| Objective: In this study,3D printing technology was used to prepare PCL/β-TCP bone repair scaffold with different mass ratios,observe its surface morphological characteristics,measure its physical and chemical properties,and test whether its pore size and mechanical properties meet the requirements of bone repair materials.The composite scaffold supported PDA microspheres were prepared,and their mechanical properties and drug release properties were tested.The cell compatibility,antibacterial activity and osteogenic properties were measured by animal and cell experiments.Method: 3D printing scaffolds were prepared by melting printing and solvent volatile printing using biological 3D machine with PCL/5%β-TCP、PCL/10%β-TCP、PCL/20%β-TCP、PCL:β-TCP=1:2、PCL:β-TCP=1:3、PCL:β-TCP=1:4.The appearance structure and microscopic characteristics of each group of scaffolds were observed by scanning electron microscopy,and the mechanical compression properties of samples with different mass ratios were tested by universal material testing machine,so as to determine the printing scaffolds that fit the mechanical structure of human spongy bone.After the polymerization reaction of dopamine in alkaline environment,PDA microspheres with different diameters were prepared by adjusting the concentration of ammonia water.The microscopic morphology of PDA microspheres was observed by scanning electron microscopy.The smallest diameter group was selected as the uploading rate and drug release performance test,which was soaked in vancomycin solution and soaked in PBS.The antibiotic upload rate and drug release performance of PDA microspheres were calculated by measuring the concentration of vancomycin in PBS solution at different time.PCL/β-TCP,PCL/β-TCP/ 1pc PDA,PCL/β-TCP/ 3pc PDA,PCL/β-TCP/ 5pc PDA 6×6×6mm cube scaffolds were constructed by adding PDA microspheres of different qualities to the optimal ratio of printing slurry obtained in the above experiments.The mechanical properties,electron microscopy,X-ray diffraction analysis,Fourier infrared spectroscopy FT-IR analysis,micro CT scanning and drug release properties of the scaffolds were tested.MC3T3 cells were inoculated with these scaffolds,and the biocompatibility of scaffolds was detected by staining of live and dead cells,CCK-8,DAPI/ ghost peptide and alkaline phosphatase.PCL/β-TCP/PDA scaffolds with different mass ratios were implanted into the frontal bones of adult New Zealand white rabbits for perforation.4 weeks later,the experimental animals were killed,and the occipital bones were taken for Micro CT examination to test the repair function of the scaffolds.Results: According to the mechanical experiment and the aperture observation under scanning electron microscope,the structure of the solvent volatile printing scaffold with PCL:β-TCP=1:4 was stable and the aperture was uniform.Under the mass ratio,there was a plateau at about 27% of the strain of the 8mm diameter and2 mm height cylindrical scaffold sample,and the compressive strength at the platform was 2.829 ± 0.992 MPa.The compressive strength of 70% strain is 19.457 ±5.328 MPa,which basically meets the requirements of human cancellous bone mechanics.By SEM observation,the diameter of PDA microspheres prepared by increasing ammonia content decreased,and the diameter of PDA microspheres prepared by adjusting the amount of ammonia was 150μm.The maximum upload rate of PDA microspheres was calculated by vancomycin loading test,and the drug release curve was gentle without obvious sudden release effect.The mechanical experiments of PCL/β-TCP/PDA scaffolds with different mass ratios show that the compressive strength of PCL/β-TCP/PDA scaffolds is greatly improved when the concentration of PDA reaches 5%.The compressive strength at the platform is 5.929±0.371 MPa,and the compressive strength at 70% strain is 13.110±1.543 MPa.The drug release rate was significantly lower than that of the other groups,and the drug release time was about 144 hours,and the drug release amount was increased by about 58.69% compared with the blank group without PDA.In vitro cell experiment CCK8 staining showed that after 1,2,and 3 days after BMSCs were cultured with scaffolded,the absorbance of BMSCS decreased at 450 nm compared with the blank group,and the difference was statistically significant(p < 0.05),indicating that the activity of cells in the experimental group was weakened to varying degrees.After 3days of culture,the cell activity of PCL/β-TCP/1%PDA scaffold was 0.851±0.082,PCL/β-TCP/2%PDA was 0.847±0.031,and PCL/β-TCP/3%PDA was 0.695±0.129,indicating that the mass ratio of PDA increased to 3% or even increased.The scaffold showed obvious inhibitory effect on cell activity.Bone density,bone volume fraction and bone trabecular number were significantly increased at 4 weeks in vivo compared with blank group,with statistical difference(p < 0.05),while there was no statistical difference in bone trabecular thickness compared with blank group(p >0.05),but there was no significant difference between different PDA mass ratio scaffolds.Bone mineral density,bone volume fraction,bone trabecular thickness and bone trabecular number increased significantly at 12 weeks compared with blank group,but bone volume fraction and bone mineral density decreased with the increase of PDA mass ratio.The results showed that PCL/ β-TCP could induce new bone formation,and the quality and bone density of new bone were better than that of bone rod and bone meal.However,with the increase of PDA mass ratio,the osteogenic quality of PDA decreased to varying degrees.Conclusions: The mass ratio of PCL/β-TCP/PDA scaffold printed by the solvent volatile printing method was 1:4,while the PDA content is 3%.On the premise of meeting the mechanical requirements of bone repair materials,the scaffold can promote the effect of bone repair without excessive inhibition of cell activity,and can load antibiotics to achieve the effect of slow release of drugs to prevent infection,so it has the prospect of clinical application. |
PDF Full Text Request