Fabrication And Properties Of Modified P(MMA-AA) Bone Cements

Polymethyl methacrylate(PMMA)bone cement is an injectable repair material commonly used in orthopedics clinics,and can be used in artificial joint replacement and spinal fixation.However,the volume contraction of PMMA bone cement during polymerization causes a slight gap between the interface and the host bone,and there are problems such as excessive elastic modulus,high setting temperature,and lack of biological activity.Although the early injectable water-swellable poly(methyl methacrylate-acrylic acid)[P(MMA-AA)] bone cement solved the problem of PMMA bone cement volume shrinkage to a certain extent,the hydrophobic phase of PMMA hindered water transfer.Therefore,the ability of P(MMA-AA)copolymer microspheres to expand outwards due to water absorption cannot be completely released,resulting in a lower expansion ratio of P(MMA-AA)bone cement and a reduction in its compressive strength.In response to the above problems,this study introduced graphene oxide(GO)into the solid phase of P(MMA-AA)bone cement by physical mixing and dispersion polymerization,while replacing it with hydrophilic hydroxyethyl methacrylate(HEMA)Part of the liquid phase monomer,in order to obtain a modified composite bone cement with both water absorption expansion and mechanical properties.The effects of GO and HEMA content on the physical and chemical properties,water absorption properties,swelling properties,mechanical properties and biological properties of composite bone cement were studied.The research results obtained are as follows:(1)P(MMA-AA)/GO composite bone cement was prepared by introducing GO through physical mixing.The experimental results show that adding GO can improve the physical and chemical properties of the composite bone cement.Prolonged to 22.4 min ~ 53.8 min,the solidification temperature was reduced to 51.1℃ ~ 87.6℃.The balanced water absorption and expansion ratio of P(MMA-AA)(MBA5)/GO1 composite bone cement in simulated body fluids(SBF)were increased by 4.2% and 4.7% respectively compared to those without GO components.The GO group increased 4.5 Mpa.In addition,the cytotoxicity results showed that the cytotoxicity of P(MMA-AA)/GO composite bone cement was lower than that of PMMA bone cement.(2)When GO is introduced by dispersion polymerization,FTIR and Raman spectra show that GO participates in the polymerization reaction,and the water absorption and expansion properties of P(MMA-AA)-GO composite bone cement are further improved,of which P(MMA-AA)-GO0.4 Compared with P(MMA-AA)(MBA5)/GO1 composite bone cement,the composite bone cement’s balanced water absorption and balanced expansion ratio were increased by 25.9% and 28.3%,and the compressive strength was increased by 7.6 Mpa compared to that without GO The cell experiment showed that the addition of GO promoted the adhesion and proliferation of cells on the surface of bone cement.(3)P(MMA-AA)-GO-PHEMA composite bone cement was prepared after partially replacing MMA liquid phase with HEMA.It was found that although the setting time shortened with the increase of HEMA content,the water absorption and swelling performance gradually improved.When the HEMA content is 40 vol.%,The composite bone cement has a very high equilibrium water absorption and equilibrium expansion ratio(105.4±2.1% and 105.2±4.7%)in SBF,and the compressive strength is significantly improved to 69.8 ± 1.8 MPa,which meets Bone implant material filling requirements,meanwhile,the cytotoxicity is reduced after adding HEMA.