| Electrospinning nanofibers have large specific surface area,large aspect ratio,and highporosity of scaffold.Among them,highly oriented nanofibers have special biological,electrical,optical and mechanical properties,which enable their huge application potential in the field of tissue engineering.Nanofibers are closer to the natural extracellular matrix,which can not only provide a template for cell adhesion and growth,but also promote the transportation of nutrients and metabolites.However,the orientation and thickness of nanofibers prepared by traditional electrospinning devices are not enough.And their receiving efficiency needs to be improved.The biomimetic bone structure scaffold mimics the pore size and porosity of natural bone tissue,not only can provide more similar mechanical properties,but also promotes tissue repairing,and has been extensively studied in bone tissue engineering.There are few reports on the use of ordered nanofibers prepared by electrospinning to simulate the collagen fibers in the osteon to obtain the structure of the biomimetic osteon.Firstly,this research designed a new type of electrospinning device with controllable nanofiber orientation and thickness.It mainly uses two parallel sliding rods and a roller as the receiver,and a crank slider mechanism is added to the sliding rod as an erasing device,keeping the electric field stable during spinning,and this device has the advantages of being able to obtain a large area of highly oriented nanofibers at a low rotation speed and high receiving efficiency.For this new device,the orientation degree of the nanofibers received under different parallel slide bar spacing,different drum rotation speed,and different receiving distance was explored.At the same time,the receiving efficiency of this new device and the traditional drum was also explored.The results show that the fiber orientation is the best when the distance between the two sliders is 7.5cm;The fiber orientation degree becomes higher with the increase of the drum rotation speed,and highly oriented nanofibers can be successfully obtained at a low rotation speed of 550r/min;The fiber orientation is best when the receiving distance is 17 cm.The new device accepts a larger fiber thickness than the traditional drum in the same time,indicating that the new device has a higher receiving efficiency.Subsequently,according to the structural characteristics of the osteon laminates,the bionic osteon structure with different fiber orientation arrangement angles and diameters was designed.The bionic structure was simulated and analyzed by using finite element analysis software ANSYS.Combined with actual experiments,the tensile,compression,shear and other mechanical properties of these bionic osteon structures are studied.The static tensile and compression simulation results show that the vertical(along the axial direction of the osteon)fibers in the laminate play an important role in the tensile and compressive resistance of the osteon.As the angles of the fibers in each layer of the bionic osteon become more concentrated,the distribution of stress become more uniform,and the stress concentration can be avoided.When the angle of each fiber layer in the bionic osteon approaches the axial direction of the bionic osteon,the smaller the elongation at break,the greater the elastic modulus and compression modulus it has.Shear simulation analysis results show that as the angle of each fiber layer approaches the axial direction of the bionic osteon,the shear modulus first increases and then decreases.In the five-layer bone plate whose fiber arrangement angles are 40°-65°-90°-115°-140° group has the largest shear modulus.The dynamic variable load tensile/compression simulation analysis results show that the40°-65°-90°-115°-140° group exhibits the best stability and resilience.As the fiber angles of each layer continue to approach the bionic osteon in the axial direction,its stability and resilience performance become worse.Various simulation results show that with the increase of fiber diameter,the elastic modulus,compression modulus and shear modulus of the bionic osteon also increase correspondingly.In order to verify the reliability of the simulation analysis results,four sets of PCL bionic osteon scaffolds were designed based on the simulation results.The actual tensile test results showed that the elastic modulus of the disordered group,the four-layer bone plates whose fiber arrangement angles are135°-90°-45°-0° group,the five-layer bone plate whose fiber arrangement angles are135°-90°-60°-30°-0°,and the six-layer bone plate whose fiber arrangement angles are135°-90°-80°-65°-40°-0° group increases successively,the ultimate tensile strength also increases successively,and the elongation at break successively decreases.The results of the cyclic tensile test show that the stability and resilience of the group of 135°-90°-45°-0°,the group of 135°-90°-60°-30°-0°,the group of 135°-90°-80°-65°-40°-0°gradually weakened,but all were stronger than the disordered group in stability and resilience.The two actual test results are consistent with the corresponding simulation results,confirming the reliability of the simulation results.Finally,combining the results of simulation analysis and the designed electrospinning device,a PCL/HA/Gel MA-based bionic osteon structure scaffold was prepared,its physical and chemical properties were studied,and its biocompatibility and osteogenic differentiation properties were verified.The physical and chemical results showed that the PCL/HA/Gel MA bionic osteon structure scaffold was successfully prepared,and the hydroxyapatite was successfully dispersed into the fibers.The addition of Gel MA and HA greatly improved the hydrophilicity of the composite scaffold.Bionics osteon scaffolds with different fiber angles showed significant mechanical differences,the 90°-ordered bionic osteon scaffold exhibited the best mechanical strength and the lowest elongation at break during static stretching,the mechanical strength and elongation at break of the 40°-65°-90°-115°-140° bionic osteon scaffold are between the disordered bionic osteon scaffold and the 90° ordered bionic osteon scaffold.During the dynamic stretching process,the 40°-65°-90°-115°-140° bionic osteon scaffold showed the best elastic performance,and in the test of using AFM to measure the surface adhesion of the scaffold,the 40°-65°-90°-115°-140° bionic osteon scaffold also showed the greatest adhesion.Thus,the 40°-65°-90°-115°-140° bionic osteon scaffold is the most adaptable to various types of mechanical environments.The biological results show that the biomimetic osteon structure scaffold of PCL/HA/Gel MA has good biocompatibility,and mouse bone marrow mesenchymal stem cells grow and proliferate better on the ordered biomimetic osteon structure scaffold,as well as the osteogenic differentiation effect is more significant. |
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