Study On The Preparation And Properties Of Hydroxyapatite/Graphene Oxide Composites

Hydroxyapatite?HAP or HA?,the major inorganic component in vertebrate calcified hard tissues,which chemical composition and structure is similatly to bone tissue and teeth,accounts for more than 75%of human bone tissue.HA has good biocompatibility,osteoconductivity,biodegradability,adsorption and interface biological activity,which is often used as substitute materials for bone tissue and carrier materials in vivo.However,the tensile strength and fracture toughness of prepared HA were poorer than that of natural bone,which limit its practical applications to the replacement of bone systems.In order to solve this problem,it is necessary to introduce a reinforcing phase.It is hoped that the mechanical properties of HA crystals will be improved and the biological properties of HA without changed.The enhancement phase introduced in this paper is graphene oxide?GO?.The surface of GO has abundant oxygen functional groups,e.g.hydroxyl,epoxy and carboxyl exist on,which can facilitate the interfacial interactions with the matrixes and provide reactive sites for functionalization.In addition,the reactive oxygenic groups on GO can stabilize its dispersion in aqueous media,enhance interfacial bonding within the components and facilitate stress transfer in the composites,which makes GO nanocomposites extended to more material fields.In this paper,HA with different morphologies?flake self-assembled spherical,rod-shaped,porous microspheres?was used as the main material.Three kinds of composites materials have been prepared by an environmentally friendly method-ultrasonic assisted solution blending method.We studied the introduction of GO on the morphology and properties of HA,and the possible properties and application of HA/GO composites were discussed.HA with different morphologies were prepared through different methods in this paper.Through the ammonia diffusion method,and Na₂EDTA were used as regulators to prepare uniform size,good dispersion of flake self-assembled spherical HA?SHA,?1 ?m?;by high temperature water bath method and Na₂EDTA were used as regulators to prepare stable morphology,uniform size,good dispersibility of rod-shaped HA?RHA,width?500 nm,length up to?5.5 ?m?;in addition,through the ammonia diffusion method,and Na₂EDTA were used as regulators to prepare uniform size,good dispersion of porous microspheres HA?NHA,?2 ?m?.The raw materials in experiments are performed on friendly and harmless.The above three kinds of HA were used to compounded with GO to prepare composites,they were two-dimensional composites SHA/GO,two-dimensional composites RHA/GO and three-dimensional porous composites NHA/GO,respectively.The HA and its composites HA/GO were characterized by SEM,XRD,FTIR,Raman,etc.The results showed that the structure of HA/GO composites changes with the content of GO or HA.The TGA thermal analysis showed that HA in the composites material has good thermal stability,and the weight change of the material is mainly due to the mass reduce of GO.In the mechanical properties test,the presence of GO has a significant effect on the mechanical properties of SHA,in composites the elastic modulus and the hardness of SHA/GO-3 are as high as 12.45±0.33 GPa and 686.67±26.95 MPa,respectively,which are higher than pure SHA,SHA/GO-1,and SHA/GO-2.The characterization of TEM/HRTEM and the biomimetic mineralization mechanism analysis showed that the HA/GO composites were well combined together and stable,and HA was corverd by GO tightly.In vitro biomimetic mineralization simulated body fluid?SBF?immersion experiments showed that the carboxylic groups on the surface of the sample can adsorb Ca²⁺ ions,which can stimulate the mineralization behavior effectively of the three kinds of composites.The mineralization behavior makes the local ions supersaturation and then promoting the apatite nucleation and growth,then a new layer of apatite was formed on the surface of the composites material.these demonstrated that the HA/GO composites have osseointegration ability.In vitro cytocompatibility of SHA/GO and RHA/GO composites,MTT test was used to estimate the cytotoxicity and proliferation of cells in composites.The growth and adhesion of cells were observed through phase-contrast microscopy photographs and SEM.these demonstrated that MC3T3-E1 cells on the surface of composites materials grew and adhered were better than on pure GO.The in-vitro drug release experiments of composites NHA/GO showed that the addition of a certain amount of GO has improved the adsorption performance of NHA,and NHA/GO has good adsorption performance for diclofenac sodium drugs.Based on the above analysis,the method for preparing the composites HA/GO is a simple,controllable and environmentally friendly method;and the composites HA/GO is a non-template,non-toxic and biologically active composite material.The composites material is expected to be used in biomedical fields such as bone replacement,repair materials,implant materials,and carrier materials.