Preparation And Properties Of Nano-Hydroxyapatite/Graphene Oxide Three-Dimensional Composite Porous Scaffold

Nano hydroxyapatite（HAp）is an important inorganic component of human bone tissue,with a much higher specific surface area,biological activity,and biocompatibility than ordinary HAp.It is a good bone filling and repair material.However,when HAp powder is used alone,there are often problems such as poor mechanical properties and poor molding ability.Therefore,improving or even solving this problem by combining HAp with other materials with good biocompatibility has become a research hotspot in recent years.Among many non-toxic materials that can be compounded with HAp,graphene oxide（GO）and its derivatives,reduced graphene oxide（RGO）,and two-dimensional（2D）Ti₃C₂（MXene）have become the focus of research due to their excellent biocompatibility,excellent formability,and high specific surface area,and have broad application prospects in the field of bone repair and bone tissue engineering scaffold materials.By combining HAp with GO or MXene,the advantages of these two or more materials can be fully exploited,and it is expected to produce composite biomaterials with superior performance compared to single materials.In this paper,three-dimensional（3D）composite porous scaffolds of HAp/RGO,Sr-HAp/RGO,and HAp/RGO/MXene were prepared by hydrothermal reduction method.The prepared samples were characterized and tested using scanning electron microscopy（SEM）,transmission electron microscopy（TEM）,X-ray diffraction（XRD）,infrared spectroscopy（FTIR）,X-ray photoelectron spectroscopy（XPS）,specific surface area analyzer（BET）,and dynamic mechanical analyzer,The drug loading and sustained release properties of the composite scaffold were further studied.Firstly,using a simple coprecipitation method and sodium citrate as a surfactant,HAp and various Sr²⁺doped HAp（Sr-HAp）colloidal solutions were successfully prepared.The doping of Sr²⁺does not change the morphology of HAp particles,which is still spindle shaped,but significantly affect the particle size and zeta potential of HAp,thereby improving the stability of the colloidal solution.When the doping ratio of Sr²⁺is 10%,the prepared Sr-HAp colloidal solution has the best dispersion and long-term stability,and has a uniform particle size of about 10 nm.The composite 3D porous scaffolds of HAp/RGO and Sr-HAp/RGO were prepared by hydrothermal reduction using GO,HAp,Sr-HAp colloidal solutions as raw materials,and ammonia as a regulator.The scaffolds all exhibit a well-developed pore structure with good connectivity.Nanoparticles of HAp or Sr-HAP are uniformly dispersed on the pore wall,which plays a strengthening role.Compared with HAp/RGO scaffolds,Sr-HAp/RGO exhibits higher Young’s modulus（211 k Pa）and specific surface area（92.55 m²/g）.Using alendronate sodium（ALN）as a drug model,the drug loading and sustained release properties of the scaffold were further studied.The results shows that Sr-HAp/RGO exhibit excellent drug loading performance,with an encapsulation efficiency of 79.3%for ALN,and has a certain drug release performance.Molecular dynamics simulation results show that the adsorption of ALN on Sr-HAp is mainly caused by Ca-O bonds and hydrogen bonds,and the adsorption of ALN on RGO is mainly caused by the formation of C-N bonds between the primary amine groups of ALN molecules and C on RGO.The HAp/RGO/MXene composite three-dimensional porous scaffold material was prepared by immersing the HAp/RGO composite scaffold in a Ti₃C₂T_x MXene dispersion.When the p H value of MXene dispersion is 6.0,the concentration is 3mg/m L,and the immersion time is 30 min,the maximum adsorption amount of MXene on the pore wall of the scaffold can be achieved,which can prepare a HAp/RGO/MXene composite scaffold with high mechanical properties.At this time,the Young’s modulus of the scaffold can reach 423.71 k Pa,which is much higher than that of the scaffold without MXene.Using doxorubicin（DOX）as a drug model,the drug loading and sustained release properties of the scaffold were further studied.The results shows that the HAp/RGO/MXene scaffold has a high DOX drug encapsulation efficiency（93.2%）and a good drug release effect,and acidic environments is more conducive to drug release.Molecular dynamics simulation results shows that the binding of DOX and HAp is achieved through hydrogen bonds and Ca-O bonds,and the binding of DOX and RGO is mainly generated through H-O and C-N bonds.