and universal mechanical testing machine. In addition, the property of drug release was also evaluated. Results demonstrate that no phase separation is found between n-HA and chitosan, and the drug of Herba epimedii is distributed in n-HA/CS composite uniformally. However, the introduction of Herba epimedii reduces the tensile strength and water adsorption. The testing results on drug release indicate that a sudden release of the drug has occurred at first, and then the release becomes mild with time. Also, the release amount is proportional to the content of the carrying drug. The cell culture results show that n-HA/CS membrane carrying Herba epimedii has excellent biocompatibility and no cytotoxicity.