The Effect Of β-CPP On Physicochemical Properties And In Vitro Bioactivity Of Calcium–phosphate–silicate Composite Bone Cement

Experimental purposes:(1) Try to compound Calcium pyrophosphate (Ca2P2O7, β-CPP) to(MCPM+C3S) system bone cement, in order to adjust the setting time, improve its degradability andbioactivity.(2) Evaluation of toxicity and effects on the bone cement in vitro MC3T3-E1cells, and therelated gene expression were studied.Experimental methods:(1) The setting time of composite bone cement was determined by the GillMorocco (Gilmore) Determination of needle, using simulated body fluid (SBF) to test biological activity ofthe cement. The effect and variation of physical and chemical properties of the bone cement with β-CPPwere described according to the changes of dissolution extracts pH value and the degradation rate atdifferent time, with the observation of its microstructure by means of SEM and XRD.(2) The expressionlevel of E-type cyclins(CyclinE1) and proliferating cell nuclear protein Ki67on MC3T3-E1cells wereresearched by using Real-time PCR as well as MTT, respectively, in order to explore the possibilityevaluating molecularly the biocompatibility of the materials and their mechanism of action.Experimental results:(1) With the increase of the β-CPP component in the composite material, asteady rise in the setting time.(2) The composite material has excellent biodegradability, and with theincrease in the percentage of β-CPP, the degradation rate of the cement is increased. The pH values of thebone cement during immersion process has been maintained between9.5-8.0.(3) The MTT results showedthat the extract of composite bone cement had no marked toxicity on MC3T3-E1proliferation when theconcentrations are between12.5mg·mL-1~100mg·mL-1. The cement of containing certain Calciumpyrophosphate content might promote MC3T3-E1proliferation.(4) Real-time PCR datas displayed that the mRNA expression of CyclinE1and Ki67derived from MC3T3-E1cells incubated with differentconcentrations of the55%wt material extract for6h increased significantly compared to that of free β-CPPmaterial extract, in which the CyclinE1mRNA level increased by90.18%and120.26%, respectively,under the conditions of50mg·mL-1and25mg·mL-1of extract concentrations. Meanwhile, the Ki67mRNAcontents increased separately by31.48%and41.61%at the same concentrations.Experimental conclusion: Adding β-CPP to (C3S+MCPM) based bone cement can prolong settingtime, and accelerate the degradation, the rate of cell proliferation and the content of gene expression areincreased to some extent. The results suggest that the calcium–phosphate–silicate composite bonecements with β-CPP has good biocompatibility, and the changes of CyclinE1and Ki67mRNA levels fromMC3T3-E1cells may be used as a potential method to evaluate material biocompatibility.