Room-temperature Preparation And Osteogenic Performance Of 3D R GO/PPY/HA Composite Scaffold

Objectice: Room-temperature preparation of the three-dimensional reduced graphene oxide/polypyrrole/hydroxyapatite(3D rGO/PPY/HA)composite scaffold and exploration of the feasibility of this scaffold for bone tissue engineering.Materials and Methods: In present study,by using nickel foam(NF)as a template,graphene oxide as the raw material,Poly(diallyl dimethyl ammonium chloride(PDDA)as the cationic crosslinker,we have successfully completed the self-assembly of graphene oxide through an electrostatic layer-by-layer(LBL)assembling strategy followed by an electrochemical deposition process at room temperature.After etching the NF template by hot FeCl3/HCl mixed solution to get the finally 3D rGO/PPY composite scaffold.The physicochemical surface state,surface morphology and crystalline structure of the prepared 3D r GO/PPY based scaffolds were characterized by Fourier infrared spectrometer(FTIR),Raman spectrometer(Raman)with a 514 nm Ar-ion laser as excitation source,X-ray powder diffraction analysis(XRD)and X-ray photoelectron spectroscopy(XPS),respectively.The mechanical properties including hardness and Young's modulus of the prepared samples were evaluated on a TI-950 Tribolndenter.Mineralization of the 3D r GO/PPY scaffold was conducted via the electro-deposition process under-1.4 V at 30 oC for 30 min.The electrolyte was a mixed aqueous solution contains 0.042 M Ca(NO3)2,0.1 M NaNO3 and 0.025 M NH4H2PO4,and the surface morphology and crystalline structure of the calcium phosphate compound were detected by XRD,SEM and XPS,respectively.Finally,the cytotoxicity,cell adhension and proliferation ability of these scaffolds(including 3D rGO/PPY and 3D rGO/PPY/HA)were evaluated by MTT,AO/EB double staining and SEM images.Results: 1.The FTIR,Raman and XRD results show that the main compositon of the 3D rGO/PPY scaffold were graphene oxide and polypyrrole,and the XPS reveals that the graphene oxide(GO)was partially reduced to reduced graphene oxide(rGO)during the electrostatic LBL assembly process.The SEM shows that the graphene oxide nanosheet tightly adhered on the skeleton of nickel foam(NF).After the electrochemical deposition process,the PPY film consisting interconnected nanoparticles with size ranging from 150-300 nm were uniformly deposited on the backbone of NF/r GO foam.Surprisingly,after NF template was completely removed,the 3D rGO/PPY composite remained the 3D cross-linked network structure of NF and demonstrate a 3D self-supported full-carbon foam.Also,it is worth noting that after being preformed shapes of the NF,it also can be easily got the 3D rGO/PPY scaffolds by using the same electrostatic LBL assembly method.2.Nano indentation experiment results showed that the PPY film can obviously improve the 3D rGO's mechanical performance,and the value of the hardnesss and Young's modulus increased from 48.59±4.96 MPa and 91.0±4.19 MPa to 92.27±4.03 MPa and 185.94±10.76 MPa,respectively.Furthermore,the Young's modulus of 3D rGO/PPY scaffold was also similar with that of nature cancellous bone of mandible(114±78 MPa)in the infero-superior direction.3.After mineralization of the 3D rGO/PPY scaffold,the XRD and XPS results showed that the main composition of the calcium phosphate compound was hydroxyapatite.SEM indicated that the HA coating consisted numerous porous HA nanosphere with the size of 50-100 nm and uniformly deposited on the backbone of the 3D rGO/PPY.4.MTT result showed that both the 3D rGO/PPY and 3D rGO/PPY/HA scaffolds could promote the proliferation of the MC3T3-E1 cells,especially for the culture period prolonged to 4 days,the proliferation rate of MC3T3-E1 cell on 3D rGO/PPY and 3D rGO/PPY/HA scaffolds tremendously increased and reached as high as 5.27 and 6.6 times,as compared to that of the control group.AO/EB double staining and SEM results showed that both the composite scaffolds had no cytotoxicity,but the number of the cells on 3D rGO/PPY/HA was always higher than that of the 3D r GO/PPY and the control group in the whole culture period.Conclusions:1.In this paper,we have successfully prepared the 3D rGO/PPY composite scaffold through electrostatic layer-by-layer(LBL)assembling strategy followed by an electrochemical deposition process at room temperature.Before self-assembly,we alter the structure of nickel foam by force and use the same method abovementioned to get the 3D rGO/PPY scaffold with the desired configuration,such as helical,O-ring,and U-shaped configuration,respectively,which would significantly facilitate its precise repair of bone defects in bone tissue engineering.2.The preparation method used in our experiment is simple but low-cost,and it also doesn'tneed any special and/or expensive equipment to get the 3D r GO/PPY composite scaffold in largequantities.3.The Young's modulus of 3D rGO/PPY scaffold is also similar to that of nature cancellous bone of mandible in the infero-superior direction,and it has a great potential for repairing of trabeculae defects.4.There is no cytotoxic for both the 3D rGO/PPY and 3D rGO/PPY/HA scaffolds to MC3T3-E1 cells,and both can promote it adhesion and proliferation,especially for 3D rGO/PPY/HA scaffold,suggesting its promising applications for repairing of bone defects in bone tissue engineering area.