Research On Printing Process And Performance Analysis Of Sodium Alginate-Gelatin Composite Gel Scaffold

As the most important application of 3D printing in bioengineering,biological 3D printing is a technology that combines 3D printing and tissue engineering.Biological 3D printing based on gel materials is using gel as printing material to fabricate 3D entities:The gel and the cells to be printed are mixed to form biomaterials,and then the material is printed into an entity.After culture,the scaffold containing cells can grow into a bioactive tissue structure,it is expected to be applied to future organ transplantation.Therefore,studying and improving the printing process of gel scaffolds,improving the accuracy and performance of printing scaffolds will promote the development of 3D printing in biological field.In this paper,the preparation of composite materials suitable for printing is studied.A mathematical model based on composite gel printing process and a finite element simulation model of extrusion process are constructed.The parameters affecting printing process are studied and analyzed,and the relevant optimization parameters are obtained.Finally,the relevant methods were verified through experiments.and the printed scaffolds were tested and analyzed.The results show that a good quality printing scaffolds can be obtained.The main research work is as follows:1.The composition and ratio of printing materials were studied:The viscosity characteristics of sodium alginate and gelatin were analyzed.The viscosity range suitable for bioplotter printing was determined by experimental method.The effect of calcium chloride on the gel was explored,and the optimum crosslinking concentration and gelatinization temperature were determined.Finally,the best ratio of composite gel was determined according to the viscosity,mechanical properties and other conditions.2.The mathematical model of composite gel extrusion printing and simulation model were constructed,and the key factors affecting the accuracy of printing process were analyzed:In order to study needle extrusion parameters and predict target parameters in experiments,on the basis of understanding the fluid characteristics of extruded gel materials,a prediction model of fluid parameters and a printing parameter prediction model are established by simplifying the conical pin model and considering the slip effect factors,which can predict the target parameters such as flow rate,line width and porosity.Then.the mathematical model is calculated by MATLAB.Finally,the fluent simulation software is used to simulate the extrudate swell phenomenon,the best range of process parameters such as air pressure,moving speed and fiber spacing can be obtained.3.The gelatin/alginate composite gel was used as the material to carry out the scaffold printing experiment on bioplotter printing equipment.The printing parameters obtained from the theoretical model and the simulation software were used as control parameters for printing experiments,and the results showed that:under the control of printing parameters such as temperature 37?.pressure 1.8 bar,moving speed 10.7 mm/s and interval 1.2 mm,better printing results can be obtained.Finally,a solution is proposed for the broken wires in printing process.4.The performance of composite gel scaffolds was tested and analyzed.lt is found that porosity,contact area between lines and relative position of lines are the three key factors affecting the mechanical properties of the scaffold,appropriate scaffolds should be selected in combination with recovery and mechanical properties.crosslinked composite scaffolds have better thermal stability and help to maintain scaffold structure.The swelling rate and degradation rate experiment results show that the swelling rate of the composite gel scaffolds reached the maximum value of 713% in a short time,and the scaffolds were degraded at relatively uniform rates.Biocompatibility experiments showed that calcium chloride cross-linking was very important for the growth of cells on scaffolds.The scaffolds had no cytotoxicity.Printing scaffolds was conducive to the growth and proliferation of cells.