Preparation Of 3D Printing Bioceramic Scaffolds And Its Application Research On Orbital Reconstruction

BackgroundThe orbit protects the eyeball and its surrounding neurovascular tissue,maintains the normal function of the visual system,and is also the main component of human facial morphology.The orbital bone is thin and easy to fracture under external force.Orbital fracture can cause midface deformity,and lead to orbital fat and soft tissue hernia into the mandibular sinus,and then cause endophthalmitis or subbulbar inflammation.Repair time,surgical intervention and implant materials are the key factors affecting the treatment effect and overall prognosis.At present,the commonly used orbital repair materials only play a supporting role by covering the defect,which cannot induce bone growth and regeneration and anchor with the bone tissue around the repair area safely.There are the possibility of displacement,rejection and infection.In the case of severe ocular trauma,endophthalmitis or intraocular malignant tumor,enucleation of the diseased eyeball should be considered.The orbital volume defect after enucleation irreversibly damages the appearance and brings heavy mental and psychological burden to the patients.Orbital implant,as another kind of orbital implant,is usually designed as a porous sphere.After the eyeball is removed,it is placed in the X non-eyeball socket of the patient,which can make up for the missing orbital volume and make the orbital film have good mobility,and repair the patient’s appearance to a great extent.However,the current clinical use of eye socket materials has low bioactivity and insufficient vascularization,which has the risk of postoperative infection and exposure.In recent years,3D printing technology is booming,which has significant advantages and broad application prospects in the field of medical implant preparation.This technology has many advantages,such as personalized customization,easy operation,multi material processing and so on.In view of the shortcomings of the current orbital implant materials,this study combines 3D printing technology with functional bioactive ceramic materials to explore a new type of orbital reconstruction implant materials applied in the repair of orbital bone defect and orbital volume defect,so as to provide a new direction for accelerating the regeneration and repair of orbital bone and orbital soft tissue and realizing efficient and personalized orbital reconstruction.The research mainly focuses on the following four parts :(1)Design,preparation and evaluation of physicochemical properties of 3D printing magnesium doped calcium silicate porous scaffolds;(2)3D printing magnesium doped calcium silicate porous scaffolds for repairing orbital bone defects in rabbits;(3)Design,preparation and evaluation of 3D printing diopside based porous scaffolds for orbital implant;(4)Bactericidal properties of diopside based bioceramics and evaluation of vascularization properties of 3D printed porous scaffolds.Part I Design,preparation and evaluation of physicochemical roperties of 3D printing magnesium doped calcium silicate porous caffolds ObjectiveMagnesium doped calcium silicate bioceramic powder was synthesized,and ultrathin and high strength porous magnesium doped calcium silicate scaffold material was prepared by 3D printing technology.The macroscopic and microscopic morphology,mechanical properties,in vitro mineralization and degradation properties of the scaffold material were evaluated.MethodsCalcium silicate powder(CSi-Mg6)containing 6 mol% magnesium ions and pure calcium silicate powder(CSi)without magnesium ion were prepared by chemical coprecipitation and micro ion doping technology.Meanwhile,calcium magnesium silicate bioceramic Akerminate(Ake)was prepared by sol-gel method.The phase structure of the synthesized powders was detected by XRD,and the elemental composition of the powders was detected by ICP.Three groups of thin-walled porous scaffolds with different ceramic materials were prepared by computer-aided design and digital light curing rapid prototyping 3D printing technology.The physical and chemical properties of the scaffolds were evaluated.The porosity of the scaffolds was detected by Archimedes drainage method.The macro and micro structure of the scaffolds was observed and evaluated by scanning electron microscope.The bending strength of the scaffolds was measured by external mechanical testing machine.The mechanical properties and in vitro mineralization ability of the scaffolds were detected by immersion test.The degradation,p H change and ion release process of the scaffolds were monitored by Tris-HCl buffer solution