Research On Mineralizaion Of CaO-（1-x） SiO₂-xB₂O₃-yP₂O₅based Xerogel And The Enhancement Of Graphene On Its Bioactivity

Since the discovery of Bioglass，it has been used in clinical for bone repair andfiller material. Generally speaking, the bioactive glasses are often synthesized by usingthe high temperature melting or sintering process. Generally, traditional bioglasspreparation needs melting or sintering process under high temperature. However, theantibiotics or bone growth factor, which is very important for clinic application ofbioactive glass can not undertake the high temperature process. Compared to thetraditional bioglass preparation, the bioacitive xerogel prepared by sol-gel method canbe fabricated under room temperature. Due to the low temperature process, antibioticsor bone growth factor can be added into the xerogel.In addition, graphene has been widely tested for both potential toxicological risks,and has been demonstrated to affect the properties of the biological properties. Thehighest mechenical strength will further benefit its application in bone repair. Graphenehas been reported to be non-toxic for human osteoblasts and have the ability tostimulate osteoblast growth. The result indicated that graphene can potentially used forengineering of new osteo-conductive/inductive implants for bone repair and fillermaterials. Considering that the bioactive xerogel also has the same uses, we try to welldisperse the two-dimensional graphene into bioactive xerogel to obtaingraphene/SiO₂–CaO–P₂O₅xerogels for bone repair or filler material. The mineralizationof the graphene xerogel and the biocompatibility of work have not seen before.Tributyl borate was first adopted for the introduction of boron in the preparation ofbioactive borosilicate xerogel and graphene/CaO-（1-x） SiO₂-xB₂O₃-yP₂O₅by sol-gelmethod. It was the first time to discuss the mineralization of graphene/CaO-（1-x）SiO₂-xB₂O₃-yP₂O₅xerogel and to display the transformation model of mineralizationand cell biological experiment. We used XRD, SEM, FTIR, ICP and Multi-labelMicroplate Reader to analysis the microstructure of xerogel, the main group, the speed of mineralization and biocompatibility.The results have shown that the boron or graphene value have a significantinfluence in the conversion rate to HA.When the two jointly exists in xerogel they mayplay a role of synergistic effect. This feature can be used in bone repair, filler materialand slow-release material.The conversion proceeds of the CaO-（1-x） SiO₂-xB₂O₃-yP₂O₅xerogel were studiedin0.25M K2HPO4solution with a starting pH value of7.0at37°C. The speed ofreaction time was cut way back on the time with the addition of boron and promore theHA content increased in the nucleation and growth.When B/Si=2:3, after reaction timeof1day, the results indicated that the xerogels were completely convet to HA. Weproposed a possible mineralization mechanisms and a qualitative model was developedfor the conversion process.Graphene/SiO₂–CaO–P₂O₅based bioactive xerogel with varying graphene contentwere prepared by sol-gel method. The conversion rate of the xerogel in0.25MK2HPO4solution at37℃increased with increasing graphene content. Particles of thexerogel （1G） were almost completely converted to HA in less than1hour.Withincreasing xerogel lixivium content,0.1and1g/L xerogel lixivium have goodbiocompatibility while the10g/L has poor biocompatibility. Also, with increasinggraphene content,0.1G and0.5G xerogel have good biocompatibility while the1.0Ghas poor biocompatibility. The high concentration lixivium and graphene produced agreater inhibition of cell proliferation in cultures performed. Little inhibition of cellproliferation occurred if the xerogel lixivium or graphene concentration in the cellculture medium was kept below a certain threshold level. We proposed a possiblemineralization mechanisms and a qualitative model was developed for the conversionprocess。The ability of mineralization of the graphene/CaO-（1-x） SiO₂-xB₂O₃-yP₂O₅basedxerogels was studied in0.25M K2HPO4solution with a starting pH value of7.0at37°C.The results were similar to Graphene/SiO₂–CaO–P₂O₅based bioactive xerogel. But thegraphene/CaO-（1-x） SiO₂-xB₂O₃-yP₂O₅based xerogels have a good advantage ofsynergistic effect which makes the speed of mineralizaion become more soomth and steady under the condition of high mineralization speed.At last, we have demonstrated the feasibility of fabricating GO/PVA compositenanofibers by electrospinning. The diameter of nanofibers ranges from50-500nm，andthe prepared nanofibers were covered with SiO₂–CaO–P₂O₅bioactive gel, we have anresearch on the mineralization of this nanofibers in0.25M K2HPO4solution with astarting pH value of7.0at37°C for1hour. The results showed that the decompositiontemperature of obtained nanofibers decreases with the addition of GO and loading of0.02wt%GO increases the tensile strength of the nanofibers42times, and after soakedin0.25M K2HPO4solution for1hour the morphology of the fibers were changed andthe products were HA.