Surface Modification And Biomineralization Of Graphene Hydrogels

In this paper,graphene hydrogels were fabricated and modified by ethylenediamine,sodium citrate and dopamine via hydrothermal approach and chemical reduction.Then artificial simulated mineralization was taken to investigate the biomineraliazation of the materials which used graphene hydrogels as substrates.The biocompatibility of the mineralized graphene hydrogels was investigated as well.Graphene/hydroxyapatite composite hydrogels were fabricated via one-pot method to compare with the mineralized graphene hydrogels on biomineralization.Study of graphene hydrogels revealed that graphene hydrogels possessed a three-dimensional network structure with graphene sheets curled up.The reduction degree of graphene hydrogels via hydrothermal approach was higher than that of the modified graphene hydrogels by dopamine,ethylenediamine and sodium citrate.Compared with graphene oxide,the thermal stability of graphene hydrogels was improved.Brunner-Emmet-Teller measurements showed that graphene/hydroxyapatite composite gels were mesoporous materials with a large number of micropores,which had a large specific surface area and a great pore size.Hydroxyapatite(HA)was deposited more easily on the mineralized graphene hydrogels.Graphene hydrogel materials could be used as substrates to induce and mineralize the nucleation of HA in simulated body fluid.Simulated body fluid and the reduction degree of graphene hydrogels played important roles on the mineralization ability of the materials.The higher concentration of simulated body fluid,the faster and more HA nucleation.But the particle size and crystal form of HA were more easily controlled in low concentration simulated body fluid.The higher reduction degree of graphene hydrogels,the less oxygen functional groups contained,which provided less active sites with the combination of calcium and phosphate ions,leading to weak mineralization ability of the materials.TGA results showed that the thermo-gravimetric rate of the mineralized materials was reduced by 40 wt%compared to prior gels,and the thermal stability was improved significantly.MTT assay and L929 cell cuture showed that cells appeared good dispersibility and strong vitality on the mineralized materials,and the proliferation ability was increased by 28%.We conclude that the mineralized graphene hydrogels possess good bioactivity and biocompatibility.