Preparation Technology And Properties Research Of Silicon Calcium Phosphorus Bone Cement

The composition of calcium phosphate bone cement(CPC)is similar to the mineral composition of human bone.And the CPC has the advantages of good bone conductivity,biocompatibility and biological activity,which has become the focus of the current biomaterials research field.Calcium phosphate bone cement with the characteristics of injectability and arbitrary plastic molding,has wide application prospects especially in traumatic bone repair surgery.Among them,tricalcium phosphate(Ca3(PO4)2、TCP)can be hydrated at room temperature to form hydroxyapatite(Ca10(PO4)6(OH)2、HA),which has become one of the most the commonly used raw materials in the preparation of calcium phosphate bone cement.However,various calcium phosphate bone cements prepared with TCP the main powder raw material are mainly used for the repair of non-load-bearing bones.In order to further improve the biological activity and mechanical properties of bone cement,it is still necessaryto modify the bone cements for promoting its further application in the clinic.In this work,a novel bone cement powder with Si-a-TCP as the main component is synthesized by high-temperature sintering method.consequent a novel silicon-doped Calcium phosphate(Si-CPC)bone cement is prepared by curing with pure water,simulated body fluid,sodium phytate solution and other curing liquids.Through X-ray diffraction analysis(XRD),scanning electron microscopy and composition analysis(SEM),Fourier transform infrared spectroscopy(FT-IR),physical and mechanical performance analysis and other characterization methods,the mechanical properties,microstructure,porosity,biological activity and other properties of silicon calcium phosphate bone cement were analyzed.Also,the preparation process and properties were systematically studied.Calcium hydrogen phosphate dihydrate(CaHPO4·2H2O、DCPD)mixed withcalcium carbonate(CaCO3、CC)and calcium silicate(CaSiO3,CS)according to a certain atomic ratio by means of wet mixing ball milling,was heated to 1250℃ for 150 min.After a rapid cooling,a bone cement powder with Si-a-TCP as the main component was prepared.The result showed that the bone cement powder mixed with DCPD,CC and CS powders according to the atomic ratio of Ca/P=1.5,after sintering at 1250℃ for 150min,formed Si-a-TCP without HA phase.The addition of Si element improves the purity of a-TCP in the raw material.But the production temperature of a-TCP is reduced by about 40℃ which leads to an increase of the instability of a-TCP during air cooling.And a small amount of a-TCP to β-TCP transition occurs.Simulated body fluid as a curing fluid has obvious advantages over pure water when curing Si-a-TCP bone cement powder.The simulated body fluid supplements the Ca element required to produce HA and improves the conversion rate of a-TCP to HA.In addition,when the doped-Si content is 3.3 at%,the good whisker toughening effect makes the compressive strength of the silicon calcium phosphate bone cement resistant increase to 35.83 MPa,which is about double the compressive strength of pure water-cured Si-a-TCP bone cement.When Tetracalcium Phosphate(TTCP)is mixed with Si-a-TCP as a powder raw material,TTCP hinders the conversion of a-TCP to HA,resulting in a lower compressive strength of bone cement.However,as the content of TTCP increases,the hindrance gradually weakened.During the immersion process of bone cement cured by simulated body fluid,while the compressive strength of the bone cement is maintained at a relatively high level,the formation reaction of HA is greater than the degradation reaction.In the end,the bone cement is completely composed of HA that is similar to the composition of human bone tissue,which performs good biological activity.The chelation of phytate can significantly improve the overall performance of Si-a-TCP bone cement.When curing Si-a-TCP bone cement with phytic acid or a curing liquid mixed with phytic acid,the mechanical properties of the bone cement are poor due to the excessive acidity of phytic acid.However,in the curing of Si-a-TCP bone cement with 4wt.%Sodium phytate solution,the chelation of phytate promotes a beneficial change in the micro-morphology of the bone cement,and improves the compressive strength of the silicon-calcium-phosphorus bone cement,which exceedsthe mechanical properties required for the repair of cancellous bone.In the bioactive immersion test,Si-a-TCP bone cement cured with 4wt.%Sodium phytate solution showed good biological activity.And its compressive strength reached 38.98 MPa after immersion for 7 daysThe mechanical properties of silicon calcium phosphate bone cement cured by disodium hydrogen phosphate solution are less affected by the concentration of the solution.The compressive strength of the prepared bone cement is above 20 MPa.However,as the concentration of the curing liquid increases,due to the lack of Ca2+ions in the system,an atypical calcium-deficient apatite(CDHA)is formed in the final product.After the disodium hydrogen phosphate solution is mixed with the SBF solution,the curing ability of the disodium hydrogen phosphate solution can be further improved.The disodium calcium phosphate solidified calcium calcium phosphate bone cement degrades faster in simulated body fluids.But the compressive strength can be maintained at a higher level during the immersion process.And the pH of the immersion solution increases first and then decreases and stabilizes in weak alkalinity,which can be compatible with human body fluid environment.To sum up,the use of disodium hydrogen phosphate solution as a conventional curing solution for bone cement powders with Si-a-TCP as the main component has proved to be wide applicability.In addition,the simulated body fluid solidified bone cement and sodium phytate chelated bone cement prepared in this experiment have relatively good mechanical properties and biological activity.Thus,they have promising clinical application prospects.