Preparation Of Reduced-Graphene Oxide/Polypyrrole Composite And Its Application In Calcium Phosphate Cement

With the piezoelectricity of natural bone, electrical stimulation has been widely used in clinic for promoting bone growth and reconstruction. It has special meaning to prepare a conductive biomaterial for bone repair. Polypyrrole(PPy) has been researched and applied a lot in biomedical engineering, such as controlled drug delivery, biosensors, tissue repair and regeneration, showing good biocompatibility. As a traditional conductive polymers, Polypyrrole and it’s composite materials has also received much attention in tissue engineering, but the current study focused on nerve tissue and the endothelial tissue, still lacking in applications of bone tissue.Due to synthesis method of PPy, the product is typically a film or particles, which can not play the role of scaffold. This is the reason PPy is difficult to be applied in bone tissue engineering. Calcium phosphate cement(CPC) can create any shape, filling the bone defect site well.In vivo environments, CPC can transform into hydroxyapatite(HA) which is similar to human bone tissue components, showing good biocompatibility and bone conductive. The CPC as the base material, PPy and its composites as conductive medium, which make prepare electrical stimulation responsive bone repair material been possible.Firstly, we study the prepare condition of PPy. The result shows FeCl3 as initiator, Sodiumsalicylsulfonate(SSNa) as dopant,reacting at -20℃ can product higher conductive PPy. And on this basis, the graphene oxide (Graphene oxide, GO) and PPy composite by in-situ polymerization. By FT-IR, XRD and SEM characterizations analysis, we successfully prepared reduced-graphene oxide (RGO)/PPy composite. Four-probe electrical conductivity test result shows RGO/PPy composite has a substantial increase over the pure PPy and GO. At the same time, after doping SSNa and citric acid (CA), the conductivity of the composite material is further improved.Considering the conductive medium should have good electrical properties and biological security, RGO/PPy doped by CA is chosen to prepare conductive bone repair material. In this paper, RGO/PPy composites with high conductivity have been added in the solid phase of CPC and the effect of this addition on the structure and properties has been investigated. The composites have a great impact on physicochemical properties of CPC. The results showed that the setting time of CPC significantly decreases with RGO/PPy adding. It has great influence of adding RGO/PPy on the mechanical properties and conductivity of CPC, but no obvious effect on the phase composition of CPC. The conductivity of CPC gradually increases with the increase of RGO/PPy adding amount, and the compressive properties show a opposite results with RGO/PPy addition. It has a dependent relationship between the adding amount of RGO/PPy and the conductivity and compressive mechanical properties.The result of osteoblast cell culture in vitro shows that RGO/PPy composites have good biocompatibility. RGO/PPy composites have no inhibitory effect on proliferation and differentiation of osteoblast cell. Meanwhile, proliferation and differentiation activity of osteoblast cell on conductive CPC were significantly increased in 5 mA micro current stimulation, indicating that electrical stimulation can promote proliferation and differentiation of osteoblast cell. Morphology of osteoblast cell on conductive CPC changed obviously after electrical stimulation.