| Seed cells,scaffold materials and osteogenic factors are the three basic elements of bone tissue engineering.The scaffold plays an important role in supporting and assisting tissue reconstruction,so compatible bone scaffolds will significantly promote the cell growth and tissue recovery.To date,conventional method including electrostatic spinning and particulate leaching posess some disadvantages such as complicated producing process,poor reproducibility,uncontrollable hole shape and residual solvents,which limites applications of scaffolds that fabricated with those techniques.Therefore,this paper aims at fabricating bone scaffolds with good properties to overcome shortcomings of those conventional techniques via3D-printing.The FDM method involves the melt extrusion of PLGA through a heated nozzle and deposition on a platform under the control of computer,which fabricated bone substitution scaffolds with regular morphology,appropriate pore size and enough mechanical performance,and then evaluated the mechanical properties,degradation rate and biological compatibility of fabricated scaffolds.The main contents of this thesis are as follows:First,fabrication and properties characterization of PLGA scaffold was investigated.The optimal process conditions were studied,then the impact of thickness,structures and porosity on mechanical properties and physical and chemical properties were investigated.The results indicated that the yield stress decreased(P<0.01)while the compressive strength had no obvious differences with the increase of thickness,the compressive strength was 0/90°>0/60/120°>0/45/90/135° while the yield stress had no obvious effects with different structures(the structures were 0/90°,0/60/120° and 0/45/90/135°,respectively),both compressive strength and yield stress decreased with the increase of porosity,which we found a negative correlation between the mechanical property and porosity.The results of fourier transform infrared spectroscopy(FTIR),X-ray diffraction(XRD)and differential scanning calorimetry(DSC)measurements showed that subcritical process had no significanteffect on the chemical structure,chemical group,crystallization and glass transition temperature of PLGA.Ultimately,the parameters of scaffold we used were porosity of 66%,thickness of 0.2 mm,structure of 0/90° and the compressive strength and yield stress were 12.69 Mpa and 5.78 Mpa(n=5).Then,the degradation rate of scaffold was investigated for ten weeks.The scaffolds were immersed in the phosphate buffered saline and enzyme hydrolysis with ratios of scaffold/solution was 1:10(V/M)in conditions of 37℃,60 rmp/min and solutions were changed for every week.Measuring the pH value for every week and took out the scaffolds in 2,4,6,8 and 10 week,rinsing for three times with ultrapure water and freeze drying for 24 hours.Then the morphology,weight loss,change of mechanical properties,DSC,gel permeation chromatography(GPC)and differential thermal analysis(DTA)of the scaffolds were analysed.The results showed that the pH value remains stable in the first five weeks and began to decrease in the six week,the physical state and volume were changed.The mechanical properties,glass transition temperature,molecular weight and thermal decomposition temperature decreased.It’s found that the rate of hydrolysis degradation was faster than that of enzymolysis degradation,the overall degradation rate was slowly and then was faster in the six week,the molecular weight decreased first,followed by mass loss and pH changes with the change of mechanical properties.Ultimately,the biological compatibility of scaffold was investigated.Cytotoxicity assay indicated that the scaffolds had no inhibitory effect on cell proliferation with different concentrations of extract(10 mg/mL,50 mg/mL,100mg/mL),cell viability was more than 91%,which was with in zero or one degree according to the toxicity degrees.Acute toxicity test showed that the weight of mice increased significantly and the liver pathology detection proved that the material fabricated was non-toxic.Hemolysis test showed that the hemolysis ratio of the materials was below the national standards of 5%,and had good blood compatibility.The adsorptive dynamics result showed that the proteins were able to absorb on the surface of the scaffold,thus cells could adhere and grow on the scaffold with the help of mediate proteins.The value of cell protein was 1.02±0.04 mg/scaffold.The cell adhesion and proliferation results showed that the scaffold was suitable for theadhesion and proliferation for cells.Cell concentration increased after incubating for7 days,and the confocal laser scanning microscopy(CLSM)revealed that the scaffold had a good biocompatibility and cells showed active above them. |
