Preparation And Biological Study Of Composite Bone Cement Consisted Of Different Particle Size Of Gelatin Microparticles And PMMA/CPC

Objectives To explore a new method for the preparation of a new type of composite bone cement mixed by gelatin microparticle with different particle sizes,calcium phosphate cement(CPC)and polymethyl methacrylate(PMMA)and to observe the biomechanical property,biosafety and histocompatibility of composite bone cement mixed by gelatin microparticle with different particle sizes,CPC and PMMA.To find the best particle size of gelatin microparticle and to confirm the effects of particle sizes on biomechanical properties,material degradation,biological safety and biocompatibility.Methods Four groups gelatin microparticles with different particle size were preparated by physical crushing mean.The particle sizes of gelatin microparticles were 50-100 ?m(1 group),100-200 ?m(2 group),200-300 ?m(3 group)and 300-500 ?m(4 group),respectively.Scanning electron microscope was used to observe the ultrastructure of gelatin microparticles after metal spraying.The solid powder of PMMA and CPC was mixed by mass ratio 1: 1.Then they were mixed with 4 groups of different particle size of gelatin microparticles with mass ratio(95: 5).The liquid phase of PMMA and CPC was added into the mixture consisted of PMMA,CPC and gelatin microparticles by solid-liquid ratio mass ratio(2.5 g: 1 mL).So bone cement specimen was preparated.The experimental groups were as follows: CPC group,PMMA group,CPC+PMMA group,gelatin microparticles with different particle size(50-100 ?m,100-200 ?m,200-300 ?m and 300-500 ?m)+ CPC+PMMA group(GP1-4+CPC+PMMA).The biomechanical properties such as compressive strength,tensile strength and flexural strength were measured.The solidification time,solidification temperature and anti collapsibility of composite bone cement were detected.The ultrastructure of composite bone cement observed by scanning electron microscopy.Extraction of bone cement in each group was preparated.Effect of extraction of bone cement on the proliferation of osteoblast precursor cell was measured.Kunming mice were administrated with extraction of bone cement(50 mL/kg)by intraperitoneal injection.The changes of the hair,skin,eyes and mucous membrane of mice were observed.The respiration,circulation and behavior of mice were observed.Changes of body weight in mice was measured.The blood was collected by orbital venous plexus.The routine blood test,blood glucose,blood lipid and liver and kidney function test were completed by automatic blood analyzer.Mice were sacrificed.The wet weights of heart,lung,liver,spleen and kidney of mice were weighed.Paraffin sections and HE staining were used to observe the morphological changes of liver and kidney after liver and kidney tissues were fixed with methanol.Results 1.Biomechanical property of composite bone cement consisted of gelatin microparticles,PMMA and CPC.Compared with the CPC group,the compressive strength,tensile strength and flexural strength of composite bone cement were significantly increased in PMMA and CPC+PMMA groups(all P<0.05).Compared with the CPC+PMMA group,the compressive strength,tensile strength and flexural strength of composite bone cement were significantly decreased in GP1-4+CPC+PMMA groups(all P<0.05).Compared with GP1(50-100 ?m)+CPC+PMMA group,the compressive strength,tensile strength and flexural strength of composite bone cement were significantly decreased in GP4(300-500 ?m)+CPC+PMMA group(P<0.05).Compared with GP1(50-100 ?m)+CPC+PMMA group,with the increase of particle size of gelatin particles,the compressive strength,tensile strength and flexural strength of composite bone cement were gradually decreased in GP2-3(100-200 ?m and 200-300 ?m)+CPC+PMMA group,but the difference was not statistically significant(all P>0.05).But the compressive strength,tensile strength and flexural strength were all higher than the normal range of cancellous bone.2.The solidification temperature,solidification time and mass loss rate of composite bone cement consisted of gelatin microparticles,PMMA and CPC.Compared with the PMMA group,the solidification temperature of composite bone cement were significantly decreased in CPC and CPC+PMMA groups(all P<0.05).Compared with the CPC+PMMA group,the solidification temperature of composite bone cement were increased in GP1-4+CPC+PMMA