immersion test.ResultsThe porous scaffolds of three kinds of bioceramics printed by digital light processing technology have a complete and uniform structure.The thickness of scaffolds is about 1.5mm,and the pore structure is a rectangular hole with a diameter of 400 μm,which is interconnected,and the porosity is more than 60%.The strength test results showed that the strength of CSi-Mg6 group(～ 22 Mpa)was significantly higher than that of CSi and Ake group,and the strength was about 1.5-3.0 times of the other two groups.After soaking in SBF in vitro for 3 weeks,the bending strength of all groups decreased in varying degrees,but the bending strength of CSi-Mg6 group was still significantly higher than that of the other two groups.After soaking for 3 weeks,hydroxyapatite mineralized layer appeared on the surface of all materials,but the mineralization rate of CSi was faster than that of CSi-Mg6 and Ake groups.Degradation testing in vitro showed that the degradation rate of CSi-Mg6 scaffolds was significantly slowed down,and each group showed the ion release rate matched with the degradation rate.ConclusionsIn this study,magnesium doped calcium silicate porous scaffolds with high strength and thin layer were successfully prepared by micro magnesium ion doping and advanced3 D printing technology.Compared with the other two groups of materials,the scaffolds showed stronger mechanical strength and optimized degradation rate,which provided a new direction for repairing bone defects,especially for thin-layer orbital bone defects with complex structure.Part II 3D printing magnesium doped calcium silicate porous scaffolds for repairing orbital bone defects in rabbitsObjectiveTo explore the effect of 3D printing scaffolds on cell adhesion,proliferation and osteogenic differentiation in vitro.To explore the ability of the scaffold to support and promote bone repair in vivo by constructing a rabbit model of infraorbital critical bone defect.MethodsMC3T3-E1 mouse osteoblast precursor cells were inoculated on the surface of three groups of scaffolds respectively.After co-cultured,the proliferation of cells was detected by CCK-8 kit,and the osteogenic differentiation degree of cells was evaluated by ALP kit.The surface morphology of cells co-cultured with scaffolds was observed by scanning electron microscope,and the cytoskeleton of the cell on the surface of materials was stained by fluorescence staining.Sixteen male New Zealand rabbits were randomly divided into 4 groups(blank group,CSi group,CSi-Mg6 group,and Ake group).The samples were taken out for X-ray and micro-CT imaging reconstruction at 4 and 12 weeks after operation to evaluate the osteogenic performance of the materials in each group,and the samples were taken out for histological examination.The amount of new bone formation was observed under microscope and quantitatively analyzed by morphology.The distribution of elements in the material and bone tissue was observed by scanning electron microscope and EDS.ResultsCytological results showed that compared with pure CSi scaffold,CSi-Mg6 scaffold could promote the proliferation of osteoblast precursor cells(p < 0.01).After long-term culture in vitro(21 days),there was no significant difference in osteogenic differentiation between CSi-Mg6 group and pure CSi group.In the experiment of New Zealand rabbits with critical bone defect of inferior orbital margin,CSi-Mg6 showed rapid new bone formation in the early stage(4 weeks)of implantation,which was significantly higher than that in CSi and Ake groups(p < 0.01).In the late stage(12 weeks),the new bone ass of CSi-Mg6 was still significantly higher than that in CSi group.Although Ake group showed higher new bone mass in the late stage,which was still slightly lower than that in CSi-Mg6 group.ConclusionsIn this study,the high-strength CSi-Mg6 thin-layer porous scaffolds were successfully used to repair the critical bone defects in the lower orbital margin of rabbits.Compared with pure CSi scaffolds and Ake scaffolds,they showed better structural stability,osteogenic induction and conduction abilities,and may become a potential orbital bone repair material.Part III Design,preparation and evaluation of 3D printing diopside based porous scaffolds for orbital implantObjectiveDiopside(DIO)and copper containing low melting bioactive glass(BG-Cu)powders were synthesized.Diopside based porous scaffolds with different amounts of Bioglass were 3D printed.The microstructure,mechanical properties and in vitro degradation properties of the scaffolds were investigated.MethodsDiopside powder was synthesized by chemical coprecipitation method,and low melting bioactive glass