Construction And Properties Of Nano-hydroxyapatite-based Composite Three-dimensional Porous Scaffold Materials

Nano-hydroxyapatite?nHAp?has higher specific surface area,better biological activity and biocompatibility than ordinary hydroxyapatite.As the main inorganic component of human bone tissue,nHAp is a good bone filling and repair material.However,the single nHAp powder often has problems such as molding difficult and poor mechanical properties during use.In order to solve these problems,compounding nHAp with other materials with good biocompatibility has become a research hotspot in recent years.Both graphene?RGO?and chitosan?CS?have good biocompatibility and moldability.They all have broad application prospects in bone repair material and bone tissue engineering scaffold material.Compounding nHAp with RGO or CS can give full play to the advantages of the two materials,so it is expected to produce biomaterials with excellent performance.In this paper,an uniformly dispersed nHAp colloidal solution was prepared by co-precipitation.The effects of sodium citrate on the dispersion performance,morphology and particle size of nHAp were evaluated in this study.The nHAp/RGO composite three-dimensional porous scaffold was prepared by hydrothermal reaction.The effects of graphene oxide concentration and nHAp content on the morphology,strength and surface area of the nHAp/RGO composite scaffold were mainly studied.Besides,the nHAp/CS composite three-dimensional porous scaffold was prepared by the blend-freeze drying,and the effects of nHAp content on the properties of composite scaffold such as morphology,porosity,swelling ratio,mechanical properties,and degradation performance were mainly studied.Transmission electron microscope?TEM?,X-ray diffraction?XRD?,infrared spectroscopy?FTIR?,particle size analysis,specific surface area tester,dynamic mechanical analysis,etc.were used to characterize and test the morphology,phase composition,particle size,surface area,and mechanical properties of the samples.An uniformly dispersed and stable nHAp colloidal solution with an average particle size of 40 nm was successfully prepared by co-precipitation method through using Ca?OH?₂-H₃PO₄ as the reaction system and sodium citrate as the additive.Sodium citrate additive can significantly improve the dispersibility and crystallinity of nHAp particles.Using graphene oxide?GO?and nHAp colloidal solution as raw materials and ammonia as a regulator,the nHAp/RGO composite three-dimensional porous hydrogel scaffolds with good binding performance and large surface area were successfully prepared by hydrothermal reduction under weak alkaline condition without chemical reducing agent and crosslinking agent.Under the same nHAp content,the strength of nHAp/RGO composite scaffold increases with the increase of GO concentration.The nHAp can significantly enhances the compressive strength of RGO.The hydrogel scaffolds prepared with 4 mg/mL GO generally have good strength,because the nHAp significantly enhances the compressive strength of RGO.Among them,the strength of the nHAp/RGO composite scaffold is much higher than that of the pure RGO scaffold.The sponge-shaped nHAp/CS composite three-dimensional porous scaffolds with high porosity and good swelling properties were successfully prepared by blend-freeze drying,using chitosan-acetic acid solution and nHAp colloidal solution as raw materials.The nHAp/CS composite scaffolds have great compressive performance.The Young's modulus of the nHAp/CS can reach up to 37.26±1.00 kPa,which is more than twice of pure CS scaffold?15.96±0.35 kPa?.The nHAp/CS composite scaffolds were partially degraded after soaking in SBF for 21 days,but they could still maintain their three-dimensional porous structure,and more new apatite was generated on the sample's surface.MC3T3-E1 cells showed good growth morphology in the nHAp/CS composite porous scaffold.The addition of nHAp can not only significantly improve the adhesion and proliferation of cells on the scaffold,but also significantly promote the alkaline phosphatase secretion of the cells and improve the differentiation ability of osteoblasts.