| In recent years,the rapid development of three-dimensional(3D)bioprinting technology based on the principle of layered manufacturing has brought new research ideas and solutions to biomedical fields such as tissue and organ regeneration and clinical repair and treatment.The bioink used in 3D printing technology must have a suitable cross-linking mechanism to complete the required structure forming and the printing materials must have stable biocompatibility and suitable mechanical properties.At present,suitable bioinks for 3D bioprinting technology have become a hindrance to the development of this technology.Silk fibroin materials have received extensive attention from researchers in the field of 3D bioprinting in recent years due to their good biocompatibility,controlled biodegradability,non-immunogenicity,and abundant sources.However,due to its slow natural gelation process and poor 3D printing formability,its application in the field of 3D bioprinting is limited.Based on the extrusion-based 3D bioprinting technology,this paper has developed a process for the preparation of pure silk fibroin ink,and successfully achieved 3D printing molding of pure silk fibroin hydrogel.Through process development and optimization,the effective control of the macro-microstructure of the printing scaffold was achieved,and the dependence of pure silk fibroin ink on the electric field and temperature was discussed,and the regulation mechanism of electric field and temperature on the silk fibroin hydrogel process is proposed.At the same time,the cytocompatibility and mechanical properties of the printed silk fibroin scaffold were also studied.Through the exploration and research of this subject,not only can solve some technical problems faced by extrusion-based 3D bioprinting,but also put forward a research idea of developing new silk fibroin.The main findings are as follows:(1)Utilizing the sensitivity of the silk fibroin material to the electric field and temperature during the gelation process,the pure silk fibroin bioink,which can be used for extrusion-based 3D bioprinting technology,can be controlled without adding any other chemical materials.The research results show that the stable electric field can effectively control the rheological properties of silk fibroin hydrogel,while the temperature-sensitive properties of silk fibroin electrogel can effectively remove the air bubbles in the gel.accurate electric field and temperature control can effectively improve the printability of pure silk fibroin ink.(2)By means of SEM observation,atomic force microscope observation,Fourier infrared and X-ray diffraction analysis,the dependence of pure silk fibroin ink on electric field and temperature was studied,and the electric field and temperature on silk fibroin hydrogel were initially proposed.The research and analysis found that the crystal structure and the secondary structure of the protein of the silk fibroin did not change significantly under the change of the electric field and temperature of the electrogel,and the silk fibroin was still dominated by the random coil structure.The transition of the gel-solution state during the electrogel process is caused by the weak hydrogen bonds,electrostatic interactions,and hydrophobic interactions between the silk fibroin nanospheres.(3)The effects of key printing parameters such as printing pressure,temperature,filling spacing and number of layers on the stucture and mechanical properties of the printed scaffold during the 3D printing process were systematically investigated,and the optimal 3D printing process parameters of the silk fibroin ink were obtained,.3D printing process parameters:the nozzle temperature and the platform temperature are 5℃,and the printing pressure is 0.4 MPa,and the pure silk fibroin 3D printed scaffold with the filling spacing of 1.5 mm has the best shape retention.The number of printed scaffolds can reach 20 layers.At the same time,the mechanical performance test results show that the silk fibroin 3D printed scaffold has good mechanical properties and stability in both dry and wet states.(4)The results of in vitro cell culture experiments show that the silk fibroin 3D printed can significantly promote the adhesion,proliferation and growth of cells on its surface,and the multi-level porous results of the silk fibroin 3D printed scaffold can significantly promote the cell to scaffold Internal migration and growth.It is worth noting that pure silk fibroin scaffolds prepared without the addition of other chemicals are essential to maintain the excellent biocompatibility of the material itself. |
