Preparation And Performance Study Of Graphene Oxide/nano-hydroxyapatite Bone Tissue Engineering Scaffold

Biomedical ceramics,owing to its biocompatibility,osteoconductivity and other excellent properties is widely used as biological scaffold material.Traditional hydroxyapatite?HAP?bioceramics have the disadvantages of large brittleness and long degradation cycle,which greatly limit their application in the biomedical field.Meanwhile,research shows that graphene oxide?GO?was perfomed for good biocompatibility,excellent mechanical properties and rich reactive functional groups,That makes the investigations of GO/HAP dual phase composite scaffolds meaningful.In this paper,the two-step experimental process was used.Firstly,to prepare the GO/n HAPscaffold,the composite powder of GO/HAP was successfully prepared using GO as the template and calcium nitrate and diammonium hydrogen phosphate as the raw materials by the methods of solution ion co-titration.Then,the powder of GO/HAP was used as the main raw materials,stearic acid as a pore-forming agent,silica gel as a binder,we extrusted molding to obtain rough blanks.After removing the stearic acid,vacuum low-temperature sintering and other series of processes,the rough blanks were successfully converted to GO/HAP porous scaffold materials.The samples were characterized the structure,morphology,phase composition,pore size and distribution.Moreover,in order to evaluate the biodegradation and biotoxicity,vitro degradation experiments and cytotoxicity experiments were carried out simultaneously.The condusious of this paper are listed as following:?1?GO was obtained by the method of the modified Hummers which with the lamellar size of 500-800 nm and more oxygen-containing groups on the surface,but with low crystallinity.Under the oxidizing action of strong oxidants,graphite undergoes intercalation reaction,which large number of oxygen-containing groups enter the graphite sheet layer.Meanwhile,a part conversion was occurred from the SP² of the graphite to SP³.?2?The HAP in the GO/HAP composite powder exhibited drusy acicular crystal structure with a uniform size distribution of 50-100 nm,a single HAP length of 30-50nm and a diameter of 5-18 nm.The addition of GO plays a important role in regulating the nucleation and promoting growth and induced of HAP with?112?plane by controlling the nucleation sites of Ca²⁺to get the purpose to modulate the size of HAP within a certain range.In GO/HAP composite powders,GO and HAP phases were combined with a complex chemical bond.The results of cytotoxic biological and biological mineralization exhibited that GO/HAP composites were no cytotoxic,and the effect of depositing calcium phosphorus salts in SBF solution was significantly increased with increasing deposition time.The Ca/P ratio of calcium phosphorus salt at the 14th day was 1.62,which was close to the Ca/P?1.64?of natural bone tissue,this indicates that the material has good osteogenic activity.?3?The porosity of the porous scaffold were 40%,50%,and 60%,corresponding to the pore size ranges of 80-250?m,100-400?m,and 180-600?m,and corresponding to the compressive strength of 1.2Mpa,2.3Mpa,4.2Mpa,respectively.The results of cytotoxic biological exhibited that:comparing with HAP and GO/HAP composites,GO/HAP porous scaffolds have higher cell proliferation and no cytotoxicity at the same extract liquid concentration.In vitro biodegradation experiments showed that:during the 0-56 days the weight of the porous scaffold was increase and the 56-100 days was decrease,according to the trend of the degradation curve,when the degradation days for 120 days,porous stent weight loss rate of 0%.The porous scaffold of the Ca/P values of deposited calcium phosphorus salts stent in14 days,56 days and 90 days corresponding to 1.60-1.63,1.57-1.59 and 1.52-1.56,respectively.?4?The results of animal experiments with the GO/HAP scaffold showed that:after implanted in the the tibial defect of Rabbit for 8 weeks,the stent was better and stable after implantation of the rabbit's tibial defect,but no osteogenesis appeared.The trend of osteogenic induction appeared at the 8th week.And then at the 12th week,the bone connection occurred at the proximal end and the scaffold partially degraded.This indicated that the GO/HAP modified composite scaffold had the osteogenesis-inducing effect.