groups,but the difference was not statistically significant(all P>0.05)and the solidification temperature was within the normal range of human tissue.With the increase of particle size of gelatin particles,the solidification temperature of composite bone cement were gradually increased.But the difference was not statistically significant(all P>0.05).Compared with the CPC group,the solidification time of composite bone cement were significantly decreased in PMMA and CPC+PMMA groups(all P<0.05).Compared with the CPC+PMMA group,the solidification time of composite bone cement were gradually increased in GP1-4+CPC+PMMA groups,but the difference was not statistically significant(all P>0.05).With the increase of particle size of gelatin particles,the solidification time of composite bone cement were gradually increased.But the difference was not statistically significant(all P>0.05).Compared with the PMMA group,the mass loss rate of composite bone cement were significantly increased in CPC and CPC+PMMA groups(all P<0.05).Compared with the CPC+PMMA group,the mass loss rate of composite bone cement were significantly increased in GP1-4+CPC+PMMA groups(all P<0.05).With the increase of particle size of gelatin microparticles,the mass loss rate of composite bone cement were gradually increased.But the difference was not statistically significant(all P>0.05).3.Ultrastructural of composite bone cement consisted of gelatin microparticles,PMMA and CPC.A large number of spherical particles were formed on the surface of the composite cement,the spherical particles were closely distributed and no microporous was observed on the surface of the composite cement in PMMA group.The granular crystal was observed on the surface of the composite cement,the micropore was distributed among particles,the micropore was uniformly distributed,the size of micropore is small,most of the size of micropore is less than 10 ?m in the CPC group.The granular crystal was observed on the surface of the composite cement,the micropore was distributed among particles,the size of micropore is less than 10 ?m in the CPC+PMMA group.In GP1-4+CPC+PMMA group,with the dissolution of gelatin particles and the degradation of CPC,the surface of composite bone cement was dry and large pore size.With the increase of particle size of gelatin microparticles,the number of macropores formed on the surface of composite bone cement was obviously increased in GP1-4+CPC+PMMA group.4.Evaluation of cytotoxicity of composite bone cement consisted of gelatin microparticles,PMMA and CPC.Compared with the control or CPC group,the level of cell proliferation was significantly decreased in PMMA group(P<0.05).No significant difference about the level of cell proliferation was observed between CPC+PMMA group and GP1-4+CPC+PMMA group.PMMA has mild cytotoxicity and the cytotoxicity grade was 2 in PMMA group.No cytotoxicity was observed and the cytotoxicity grade was 1 or 0 in CPC group and GP1-4+CPC+PMMA groups.5.Acute animal toxicity test.No significant difference in changes of general state,respiration,circulation,behavior and body weight of mice was observed among experimental groups.No significant difference in routine blood test,liver and renal function was observed among experimental groups(all P>0.05).No significant difference in wet weight of lung,heart,liver,spleen and kidney and body weight of mice was observed among experimental groups(all P>0.05).The morphology of the cells in liver and kidney of mice was normal,the arrangement of cells was orderly and the structure of cells was clear in each group.there was no obvious edema,congestion and necrosis in liver and kidney of mice in each group.Conclusions 1.The solidification temperature of composite bone cement consisted of gelatin microparticles,PMMA and CPC is close to the normal temperature of human tissue.The coagulation time of composite bone cement is within the range of normal operation.Composite bone cement has large pores and is easily degraded.The composite bone cement consisted of gelatin microparticles,PMMA and CPC is a new bone cement material with good biomechanical properties.2.When the size of the gelatin microparticle is 200-300?m,the porous cement has larger pores,and the biomechanics can meet the clinical needs.3.Gelatin microparticles and PMMA / CPC composite bone cement can reduce the cytotoxicity of bone cement cells.