| Objective: To study the characteristics,related mechanical properties and antibacterial ability in vitro and vivo of 3D printing of a tricalci?m phosphate scaffold for the loading of isoniazid,rifampicin / poly lactide-glycolide acid sustained release microspheres.To establish the model of chronic osteomyelitis in rabbits' femoral condyles,and put the composite material into the bone defect and to observe the therapeutic effect.To create a new substitute material for the treatment of infectious bone defects,which has a good local antibacterial ability,but also can induce bone growth.The aim of this study was to find a new method for the treatment of chronic osteomyelitis,as well as to provide experimental evidence for clinical application.Method: The experiment consists of three parts 1?To study the characteristics,related mechanical properties and antibacterial ability in vitro of 3D printing of a tricalci?m phosphate scaffold for the loading of isoniazid,rifampicin / poly lactide-glycolide acid sustained release microspheres.Isoniazid,rifampicin / poly lactide-glycolide acid sustained release microspheres were prepared by W/O/W multiple emulsion method;?-tricalci?m phosphate scaffold model was designed by CAD software,and porous ?-tricalci?m phosphate scaffold was produced by a 3D-Bioplotter printer;finally,the microspheres were loaded into the porous ?-tricalci?m phosphate scaffold by centrifugal shock and to complete the preparation of composite.The surface condition,porosity and the fusion between the microspheres and the scaffolds were examined by gross observation,optical microscopy and scanning electron microscopy;the mechanical properties of the composite were tested by compressive strength;the inhibition ring test and plate-counting method was used to evaluate anti-bacterial ability for the composite materials in vitro.2?The establishment and evaluation of the model of chronic osteomyelitis in rabbits' femoral condyles A hole was drilled in lateral of the rabbit femoral condyle,five percent sodi?m morrhuate injected into the hole lead to the local vascular occlusion necrosis and MRSA injected to induce the rabbits' model of chronic osteomyelitis.To explore the relationship between the dose of the bacteria and chronic osteomyelitis and s?m up the most suitable concentration for future experimental study to provide an ideal animal model.3?Experimental study on treatment of femoral condylar chronic osteomyelitis in rabbits with porous ?-TCP scaffold loaded release microspheres After establishing the model of chronic osteomyelitis successfully,the lesions were thoroughly debrided.The experiment was divided into 5 groups:debridement group,release microspheres group,scaffold group,composite group and blank group.The local anti-bacterial effect of the material was observed by general observation,radiology,histopathology,immunohistochemistry and bacterial culture in 4w,8w,12 w respectively;then the osteogenesis effect observed through the radiology,Micro CT,immunohistochemistry and PCR.Results: 1?The characteristics,related mechanical properties and antibacterial ability in vitro of 3D printing of a tricalci?m phosphate scaffold for the loading of isoniazid,rifampicin / poly lactide-glycolide acid sustained release microspheres.The pore size was observed about 400?m by scanning electron microscopy and the porosity was(66.34 ± 2.76)% by weight vol?metric method;the maxim?m load and compressive strength was 114.5±13.8N and 5.8±0.7MPa by compressive strength test,which afford the compressive strength of cancellous bone(2-12 Mpa).Inhibition ring test show that the composite materials has obvious anti-bacterial ability to MRSA.2?The establishment and evaluation of the model of chronic osteomyelitis in rabbits' femoral condyles Animals were divided into 5 groups,A0 group(0.1 ml normal saline was inoculated),A1 group(0.1 ml 10 x 106 CFU / ml MRSA was inoculated),A2 group(0.1 ml 10 x 107 CFU / ml MRSA),A3 group(0.1 ml 10 x 108 CFU / ml MRSA),A4 group(0.1 ml 10 x 109 CFU / ml MRSA).One week after operation,there were sinus,pus and local swelling in the surgical sites except the A0 group;radiography found out there were different degrees of soft tissue swelling,cortical bone changed thinner,the n?mber of trabecular bone reduced,bone sclerosis and osteolysis,sequestra formation in experimental groups four weeks after surgery.Histomorphology showed that there were a large n?mber of inflammatory cell infiltration,we took local tissue for bacterial culture and colonies grow well,which bacteria confirmed as MRSA.Gross observation and radiographic criteria was used to grading the severity of osteomyelitis in rabbits: the experimental groups A1-A4 were respectively stage 0;stage1;stage2~3;stage3~4.3?The treatment of femoral condylar chronic osteomyelitis in rabbits with porous ?-TCP scaffold loaded release microspheres After establishing the model of chronic osteomyelitis successfully,the composite materials were implanted into the bone defect.Through the gross observation,imaging,Micro CT,PCR,histopathology,immunohistochemistry found that only the composite group can control the local inflammation of chronic osteomyelitis effectively,and there was a significant osteogenesis effect;imaging found that inflammation gradually reduced,cortical began to change continuously,the material began to break down quickly and bone grow through the pore after 12 weeks;immunohistochemistry showed a large n?mber of BMP-2 expression around the new bone,PCR showed type 1 and type 2 collagen were expressed in large quantities.The other groups had poor control inflammation and osteogenesis.Conclusion: 3D printing of a tricalci?m phosphate scaffold for the loading of isoniazid,rifampicin / poly lactide-glycolide acid sustained release microspheres have a good effect in the treatment of chronic osteomyelitis,not only with satisfactory biocompatibility and biological properties,but also the local anti-bacterial effect and osteogenesis.In the treatment of osteomyelitis,the experiment provides a strong experimental basis in the future. |
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