Study Of The Preparation Of CPC/PMMA-BMP2 For Biological Composite Bone Cement

ObjectiveThis study intends to research the biomechanics,biological safety,tissue compatibility and induced osteogenic activity of CPC bone cement and PMMA with BMP2 composite bone cement mixed in different ratios.Material and MethodsCPC,PMMA and BMP-2 were mixed in different ratios.The BMP-2concentration of compound bone cement in each group was kept at the level of100 mg/L.The experiment was divided into five groups: A group CPC-BMP2,B group CPC/PMMA(1:1)-BMP2,C group CPC/PMMA(2:1)-BMP2,D group CPC/PMMA(3:1)-BMP2 and E group PMMA-BMP2.PMMA solvent was a general solvent containing a dissolved preparation of the composite bone cement specific to a given specimen to determine biomechanics,biological safety,tissue compatibility and osteogenic activity.Results1.Mechanical strength measurementCompared with the control group(E group PMMA-BMP2),the compressive strength of A group CPC-BMP2,B group CPC/PMMA(1:1)-BMP2,C group CPC/PMMA(2:1)-BMP2 and D group CPC/PMMA(3:1)-BMP2 were found to gradually increase with increasing PMMA concentration and decreasing CPC concentration in each test group.As shown,there were significant differences between the compressive strength,tensile strength and flexural strength of each test group(P<0.05).2.Cell toxicity testCompared with the control group(E group PMMA-BMP2),differences were found between the groups(A group CPC-BMP2,B group CPC/PMMA(1:1)-BMP2,C group CPC/PMMA(2:1)-BMP2,D group CPC/PMMA(3:1)-BMP2).(P<0.05).And bone cement extracts of A,B,C and D groups had no effect on the MC3T3-e1 cell relative growth rate,and the toxic reaction was level 1(i.e.,non-toxic).3.Measurement of curing timeCuring time of B group CPC/PMMA(1:1)-BMP2 and C group CPC/PMMA(2:1)-BMP2(less than 5-6 min)was shorter than that of D group CPC/PMMA(3:1)-BMP2(more than 9-10 min),and curing time of A group CPC-BMP2 was much longer(more than 11 min)than that of E group PMMABMP2(about 2 min).There were significant differences between A,B,C,D and E groups(P<0.05)(Fig.3).4.Measurement of solidification temperatureSolidification temperature was about 25.5? in A group CPC-BMP2,and solidification temperature of B,C and D groups was between 36.1? and 39.1?.They were all much lower than the solidification temperature of E group PMMA-BMP2(about 73.5?).There were significant differences between A,B,C,D and E groups(P<0.05),but there were no significant differences between B,C and D groups(P>0.05).5.Scanning electron microscopy morphologyBy means of scanning electron microscopy observation,it was demonstrated that bone cement particles were spherical;the apertures of A group CPC-BMP2 particles were loose,which were between 100-400 ?m;spherical particles of E group PMMA-BMP2 were densely arranged,whose pore apertures were between 50-100 ?m;pore apertures of B group CPC/PMMA(1:1)-BMP2,C group CPC/PMMA(2:1)-BMP2 and D group CPC/PMMA(3:1)-BMP2 were between A group and E group,which were about 100-200 ?m.Pore apertures in Control group CPC/PMMA is between about 100um-200 u.6.Histopathological examinationCells had normal morphology,arranging in an orderly manner,and no signs of edema,congestion and necrosis were observed by HE staining under the microscope.7.X-ray observationX-ray examinations of SD rats' bone defects model were performed after 4weeks.There were no significant degradations in any of the groups.X-ray examinations of the bone defects model were also performed after 12 weeks.There were significant degradations in CPC/PMMA-BMP2 groups and CPCBMP2 group,except PMMA-BMP2 group.CPC/PMMA-BMP2 composite bonecement groups and CPC-BMP2 bone cement group were degraded,and bone cells' growth was found to have integrated with the surrounding bone tissues closely.The formation of new bone in CPC/PMMA-BMP2 composite bone cement groups was significant after transplantation in vivo 12 weeks.8.Histopathological examinationCells had normal morphology,arranging in an orderly manner,and no signs of edema,congestion and necrosis were observed by HE staining under the microscope.9.HE staining observationBone defect was occupied by bone cement.No new bone trabecular structure,loose and disorderly bone cells were observed around PMMA in E group PMMA-BMP2.There were some new trabecular bone whose quantity was larger and whose arrangement was looser in the bone defect,and there were some cavities in the new bone in A group CPC-BMP2.A small number of new loose trabecular bones were observed in CPC degradation of bone defects.Repair of the bone defect was continuous,complete and uniform.Cavities in the new bone without degradation were occupied by PMMA in B,C and D groups CPC/PMMA-BMP2.So,induced osteogenic activity of BMP2 was released and this accelerated the formation of new bone after transplantation in vivo 12 weeks.10.Measurement and analysis of the new bone areaThe formation areas of new bone can be up to 5.32%-6.76% in CPC/PMMA-BMP2 groups,which were far higher than that of the PMMABMP2 group and maintained a certain degree of mechanical strength.Conclusions1.Preliminary experiments certify that CPC/PMMA/ BMP-2 composite bone cement in the preparation process does not affect their phase composition and the biological activity of BMP-2.B,C,and D groups maintained the more similar to the cancellous bone of the human body of mechanical strength of compressive strength,tensile strength and flexural strength.2.B,C,and D groups were better than A and E groups in biomechanics,biological safety,tissue compatibility and induced osteogenic activity.B group provided better induced osteogenic activity and its compressive strength was more similar to the compressive strength of the cancellous bone of the human body,so B group was selected for the composite bone cement to obtain a better application.3.The formation of new bone in CPC/PMMA-BMP2 composite bone cement groups was significant during the repair process of SD rats' bone defects.CPC/ PMMA-BMP2 composite bone cement was of induced osteogenic activity,and BMP2 released and accelerated the formation of new bone.Our experiment provides the laboratory data for study a kind of good biological activity material by inducing osteogenic activity.