powder containing copper was prepared by sol-gel method.The phase structure of the synthesized powder was detected by XRD,and the elemental composition of the powder was detected by ICP.Three kinds of 3D printing bioceramic nks were prepared by mixing 0%,5% and 10% bioactive glass in diopside powder with polyvinyl alcohol binder.Diopside based porous scaffolds were prepared by direct writing 3D printing technology,and then sintered at 1150℃.Diopside with 10% BG content was sintered at 1150℃ and 1250℃ separately.Four groups of bioceramic scaffolds were prepared: DIO(1150℃),DIO/5BG(1150℃),DIO/10BG(1150℃),and DIO/10BG(1250℃).The physical and chemical properties of the scaffolds were evaluated.The porosity of the scaffolds was detected by drainage method.The macro and micro structure of the scaffolds was observed and evaluated by scanning electron microscope.The bending strength of the scaffolds was detected by external energy mechanical testing machine.The degradation of the materials,the change of p H and the process of ion release were monitored by Tris-HCl solution immersion test.ResultsThe four groups of bioceramic scaffolds had uniform macrostructure,uniform pore size and porosity between 62% and 65%.The mechanical strength of scaffolds was increased from ~ 12.3 MPa of DIO(1150℃)to ~ 19.4 MPa of DIO/10BG(1150℃).When the sintering temperature increased to 1250℃,the compressive strength of DIO/10BG(1250℃)scaffolds decreased to ~ 11.1 MPa,which was about 42% lower than that of DIO /10BG(1150℃)(p < 0.05).Although the results of immersion test in vitro showed that the degradation rate of DIO bioceramics could be accelerated by adding BG,the degradation rate was still at a low level after 8 weeks.The results of in vitro ion release experiments showed that the diopside based bioceramic scaffold could stably release trace Cu ions.ConclusionsIn this study,diopside based porous bioceramic scaffolds with precise pore structure were successfully prepared by direct writing 3D printing technology.At the sintering temperature of 1150℃,5% or 10% bioactive glass was mixed to improve the mechanical trength of the porous scaffolds,ensure the structural stability of the scaffolds,and the scaffolds can degrade stably in vitro,and release a small amount of bioactive Cu ions.Part IV Bactericidal properties of diopside-based bioceramics and evaluation of vascularization properties of 3D printed porous scaffoldsObjectiveThe bactericidal properties of DIO/x BG bioceramics were evaluated by in vitro antibacterial test,and the angiogenesis properties of DIO/x BG scaffolds in vivo were evaluated by New Zealand rabbit dorsal muscle embedding test.MethodsGram-positive Staphylococcus aureus and gram-negative Pseudomonas aeruginosa were inoculated on the surface of four groups of bioceramic materials.After co-culturing with the materials for 4,8 and 12 hours,the bacterial activity was detected and the bactericidal rate was calculated.The morphology of bacteria on the ceramic surface was observed by scanning electron microscope,and the surface elements were analyzed by X-ray photoelectron spectroscopy.Eight male New Zealand white rabbits were randomly divided into four groups: DIO(1150℃),DIO/5BG(1150℃),DIO/10BG(1150℃),and DIO/10BG(1250℃).The materials were taken out 2 and 6 weeks after implantation.The degree of scaffolds vascularization was observed by histological staining,and the number of vessels in the scaffolds was calculated quantitatively.ResultsThe results of antibacterial test showed that DIO/5BG and DIO/10 BG bioceramic howed excellent germicidal efficacy against gram-positive Staphylococcus aureus.After co-culture for 4 hours,the logarithmic germicidal efficacy was more than 2(> 99%),while the germicidal efficacy of pure DIO decreased from ~ 1.05 to ~ 0 with the extension of co-culture time.For gram-negative Pseudomonas aeruginosa,DIO/10BG(1150℃)and DIO/10BG(1250℃)showed higher germicidal efficacy than DIO/5BG(1150℃),while the logarithmic bactericidal rate of pure DIO group gradually decreased with time.In vivo vascularization experiment showed that the number of blood vessels in DIO/5BG(1150℃)and DIO/10BG(1150℃)groups was similar,and they were significantly higher than that in pure DIO.DIO/10BG(1250℃)group showed the highest number of blood vessels at 2 and 6 weeks.ConclusionsWith the increase of BG content,the bactericidal performance of diopside bioceramics is further improved.DIO/10 BG porous diopside based bioceramics showed good biocompatibility and excellent vascularization properties in New Zealand rabbit dorsal muscles.The diopside based porous bioceramic scaffold may be a potential orbital implant material.